DIY Adjustable Constant Load (Current & Power)
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- Опубликовано: 25 авг 2018
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1x ACS712 Current Sensor: s.click.aliexpress.com/e/_dSK...
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In this project I will show you how I combined an Arduino Nano, a current sensor, an LCD, a rotary encoder and a couple of other complementary components in order to create an adjustable constant load. It features a constant current and power mode and can handle a maximum of 30V and 20A if your heatsink design can handle it. Let's get started!
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Music:
2011 Lookalike by Bartlebeats
Killing Time, Kevin MacLeod
(incompetech.com) 
Наука
This is an old video and I'm just realizing how happy it makes me to see somebody assemblying circuitry the way I always wanted to... in free-air. Now that I've been in the research/educational industry, it makes me very happy to know that this haphazard approach isn't so rare. I'm constantly opening old equipment to fix, or reverse engineer them and finding this type of assembly. Love it! Wish I wasn't so afraid when I was younger of making a mistake :)
I really like your in depth insight on your tutorials, without dragging it on....straight up and to the point with excellent video editing, parts list, schematic, and links...truly professional work, and vast knowledge of electronics. Keep up the great work, and thank you for the videos, have enjoyed every one and will be building this tonight as I have all the components, plus always have nano's on hand, these days more and more hobbyists are incorporating them straight in the the schematic as above...awesome
Your videos never fail to pique curiosity in creating something new. And amazing thing is the project you choose are perfect in scope. Keep inspiring and leading the DIY world!
I always get excited for a GreatScott notification!
Glad to hear that :-)
Me too
Me I am getting sweat (not wet because language) IRL
A GreatScott notification... or a Great Scott notification. Either one works!
@@greatscottlab can you make a 12Vdc to 220Vac inverter please?
I like the old school way that you pitch a product in your videos - it makes a connection to the things you try to teach, thanks.
I just recreated your circuit today! it was Awesome! This is very useful diy constant current load, I like it, and I'm happy to say that this is my first time using Arduino, Awesome!
Perfect timing for this video, exactly what I need. Very good explanation, thanks.
Good opportunity to get your sponsor involved - do a part B where you put the design into their online PCB software and order a PCB. Then build and show off how much tidier and easier the PCB option is.
Yeah.
I thought same, but it would be premature.
This is really only a very rough prototype.
The theoretical power it MIGHT handle is never going to be seen because of thermal limitiations.
He mentions 3amps at 6 volts is what it WILL do.
So that's 3% of the theoretical potential.
See my reply on its own.
This is great! I will build one.
One suggestion:
Add mAH discharging so I can discharge my batteries down to a specific capacity and add a discharge voltage cutoff mode:
The Arduino will discharge at a set current until a specified voltage is reached
Really, Really like this build, thank you! Love the Arduino display programming, been trying to figure out how to do this. I might try to build it now. :-) Great Scott, I’d also like to put in a vote for a nice Class A Amplifier, I really think you are the man to take on the task. Stay super creative my friend, you have to take up all the slack I leave...
Hey, did you ever build this project? I'm working on it now and having some trouble.
Happiness is suddenly watching the notification of new video from great scott!!
You can use a differential amplifier to not only drop the hall sensor output voltage at 0A to 0V but also amplify the output at max current to 5V giving you as much resolution as possible for the current sensing.
The STM32F103 would be nice, with its 12 bit ADC, and higher resolution timers. But a great tool for the workbench. Nice job!
ADC in STM32F103 are also much faster and have DMA capability. You can get 1MS/s. and uC itself is faster, so you can get tighter regulation. But I think max voltage is 3.6V. Unfortunately even STM32F103 doesn't have DACs. Only timers, but they are 16-bit ones, which is nice.
@@movax20h no DAC on STM32F103RB ? Oo
Project idea: since you have already attempted to build a simple radio receiver, how about some kind of radio transmitter? The simple low power ones are pretty easy to build...
This could be a great opportunity to show how AM and FM work in detail.
Greetings from Gotha, Thuringia, Germany.
yeees, or maybe an DIY radio transmitter for old cars (with aux input)
Great scott is amazing. The king of electronic projects
It's greatscott day!!! This is awesome!
