I just want you you to be happy so so cute far with with you too too too much to to to to sleep lol lol I’m I love just you love love you love love to love love mommy love love love mommy mommy daddy daddy love mommy mommy love love you love mommy mommy daddy daddy daddy love love love you you guys guys guys too too much too too too bad to to hear hear you you have later later tonight I I hope you have you have a fun thanksgiving and and your love family and and your your dad dad love mommy mommy daddy daddy mommy mommy love love you mommy daddy daddy mommy daddy daddy dad daddy daddy love you you deserve deserve deserve deserve you deserve it deserve better love mommy you deserve deserve better love mommy mommy daddy daddy mommy daddy daddy mommy daddy daddy mommy daddy daddy kiss mommy mommy mommy daddy love love you you mommy deserve mommy deserve mommy daddy daddy mommy daddy mommy daddy daddy mommy love mommy love mommy daddy mommy mommy love mommy daddy daddy mommy daddy love kiss mommy mommy mommy mommy love love you you deserve deserve it it mommy it it was was was was good good morning morning love love you mommy daddy mommy daddy daddy mommy mommy daddy daddy mommy love love love mommy you you mommy mommy mommy mommy love mommy mommy daddy daddy mommy daddy kiss kiss mommy kiss kiss me me and and and mommy and kiss kiss kiss daddy mommy daddy daddy mommy mommy daddy mommy mommy mommy daddy daddy mommy daddy kiss kiss kiss kiss kiss hug hug hug hug hug mommy mommy mommy mommy mommy mommy mommy daddy daddy mommy daddy mommy daddy mommy daddy daddy mommy daddy mommy love mommy daddy daddy mommy mommy mommy daddy mommy daddy mommy mommy mommy mommy mommy love love love you love love love daddy mommy daddy daddy love love mommy you you you mommy mommy mommy mommy mommy mommy daddy daddy mommy daddy mommy daddy mommy daddy mommy daddy mommy daddy mommy love love you you mommy you you you you you you you you you you you you you you mommy daddy daddy mommy daddy mommy daddy mommy daddy mommy daddy mommy daddy mommy mommy daddy daddy mommy daddy mommy love mommy love love you love love love you you mommy mommy love love love love love love you you guys guys guys too good good too good good good good good good good good good too too good good good good too good good good good good good morning morning morning morning morning morning love mommy love mommy love love you you you deserve deserve it love love you you mommy mommy daddy daddy mommy mommy daddy daddy mommy daddy love mommy love mommy mommy mommy love daddy mommy mommy daddy daddy mommy mommy mommy love love mommy daddy daddy mommy daddy daddy daddy daddy daddy daddy daddy daddy daddy daddy love love love love you you guys are are are you you you deserve deserve it it it it it it was just a a lot and and and I I hope hope you’re all all all all all all all all all all all all all all yours yours yours yours yours is is is is is is is is is is what what what what do do do with it it it it it it it it it it it it it you like like that that that that that works works works works out better than than me but but I’m still still still still still still still still still still still still still still still still still still still talking talking to to to to to to to to let mommy mommy how you are are we all love mommy mommy daddy daddy mommy daddy mommy daddy love love love love love mommy daddy daddy mommy mommy mommy mommy mommy mommy love love you you deserve better mommy mommy mommy mommy mommy mommy love love
@hla27b Yeah, in all that ranting I forgot to mention the battery life! More than 200 hours. I determined that it wasn't worthwhile to add an auto-off function to this first version, as that would have required an intelligent device to do it properly.
Dave you are amazing man. Thank you soo much for sharing with us your design. I am so happy that here are ppl like yourself who manage to find time to show, explain and put on youtube videos so that we could watch and learn. I am shaking your hand and saying "Thank you Sir, we are glad to have you as our teacher "
It's definitely a great video, but the problem is that nowadays the Chinese will knock off any product despite its patents, and often butcher the design of the original product. It's a nightmare once one has spent countless hours developing, building, debugging, and marketing their product.
@@BillAnt Don't worry about it, because they don't tend to make counterfeit products if it is not sold over thousands, the circuits like this will not be copied because of feasibility.
