I just got a couple more of these in the mail yesterday. They are slightly different. If I get a chance I'll try to create a modified schematic on the latest one and add it to GitHub. The resistors are a bit different, and they have a programming port with 6+2 holes instead of 8+2. After quickly testing the pinout of the latest ones it looks like it is connected to the hardware SPI interface instead of the UART+SWIM pin like the one shown here. The latest ones I received have unmarked chips but the power, ground, Vcap pin, ADC inputs, and LED display are all connected just the same. There are a couple of odd smd resistor type mounting pads on the front side of the PCB just opposite to the microcontroller, and in the trace path of the programming port. I'm not sure what those were intended for, but they are unpopulated. The lowest 2 pins of the programming port are Regulated 3.3v Vcc for the chip (aka the linear regulator's output pin), and the other pin is ground. There is no connection for the voltage sense pin on this header, and the swim port is not connected (bummer). It looks like they also eliminated a couple of resistors by using 50k pots instead of 20k. The overall single side gain stage of an LM358 op amp is still used just the same.
So I've been YT-content-MIA for awhile after getting really sick with the Flu at the beginning of the year. Hopefully this little upload helps get me back in gear. I've got a few things I hope to share on here soon about the AVR TT, and a couple of other projects I've built recently. -Jake
Upcycle Electronics, do you really think this video helps to understand how this dsn-vc288 works? The video itself would be really nice with some spoken comments. But just nice music is not helpful at all.
Many people feel otherwise about these things. This is a tool not entertainment. If you have trouble using the tool feel free to use a different one. I create the kind of content I find useful. I'm not a fan of endless blabbering on most electronics channels. I don't care to do that. Nobody asked you to watch, but you won't find a schematic anywhere else other than here and my GitHub. -Jake
Thanks for the schematics! Just used this to convert a two wire 7-100v volt/ammeter into a three wire (disconnected the 270k resistor for the voltage input from the vcc input, so now it can measure down to 0 volts instead of dying at 6v :)
Thanks for your hard work friend. I am greatly helped by your work because it has answered my curiosity as mine has the main IC with no marking code at all. I really appreciate it.
The LM358 isn't the best op-amp to amplify the tiny voltage across the 5mΩ CS resistor. This can be fixed with modifications. The most annoying problem I found is the way the firmware discards the first few counts causing an unavoidable negative offset mainly in the current range despite the meter having been zeroed. This causes readings to be higher than actual at the high end of the range. If this is corrected with the pot, the low end will then read lower than actual.
I have replaced the 180k resistor from the closed loop of the op-amp with a 1k resistor. (this to reduce the gain and make the measurements less sensible to noise). And replaced 8k2 resistor from the inverting input to ground with a 100 ohm resistor (this to have more resolution from the shunt resistor). And added a 10nF from the output of op-amp to ground. Now is hard to calibrate with the 20k pot (i don't have another) but the ammeter is stable and precise. Thank you for the schematic. (The op-amp can drive 30mA so 100 ohm + 1k to ground is more then safe)
I think its ironic that we are reverse engineering stuff made in China. I use these little guys on my CNC machine! Glad to have this info. Glad you did this work!
The funny thing is that most of them are actually projects from old magazine articles, or other open source hobby projects. We are just retracing, a recycler's latest revision of an ancient project. I've been goofing around with the $5 Linear Power Supplies that use 3× TL081 op amps recently. That's just a design based on a project from Elektor magazine that was published in the 1970's. I think most of the Chinese kits and devices are simply projects that have been sent to Chinese board houses for manufacturing so much someone finally realized it makes more sense to build and sell this stuff directly. All of the Jellybean components hobbyists use are made in China already and most of that is made in the same area as the board houses. -Jake
Great article, thanks to it I can finally stop thinking about replacing the burnt STM8S103F3 with a new one, throw away the DSN-VC288 with a clear conscience and take care of something new :). Best wishes ! Marek
Wow! Great work and thank you so much. I need to improve the current calibration by changing the resistor values. Could not do it without your schematics. Thanks again!
@@jorgeneo560 Hi. It depends on whether your Ammeter was over reading or under reading. If the provided trim potentiometer is not able to adjust the readout to within an acceptable value then you may have to change the operational amplifier gain. I left the 8K2 resistors as is and replaced the feedback resistors with either a greater value resistor if the meter was under reading, thereby increasing the gain, or a lessor value resistor if it was over reading, thereby reducing the gain. First center the trim potentiometer so as to leave some adjustment room. Calculate the gain of the op-amp from the resistors used in the circuit. Google non-inverting op-amp. Then calculate your erroneous op-amp gain. Calculate the factor by which the reading needs to be reduced. Then calculate the correct gain to get the reading within the potentiometer’s range. Use the non-inverting op-amp formula to calculate the feedback resistance required. Replace the feedback resistor with the correct value, then use the trim pot to adjust the readout properly. Alternatively you can try different feedback resistor values by trial and error. I hope this helps someone.
Muitíssimo obrigado, você salvou minha vida, estava querendo captar o sinal do amperímetro para enviar o sinal para um Arduino, mas estava com problema de conseguir o diagrama. Que você tenha muito sucesso na sua vida. 😉😃
Thanks for taking effort in reverse engineering and thanks for schematic! :) Yes, there are several modifications of DSN-VC288 in market but basic schematic is the same.. In my case R3 - 47K, R4 - 2.2K.. RV2 same - 20K..
you right amazing vid, full of info!! You should change R3-47k >>> 39K, just near the pot of amp calibration. After this remplacement, the calibration is better, I mean here the bidul show much close precise amp consuption 😉
Thanks for the video and schematics! Can you tell what connector is used on the PCB for the current measurement? (the wider one). I would like to place the same on my PCB.
Thank you for sharing, you saved me a lot of time. I would have a question. My needs are for tensions ranging 48...60V. Worth testing a simple 1 transistor tension regulator to feed the ME6203 LDO from the circuit to monitor ? I have no experience in cascading two regulators. Any clue... ?
I have modified 10Amps DSN-VC288 to 100AMPS using external shunt with 75mA. I have removed the internal shunt, I am getting display of 0.256 Amps. instead of 2.56 Amps. How to shift the decimal point? Should I have to reprogram the chip. Please suggest. Urgent please
Hi. I have this model of voltampmeter.but from the begining i have a zero indication about amps all the time...or 99,9 if i switch thin wires. Where should i loock,or what to check to fix the problem?
making box for measuring low resistance, utilizing LM317 (and/or LM338)... Current Output will be set to 100mA, using 12.5 Ohm "adjust" circuit: DSN-VC288 On-hand (1000mA - no 10A shunt); using common SMPS (12VDC)... Question1: should thin yellow be connected to LM317 "VCC IN"? or or LM317 "Output"... or use separate PSU (5VDC)for meter power (thin Black connected or no?) Question 2: pre-wired VC288 for "reset" button; press "reset" (2 -3 seconds) at power up? or while unit is already in operation? many thanks for your insight(s) will confirm accuracy with benchtop DVM, using "I adj' and "V adj".
You would have to have a completely different type of design to do this. The big difference between the VC288 and what you're looking for is the way the circuit is powered and the op amp specifications. Basically, you need a circuit with an op amp capable of (designed for) differential measurements. A cheap little LM358 is not capable of this. You need an instrumentation style op amp designed to measure tiny differences between two large floating voltages. The VC288 is just measuring the difference between it's circuit ground and the tiny difference on the other side of the current shunt. This only works because the circuit ground for the VC288 is connected to the same ground as the circuit you're measuring. You might be able to do something with a completely separate isolated power supply for the VC288. It has been awhile since I worked on this and I don't recall why this is a problem but something in the back of my mind keeps hinting that an isolated supply doesn't solve the problem either. I recall noting to myself that these meters must ALWAYS connect to the measured circuit ground, but the details are fuzzy. I'm just a casual hobbyist so don't take my words as anything more than a simple hobbyist's opinion. Good Luck. -Jake
Great work, great resource, plus great music. A very worthwhile contribution appreciated by many. I am about to try to measure an active load a blocking diode should do the trick ( I hope).. Solar panel via a regulator to a 12v battery
Probably not. I assume you saw the stuff on the eevblog forum/my github? I'm actually working on a project to show how to rebuild a high end shimano rear brake for a road bike right now. I'm probably going to post it here so I see any questions in the comments. There's zero info on how to do this anywhere online The brake has been around for 6 years on lots of bikes so it's kinda sad no one has tried and documented this. Shimano USA doesn't even sell the tool to take the thing apart, nor does anyone else in the US. I've recorded how to make the tool, and logging days of testing, on d5 now. ...it's the first time I've been motivated to make video content in quite awhile. Maybe it will motivate me to make more electronic stuff too. There are a bunch of things I've been doing lately that are not very well documented on YT. We'll see :-) -Jake
Nope. I've tried to modify the gain circuit before and didn't have much luck. Either the software is doing something odd, or the rail to rail voltage of the op amp is not sufficient for other gain settings. The output of the op amp must line up with whatever the ADC is set for in the μC. I don't know if that μC has different reference voltages, or how it is multiplexed. Even on the analog side, I must confess, I still don't entirely understand how their bias circuit works. The bias circuit is the series resistor in line with the current shunt. I know a small current source is required to get the lm358 operating linearly, but I'm not sure how this is influenced by the gain setting. I've gotten a similar circuit working with an arduino uno but I skipped their bias setup, went old skool, and just used a diode between the op amp output pin and the rest of the circuit. I never got into the STM8's anyways. I started to work on the toolchain at one point but had STLink (clone) issues and moved on to other interests.
Mr,, permission to ask, if the DSN-VC288 module is dual volt and ampere meter, the ic code STM8103F3 is shot (dead), then replaced with the same ic code, can this module immediately turn on normally. thank you.
Excellent work. Thanks for sharing this. May I ask for advice? I have a project with 3 DC CV/CC supply rail voltages 15v 500mA, 12v 2A, and 5v 5A . These 3 supplies share a common ground due to mosfet and darlington switching of 12v lighting and motors from a 5v control. I was hoping to use 3 of these meters to monitor these rails but I can't see a way of modifying them to sense the +ve current of each supply rather than the GND return which would carry currents from other supplies. Any ideas would be gratefully received. Thanks.
Excelente trabajo generosamente compartido. Tuve sistemáticos problemas con este voltamperímetro. En primer lugar el ajuste de los indicadores de tensión y de corriente son pésimos. Sería lo de menos porque se soluciona con un poco de trabajo y cambiando los presets por resistores fijos que supuestamente debieran erradicar el problema para siempre pero hay un tema no menor: ambos medidores tienen problemas de linealidad. Ignoro si fueron programados para otras funciones específicas cosa que por cierto es bastante improbable. Así las cosas, cuando se ajustan los indicadores para un determinado valor, las lecturas por arriba y por abajo de dicho punto no coinciden con el verdadero valor. En el caso del medidor de intensidad, con el potenciómetro al máximo, no se logra una indicación correcta. Hay que modificar el resistor que está asociado al preset y que regula la realimentación negativa del amplificador operacional (LM358). Es poco probable que el conversor ADC del uC carezca de linealidad y que el diseñador tuviera que recurrir a una tabla de corrección. En algunas ocasiones el indicador de corriente no retorna a cero cuando se desconecta la carga (o sea I = 0). Esa condición persiste aún cuando se desconecte la alimentación del dispositivo. En el borde izquierdo del PCB, cercano al uC hay un par de pads que parecen ser un reset. Cortocicuitando el pad la lectura de intensidad. puede retornarse a cero. Algo parecido sucede con la parte de medición de tensión. Especialmente cuando la tensión de salida es menor que 5 volts. Un like y un saludo.
Hi, i've gotten myself 3 of these modules(seems to be the same configuration as shown here) but the measured current has an offset of factor 3. That means if i apply a load of rouhgly 1A it reads 3A. naturally i cant compensate that with the potentiometer. My Question is: Can I replace the resistor R3 with a higher one to compensate this behaviour or is there another way?
You should return them. These aren't easy to modify. I tried it, but they are doing funny stuff in software. It wasn't designed around a divisible ratio. I think they are using look up tables for compensation in software.