Halogen Lightbulbs make an Awesome, Cheap power resistor for such a project!
Thanks for this Project.
With it I learned how to build Menu for LCD screen.
I didn't have a 16x2 LCD, but I did have a few Nokia 5110 LCDs, so I decided to adjust the code for that LCD.
And guess what... It works :)
love the way you make circuit boards. Dead bug wiring taken to the point of art
Your videos are so informative and project inspiring. If only I were not so high right now I just might try this!
OMG I ACTUALLY UNDERSTAND THIS ONE! I've cooked plenty of 3D printer control boards by putting a big load on the MOSFET and overheating RAMPS Q3. Guess it's time to add Electronics Engineer to my resume. Thanks Scott!
I literally just looked for videos like this yesterday.
Great, Scott!
You are my favorite.
Fantastic work, dude! Awesome!
Hi Scott, the current ADC should be suitable when increasing the sensor voltage range. the range in your setup is around 300mV. by amplifying (with a opamp) this signal and correcting the 2.5V, you can transform your 300mV sensor signal into 0 till 5V
Instead of "don't touch it" for the undervoltage pot, I learned how to tune it so that it's least likely to cause problems:
I accidentally fried my LTC3780, and I did a lot of probing and I noticed that the under voltage regulation caused some problems when set to 0.
The fried LTC3780 could only tune from 0.8v to 2.5v (fault light on above that) and had no current limiting.
So here's what I learned:
If you set the under-voltage pot to as low as it goes, then the full supply voltage will pass to the LM358 to an opamp input while the supply voltage is at a regulated 5v. Even though it's supposed to only produce 5v out, it started to fail for me and will go up to near the supply voltage which feeds the run pin of the LTC3780. The LM358 still worked if the trimmer was set closer to the supply voltage though, so clearly it puts more stress on the LM358 to pass much higher voltages to the inputs than the 5v regulated voltage. If the undervoltage pot is tuned closer to the supply voltage this creates a voltage divider that will make the input voltage to the LM358 closer to the regulated voltage.
Any voltage above about 6v to the LTC3780 on the run pin will destroy it.
So, my advice is turn the undervoltage regulator all the way up, so that you get the fault light and the output goes to 0, and then turn it down until the fault light turns off, and overshoot a little (but don't set it to the minimum). As long as you're using a constant supply voltage it'll continue to run, and this will reduce risk of frying the LM358 which will fry the LTC3780 (The IC is same cost as the whole board really, so you don't want to have to replace it).
Thanks, buddy!
I like your videos, very informative! Keep it up!
I would actually love a tour of your work space, seems like its completely decked out!
Always came up with the best explanation Nice...............
another good one Scott, this is a good start point or as is project. thanks
For the current reading on my PWM charge controller using the same current sensor I used a loop which runs for a full second counting the current values, then dividing by the number of loops it did to get an average. I found this gave me a much more stable value. However, if you're using it to control current that wouldn't work so you'd need both the instantaneous value and an averaged one. Instantaneous used in your control loop but the averaged value shown on the screen.
After watching this man, I realize my knowledge of electronics
is that of a tiny child. Always impressed by him.
Hey! Don’t be ashamed of yourself, you will eventually be better than him if you try hard enough!
You lost me at the intro...so many leds and so many solder! Hahaha awsome vid. Love it.
Good video! Constant Load and Constant current is very useful!. I remember the mosfet work like resistor in linear (ohmic) region and it's use in switching mode in saturation region for increase efficency.
If you want to use a MOSFET as a switch, you use it in the omic region.That is the reason, why the RDS-on is stated in the datasheet as static on resistance. This is because, when the MOSFET switch is in the 'ON' state, it has a almost constant resistance, as opposed to a bipolar transistor. The confusion arises, because in a bipolar transistor the saturation region is where the Vbe is so high, that an increase in Vbe does not decrease Vce (Vce,sat is reached). On a MOSFET on the other hand, the saturation region is the region, where an increase in Vds does not increase Ids, that means, even though you apply more voltage across the MOSFET, the current does not increase. But if you increase Vgs in the saturation region, the current does increase.
The terminology is really confusing, because in bipolar transistors you want to switch in the saturation region, but in MOSFETs, the saturation region is completely different.