@@myetis1990 < I'm not talking about about small run products, but in general. Feasibility? Anything is feasible, it's just a matter of return on investment. I've read that in a particular Chinese city there are actual factories which only do counterfeit products. They have reverse engineering departments, along with China's lax intellectual property laws, they can operate just like any other factory. It's sad but true.
I took a crack at deciphering the uCurrent schematic but a few things were leaving me scratching my head. This explains everything so clearly. In the first 25 minutes of this video I've gained so much knowledge.
From urban dictionary: schmick 1. I say this in Australia to mean anything sick, cool, tight or excellent. Usually the item is new, shiny, fresh and mad bling-bling style.
Ten years late to the show, but love the content. Was trained in electrical engineering and took a different path, but wanted to get back in as a hobby. This was exactly what I was looking to walk me through the thought process. Love it!
When you talk about contact resistance needing to be taken into consideration takes me back to in tech school how we took "ideal"components most of the time but even "simple"pieces of equipment you have to be very precise.like taking even say the resistance of conductors or stray capacitance into consideration.enjoyed the presentation.
@xspoonedx Interesting question. If you have the LED operate the other way around and have it only come on when the battery is low, then if you go to turn the unit on and the battery is completely flat, then it won't come on and you'll think your product can be used. So in this case (with no power LED), it's better to have it the other way around so you can check the battery is OK before you use it. So you could say it's more important to know that battery is OK, than know if it's flat!
I'm 3 minuets into this things and I can already tell you've knocked this one out of the ball park. I'm going to grab a beer and some popcorn and enjoy my next hour of engineering bliss. Cheers. George Graves
I watched this over the last two nights with my 4 year old inventor son, for his bedtime story :) To his credit he was really listening for the first 10 minutes of each 25 minute night... and he loves the way you say "banana" Dave. I really enjoyed the video and all of the information. Thanks for taking the time to put it together!
Dave, I just saw this great video! Better than a book! Better than a seminar! Better than college courses! You have inspired me to follow through on an idea I have DaveCadded. When done the finished product will be much better because of your generosity. THANK YOU AND KUDOS TO YOU!
I'm incredibly impressed. These should be selling by the truckload. It's elegant, compact, functional, ergonomic, producible, and economical! You just proved that simple is better. Your attention to detail shows the importance of creative skills that many engineers lack. Most engineers likely forget about how the product feels when they get too caught up in the circuit. Yeah, their circuit might be good, but it looks and feels like garbage.
Your best video yet Dave, length was perfect for such a complex topic. Please keep up the longer format from time to time, don't wait another year for one! Cheers!
This is such an interesting video. I love seeing how you develop that circuit and the thoughts and considerations that go into the product. I stopped watching TV a long time ago and started watching videos like yours.
@BitEntropy No, the LED does not switch on if you move the switch quickly enough, a nice side benefit. It's easier to move the switch all the way to one side than centre it, so it's easier to switch it off.
Just wanted to say, love the videos man. I've been an electronics hobbyist since my teens (Amateur Radio operator since age 14 and I dabble in guitar amp and effect design/repair as well). I finally took the plunge and enrolled in a BS Electrical Engineering program this year. After 7 years of working security all over the world I'm definitely ready for a career change haha I have several similar channels I follow but the wit, sarcasm, and humor you bring to the videos definitely make this the most enjoyable to watch. Not to take away from the value of the other channels but some can have a very dry delivery of the knowledge. Great channel, and keep it up. -KC9FJE
You actually can use a reversed LED as a light sensor, with some careful filtering and amplifying. But obviously it's inferior to proper light sensors (e.g. LDR, PT, PM).
That was a really interesting and nice video. Don't hold back on these please, I loved it. Goes to show that getting exactly the right components (not overkill or underestimated) takes so much more than actually thinking of the circuit and simulating/testing it. Thanks for the tips!