EDIT: Ok forget what i said. This is a problem of measuring with common ground with seperate voltage supply for the lcd and the actual Powersupply. On testing i used a Battery and my DIY lab bench powersupply and got the good values for the current. To solve this you have to place a wire (the bigger the better) between the two input grounds. That's it, costed me just a day to get a solution for this x-D
3:49 In my schematic, RV1 is a very minor adjustment to the voltage divider for the voltmeter. RV2 adjusts the feedback gain setting of the op amp. They both basically calibrate the voltage going into the ADC of the microcontroller by somewhere around 5%. The microcontroller is then programmed with a table that references the ADC pin voltage to a numerical display output. These pots are mostly useful if your building something with more than 1 of these devices. The pots should enable you to manually calibrate multiple devices manually so that they read the same voltage/current. They will always track independently due to component variations, but at least they can be calibrated at a certain voltage and current where they will read the same. -Jake
The unit I have came without 10A Shunt (intend to use for 100mA... keeping test leads short... for setting LM338 current for low ohm measurements) upper/left 2 holes for Reset?
I bought a couple of the volt amp meters, with internal shunt. Is it possible to convert to external shunt, for higher current? I'd like to read atleast 50a, great video,
Hey James Thanks. It's more difficult than it's worth to modify them. The current shunt amplifier part of the circuit (the op amp/LM358) has a voltage bias and a feedback gain element. The bias is the 3V3 + 270k + 330R + shunt, part of the circuit. The gain is the 20k trimpot + 180k / 8k2 part. This isn't an easy amount of gain to mess with. After the op amp's output goes into the microcontroller's ADC the STM8 software is doing math based on the amount of gain in order to display a value. This makes it very difficult to modify the circuit accurately without reprogramming the microcontroller. It's far easier to just buy one with the correct range. Your time is worth much more than the cost of the correct part, unless you're super familiar with the STM8 toolchain already. -Jake
Does anyone ever get one of those meters to give reliable current measurements over a wider range? Or is the design just not that good? Thank you for your work!!
I don't know why you would program the chip. You could try, but the original software is not available as far as I know. Maybe someone has recreated it on GIThub or elsewhere, but I haven't looked or seen anything. The way the current sense is amplified is not linear or divisible by 10 so it's impossible to change the scale of the reading without reprogramming the thing. Of course, none of this matters if you're just trying to hook it up and use it. This upload just shows how everything is connected. If someone wants to know why the meter must be configured in a single ended measurement (circuit ground for the meter must be circuit ground for the measurement), instead of a differential arrangement (like a typical hand held multimeter), this schematic and upload make it clear. That's why I made this. If you're just trying to connect stuff, check out the links in the description. If you're really looking to program this, that's beyond my knowledge and abilities. I had the STM8 toolchain working years ago, but didn't really use it for anything, and moved on to other chips brands and toolchains. -Jake
So these little lovelies are great... Thanks so much for doing this!! Can you post the schematics here? Did you have a go at getting the code out and reverse assembling it? Or is the security fuse blown? Let's face it the Chinese can't be beat for value for money ... but we could make some changes... Like removing the amps input port and hooking an Agilent ACS758LCB hall current sensor (remote with balanced pair drop cable?) straight to the port that reads amps, so that "amps out" from the ACS758 displays properly on the panel meter. And an output on the I2C? so that it can go into something else... like a CAN bus appliance? I asked the manufacturers if they could do custom versions if I provided the code and their straightforward answer was "how many?"
What are your thoughts on the linearity of this little beauty. The data sheet says ±0.1% voltage error is possible, what's your findings? Reality is often different to spec.
Lol. Datasheet? I'm no expert at such things. You probably know far better than I do, given how often I see you in the comments of several channels I watch regularly on electronics ;) The best I can tell, the op amp gain is not linear for the current sense circuit. I assume they are using some kind of lookup table in the uC. I imagine this is not a very accurate way of doing things. The voltage sense circuitry is on a board with a linear regulator specified for a large voltage drop with a LED display and dropping resistors. While I don't know the sense resistor specs they are using, I know most SMD resistors with a 3 digit part number are usually pretty low tolerance with a larger temperature drift. In a circuit like this with a few potential temperature variables, I don't expect much accuracy there either. I assume the trim pots are there for loosely matching display readings at a certain voltage/current in situations where someone is using multiple copies of this device in a project. I don't think the pots are intended to be used for accuracy across the input range. I'm sure someone on reddit or the eevblog forum has gone into depth about this though if your really interested, but I haven't searched for info on this in awhile. -Jake
Im just a nosey bloke that repairs things, i loved taking things apart as a kid, it was my way of learning :-D. You will have a different set of knowledge to me and a different level of understanding, i never under estimate anyone, people are clever in many ways :-D. It sounds like the dual digital meter is a bit of a bodge, the voltage is the best input. Better the devil you know :-D
It was a very useful video, I have a question about my problem, I would appreciate it if you could answer it. If possible I need the model number of the diode next to the 7133-1.
I have no idea what the model number is. That footprint is too small for markings. However, I just tested one of these in-circuit with a DMM and the forward voltage is 0.254V. So it is a schottky. I imagine it's most likely some SMD equivalent of a 1N5819 or similar. Most of this type of dirt cheap hardware uses the most generic of jellybean components.
@@UpcycleElectronics Thank you for your answer. When I look through the microscope, I see that it only has B3 written on it. I will consider your suggestion and try 1N5819.
Thanks for your schematics. i bought one of these and the reading were very inaccurate, i tried calibrating them with the trimmers but i cannot get enough accuracy. i just measured the resistor marked 270k on the voltmeter voltage divider and it reads 21k ohm. Again thank you very much, i'll replace the resistor in the dividers and the trimmers
To calibrate the current reading, there is a set of through hols left to the marking "I-ADJ-Z" (J2) for that. Left Ammeter Input with no load. Jump with a few kohm resistor that will zero the current reading. Remove the jumper and put a known load. Adjust I-ADJ to the correct reading. The J2 should be marked as " l-ZERO". The DSN-VC288 uses 5% components. Don’t expect to get a 1% accuracy reading. One digit is more likely.
@@terrywey8347 thanks, i noticed that empty header pad from the schematic and tinkered with it. But the thing is the voltmeter reading is not so accurate either, above 5%. even if i calibrate the readings to some load value, the readings change again with other loads. So i designed a little board with attiny85, oled screen and hall effect sensor. might not be economical but its more fun this way and now i can tweak them as much as i like. Thanks for the reply though, I'm sure many more will find it useful
@@rengpuiacolney7328 Same here. This device is more like to be use for a single voltage monitoring instead of use as a "volt meter". It is especially bad for the low end.
I just found your video, thank you! I'm wondering if you are aware of the fact that these come programmed with DIFFERENT decimal point precision, depending on whether you buy the 10A internal shunt, 50A external shunt, and 100A external shunt. I just found that out the hard way, & wondering if you have any advice on how to set it or programming it.
I don't know of anyone that has reverse engineered the software. If you find something that works let me know and I'll post it in the description. There are (were a couple of years ago) 4 and 5 digit versions of these that have external 12 and I think 16 bit ADC's too. GL -Jake
@@Karl_Levine It's using scaling in software. It's not done cleanly where it is easy to shift the decimal point. I tried modifying the LM358 circuit on a breadboard and changing the gain but I think it gets too far outside of the operating range of the LM358 with ground to 3v3 power rails...I think... I couldn't get it to work linearly with any other op amp gain setting and the way they are doing the current bias circuit. Maybe I just don't fully understand some part of this. I know the old school fix for op amp bias is to place a diode on the output inside the feedback loop, but this didn't work with the low voltage power rails of this circuit.
Good Job. I know how much time went into this project. I do have a few concerns. First, I'm looking at "V1.1 DSN-VC288.PDF". On the right hand side is the shunt, with pin 1 (black) going to pin 4 of the LM358 op amp. Shouldn't that connection also go to pin 2 (black) of J3 at the bottom right of the schematic? Otherwise I don't see how the shunt (Pin 1) is internally grounded, nor do I see how the op amp (Pin 4) is grounded. Second. R6, coming from Pin 2 (red) of the shunt goes to pin 5 of the op amp. That side of R6 also goes back to Pin 1 of the shunt (black), effectively putting R6 across the shunt. And also putting Pin 5 of the op amp to ground. This positioning of R6 does not agree with the small schematic of the op amp in "V2.0 DSN-VC288.PDF", which I believe is the correct schematic. I know I can look at a schematic I have drawn myself for hours without seeing my errors. I'm not trying to be nit picky here; just trying to understand. Thank you for your patience and clarification. Gene
Hey Gene, At a glance I think you're right. The schematic 1v1 was primarily used as I was tracing connections. I didn't spend a ton of time on it. Version 2 is the one that is compartmentalized and flows the way I need in order to understand how this works. Sorry for the errors. This is why I try to show my work at the board/trace level. I actually used the topology from the V2 schematic in a 4 channel LED strip switching controller with current sense. It works fine... so if I made a mistake on that one my bench light must be magic :-) -Jake
Hi Jake, Sometimes the FM (I think “Fancy Magic”, others have a different take) on the workbench means the circuit and its construction is correct. In this case you have proven the op amp circuit of V2 is correct. No FM involved. I would suggest for any one else who has downloaded and printed the 1v1 schematic the following small corrections. First, draw a line from pin 4 of the LM358 op amp to pin 2 of J3 (at the bottom right of the schematic). This connects internal ground to the op amp and the shunt. Second, “XX” out the line immediately above the LM358 op amp. This small change will make the op amp circuit of 1v1 agree with op amp circuit of V2. V2 is correct. I have seen the 1v1 schematic reposted on other websites. So I would also suggest that 1v1 be deleted from github and a corrected 1v2 be uploaded in its place. Later, Gene @@UpcycleElectronics
Tenha certeza que o teu esforço ajudou muitos. Como vou utilizar para medir tensões abaixo de 10v , vou modificar o divisor de tensão do voltímetro, assim terei medição mais precisa. O ponto decimal vou ver se é mais fácil por hardware ou software. Por software, logicamente seria mais fácil, mas vou ter que fazer, já que não tenho o original. Por hardware não é difícil, mas posso acabar destruindo o circuito. Muito obrigado !
Many thanks, but some libraries are missing. Where can I find them? atmel.lib contrib.lib valves.lib \home\jake\Desktop\KiCAD TT Projects\MY KICAD\tt ATmega328\TT\Jellybean Op Amp Dual.lib ST Micro STM8S103F3.lib LED Segment Display 3 Digit 0.28" MCD-2831A.lib Regulator ME6203.lib
Unfortunately I'm having lots of trouble with this same stuff now that KiCAD5 has changed how libraries work. They really need to get it streamlined. I've been hesitant to start reorganizing my stuff because I keep seeing major changes when I do repository updates through Ubuntu... and I'm no expert running nightly builds or anything either. They are making the changes on the standard stable release version that I'm using. I've had to download around a gig of KiCAD related data in the last week or so. On github I think I included all the files that were associated with my original schematic. IIRC I downloaded the repository in a separate folder, after I had uploaded it to GIT, and it worked in KiCAD4. I think the old .libs need to be added to the new library manager manually now. At least that's what I've had to do. I've only seen this problem once though when I copied a folder with a KiCAD project on my electronics computer. I tried to clean up the folder by deleting some of the redundant rescue files KiCAD automatically created. After that, KiCAD couldn't find any of my custom libraries. I had to go into the original file and save all of the custom libraries in the new library manager. After saving each of them manually the custom libraries worked in the copy version too. I'll add the disclaimer that I could have easily misunderstood what happened or what I was doing entirely. If you know KiCAD better than me, by all means, simply tell me what I need to do and I'll try to help in any way possible. Personally I'm still a bit lost with what to do with all of this. Heck I don't understand why KiCAD locks the default libraries, but lacks a function to create a library folder and index, or even an entirely separate directory index for custom parts. The purpose of .mod AND .lib files is also beyond me. I have no idea why these are separate or what is the reason anyone would need one of these files exclusive of the other. Sorry for the soapbox, I'm just not quite sure how I can fix this in practice. -Jake
Thanks for your work. DSN-VC288 is very inaccurate measuring amps. Reseting or adjusting did not work. When I reset using jumper, only the voltmeter display an 0, nothing on blue display. Anyone can confirm or do a video how the display look when reseting? Thanks.