It's the other way around, the typical mosfet Ids over Vds graphs, Vds is on the x axis and Ids on the y axis. So in the omic region an increase in Vds creates a proportional increase in Ids, but in the saturation region (line is almost flat) an increase in Vds does not increase Ids (or only very slightly)
Yes, i think he has it confused in this tutorial. I am making a similar device using IRFZ44N and by using the low pass filter, the mosfets keep getting cooked since they are in linear mode. Using a PWM signal at the mosfet gate is less stable, but it also allows the mosfet to function without breaking and shorting out after a few seconds/minutes with any real power dissipation.
I love your video, every week I am waiting for your video online.
Thank you
I watch you from Sénégal in Africa
Awesome as always!
Excellent, as usually.
your videos are very interesting and knowledge full
Thanks for the code on instructables I'm working on a lab power supply and I'm reverse engineering your code to build my menu without your code I'd be so lost thank you
Great video. Great project.
Very nice project!
Thank you very much, this is what i am looking for
Thanks again Keep up the inspiration
Nice penmanship!
Great Videos like everytime😊
Those ACS sensors seem like a good alternative to a current sense resistor...got myself some and I plan to use them on some motors to stop them when the current gets too high.
This could have been a Diy vs Buy episode. You could compare it to the commercial available ones and tell which option is better
I love your videos ❤
It would have been great if you used an op amp to drive the MOSFET. But, whatever, Great job!
Please use op amp in next version, that should get rid of the oscillation and would make it more precise.
This project is somthing new and interesting
One possible issue with this type of load is the control loop which is run by the microcontroller. That would make it quite slow which could possible create oscillation under the right conditions or even worse it could react very slow to a rapid change in current.
I am sweating with the heat of the constant load. Thanks to SweatScott for the good job and nice video 💓 💝 💟 💖 👏 👏 👏 🎉 🎉 🎉
100% building myself one of these !!!
You can use use STM32 in place of atmega328 for better ADC and PWM resolution. Or INA219 with a lower value shunt resistance can offer you higher current range and stable power measurement.
Excellent project
Great video, thank you.
Great Scott ...Plz continue ESC project
I have been wanting to get familiar with electronics like this strictly because I think it would be handy for playing with my car lol.
Have a couple ideas but no skill in making them happen!
i am a really big fan of you
Very helpful! Thanks colleague:)
9:07 You can do small improvement by not subtracting OCR1A when curcurrent = current to prevent oscillations.
Great project! Interesting to see a take on this using an Arduino (instead of the op-amp analog solution).
GeatScott
you are great
Hey good video! What if I am looking to build a basic AC current Source to test ground fault interrupter that trip between 20-40 mA AC. Is this a possible task?
This is 🔥
Great project! Did you measure the maximum power draw by the heatsink used?
Hi Great Scott, would you mind explaining how current voltage conversion work like in solar(20v) to battery(12v) as they have specific watt output and input. In paper it is convincing to use formula but in real situation how does that work. Solar may be sending 10A over 20V and will battery receive only that much amp or is there any other conversion stuff going on to equalize output and input power?
And can you please make video on circuit which gives off alarm ring when circiut gets closed for few seconds or make it alarm as wish but only during closed circuit and for few more seconds even when circuit is closed to few milliseconds.
Some times when I'm in the dark looking for which button to press on my tv or on some other devices I need to whip out my phone most of the time to know where to place my finger.
I've tought about a simple and compact light that would illuminate a area for certain amout of time or turn on only when there is finger looking for a button near by, one problemo is that i have no idea how to execute my plan. Would you care to look into it?
That sounds pretty cool huh
Hi great Scott
Can we make an high power of 450w smps using sg3524 integer ic with high power switching mosfet
great video!
Nice project
I love the idea of building one of these so I can use it for logging discharge curves and testing my batteries. I would need much better precision though, so here are some thoughts on this.
The interface between the digital electronics and the analog electronics is the biggest limitation in precision here. Both the reading of current and voltage, and the control of the power MOSFET are noisy because of the limited resolution of the ADC and PWM. I was thinking of using a SPI controlled 16-bit variable potentiometer and an opamp to assist with driving the MOSFET. By using the feedback of the current sensor and the variable potentiometer connected to an opamp, would it not be possible to very precisely control the driving of the MOSFET?