I had bought an electronic blanket from a second hand store. It worked great I thought. It only used 8 watts. I thought "wow they have cone a long way. 8 watts nice.' then it broke a few years later. I went to buy another one to find out that I could not replace it. Every blanket I got was at least 150 watts. Devistated I didn't know what to do. I live in my RV. And to have an electric blanket that I could use for 3 or 4 days on my batteries was I wonderful thing. To use one that eats up 150 watts they would be dead in no time. 1 to 2 hours. The one I bought from the second hand store was clearly defective. But for me, it couldn't have been better. I need to find a way to bring a new blanket from 150 watts to 8 to 15 watts. So many of us love in RVs. And then there are the penny Pinchers. This would be a great thing to bring to market. Who needs 150 watts? That gets so warm it's uncomfortable. Can I just add a resister to the board somewhere to bring that down? Please help. And if you can't, can you point me in the right direction?
when you said the product was included in the 2009 catalogue, I thought you might have been taking a trip down memory lane, until I noticed this video is almost 11 years old. great standard of video for the time, and today!
Dave, it's one of Your older videos. After few dozen of projects, i have to tell You that You opened my eyes and showed me how to do stuff. I'm so glad and thankful... I want to buy You a coffee and meet in 4 eyes :) Maybe one day i'll visit Australia. I hope to do so.
Thanks Dave. You have inspired me to design my own dual power / microprocessor controlled lab power supply. I don't really intend to sell it, but thought it might be a great challenge and something to concentrate on, after work and on weekends. About 75% there... as of today.
@oehrlein49 I use PCBcart, cheap and plenty of options. No special deals for Altium Designer unless you are a student. Otherwise it's $3900/year or $5K outright for the PCB version. That's less than half the price it used to be.
@@hansdietrich83 In all cases, every pole of the (ganged) switch is connected through to itself, unless it needs to function in a non-ganged configuration, and then I admit I don't know what the purpose of the circuit is. If they are truly ganged, this means an optimization can take place. If you used the poles of the switch to select which input resistance you need, into a common input node to the op-amp, then yes it CAN be reduced to a single pole triple throw switch. Simpler design means less prone to failure. I think Dave would agree.
There is an alternative configuration that Dave neglected to show which only uses 2 banana jacks, and a single SP3T switch. Wire the 3 poles of the switch to each resistor to ground. Wire the common from the SP3T to the input banana jack, as well as the op amp input.
A subtle little thing... If I were to use AA/AAA's for this project I might've used three batteries instead of two, to avoid wasting battery power and having to switch batteries more often than needed. (2.6V/2=1.3V/cell vs 2.6V/2=0.87V/cell) Of course you'd have to consider battery impedance and such. Which brings me to something I'd like you to speak about when seeing this: The black art of bypass capacitors, which would probably deserve an episode on its own merits.
About 45:xx I was thinking "how do you test the outputs" and the following discussed how to test for interference. Would be interested in seeing more about verifying the outputs to be correct.
37:53 when I realise that the thing is bright red instead of the normal phenolic cacky brown, and it's like that on purpose not cause you cheaped out on the solder mask.. The joys of being colourblind :P
I find the real problem is how to design the front panel and how to imagine switches that can operate deep inside the boxed housing electronics. I think it becomes a mechanical engineering problem which strays from all the effort and excitement of realising the design. What's needed is that front end design handled by some computer process so that the electronic engineering is separated from it's commercial realisation but is automated if the design is taken to fruition by paying the cost.
@gameboygenius - If you were using AAs your idea of using 3 would allow use of NiCads/NiMHs (whereas a 2 battery design wouldn't (only 2.4v). I like this versatility. But rechargeables aren't ideal for an occasionally used low-drain piece of test equipment due to internal discharge, so accommodating rechargeables isn't as big an issue. Although generally I like using an even number of AAs as they come in 2s and you don't have one left over when you need to change them.
Your approach to subject is lucid and spot on. But I have one point to make. Can you not design chopper stabilized amplifier to combat voltage drift? Whenever we measure low voltage this drift is comparable to input voltage being measured.
absolutely brilliant video, really helped. My only question (from a noobie perspective) does the 100 ohm resistor that provides overload protection affect the final readings? Surely they will in series with the 3 resistors you can choose from? Many thanks!