Buen video, el mio tenia el código del microntrolador lijado. No sabia que usaban ese micro hasta existe un proyecto llamado sduino para programar esos micros con el ide de arduino.
The measured circuit is grounded through the shunt resistor. The Current across this shunt resistor creates a tiny voltage drop. This means the voltage on the circuit side of the shunt is slightly higher than Circuit Ground on the other side. This voltage is too small to be measured directly by a microcontroller's analogue to digital converter. The tiny voltage must be amplified to a level that can be measured by the microcontroller. This amplification is accomplished using the LM358 op amp. After the tiny voltage is amplified the signal is sent to the microcontroller to measure. The microcontroller uses a lookup table to relate the voltage from the amplifier to an output it can display. The circuit around the LM358 is mostly the feedback loop that sets the gain of the amplifier, but there are also a couple of things added to bias the input offset current. Cheap bipolar junction transistor based op amps like the LM358 are far from perfect and require an offset current to get them into linear operation. This is the main reason I created this video, to document this circuit block for others to use elsewhere. Basically this example shows how measure current cheaply without the need for complicated differential op amp circuits. -Jake
@@UpcycleElectronics My PS cant have the - Ground output opened up. Can one put the shunt on the positive side and then put the the big red and big black wires across the shunt (black on the load side) . I have 100A shunt version from EBAY.
@@lackeydehackey405 No it is not possible with this topology. That requires a differential amplifier and is a lot more complex to do. It's much easier to design a circuit that measures voltages where circuit ground is setting the low voltage threshold. Think of this "low voltage threshold" like an anchor. The voltage can go all over the place but never below the anchor. The microcontroller must operate with a very small range of voltage, and is actually measuring against the anchor to calculate a value. The STM8 used in this runs on 3.3v so it can't measure anything above that. It's very easy to make a resistor divider between power and ground and calculate voltages. While the current measurement circuit here isn't exactly as simple as a resistor divider, it's still referencing ground and VCC just the same. When you want to measure something on the positive rail, you lose that easy grounded anchor point. The problem becomes, how do you establish a new anchor point to measure from, and how do you power the microcontroller so it can measure the difference. It's really easy if your PSU never goes above VCC for the μC. There are many topologies for this kind of circuit, but I am not aware of any cheap Asian products that work for this. The little hall effect current sensors can do this, but that requires some programming and a weekend project.
hi, i have working on curve of processor .it seems to display 0 to 10 amperes for input of 0 to 2 volts . I draw his curve and it seems to be linear. but sensibility is low .in your commentary you say that here is a program in processor . i have question for you : do you know the type of programming (ass, C , C+ ?) and how to read this program ? i wish working read amp 0 to 1 amp and make a new card i, i like look of this device and hole in my transverter project are already makes .thank you johan f5iqx
Hey, I haven't found the source code. I haven't played around with ST's microcontrollers a whole lot yet either. I just have a ST Link V2 programmer clone from AliEx. I use Ubuntu Linux on my computer and I installed the STM8Flash command line compiler. I think it should be able to read the program memory from a microcontroller. Of course, that will just get you a bunch of useless Hex code. The program itself is going to be really simple. The analogue code should be really short. Multiplexing the displays will be the bulk of the code I hope I get a chance to play around with ST microcontrollers one of these days. I stopped researching them once I saw that the official ST Discovery boards are only supported by a Windows software toolchain. If you want to change the range of the display, remember you already have an op amp with a feedback amplifier circuit. Look at the schematic at 3:50 - Swap R4 for a 20k 10× turn trimmer pot and you'll be able to change the feedback loop gain. You should also add a 10nF capacitor in parallel with the trimming pot. You don't have to, but it's just good practice to add a small capacitor here to smooth and remove any noise from this point. If you really want to play with the STM8 I have a few videos saved in a STM8 playlist. I don't use my playlists for self promotion, I use them as a form of personal notes. Everything I watch on YT about electronics and find helpful gets saved in a playlist. I don't think you can see my playlists in alphabetical order like I do/how I use them, but you might find them useful. I watch and try to learn from other RUclips'rs far more than I care to create content. I keep it all publicly listed, even my likes playlist. Best of luck. -Jake ;)
mordal johan No, at least not yet. I started playing with electronics after becoming disabled. I have a rare type of neck and back injury that makes sitting or standing very hard. I don't leave my house much. There is no way I could get to somewhere to take the test to get a radio license right now. I haven't tried to learn much about radio. Maybe in the future I will if my circumstances change ;)
Upcycle Electronics good luck for radio licence , you can enjoy this hobby working a little électronique bases but it seem you are good in this subject ! Best wish !
Hi, my "DC0-10A Digital Ammeter Current 0.36in" stopped working, i accidentally shorted measuring leads 5-8x, i think its because of that. Or China high quality... If main IC is burnt, can i use same model from 999mA I found picture online with model number STM8S003F3, I cant find one for 10A if exists, or those values are just shunt values, "1-100A". Mine IC is blank BTW.
No. The microcontroller uses a lookup table for the readings. You need the code for the specific model and batch of your device. It's better to just buy another one. The ones I have seen fail are total junk. The regulator fails short circuit and everything is toast. You can save the shunt and maybe the displays but the displays are a pain to remove. You can get these from AliExpress for less than $2 each. If you're not familiar with AliEx, just be aware it takes a long time to receive an order. Some sellers are quicker and I receive orders within 2 weeks, but most orders take 1 to 2 months for me to receive. I'm just south of Los Angeles California which is one of the quickest places for recieving orders like this. Some places take much longer to receive shipments. -Jake
@@UpcycleElectronics Good thing I asked. I later thought it was that regulator or diode S4 bad, or 12V voltage fault. I removed display to get to SMDs, yes it was tricky both sides had solder. I order already 1A "999mA" same type 2.65$ Aliex, i know it takes a while, usually 2-3 weeks to Croatia. I wonder will that one last or fail. Maybe ill buy for 5$ official one for my DIY rework station. But Ive read: "Turns out these $5 999ma Ammeters are low-side only" do you know what low-side means ? Shame its too complicated to fix, it was nice compact ammeter. And I think displays are toast too, nothing lights up with buzzer but batt low, ill test them better later. I actually got two 10A ammeters, both stopped working same seller on ebay.
@@dev1ator_yt Low side means it must be placed between the return voltage (circuit ground) and the power supply ground terminal. The technical reason is because, on the meter, it's circuit ground is connected to the circuit ground for the ammeter/shunt. When designing a current shunt amplifier it is easier and cheaper to build a circuit like this. The other type of circuit is the "high side" type. This gets a lot more complicated because the measurement of current involves a differential voltage. When your measuring from the low side the actual measurement is just the tiny difference between the power supply "ground" and the voltage drop of the shunt resistor. This should only be a few millivolts (which is why you need to amplify it in the first place). The amplifier (op amp) has an easy job because it is usually connected to the same circuit ground where it is sinking the power it receives to operate already. If you use this same op amp amplifier on the "high side," you are trying to measure a much higher voltage potential. The shunt resistor will still have a tiny voltage drop across it, but the power being supplied to the op amp is still referenced to circuit ground. This means your trying to amplify a tiny voltage difference that is very high and usually about the same as the positive power supply rail of the op amp. Most cheap op amps do not like this kind of thing. In these types of circuits you'll need a differential amplifier. A differential amplifier is a special design that is able to measure the difference between two points. Their inputs and outputs are somewhat independent from their supply voltage. These types of amplifiers are more advanced and less versatile in the number of circuits they are used in and therefore more expensive. There are other ways to do high side measurements with cheap op amps but they require an isolated and independent power supply rail. All of these options would have doubled the price of these little ammeters. These generally fail because of the voltage drop of the linear regulator. They require a lot of current for that tiny regulator and the voltage drop is far too much for it to handle. They say these are 0-30v but if you read the regulator's specs it can't handle this kind of drop. The circuit is 3.3volts. Power the thing from a stable 5 volt rail and it will work for much longer. You could also add a small PTCC rated for somewhere around 150mA along with a TVS diode to prevent static spikes from killing it.
@@UpcycleElectronics Thank you for explaining everything. I was searching for specs/datasheet for M5333B regulator but didnt find, I know its 3.3V obviously. I measured yesterday 9V drop from 12V lines, used DC Adaptor 500mA 12V, 2.4V was on burnt regulator, like you said it cant handle big drops. "Power supply range: 4V-30V" for shared and independent power supply they say. It should be 5V limit written, like some programimg boards on 5V USB and 3.3V regulator.
Hello, can someone help me here. I tried to reset device by connecting two holes on upper corner but it did not worked for me. Amp meter always swhos 0.25a without load. Please help.
Hello, I would watch it, but I don't think I'm at that kind of level with my skills. I've been playing with pcb layout and design a good bit, and am beginning to get familiar with C/C++, but I'm no expert. It would be too much of a pain in the a* to work with me anyways. I'm partially disabled with major back problems from getting hit by a car at 30mph on a bicycle commute to work in 2014. It takes me ages to work on anything now. I have 1 to 2 hours I can work on something on my good days and sometimes those are few and far in between. I play with things I can accomplish mostly from my computer from a bed with a bit of time working with my hands at the bench. My health issues cause me to go for long periods without much sleep. So when I'm not doing well I'm pretty much useless. It sucks. I don't need you to feel sorry for me or anything like that. This is just why I don't do much or work with others. I would love to have a different situation where I could say yes, but these are the cards I was dealt in the game of life. I have several projects I'm working on. My largest and main current project has taken me well over a year and isn't more than 2 weeks worth of solid work from an able bodied person. (
@@UpcycleElectronics The idea was that we could do the video and then you could post it. As a personal note, I can send you one of the kits if you like.
Very nice video! Congratulations! I have one and I want to put it in my 3D printer, but the power supply is an 12 V 30 A model. Is it possible to modify this circuit to work with 30 A?
Maiko Lopes de Sousa You will need an external current shunt and you will need to reprogram the MCU from scratch. If you can measure the shunt with a DMM capable of doing a 4 wire Kelvin measurement you might be able to figure out the shunt and then figure out the op amp's gain setup. I'm not sure what the shunt measures. I just received my first real (5.5 digit) bench DMM a couple of days ago, but I haven't set it up yet so I still don't know the actual voltage divider ratio/amplification factor/gain. If you know the gain you might be able to change resistors to match the scale you need. All that said, it's much cheaper and more simple to order one of these units set up for an external shunt. There are many sellers on AliEx selling these with/set up for 50amp shunts. I'd go that route myself. -Jake
Можно как нибудь разделить общий минус? отдельно минус шунта, и отдельно минус питания? проблема с Ампер-Регулятором (на основе lm358, регулировка идет через минус). Если кинуть минус до регулятора то регулятор не работает зато всё показывает, если после регул-ра, то он вырубается при регулировке тока.
На плате VSN-VC288 перерезал дорожку идущую от коннектора к шунту (серая). Показания амперметра теперь 9.99, как временный костыль - пущу питание Digital-Meter по изолированному DC-DC-5v преобразователю через lm7805, идей других нету...
I don't have it. I have not played with a STM8 much, I doubt you would get anything useful from hooking up a STLink to one of these. I assume they set the lock bit for the controller. Most of the time they even scrape off the part number for the controller. You could always try to write something from scratch, but you need to be familiar with the controller and toolchain first. I reverse engineered the schematic and destroyed one of these that I had to pay for just to do it. Good Luck
Boa!!!! muito bom seu trabalho! estou tentando reparar esse voltimetro mas ta dificil, ele e vendido falando que alimentação e de 4vcc até 30vcc, fiz um teste com 5vcc funcionou quando passei para 24vcc não funcionou mais.
I made a Lab power Supply with those 2 modules: XL4015 + LCD Voltmeter 4 digits ( the good model, cause 3 digits is not the best) When I turn potentiometer to set voltage on XL4015, there is a some delay before the actual voltage is displayed on the LCD. I tried XL4015 + Ordinary Multimeter, this delay is not present, the voltage is displayed live while turning the pot. But as said XL4015 + LCD voltmeter Display combo, there is some delay, like the voltmeter is analysing the new voltage value. I would like it to be instentanatly, no delay, while I turn the pot, the voltage is display directly, without this delay. Maybe somebody encounter this, and got some idea?? Thx
I bought a DSN-VC288 off eBay but it has no internal shunt. Is this a manufacturing error or are there DSN-VC288 meters out there that have no shunt there? If it's a manufacturing error can I solder a shunt in there? if so, what value?