When reading the current and voltage values, of course using a more precise DAC would be simplest as you have mentioned. But if I wanted to experiment with getting more precision with the 10 bit ADC we have already have, How does this scheme sound: Read the voltage from the voltage divider with the ADC (10 bit). Output the read value via SPI to a variable potentiometer . Using an opamp, we can connect the digital pot and the voltage we want to measure, and the opamp will amplify the difference in voltage so we can read that error difference with another ADC on the Arduino. The second ADC read would be a measure of how far off our originally read value is from the actual value, which we could calibrate against. We have more precision in the digital potentiometer than our ADC, so we would just nudge up or down the output value of the digital pot until the error feedback on the second ADC goes as close to zero as possible. Then we know based on what value we write to the digital pot what the actual voltage must be.
Let's walk through an example; it might make this more clear. Say we want to measure a current coming from the current sensor. It is outputting 2.954265v, which obviously our ADC can't even come close to in precision. Our 10 bit ADC can only read in steps of 0.00488 mv, so the value is going to be 605 or 606, giving us a reading somewhere around 2.951 to 2.956 volts. We spilt the difference and output 2.9535v to the digital pot. If the digital pot is 16 bits, that would be a value of 38711d, giving an output value of somewhere between 2.9534v to 2.9535v. The opamp magnifies the error difference between our actual 2.954265v and our pots output by say, 500x the voltage difference. We set it up so that the opamp output range is 0 to 5 volts, and a center voltage of 2.5v means no difference between the digital pot and the actual voltage from the current sensor, and it amplifies any difference in the two inputs by 500x the voltage difference. In this example, our voltage difference woudl be around 0.000765v, so let's say the opamp is actually putting out 2.1175v now, which our second ADC reads as 433 or 434, giving us a reading of 2.11v to 2.12v. We split the difference to 2.115. Now we have to adjust the digital pot output by some value to see how much closer we get. We calculate it like this. Subtract 2.5 from the new reading to find out how far off we are from center (-0.385v), divide by 500 (to scale it down by the amplified value of the opamp), which gives us -0.00077v. We now know we are reading higher on the ADC than we should be, so we adjust out output up. (or the other way around if we get a positive value instead of negative, of course). We subtract this calculated value from the value we last wrote the digital pot, giving us 2.95427v, which we write to the digital pot as 38721. Our new output is 2.954222v to 2.954299v. Do the whole feedback read again, and we get a much smaller error reading from the opamp. Every time we nudge up or down slightly in this way, we in theory get closer to the real world value.
Since we are reading with a 10 bit DAC, 9 bits of which we consider significant figures we magnify the error by 500 (512 would sound better, but I'm approximating), then reading again, we can probably get closer to 14 significant bits of precision. Of course, every time our most significant bits (first ADC read) change by more than 3 or so up or down, we have to start over in our calculations, but it should only take 2 or 3 cycles to gain enough precision again to be confident. The ADC takes like 1/10,000th of a second to read a value. So, I figure we can read at least 400-500 times a second. with calculations and re-reads, every 5-10 ms we should be able to get a very accurate read. We use the 10 bit course read for fast responses, and the higher precision reads for accurate adjusting of our MOSFET. Before, we were limited to 0.00448mv resolution in the ADC. We might be able to achieve an effective resolution of 0.0003v this way (that's about 14 bits). That's enough for millivolt measurements anyway. Most times, such short durations of time are not going to result in very much change in readings, and therefore we will spend most of our time in precision calculation, giving us very good accuracy.
How plausible does this sound? Worth putting the time into building to test out, or a waste of time and never going to work out correctly? I know this is bonkers over the top complicated compared to just getting a better ADC and calling it good, but I like the idea of something like this if it can be done.
At 3:38, you use your yellow grabber leads, I'm curious where I could get something like that.
Thanks!
Really good video. However, can this system (with modifications) be used for much higher voltage values for examble load for tubes. For example 500V 300 mA load.
What's the purpose of the MOSFET driver (instead of using the Arduino directly with RC filter) since it's only being supplied 5V?