There are units with external shunts, but you need to know the required resistance. They should have listed this. I don't have a precision milliohm meter to test anything I have accurately. Using my 5.5 digit ancient keithley and kelvin connections I get a reading around 0.1R but I don't completely trust this. I assume it's less than 0.3R. The problem is that the circuit is software calibrated. The gain of the op amp is not Base-10 so it's not easy to modify and get an accurate reading. I would return the product.
Chez BangGood, le shunt de 50 Amp qui est fourni avec le meter est classifier à 75mv (donc lorsque il y a un courant de 50amps) ca voudrais dire que le shunt est a 1.5 milliohms !!
Excelente! Y la música de fondo va de la mano! Compré uno, funciona bien. Lamentablemente me hace un ruido que pasados unos minutos se vuelve insoportable. Alguno sabrá a qué se debe?
bonjour je viens d acquerir 3 dsn vc 288 1750vt .malgre les essais des 2 types de branchements il affiche une tension correcte mais des valeurs de courants completement fausses et ce sur les trois .d abord felicitation pour votre travail de retre ingenieurie sur des produits livres sans explications aucunes .je viens aussi de recevoir 3 doubles thermometres du meme format et apparence que ce volt amperemetre .que pensez vous de ces fausses indications de courant , quelqu un a t il deja eu ce type de problemes .la comparaison est faite par rapport a une triple alim de labo ..... merci johan f5iqx
Bonjour, Il y a beaucoup de potentiel pour de mauvais joints de soudure sur ces cartes de circuits imprimés. Après avoir fait cette vidéo, j'ai construit quelques circuits en utilisant un design d'amplificateur de détection de courant similaire. J'espère pouvoir vous expliquer quelques détails ici pour vous aider à mieux comprendre le circuit. J'espère que vous comprenez ce que je vais dire. Je ne parle que l'anglais, mais j'essaie d'utiliser Google Translate pour communiquer et traduire en double jusqu'à ce que mon texte ait du sens une fois traduit en anglais. La conception de l'amplificateur de détection de courant utilise une résistance de 270 000 ohms et de 330 ohms en série avec la résistance de shunt de courant. Le noeud entre ces deux résistances est l'entrée de l'entrée non-inverseuse (+) de l'ampli op. L'autre côté de la résistance de 270k est connecté au rail d'alimentation régulé linéaire de 3,3 volts. Le but de cet arrangement est de surmonter le décalage de courant de polarisation d'entrée de l'ampli op Bipolar LM358. La plupart des amplis op Bipolar ne sont pas des appareils linéaires tant qu'ils ne reçoivent pas une certaine quantité de courant pour faire fonctionner le circuit. Après avoir reçu suffisamment de courant pour surmonter le biais d'entrée, ils deviennent beaucoup plus linéaires. Cette conception ne sera jamais très précise mais elle devrait être précise entre 100 et 200 millivolts ou milliampères. Le courant de polarisation d'entrée de l'ampli op est la partie de ce circuit qui n'est pas standardisée. Le courant de polarisation sera légèrement différent d'un amplificateur opérationnel à l'autre. Cependant, les résistances de polarisation utilisées dans ce circuit sont une valeur fixe avec une tolérance de plus ou moins cinq pour cent. Si vous voyez une lecture en cours sur l'écran mais qu'elle n'est pas linéaire, il y a de fortes chances que le courant de polarisation soit le problème. La première chose que je ferais est de ressouder toutes les connexions sur le tableau. Si cela ne fonctionne pas votre problème. Ces appareils sont très bon marché car ils sont fabriqués en série et ne sont pas testés individuellement comme une entreprise traditionnelle devrait le faire. Ils ne coûtent pas cher parce que vous ne payez pas pour un employé qui teste des produits ou un département de marketing etc. Si resoldering tout ne résout pas vos problèmes votre problème. Il n'y a pas beaucoup de solutions disponibles pour une configuration différente car la tension de cet ampli op est très faible. Normalement, ce problème de courant de polarisation est résolu en plaçant une petite diode au silicium en série avec la broche de sortie de l'ampli op. La sortie de la diode en silicone est ensuite connectée au reste du circuit, tout comme la sortie de l'ampli op. Cette diode sera à l'intérieur de la boucle de rétroaction négative de l'ampli op. La rétroaction négative compensera la chute de tension de la diode et cela forcera l'ampli op dans sa région de fonctionnement linéaire. Malheureusement, l'ampli op utilisé ici n'est pas un ampli op de tension de rail à rail et il fonctionne entre 3,3 volts et la terre. Vous pouvez essayer le circuit à diodes mais je ne pense pas qu'il fonctionnera avec ces tensions. Je n'ai pas essayé d'utiliser une diode schottky mais je sais qu'une diode au silicium est plus linéaire qu'un schottky, donc je ne pense pas que cela fonctionnera bien. Le microcontrôleur est également programmé pour le gain de l'amplificateur de détection de courant. Cela signifie que le microcontrôleur pourrait être mal programmé. J'ai reçu 2 versions différentes de ce double volts et compteur de courant. Les deux versions différentes utilisent un en-tête de programmation différent et le diviseur de tension est légèrement différent. La version que j'ai montrée dans cette vidéo a l'interface de programmation "SWIM". L'autre version, j'ai seulement accès aux pins série "UART". Cela signifie qu'il y a au moins 2 façons différentes de programmer. J'ai cherché le code source de ce projet mais je n'ai rien trouvé. Il est probablement disponible quelque part mais je ne sais pas où regarder. Je n'ai rien trouvé après avoir cherché duckduckgo pendant un moment. Si vous ne trouvez pas de solution, vous pouvez toujours couper la trace sur la broche analogique à numérique du microcontrôleur. Si vous connectez une petite source de courant à tension limitée et que vous appliquez moins de 3,3 volts sur cette broche, vous pourrez calculer le rapport entre l'entrée et la sortie. Une fois que vous connaissez ce rapport, vous pouvez construire n'importe quel circuit que vous voulez utiliser cette gamme et ce ratio. Original English Text: Hello, There is a lot of potential for bad solder joints on these circuit boards. After I made this video, I built a few circuits using a similar current sense amplifier design. Hopefully I can explain a few details here to help you understand the circuit better. I hope you understand what I am about to say. I only speak English, but I try to use Google Translate to communicate and double translate this until my text makes sense when translated back into English. The current sense amplifier design uses a 270,000 ohm and a 330 ohm resistor in series with the current shunt resistor. The node between these two resistors is the input for the noninverting (+) input of the op amp. The other side of the 270k resistor is connected to the 3.3 volt linear regulated power supply rail. The purpose of this arrangement is to overcome the input bias current offset of the LM358 Bipolar op amp. Most cheap Bipolar op amps are not linear devices until they receive a certain amount of current to get the circuit going. After they receive enough current to overcome the input bias, they become much more linear. This design is never going to be very precise but it should be accurate within 100 to 200 millivolts or milliamps. The input bias current of the op amp is the one part of this circuit that is not standardized. The bias current will be slightly different from one op amp to the next. However the bias resistors used in this circuit are a fixed value with a plus or minus five percent tollerence. If your seeing a current reading on the display but it isn't linear there is a good chance the bias current is the problem. The first thing I would do is resolder all of the connections on the board. If that doesn't work your in trouble. These devices are very cheap because they are mass produced and they are not individually tested like a traditional company should be doing. They are cheap because your not paying for an employee that tests products or a marketing department etcetera. If resoldering everything doesn't solve your problems your in trouble. There are not many solutions available for a different configuration because the voltage swing of this op amp is very small. Normally this bias current issue is solved by placing a small silicon diode in series with op amp's output pin. The output of the silicone diode is then connected to the rest of the circuit just like it's the output of the op amp. This diode will be inside the negative feedback loop of the op amp. The negative feedback will compensate for the voltage drop of the diode and this will force the op amp into it's linear region of operation. Unfortunately the op amp used here is not a rail to rail voltage swing op amp and it is operating between 3.3 volts and Earth ground. You could try the diode circuit but I don't think it will work with these voltages. I haven't tried using a schottky diode but I know a silicon diode is more linear than a schottky, so I don't think that will work well. The microcontroller is also programmed for the gain of the current sense amplifier. This means the microcontroller could be programmed wrong. I have received 2 different versions of this dual volts and current meter. The two different versions use a different programming header and the voltage divider is slightly different. The version I showed in this video has the "SWIM" programming interface. The other version I have only has access to the "UART" serial pins. This means there are at least 2 different ways to program. I have looked for the source code for this project but I did not find anything. It's probably available somewhere but I just don't know where to look. I didn't find anything after searching duckduckgo for awhile. If you can't find a solution, you can always cut the trace at the analogue to digital pin of the microcontroller. If you connect a small current limited voltage source and apply less than 3.3 volts on this pin, you will be able to calculate the input to output ratio. Once you know this ratio you can build any circuit you want that uses this range and ratio. Thanks, -Jake
Upcycle Electronics hélo jake thank you for this lot of information . the thermomèters are OK . i have mounting kikad on my PC . i m working on a transverter 144 MHz to 1296 MHz . he work perfectly on 20 watts pep . this meters are just for looking U and I on the transverter 13 g2 b mk2 of kuhne electronic . i go working on the op amplifier , i thing trouble are hère . i tell you about this troubles of amperemeter . thank you excuse for m'y pour english but its a good way for me to used it . i wish you understand me . i am radio amateur my call is F5IQX. My hobby is hyper frequency . congratulation . happy speak to you again . johan !
Thanks for the reverse engineering. I seem to have a version that works well with the integrated 10A shunt (measured as 6 milliOhm) but fails to give any correct current reading with the external 75mv/50A shunt - even when removing the internal shunt. The external shunt is measured at 2 milliOhm, so it's a factor 3 off. Likely I have to replace the resistors around the opamp to get the right amplification. Somebody experienced the same issue ?
I just got a couple more of these in the mail yesterday. They are slightly different. If I get a chance I'll try to create a modified schematic on the latest one and add it to GitHub. The resistors are a bit different, and they have a programming port with 6+2 holes instead of 8+2. After quickly testing the pinout of the latest ones it looks like it is connected to the hardware SPI interface instead of the UART+SWIM pin like the one shown here. The latest ones I received have unmarked chips but the power, ground, Vcap pin, ADC inputs, and LED display are all connected just the same. There are a couple of odd smd resistor type mounting pads on the front side of the PCB just opposite to the microcontroller, and in the trace path of the programming port. I'm not sure what those were intended for, but they are unpopulated. The lowest 2 pins of the programming port are Regulated 3.3v Vcc for the chip (aka the linear regulator's output pin), and the other pin is ground. There is no connection for the voltage sense pin on this header, and the swim port is not connected (bummer). It looks like they also eliminated a couple of resistors by using 50k pots instead of 20k. The overall single side gain stage of an LM358 op amp is still used just the same.
Very grateful for the schematic, and appreciate the effort you've put in to trace the circuit out!
what a lad, very nice of you to do the job the provider didn't. Very much appreciated!!!
Excellent work, very good video, it helped me a lot, the manuals, the detailed pins and lines; I am very grateful. Greetings from Colombia.
So I've been YT-content-MIA for awhile after getting really sick with the Flu at the beginning of the year. Hopefully this little upload helps get me back in gear. I've got a few things I hope to share on here soon about the AVR TT, and a couple of other projects I've built recently.
-Jake
Upcycle Electronics, do you really think this video helps to understand how this dsn-vc288 works? The video itself would be really nice with some spoken comments. But just nice music is not helpful at all.
Many people feel otherwise about these things. This is a tool not entertainment. If you have trouble using the tool feel free to use a different one. I create the kind of content I find useful. I'm not a fan of endless blabbering on most electronics channels. I don't care to do that. Nobody asked you to watch, but you won't find a schematic anywhere else other than here and my GitHub.
-Jake
Thanks for the schematics! Just used this to convert a two wire 7-100v volt/ammeter into a three wire (disconnected the 270k resistor for the voltage input from the vcc input, so now it can measure down to 0 volts instead of dying at 6v :)
Thanks a lot for this info. Ali forgot to put in the shunt, so I got some crazy Amp-values. An external shunt is obviously needed.
Thanks for your hard work friend. I am greatly helped by your work because it has answered my curiosity as mine has the main IC with no marking code at all. I really appreciate it.
The LM358 isn't the best op-amp to amplify the tiny voltage across the 5mΩ CS resistor.
This can be fixed with modifications.
The most annoying problem I found is the way the firmware discards the first few counts causing an unavoidable negative offset mainly in the current range despite the meter having been zeroed.
This causes readings to be higher than actual at the high end of the range. If this is corrected with the pot, the low end will then read lower than actual.
I have replaced the 180k resistor from the closed loop of the op-amp with a 1k resistor. (this to reduce the gain and make the measurements less sensible to noise). And replaced 8k2 resistor from the inverting input to ground with a 100 ohm resistor (this to have more resolution from the shunt resistor). And added a 10nF from the output of op-amp to ground. Now is hard to calibrate with the 20k pot (i don't have another) but the ammeter is stable and precise. Thank you for the schematic. (The op-amp can drive 30mA so 100 ohm + 1k to ground is more then safe)
I think its ironic that we are reverse engineering stuff made in China. I use these little guys on my CNC machine! Glad to have this info. Glad you did this work!
The funny thing is that most of them are actually projects from old magazine articles, or other open source hobby projects. We are just retracing, a recycler's latest revision of an ancient project.
I've been goofing around with the $5 Linear Power Supplies that use 3× TL081 op amps recently. That's just a design based on a project from Elektor magazine that was published in the 1970's. I think most of the Chinese kits and devices are simply projects that have been sent to Chinese board houses for manufacturing so much someone finally realized it makes more sense to build and sell this stuff directly. All of the Jellybean components hobbyists use are made in China already and most of that is made in the same area as the board houses.
-Jake
Great article, thanks to it I can finally stop thinking about replacing the burnt STM8S103F3 with a new one, throw away the DSN-VC288 with a clear conscience and take care of something new :). Best wishes ! Marek
Lots of thanks for the schematics. Very helpfull to me. Awesome 👍
Excelente iniciativa, mis felicitaciones y agradecimiento por este importante aparte
Wow! Great work and thank you so much. I need to improve the current calibration by changing the resistor values. Could not do it without your schematics. Thanks again!
agg bro, i was looking to do the same, what values do had used?
@@jorgeneo560 Hi. It depends on whether your Ammeter was over reading or under reading. If the provided trim potentiometer is not able to adjust the readout to within an acceptable value then you may have to change the operational amplifier gain. I left the 8K2 resistors as is and replaced the feedback resistors with either a greater value resistor if the meter was under reading, thereby increasing the gain, or a lessor value resistor if it was over reading, thereby reducing the gain. First center the trim potentiometer so as to leave some adjustment room. Calculate the gain of the op-amp from the resistors used in the circuit. Google non-inverting op-amp. Then calculate your erroneous op-amp gain. Calculate the factor by which the reading needs to be reduced. Then calculate the correct gain to get the reading within the potentiometer’s range. Use the non-inverting op-amp formula to calculate the feedback resistance required. Replace the feedback resistor with the correct value, then use the trim pot to adjust the readout properly. Alternatively you can try different feedback resistor values by trial and error. I hope this helps someone.
Muitíssimo obrigado, você salvou minha vida, estava querendo captar o sinal do amperímetro para enviar o sinal para um Arduino, mas estava com problema de conseguir o diagrama. Que você tenha muito sucesso na sua vida. 😉😃
Just found your channel, such a great resource! Immediately subscribed, thank you!
Thanks for taking effort in reverse engineering and thanks for schematic! :) Yes, there are several modifications of DSN-VC288 in market but basic schematic is the same.. In my case R3 - 47K, R4 - 2.2K.. RV2 same - 20K..
you right amazing vid, full of info!!
You should change R3-47k >>> 39K, just near the pot of amp calibration. After this remplacement, the calibration is better, I mean here the bidul show much close precise amp consuption 😉
Jumbled mess for those who don't understand but every frame is golden for those who do.
Thanks! very useful material :)
Really amazing
Such a lot of works and know how 👍
Thanks for the video and schematics! Can you tell what connector is used on the PCB for the current measurement? (the wider one). I would like to place the same on my PCB.
thanks for the schematic. very useful
amazing , Very grateful for the schematic
Thanks a lot for this content, it was super helpful. Just a side note: 3:43 Shunt 1 to ground connection missing.
Can you share the BOM? Especially for the connectors on the PCB for the wires?
Thank you for sharing, you saved me a lot of time.
I would have a question. My needs are for tensions ranging 48...60V.
Worth testing a simple 1 transistor tension regulator to feed the ME6203 LDO from the circuit to monitor ?
I have no experience in cascading two regulators. Any clue... ?
I have modified 10Amps DSN-VC288 to 100AMPS using external shunt with 75mA. I have removed the internal shunt, I am getting display of 0.256 Amps. instead of 2.56 Amps. How to shift the decimal point? Should I have to reprogram the chip. Please suggest. Urgent please
Hi. I have this model of voltampmeter.but from the begining i have a zero indication about amps all the time...or 99,9 if i switch thin wires. Where should i loock,or what to check to fix the problem?
VERY GOOD VIDEO, I SOLVED MY PROBLEM TO IDENTIFY A COMPONENT
good job,because i need one schematic digital voltmeter.Thanks a lot Pro
making box for measuring low resistance, utilizing LM317 (and/or LM338)... Current Output will be set to 100mA, using 12.5 Ohm "adjust" circuit: DSN-VC288 On-hand (1000mA - no 10A shunt); using common SMPS (12VDC)...
Question1: should thin yellow be connected to LM317 "VCC IN"? or or LM317 "Output"... or use separate PSU (5VDC)for meter power (thin Black connected or no?)
Question 2: pre-wired VC288 for "reset" button; press "reset" (2 -3 seconds) at power up? or while unit is already in operation? many thanks for your insight(s)
will confirm accuracy with benchtop DVM, using "I adj' and "V adj".
You would have to have a completely different type of design to do this. The big difference between the VC288 and what you're looking for is the way the circuit is powered and the op amp specifications. Basically, you need a circuit with an op amp capable of (designed for) differential measurements. A cheap little LM358 is not capable of this. You need an instrumentation style op amp designed to measure tiny differences between two large floating voltages. The VC288 is just measuring the difference between it's circuit ground and the tiny difference on the other side of the current shunt. This only works because the circuit ground for the VC288 is connected to the same ground as the circuit you're measuring. You might be able to do something with a completely separate isolated power supply for the VC288.
It has been awhile since I worked on this and I don't recall why this is a problem but something in the back of my mind keeps hinting that an isolated supply doesn't solve the problem either. I recall noting to myself that these meters must ALWAYS connect to the measured circuit ground, but the details are fuzzy.
I'm just a casual hobbyist so don't take my words as anything more than a simple hobbyist's opinion.
Good Luck.
-Jake
Thank you very much, I saw a video that shows that it is a bit inaccurate, what modification could I make to make it more accurate?
Great work, great resource, plus great music. A very worthwhile contribution appreciated by many. I am about to try to measure an active load a blocking diode should do the trick ( I hope).. Solar panel via a regulator to a 12v battery
Are you going to post about the CH341A?
Probably not. I assume you saw the stuff on the eevblog forum/my github?
I'm actually working on a project to show how to rebuild a high end shimano rear brake for a road bike right now. I'm probably going to post it here so I see any questions in the comments. There's zero info on how to do this anywhere online The brake has been around for 6 years on lots of bikes so it's kinda sad no one has tried and documented this. Shimano USA doesn't even sell the tool to take the thing apart, nor does anyone else in the US. I've recorded how to make the tool, and logging days of testing, on d5 now.
...it's the first time I've been motivated to make video content in quite awhile. Maybe it will motivate me to make more electronic stuff too. There are a bunch of things I've been doing lately that are not very well documented on YT.
We'll see :-)
-Jake
my ampere reading is shifted to one decimal place to the right. any solution?
Nope. I've tried to modify the gain circuit before and didn't have much luck. Either the software is doing something odd, or the rail to rail voltage of the op amp is not sufficient for other gain settings. The output of the op amp must line up with whatever the ADC is set for in the μC. I don't know if that μC has different reference voltages, or how it is multiplexed. Even on the analog side, I must confess, I still don't entirely understand how their bias circuit works. The bias circuit is the series resistor in line with the current shunt. I know a small current source is required to get the lm358 operating linearly, but I'm not sure how this is influenced by the gain setting. I've gotten a similar circuit working with an arduino uno but I skipped their bias setup, went old skool, and just used a diode between the op amp output pin and the rest of the circuit.
I never got into the STM8's anyways. I started to work on the toolchain at one point but had STLink (clone) issues and moved on to other interests.
@@UpcycleElectronics opps, you wrote my degree paper.
i have the same problem but my model is HKS-VA028_V2.0
mr, is there a flash ic tutorial stm8s10+file&tool for dual volt&metr. thanks
Nice job! Many thanks.
Thank you for well done Job!!
Mr,, permission to ask, if the DSN-VC288 module is dual volt and ampere meter, the ic code STM8103F3 is shot (dead), then replaced with the same ic code, can this module immediately turn on normally. thank you.
Excellent work. Thanks for sharing this. May I ask for advice? I have a project with 3 DC CV/CC supply rail voltages 15v 500mA, 12v 2A, and 5v 5A . These 3 supplies share a common ground due to mosfet and darlington switching of 12v lighting and motors from a 5v control. I was hoping to use 3 of these meters to monitor these rails but I can't see a way of modifying them to sense the +ve current of each supply rather than the GND return which would carry currents from other supplies. Any ideas would be gratefully received. Thanks.
You need a design based on a differential amplifier. That is a whole different topology. You will not be able to do this using these meters.
@@UpcycleElectronics Thanks for the reply, even if the answer is not what I was hoping for!
Thanks for you schematic 😘
Excelente trabajo generosamente compartido.
Tuve sistemáticos problemas con este voltamperímetro.
En primer lugar el ajuste de los indicadores de tensión y de corriente son pésimos.
Sería lo de menos porque se soluciona con un poco de trabajo y cambiando los presets por resistores fijos que supuestamente debieran erradicar el problema para siempre pero hay un tema no menor: ambos medidores tienen problemas de linealidad.
Ignoro si fueron programados para otras funciones específicas cosa que por cierto es bastante improbable.
Así las cosas, cuando se ajustan los indicadores para un determinado valor, las lecturas por arriba y por abajo de dicho punto no coinciden con el verdadero valor.
En el caso del medidor de intensidad, con el potenciómetro al máximo, no se logra una indicación correcta.
Hay que modificar el resistor que está asociado al preset y que regula la realimentación negativa del amplificador operacional (LM358).
Es poco probable que el conversor ADC del uC carezca de linealidad y que el diseñador tuviera que recurrir a una tabla de corrección.
En algunas ocasiones el indicador de corriente no retorna a cero cuando se desconecta la carga (o sea I = 0).
Esa condición persiste aún cuando se desconecte la alimentación del dispositivo.
En el borde izquierdo del PCB, cercano al uC hay un par de pads que parecen ser un reset.
Cortocicuitando el pad la lectura de intensidad. puede retornarse a cero.
Algo parecido sucede con la parte de medición de tensión.
Especialmente cuando la tensión de salida es menor que 5 volts.
Un like y un saludo.
Hi, i've gotten myself 3 of these modules(seems to be the same configuration as shown here) but the measured current has an offset of factor 3. That means if i apply a load of rouhgly 1A it reads 3A. naturally i cant compensate that with the potentiometer. My Question is: Can I replace the resistor R3 with a higher one to compensate this behaviour or is there another way?
You should return them. These aren't easy to modify. I tried it, but they are doing funny stuff in software. It wasn't designed around a divisible ratio. I think they are using look up tables for compensation in software.
@@UpcycleElectronics well thanks for the quick reply, returning them and getting new ones will be a hassel atm but if there is no way around it...
EDIT: Ok forget what i said. This is a problem of measuring with common ground with seperate voltage supply for the lcd and the actual Powersupply. On testing i used a Battery and my DIY lab bench powersupply and got the good values for the current.