Interresting project! It's always usefull to have a load that can be ajustable. Could be programmable too. I was wondering if you know some PSU like your DPS5315 which is programmable and not too expensive. The problem with the DPS 5315 is that everything is in German. Not sure if it can communicate with SCPI protocole as well...
Thanks
Hi, I'm nearly finished building this project and the output voltage (measured with a multimeter) of my setup doesn't change when I set an output via the interface. I'm using Scott's code and the same components that were recommended. The only difference is that I'm using an Arduino pro mini.
I'm using a 20V 6A power supply to supply any load and a buck converter to supply power to the equipment. I lost my 5 volt regulators and I had a spare buck converter.
Regardless of the value I change the either the current or load values to, I always get a 2.4V output. The voltage drops to 0 when I 'stop' the output but it seems as though the duty cycle of the PWM signal doesn't change. I tied pin 9 directly the gate of the mosfet and the my output voltage was 2.1V and didn't change when I varied any values in settings.
My mosfet is fine, I tried 2 of them, and bot were adjustable with a 50k pot.
Can anyone help me here?
Hey,
Very good explained, like your other videos. Can you do something about DIY low range dipole antenna receiver and sender?
Hi GreatScott! I loved your videos I really do. I just have one question that might save my research product. Is it possible to increase the ampere of 5v dc power supply? Or just build my own supply? I am working with my GSM module and I can't make it stable to work properly. Plus i'm using Arduino Uno anyways. Thankyou very much!
Is there any advantage of using a mosfet in the saturation region compared to a bjt in the linear region?
Hey GreatScot, I was wondering if you could make a tutorial of how to build a frequency compensated attenuator for a guitar tube amplifier. That would be great. Thumbs up for your great work so far!
se podria usar un lcd full graphics?? o el codigo cambia?
Could those oscillations be reduced by feeding the output of the current sensor back (via an opamp) to drive the MOSFET? EEVBlogs simple constant current load uses this approach although uses a resistor bank to dissipate energy. Your approach, however, will have a more consistent current draw.
I've been meaning to build one of these. I'm currently planning on building this to stress test 3∅ 30A connectors.
Our Hubbell supplier in the US has been pushing spring-loaded clamp connectors instead of the standard screw-clamps. If they didn't come from Hubbell, I would've already said "No" to them but I want to be sure they won't fail under full load
Very nice build. I will definitely check out your code
Finally but I was waiting so long for this video that I already made one 😂😂😂
Hey, did you ever build this project? I'm working on it now and having some trouble.
How does yours work?
Great info. I've been looking for a PSU that can output 0.7~0.9 Volts and 'push' out a constant current at ~0.5 Amps and up (both adjustable) for electroforming/copper plating small hobby projects. Sadly the Lab PSU's I've bought do not work well for me so I would have to start making my own. Do you think it's even possible for a PSU to 'push' out constant current at such a low voltage? Apparently most Lab PSU's are not able to do this.
great one but just 1 question for some reason i need 30A not 3A what should i change to be able achieve this?
Thank you very much for this device. I need your help. When I press the start button, the load (which is my bench power supply, voltage set to 4v, current limited to 1 amp), output load shows short circuit. If I press the stop button, short circuit gone. Also I see negative current on lcd when I press start button. I cannot find the problem. Please help me! I stuck on this and can't move on.
Sir, can you make a video that automatic transfer the switch from grid to solar panel when there is a power outage using arduino?
Very nice video :))
Very inspirational stuff.
Why do you use mosfet drivers instead an op-amp (like lm358) in a negative feedback configuration? What are the drawbacks of the latter?
Thanks for answer, I am waiting for next week video.
Probably the MOSFET driver is easier and more convenient.
Can you suggest me a good tda2030 single supply amplifier circuit. Please😫🙏🙏💓
Awesome Bro, Thanks...
What kind of pens do you use?
Do you have any ideas for a 20A load? Voltage up to 5V (or 100W total). For battery testing.
Hello, Scott is it possible to get a variable DC Voltage on the Gate of the MOSFET without the TC4420? A simple low pass filter on the PWM PIN should be good enough or not? What do you mean?
Thank you for the short and informative Video ;)
Nice project! Great Scott, have you done anything with ultrasonic pulser-receivers? I'd love to see your design for one similar to the olympus 5077pr :D