To solve this you have to place a wire (the bigger the better) between the two input grounds. That's it, costed me just a day to get a solution for this x-D
Thank you, I exploded my 358 and couldnt figure out the specific component from the rubble. Preeesh......
what does the pot do?
3:49
In my schematic, RV1 is a very minor adjustment to the voltage divider for the voltmeter.
RV2 adjusts the feedback gain setting of the op amp. They both basically calibrate the voltage going into the ADC of the microcontroller by somewhere around 5%.
The microcontroller is then programmed with a table that references the ADC pin voltage to a numerical display output.
These pots are mostly useful if your building something with more than 1 of these devices. The pots should enable you to manually calibrate multiple devices manually so that they read the same voltage/current. They will always track independently due to component variations, but at least they can be calibrated at a certain voltage and current where they will read the same.
-Jake
@@UpcycleElectronics thank you very much :D
The unit I have came without 10A Shunt (intend to use for 100mA... keeping test leads short... for setting LM338 current for low ohm measurements) upper/left 2 holes for Reset?
I bought a couple of the volt amp meters, with internal shunt. Is it possible to convert to external shunt, for higher current? I'd like to read atleast 50a, great video,
Hey James
Thanks. It's more difficult than it's worth to modify them. The current shunt amplifier part of the circuit (the op amp/LM358) has a voltage bias and a feedback gain element. The bias is the 3V3 + 270k + 330R + shunt, part of the circuit. The gain is the 20k trimpot + 180k / 8k2 part. This isn't an easy amount of gain to mess with. After the op amp's output goes into the microcontroller's ADC the STM8 software is doing math based on the amount of gain in order to display a value. This makes it very difficult to modify the circuit accurately without reprogramming the microcontroller.
It's far easier to just buy one with the correct range. Your time is worth much more than the cost of the correct part, unless you're super familiar with the STM8 toolchain already.
-Jake
Hallo,
könntest Du einen Link zum Schaltplan senden,
im Video ist die Auflösung nicht gut.
Danke
How tô obtain schematic please
Does anyone ever get one of those meters to give reliable current measurements over a wider range?
Or is the design just not that good?
Thank you for your work!!
Do we need to program the main chip or not?
I don't know why you would program the chip. You could try, but the original software is not available as far as I know. Maybe someone has recreated it on GIThub or elsewhere, but I haven't looked or seen anything. The way the current sense is amplified is not linear or divisible by 10 so it's impossible to change the scale of the reading without reprogramming the thing. Of course, none of this matters if you're just trying to hook it up and use it.
This upload just shows how everything is connected. If someone wants to know why the meter must be configured in a single ended measurement (circuit ground for the meter must be circuit ground for the measurement), instead of a differential arrangement (like a typical hand held multimeter), this schematic and upload make it clear. That's why I made this. If you're just trying to connect stuff, check out the links in the description. If you're really looking to program this, that's beyond my knowledge and abilities. I had the STM8 toolchain working years ago, but didn't really use it for anything, and moved on to other chips brands and toolchains.
-Jake
So these little lovelies are great... Thanks so much for doing this!!
Can you post the schematics here? Did you have a go at getting the code out and reverse assembling it? Or is the security fuse blown?
Let's face it the Chinese can't be beat for value for money ... but we could make some changes...
Like removing the amps input port and hooking an Agilent ACS758LCB hall current sensor (remote with balanced pair drop cable?) straight to the port that reads amps, so that "amps out" from the ACS758 displays properly on the panel meter.
And an output on the I2C? so that it can go into something else... like a CAN bus appliance?
I asked the manufacturers if they could do custom versions if I provided the code and their straightforward answer was "how many?"
Very good 👍
Muito obrigado por disponibilizar este video...
What are your thoughts on the linearity of this little beauty.
The data sheet says ±0.1% voltage error is possible, what's your findings?
Reality is often different to spec.
Lol. Datasheet? I'm no expert at such things. You probably know far better than I do, given how often I see you in the comments of several channels I watch regularly on electronics ;)
The best I can tell, the op amp gain is not linear for the current sense circuit. I assume they are using some kind of lookup table in the uC. I imagine this is not a very accurate way of doing things. The voltage sense circuitry is on a board with a linear regulator specified for a large voltage drop with a LED display and dropping resistors. While I don't know the sense resistor specs they are using, I know most SMD resistors with a 3 digit part number are usually pretty low tolerance with a larger temperature drift. In a circuit like this with a few potential temperature variables, I don't expect much accuracy there either. I assume the trim pots are there for loosely matching display readings at a certain voltage/current in situations where someone is using multiple copies of this device in a project. I don't think the pots are intended to be used for accuracy across the input range. I'm sure someone on reddit or the eevblog forum has gone into depth about this though if your really interested, but I haven't searched for info on this in awhile.
-Jake
Im just a nosey bloke that repairs things, i loved taking things apart as a kid, it was my way of learning :-D.
You will have a different set of knowledge to me and a different level of understanding, i never under estimate anyone, people are clever in many ways :-D.
It sounds like the dual digital meter is a bit of a bodge, the voltage is the best input.
Better the devil you know :-D
Do you have for dsn vcn 568?
It was a very useful video, I have a question about my problem, I would appreciate it if you could answer it. If possible I need the model number of the diode next to the 7133-1.
I have no idea what the model number is. That footprint is too small for markings. However, I just tested one of these in-circuit with a DMM and the forward voltage is 0.254V. So it is a schottky. I imagine it's most likely some SMD equivalent of a 1N5819 or similar. Most of this type of dirt cheap hardware uses the most generic of jellybean components.
@@UpcycleElectronics Thank you for your answer. When I look through the microscope, I see that it only has B3 written on it. I will consider your suggestion and try 1N5819.
Thanks for your schematics. i bought one of these and the reading were very inaccurate, i tried calibrating them with the trimmers but i cannot get enough accuracy. i just measured the resistor marked 270k on the voltmeter voltage divider and it reads 21k ohm. Again thank you very much, i'll replace the resistor in the dividers and the trimmers
I'm glad it is useful for you.
To calibrate the current reading, there is a set of through hols left to the marking "I-ADJ-Z" (J2) for that. Left Ammeter Input with no load. Jump with a few kohm resistor that will zero the current reading. Remove the jumper and put a known load. Adjust I-ADJ to the correct reading. The J2 should be marked as " l-ZERO".
The DSN-VC288 uses 5% components. Don’t expect to get a 1% accuracy reading. One digit is more likely.
@@terrywey8347 thanks, i noticed that empty header pad from the schematic and tinkered with it. But the thing is the voltmeter reading is not so accurate either, above 5%. even if i calibrate the readings to some load value, the readings change again with other loads. So i designed a little board with attiny85, oled screen and hall effect sensor. might not be economical but its more fun this way and now i can tweak them as much as i like. Thanks for the reply though, I'm sure many more will find it useful
@@rengpuiacolney7328 Same here. This device is more like to be use for a single voltage monitoring instead of use as a "volt meter". It is especially bad for the low end.
@@terrywey8347 yeah its for my bench power supply so i need it fairly accurate especially the ammeter
I just found your video, thank you!
I'm wondering if you are aware of the fact that these come programmed with DIFFERENT decimal point precision, depending on whether you buy the 10A internal shunt, 50A external shunt, and 100A external shunt.
I just found that out the hard way, & wondering if you have any advice on how to set it or programming it.
I don't know of anyone that has reverse engineered the software. If you find something that works let me know and I'll post it in the description.
There are (were a couple of years ago) 4 and 5 digit versions of these that have external 12 and I think 16 bit ADC's too.
GL
-Jake
Thank you.
Do you know how these are pre-set for a specific shunt?
Is done on the pcb? via software?
@@Karl_Levine
It's using scaling in software. It's not done cleanly where it is easy to shift the decimal point. I tried modifying the LM358 circuit on a breadboard and changing the gain but I think it gets too far outside of the operating range of the LM358 with ground to 3v3 power rails...I think... I couldn't get it to work linearly with any other op amp gain setting and the way they are doing the current bias circuit. Maybe I just don't fully understand some part of this. I know the old school fix for op amp bias is to place a diode on the output inside the feedback loop, but this didn't work with the low voltage power rails of this circuit.
Aha... maybe that's why it doesn't give any more or less correct reading except when using the internal. Is it re programmable with other firmware ?
@@Compasscard
I haven't seen any examples of reprogramming these. I can't.
Good Job. I know how much time went into this project. I do have a few concerns.
First, I'm looking at "V1.1 DSN-VC288.PDF". On the right hand side is the shunt, with pin 1 (black) going to pin 4 of the LM358 op amp. Shouldn't that connection also go to pin 2 (black) of J3 at the bottom right of the schematic? Otherwise I don't see how the shunt (Pin 1) is internally grounded, nor do I see how the op amp (Pin 4) is grounded.
Second. R6, coming from Pin 2 (red) of the shunt goes to pin 5 of the op amp. That side of R6 also goes back to Pin 1 of the shunt (black), effectively putting R6 across the shunt. And also putting Pin 5 of the op amp to ground. This positioning of R6 does not agree with the small schematic of the op amp in "V2.0 DSN-VC288.PDF", which I believe is the correct schematic.
I know I can look at a schematic I have drawn myself for hours without seeing my errors. I'm not trying to be nit picky here; just trying to understand.
Thank you for your patience and clarification.
Gene
Hey Gene,
At a glance I think you're right. The schematic 1v1 was primarily used as I was tracing connections. I didn't spend a ton of time on it. Version 2 is the one that is compartmentalized and flows the way I need in order to understand how this works.
Sorry for the errors. This is why I try to show my work at the board/trace level.
I actually used the topology from the V2 schematic in a 4 channel LED strip switching controller with current sense. It works fine... so if I made a mistake on that one my bench light must be magic :-)
-Jake
Hi Jake,
Sometimes the FM (I think “Fancy Magic”, others have a different take) on the workbench means the circuit and its construction is correct. In this case you have proven the op amp circuit of V2 is correct. No FM involved.
I would suggest for any one else who has downloaded and printed the 1v1 schematic the following small corrections.
First, draw a line from pin 4 of the LM358 op amp to pin 2 of J3 (at the bottom right of the schematic). This connects internal ground to the op amp and the shunt.
Second, “XX” out the line immediately above the LM358 op amp. This small change will make the op amp circuit of 1v1 agree with op amp circuit of V2. V2 is correct.
I have seen the 1v1 schematic reposted on other websites. So I would also suggest that 1v1 be deleted from github and a corrected 1v2 be uploaded in its place.
Later,
Gene
@@UpcycleElectronics
Tenha certeza que o teu esforço ajudou muitos.
Como vou utilizar para medir tensões abaixo de 10v , vou modificar o divisor de tensão do voltímetro, assim terei medição mais precisa. O ponto decimal vou ver se é mais fácil por hardware ou software. Por software, logicamente seria mais fácil, mas vou ter que fazer, já que não tenho o original. Por hardware não é difícil, mas posso acabar destruindo o circuito.
Muito obrigado !
Many thanks, but some libraries are missing.
Where can I find them?
atmel.lib
contrib.lib
valves.lib
\home\jake\Desktop\KiCAD TT Projects\MY KICAD\tt ATmega328\TT\Jellybean Op Amp Dual.lib
ST Micro STM8S103F3.lib
LED Segment Display 3 Digit 0.28" MCD-2831A.lib
Regulator ME6203.lib
Unfortunately I'm having lots of trouble with this same stuff now that KiCAD5 has changed how libraries work. They really need to get it streamlined. I've been hesitant to start reorganizing my stuff because I keep seeing major changes when I do repository updates through Ubuntu... and I'm no expert running nightly builds or anything either. They are making the changes on the standard stable release version that I'm using. I've had to download around a gig of KiCAD related data in the last week or so.
On github I think I included all the files that were associated with my original schematic. IIRC I downloaded the repository in a separate folder, after I had uploaded it to GIT, and it worked in KiCAD4. I think the old .libs need to be added to the new library manager manually now. At least that's what I've had to do.
I've only seen this problem once though when I copied a folder with a KiCAD project on my electronics computer. I tried to clean up the folder by deleting some of the redundant rescue files KiCAD automatically created. After that, KiCAD couldn't find any of my custom libraries. I had to go into the original file and save all of the custom libraries in the new library manager. After saving each of them manually the custom libraries worked in the copy version too.
I'll add the disclaimer that I could have easily misunderstood what happened or what I was doing entirely. If you know KiCAD better than me, by all means, simply tell me what I need to do and I'll try to help in any way possible.
Personally I'm still a bit lost with what to do with all of this. Heck I don't understand why KiCAD locks the default libraries, but lacks a function to create a library folder and index, or even an entirely separate directory index for custom parts. The purpose of .mod AND .lib files is also beyond me. I have no idea why these are separate or what is the reason anyone would need one of these files exclusive of the other. Sorry for the soapbox, I'm just not quite sure how I can fix this in practice.
-Jake
Thanks for your work. DSN-VC288 is very inaccurate measuring amps. Reseting or adjusting did not work. When I reset using jumper, only the voltmeter display an 0, nothing on blue display. Anyone can confirm or do a video how the display look when reseting? Thanks.
Buen video, el mio tenia el código del microntrolador lijado. No sabia que usaban ese micro hasta existe un proyecto llamado sduino para programar esos micros con el ide de arduino.
great job! thanks.
Can I reach you through here re DSN VC288?
How does it measure current?
The measured circuit is grounded through the shunt resistor. The Current across this shunt resistor creates a tiny voltage drop. This means the voltage on the circuit side of the shunt is slightly higher than Circuit Ground on the other side. This voltage is too small to be measured directly by a microcontroller's analogue to digital converter. The tiny voltage must be amplified to a level that can be measured by the microcontroller. This amplification is accomplished using the LM358 op amp. After the tiny voltage is amplified the signal is sent to the microcontroller to measure. The microcontroller uses a lookup table to relate the voltage from the amplifier to an output it can display. The circuit around the LM358 is mostly the feedback loop that sets the gain of the amplifier, but there are also a couple of things added to bias the input offset current. Cheap bipolar junction transistor based op amps like the LM358 are far from perfect and require an offset current to get them into linear operation. This is the main reason I created this video, to document this circuit block for others to use elsewhere. Basically this example shows how measure current cheaply without the need for complicated differential op amp circuits.
-Jake
@@UpcycleElectronics My PS cant have the - Ground output opened up. Can one put the shunt on the positive side and then put the the big red and big black wires across the shunt (black on the load side) . I have 100A shunt version from EBAY.
@@lackeydehackey405
No it is not possible with this topology. That requires a differential amplifier and is a lot more complex to do. It's much easier to design a circuit that measures voltages where circuit ground is setting the low voltage threshold.
Think of this "low voltage threshold" like an anchor. The voltage can go all over the place but never below the anchor. The microcontroller must operate with a very small range of voltage, and is actually measuring against the anchor to calculate a value. The STM8 used in this runs on 3.3v so it can't measure anything above that. It's very easy to make a resistor divider between power and ground and calculate voltages. While the current measurement circuit here isn't exactly as simple as a resistor divider, it's still referencing ground and VCC just the same. When you want to measure something on the positive rail, you lose that easy grounded anchor point. The problem becomes, how do you establish a new anchor point to measure from, and how do you power the microcontroller so it can measure the difference. It's really easy if your PSU never goes above VCC for the μC. There are many topologies for this kind of circuit, but I am not aware of any cheap Asian products that work for this. The little hall effect current sensors can do this, but that requires some programming and a weekend project.
hi, i have working on curve of processor .it seems to display 0 to 10 amperes for input of 0 to 2 volts . I draw his curve and it seems to be linear. but sensibility is low .in your commentary you say that here is a program in processor . i have question for you : do you know the type of programming (ass, C , C+ ?) and how to read this program ? i wish working read amp 0 to 1 amp and make a new card i, i like look of this device and hole in my transverter project are already makes .thank you johan f5iqx
Hey,
I haven't found the source code. I haven't played around with ST's microcontrollers a whole lot yet either. I just have a ST Link V2 programmer clone from AliEx. I use Ubuntu Linux on my computer and I installed the STM8Flash command line compiler. I think it should be able to read the program memory from a microcontroller. Of course, that will just get you a bunch of useless Hex code. The program itself is going to be really simple. The analogue code should be really short. Multiplexing the displays will be the bulk of the code
I hope I get a chance to play around with ST microcontrollers one of these days. I stopped researching them once I saw that the official ST Discovery boards are only supported by a Windows software toolchain.
If you want to change the range of the display, remember you already have an op amp with a feedback amplifier circuit. Look at the schematic at 3:50 - Swap R4 for a 20k 10× turn trimmer pot and you'll be able to change the feedback loop gain. You should also add a 10nF capacitor in parallel with the trimming pot. You don't have to, but it's just good practice to add a small capacitor here to smooth and remove any noise from this point.
If you really want to play with the STM8 I have a few videos saved in a STM8 playlist. I don't use my playlists for self promotion, I use them as a form of personal notes. Everything I watch on YT about electronics and find helpful gets saved in a playlist. I don't think you can see my playlists in alphabetical order like I do/how I use them, but you might find them useful. I watch and try to learn from other RUclips'rs far more than I care to create content. I keep it all publicly listed, even my likes playlist.
Best of luck.
-Jake ;)
yes i go looking on yourplaylist , excuse me for my poor english ,thanks ! you are not ham radio ?
mordal johan
No, at least not yet. I started playing with electronics after becoming disabled. I have a rare type of neck and back injury that makes sitting or standing very hard. I don't leave my house much. There is no way I could get to somewhere to take the test to get a radio license right now. I haven't tried to learn much about radio. Maybe in the future I will if my circumstances change ;)
Upcycle Electronics good luck for radio licence , you can enjoy this hobby working a little électronique bases but it seem you are good in this subject ! Best wish !
Hi, my "DC0-10A Digital Ammeter Current 0.36in" stopped working, i accidentally shorted measuring leads 5-8x, i think its because of that.
Or China high quality...
If main IC is burnt, can i use same model from 999mA I found picture online with model number STM8S003F3, I cant find one for 10A if exists, or those values are just shunt values, "1-100A".
Mine IC is blank BTW.
No. The microcontroller uses a lookup table for the readings. You need the code for the specific model and batch of your device. It's better to just buy another one. The ones I have seen fail are total junk. The regulator fails short circuit and everything is toast. You can save the shunt and maybe the displays but the displays are a pain to remove.
You can get these from AliExpress for less than $2 each. If you're not familiar with AliEx, just be aware it takes a long time to receive an order. Some sellers are quicker and I receive orders within 2 weeks, but most orders take 1 to 2 months for me to receive. I'm just south of Los Angeles California which is one of the quickest places for recieving orders like this. Some places take much longer to receive shipments.
-Jake
@@UpcycleElectronics Good thing I asked. I later thought it was that regulator or diode S4 bad, or 12V voltage fault. I removed display to get to SMDs, yes it was tricky both sides had solder.
I order already 1A "999mA" same type 2.65$ Aliex, i know it takes a while, usually 2-3 weeks to Croatia. I wonder will that one last or fail.
Maybe ill buy for 5$ official one for my DIY rework station. But Ive read: "Turns out these $5 999ma Ammeters are low-side only" do you know what low-side means ?
Shame its too complicated to fix, it was nice compact ammeter. And I think displays are toast too, nothing lights up with buzzer but batt low, ill test them better later.
I actually got two 10A ammeters, both stopped working same seller on ebay.
@@dev1ator_yt
Low side means it must be placed between the return voltage (circuit ground) and the power supply ground terminal. The technical reason is because, on the meter, it's circuit ground is connected to the circuit ground for the ammeter/shunt.
When designing a current shunt amplifier it is easier and cheaper to build a circuit like this. The other type of circuit is the "high side" type. This gets a lot more complicated because the measurement of current involves a differential voltage.
When your measuring from the low side the actual measurement is just the tiny difference between the power supply "ground" and the voltage drop of the shunt resistor. This should only be a few millivolts (which is why you need to amplify it in the first place). The amplifier (op amp) has an easy job because it is usually connected to the same circuit ground where it is sinking the power it receives to operate already.
If you use this same op amp amplifier on the "high side," you are trying to measure a much higher voltage potential. The shunt resistor will still have a tiny voltage drop across it, but the power being supplied to the op amp is still referenced to circuit ground. This means your trying to amplify a tiny voltage difference that is very high and usually about the same as the positive power supply rail of the op amp. Most cheap op amps do not like this kind of thing. In these types of circuits you'll need a differential amplifier.
A differential amplifier is a special design that is able to measure the difference between two points. Their inputs and outputs are somewhat independent from their supply voltage. These types of amplifiers are more advanced and less versatile in the number of circuits they are used in and therefore more expensive.
There are other ways to do high side measurements with cheap op amps but they require an isolated and independent power supply rail. All of these options would have doubled the price of these little ammeters.
These generally fail because of the voltage drop of the linear regulator. They require a lot of current for that tiny regulator and the voltage drop is far too much for it to handle. They say these are 0-30v but if you read the regulator's specs it can't handle this kind of drop. The circuit is 3.3volts. Power the thing from a stable 5 volt rail and it will work for much longer. You could also add a small PTCC rated for somewhere around 150mA along with a TVS diode to prevent static spikes from killing it.
@@UpcycleElectronics Thank you for explaining everything.
I was searching for specs/datasheet for M5333B regulator but didnt find, I know its 3.3V obviously.
I measured yesterday 9V drop from 12V lines, used DC Adaptor 500mA 12V, 2.4V was on burnt regulator, like you said it cant handle big drops.
"Power supply range: 4V-30V" for shared and independent power supply they say. It should be 5V limit written, like some programimg boards on 5V USB and 3.3V regulator.
Un très bon "Reverse Engineering" !! c'est pas évident d'avoir les schématiques des bidules électronique que l'on achète des amis asiatique. Merci!!
Nice video you did here!.
Thanks
Great Job !!!
Muy buen trabajo. Gracias
Hello, can someone help me here. I tried to reset device by connecting two holes on upper corner but it did not worked for me. Amp meter always swhos 0.25a without load. Please help.
It's broken. Replace it. There is no "reset" function broken out on pins.
@Upcycle Electronics
We'd like to do a video on how to upcycle old Android phones into robotics platforms. Would this interest you?
Hello,
I would watch it, but I don't think I'm at that kind of level with my skills. I've been playing with pcb layout and design a good bit, and am beginning to get familiar with C/C++, but I'm no expert.
It would be too much of a pain in the a* to work with me anyways.
I'm partially disabled with major back problems from getting hit by a car at 30mph on a bicycle commute to work in 2014. It takes me ages to work on anything now. I have 1 to 2 hours I can work on something on my good days and sometimes those are few and far in between. I play with things I can accomplish mostly from my computer from a bed with a bit of time working with my hands at the bench. My health issues cause me to go for long periods without much sleep. So when I'm not doing well I'm pretty much useless. It sucks. I don't need you to feel sorry for me or anything like that. This is just why I don't do much or work with others. I would love to have a different situation where I could say yes, but these are the cards I was dealt in the game of life.
I have several projects I'm working on. My largest and main current project has taken me well over a year and isn't more than 2 weeks worth of solid work from an able bodied person. (
@@UpcycleElectronics The idea was that we could do the video and then you could post it.
As a personal note, I can send you one of the kits if you like.
how to upgrade to 100A
Muito Obrigado bom trabalho.
Thank you Thank you Thank you!!!
Very nice video! Congratulations!
I have one and I want to put it in my 3D printer, but the power supply is an 12 V 30 A model. Is it possible to modify this circuit to work with 30 A?
Maiko Lopes de Sousa
You will need an external current shunt and you will need to reprogram the MCU from scratch. If you can measure the shunt with a DMM capable of doing a 4 wire Kelvin measurement you might be able to figure out the shunt and then figure out the op amp's gain setup. I'm not sure what the shunt measures. I just received my first real (5.5 digit) bench DMM a couple of days ago, but I haven't set it up yet so I still don't know the actual voltage divider ratio/amplification factor/gain. If you know the gain you might be able to change resistors to match the scale you need.
All that said, it's much cheaper and more simple to order one of these units set up for an external shunt. There are many sellers on AliEx selling these with/set up for 50amp shunts. I'd go that route myself.
-Jake
Upcycle Electronics Thanks for your explanation, I hoped the chip was universal and just replacing the shunt would be enough.
Можно как нибудь разделить общий минус? отдельно минус шунта, и отдельно минус питания? проблема с Ампер-Регулятором (на основе lm358, регулировка идет через минус). Если кинуть минус до регулятора то регулятор не работает зато всё показывает, если после регул-ра, то он вырубается при регулировке тока.
На плате VSN-VC288 перерезал дорожку идущую от коннектора к шунту (серая). Показания амперметра теперь 9.99, как временный костыль - пущу питание Digital-Meter по изолированному DC-DC-5v преобразователю через lm7805, идей других нету...
Could you share the microcontroller code? Please ?
I don't have it. I have not played with a STM8 much, I doubt you would get anything useful from hooking up a STLink to one of these. I assume they set the lock bit for the controller. Most of the time they even scrape off the part number for the controller. You could always try to write something from scratch, but you need to be familiar with the controller and toolchain first. I reverse engineered the schematic and destroyed one of these that I had to pay for just to do it. Good Luck
Very good
Thank you
Boa!!!! muito bom seu trabalho! estou tentando reparar esse voltimetro mas ta dificil, ele e vendido falando que alimentação e de 4vcc até 30vcc, fiz um teste com 5vcc funcionou quando passei para 24vcc não funcionou mais.
Thanks very good
Super thanks brother super
I made a Lab power Supply with those 2 modules: XL4015 + LCD Voltmeter 4 digits ( the good model, cause 3 digits is not the best)
When I turn potentiometer to set voltage on XL4015, there is a some delay before the actual voltage is displayed on the LCD.
I tried XL4015 + Ordinary Multimeter, this delay is not present, the voltage is displayed live while turning the pot.
But as said XL4015 + LCD voltmeter Display combo, there is some delay, like the voltmeter is analysing the new voltage value.
I would like it to be instentanatly, no delay, while I turn the pot, the voltage is display directly, without this delay.
Maybe somebody encounter this, and got some idea??
Thx
Это МОЩНО !!!!
good
Thanks you!!!
buen trabajo
I bought a DSN-VC288 off eBay but it has no internal shunt. Is this a manufacturing error or are there DSN-VC288 meters out there that have no shunt there?
If it's a manufacturing error can I solder a shunt in there? if so, what value?
There are units with external shunts, but you need to know the required resistance. They should have listed this.
I don't have a precision milliohm meter to test anything I have accurately. Using my 5.5 digit ancient keithley and kelvin connections I get a reading around 0.1R but I don't completely trust this. I assume it's less than 0.3R. The problem is that the circuit is software calibrated. The gain of the op amp is not Base-10 so it's not easy to modify and get an accurate reading. I would return the product.
@@UpcycleElectronics Thank you, I'll start the return.
Chez BangGood, le shunt de 50 Amp qui est fourni avec le meter est classifier à 75mv (donc lorsque il y a un courant de 50amps) ca voudrais dire que le shunt est a 1.5 milliohms !!
Excelente! Y la música de fondo va de la mano!
Compré uno, funciona bien. Lamentablemente me hace un ruido que pasados unos minutos se vuelve insoportable. Alguno sabrá a qué se debe?
bonjour je viens d acquerir 3 dsn vc 288 1750vt .malgre les essais des 2 types de branchements il affiche une tension correcte mais des valeurs de courants completement fausses et ce sur les trois .d abord felicitation pour votre travail de retre ingenieurie sur des produits livres sans explications aucunes .je viens aussi de recevoir 3 doubles thermometres du meme format et apparence que ce volt amperemetre .que pensez vous de ces fausses indications de courant , quelqu un a t il deja eu ce type de problemes .la comparaison est faite par rapport a une triple alim de labo ..... merci johan f5iqx
Bonjour,
Il y a beaucoup de potentiel pour de mauvais joints de soudure sur ces cartes de circuits imprimés. Après avoir fait cette vidéo, j'ai construit quelques circuits en utilisant un design d'amplificateur de détection de courant similaire. J'espère pouvoir vous expliquer quelques détails ici pour vous aider à mieux comprendre le circuit. J'espère que vous comprenez ce que je vais dire. Je ne parle que l'anglais, mais j'essaie d'utiliser Google Translate pour communiquer et traduire en double jusqu'à ce que mon texte ait du sens une fois traduit en anglais.
La conception de l'amplificateur de détection de courant utilise une résistance de 270 000 ohms et de 330 ohms en série avec la résistance de shunt de courant. Le noeud entre ces deux résistances est l'entrée de l'entrée non-inverseuse (+) de l'ampli op. L'autre côté de la résistance de 270k est connecté au rail d'alimentation régulé linéaire de 3,3 volts. Le but de cet arrangement est de surmonter le décalage de courant de polarisation d'entrée de l'ampli op Bipolar LM358. La plupart des amplis op Bipolar ne sont pas des appareils linéaires tant qu'ils ne reçoivent pas une certaine quantité de courant pour faire fonctionner le circuit. Après avoir reçu suffisamment de courant pour surmonter le biais d'entrée, ils deviennent beaucoup plus linéaires. Cette conception ne sera jamais très précise mais elle devrait être précise entre 100 et 200 millivolts ou milliampères.
Le courant de polarisation d'entrée de l'ampli op est la partie de ce circuit qui n'est pas standardisée. Le courant de polarisation sera légèrement différent d'un amplificateur opérationnel à l'autre. Cependant, les résistances de polarisation utilisées dans ce circuit sont une valeur fixe avec une tolérance de plus ou moins cinq pour cent. Si vous voyez une lecture en cours sur l'écran mais qu'elle n'est pas linéaire, il y a de fortes chances que le courant de polarisation soit le problème.
La première chose que je ferais est de ressouder toutes les connexions sur le tableau. Si cela ne fonctionne pas votre problème. Ces appareils sont très bon marché car ils sont fabriqués en série et ne sont pas testés individuellement comme une entreprise traditionnelle devrait le faire. Ils ne coûtent pas cher parce que vous ne payez pas pour un employé qui teste des produits ou un département de marketing etc.
Si resoldering tout ne résout pas vos problèmes votre problème. Il n'y a pas beaucoup de solutions disponibles pour une configuration différente car la tension de cet ampli op est très faible. Normalement, ce problème de courant de polarisation est résolu en plaçant une petite diode au silicium en série avec la broche de sortie de l'ampli op. La sortie de la diode en silicone est ensuite connectée au reste du circuit, tout comme la sortie de l'ampli op. Cette diode sera à l'intérieur de la boucle de rétroaction négative de l'ampli op. La rétroaction négative compensera la chute de tension de la diode et cela forcera l'ampli op dans sa région de fonctionnement linéaire. Malheureusement, l'ampli op utilisé ici n'est pas un ampli op de tension de rail à rail et il fonctionne entre 3,3 volts et la terre. Vous pouvez essayer le circuit à diodes mais je ne pense pas qu'il fonctionnera avec ces tensions. Je n'ai pas essayé d'utiliser une diode schottky mais je sais qu'une diode au silicium est plus linéaire qu'un schottky, donc je ne pense pas que cela fonctionnera bien.
Le microcontrôleur est également programmé pour le gain de l'amplificateur de détection de courant. Cela signifie que le microcontrôleur pourrait être mal programmé. J'ai reçu 2 versions différentes de ce double volts et compteur de courant. Les deux versions différentes utilisent un en-tête de programmation différent et le diviseur de tension est légèrement différent. La version que j'ai montrée dans cette vidéo a l'interface de programmation "SWIM". L'autre version, j'ai seulement accès aux pins série "UART". Cela signifie qu'il y a au moins 2 façons différentes de programmer. J'ai cherché le code source de ce projet mais je n'ai rien trouvé. Il est probablement disponible quelque part mais je ne sais pas où regarder. Je n'ai rien trouvé après avoir cherché duckduckgo pendant un moment.
Si vous ne trouvez pas de solution, vous pouvez toujours couper la trace sur la broche analogique à numérique du microcontrôleur. Si vous connectez une petite source de courant à tension limitée et que vous appliquez moins de 3,3 volts sur cette broche, vous pourrez calculer le rapport entre l'entrée et la sortie. Une fois que vous connaissez ce rapport, vous pouvez construire n'importe quel circuit que vous voulez utiliser cette gamme et ce ratio.
Original English Text:
Hello,
There is a lot of potential for bad solder joints on these circuit boards. After I made this video, I built a few circuits using a similar current sense amplifier design. Hopefully I can explain a few details here to help you understand the circuit better. I hope you understand what I am about to say. I only speak English, but I try to use Google Translate to communicate and double translate this until my text makes sense when translated back into English.
The current sense amplifier design uses a 270,000 ohm and a 330 ohm resistor in series with the current shunt resistor. The node between these two resistors is the input for the noninverting (+) input of the op amp. The other side of the 270k resistor is connected to the 3.3 volt linear regulated power supply rail. The purpose of this arrangement is to overcome the input bias current offset of the LM358 Bipolar op amp. Most cheap Bipolar op amps are not linear devices until they receive a certain amount of current to get the circuit going. After they receive enough current to overcome the input bias, they become much more linear. This design is never going to be very precise but it should be accurate within 100 to 200 millivolts or milliamps.
The input bias current of the op amp is the one part of this circuit that is not standardized. The bias current will be slightly different from one op amp to the next. However the bias resistors used in this circuit are a fixed value with a plus or minus five percent tollerence. If your seeing a current reading on the display but it isn't linear there is a good chance the bias current is the problem.
The first thing I would do is resolder all of the connections on the board. If that doesn't work your in trouble. These devices are very cheap because they are mass produced and they are not individually tested like a traditional company should be doing. They are cheap because your not paying for an employee that tests products or a marketing department etcetera.
If resoldering everything doesn't solve your problems your in trouble. There are not many solutions available for a different configuration because the voltage swing of this op amp is very small. Normally this bias current issue is solved by placing a small silicon diode in series with op amp's output pin. The output of the silicone diode is then connected to the rest of the circuit just like it's the output of the op amp. This diode will be inside the negative feedback loop of the op amp. The negative feedback will compensate for the voltage drop of the diode and this will force the op amp into it's linear region of operation. Unfortunately the op amp used here is not a rail to rail voltage swing op amp and it is operating between 3.3 volts and Earth ground. You could try the diode circuit but I don't think it will work with these voltages. I haven't tried using a schottky diode but I know a silicon diode is more linear than a schottky, so I don't think that will work well.
The microcontroller is also programmed for the gain of the current sense amplifier. This means the microcontroller could be programmed wrong. I have received 2 different versions of this dual volts and current meter. The two different versions use a different programming header and the voltage divider is slightly different. The version I showed in this video has the "SWIM" programming interface. The other version I have only has access to the "UART" serial pins. This means there are at least 2 different ways to program. I have looked for the source code for this project but I did not find anything. It's probably available somewhere but I just don't know where to look. I didn't find anything after searching duckduckgo for awhile.
If you can't find a solution, you can always cut the trace at the analogue to digital pin of the microcontroller. If you connect a small current limited voltage source and apply less than 3.3 volts on this pin, you will be able to calculate the input to output ratio. Once you know this ratio you can build any circuit you want that uses this range and ratio.
Thanks, -Jake
Upcycle Electronics hélo jake thank you for this lot of information . the thermomèters are OK . i have mounting kikad on my PC . i m working on a transverter 144 MHz to 1296 MHz . he work perfectly on 20 watts pep . this meters are just for looking U and I on the transverter 13 g2 b mk2 of kuhne electronic . i go working on the op amplifier , i thing trouble are hère . i tell you about this troubles of amperemeter . thank you excuse for m'y pour english but its a good way for me to used it . i wish you understand me . i am radio amateur my call is F5IQX. My hobby is hyper frequency . congratulation . happy speak to you again . johan !
i shorted some of them :D
obrigado
Woww
Thanks for the reverse engineering. I seem to have a version that works well with the integrated 10A shunt (measured as 6 milliOhm) but fails to give any correct current reading with the external 75mv/50A shunt - even when removing the internal shunt. The external shunt is measured at 2 milliOhm, so it's a factor 3 off. Likely I have to replace the resistors around the opamp to get the right amplification. Somebody experienced the same issue ?
Like super