David Mason Solo la afecta en un 0.0001%. El MAX4239 entrega su tensión sobre el divisor formado por el resistor de 100 ohm y la impedancia de entrada del voltímetro, que es del orden de los 10 Mohm. Por lo tanto el 99.999% de la tensión que entrega el MAX4239 es leída por el multímetro.
Thank you for such a great tutorial. I wish I saw this job long before. One thing I wonder about PCB layout, is there any countermeasure or consideration for precision measurement (opamp stage)? The second thing is how should protection be for overcurrent?
A pitty that Dave did not respond on your legitimate remark. A "battery low" indication would show during measurements that the battery voltage came to low and not only when switching to power on, where the battery would come from a no load, recovered mode.
Actually wouldn't it be possible to build this with an opamp working as transimpedance amplifier? That should (theoretically) lower the shunt resistance to zero and the shunt resistance was the main driver behind this project right?
Great advice ! did you make a video about the decisions made when you decided to make the Gold version ? that would be so useful to have you thoughts on the products evolution.
one more thing you can use op-amp if current usage less like 10 ma (max output of current of opamp) you can use tl431 its even cheaper and current is upto 100ma and can use a transistor to increase current
Excellent video Dave, instead of fortuitous one may even say "elementary my dear Watson". Love the look of the end product, where can I buy one here in Australia?
This is a great idea, but you would think multimeter companies would just add in smaller loads and an amplification stage in their meters. Is there any reason why this isn't already incorporated in most multimeters? Assuming all DC measurements, I don't see why not. Maybe power?
If you could make the PCB quick to open by using a hinge or a magnet etc. then you would be able to store banana cables in the box to connect the output to your DVM. Or leave it as is and secure a spare battery in there. Or slap some googly eyes on it and "Bob's your uncle".
Wow Dave 51 minutes and you didn't waste a second. I couldn't fill 51 minutes in front of the camera. One question, how long does the battery last? Say if you forget it switched on?
Or anyone interested in Designs in general.. As products of universal inherent quantization "computation".., default time-timing designs, ..of course the elemental mechanisms are of total importance. Functional Devices focus attention on what, how and why.
I know this is old, but I thought I'd reply as I didn't see anyone comment on this. Really what he's doing is providing a 1.5V DC offset to the input of the MAX3249 to allow negative input current measurements, so all opamps are supplied with 3V and 0V from the battery, referenced from the battery. The CMRR of the Opamp takes care of the offset voltage.
Nice product... but why don't the multimeter companies build that functionality straight into the meter? Forgive me if there is a really obvious reason I'm missing.
So, I think I will just do a "parametric" search for multimeters that have the same or better current range as Daive's Device here. Stellar work here by Daive. An engineer can create for $10 what any person in a garage would need $100 to make.
You need it so the ground will stay stable "whatever" impedance you connect to it. If you don't put any voltage follower, the ground you created will swift away from the average of the positive and negative power nodes. The resistance at the output of the voltage follower is used to limit the current driven by the node. So you typically want an op-amp that drifts low current so there's no voltage growing at the sides of the resistor.
It has to do with output impedance. A voltage divider, as you learn, cannot output much current before the voltage begins to sag. A LOT. (more technically the output impedance is defined as voltage over current, or change in voltage over change in current. It defines how much the output voltage will sag if some amount of current is drawn from it.) The voltage follower or _buffer_ will have a non-changing input impedance thats nearly infinite (no current draw almost) and the output is essentially regulated so that unless more than many dozens of milliamps are drawn, the output voltage will remain exactly the same. In other words, the output of the buffer will not change with respect to the current drawn so the output impedance is nearly zero. (until you overload the op amp obviously.)
![Electronic Circuitry Diagnosis And Fault Finding! [Repair]](/img/1.gif)
1000 videos later. It is still most comprehensive video, and simply awesome. A sneak peak into mind of a designer.
Best EEVblog video ever. Loaded with amazing advice from start to finish.
@killerman4ever
Bloody youtube privacy bug again! No one was supposed to see the video before it finished processing and I had added the detail!
Doc Brown would be proud!
I just want you you to be happy so so cute far with with you too too too much to to to to sleep lol lol I’m I love just you love love you love love to love love mommy love love love mommy mommy daddy daddy love mommy mommy love love you love mommy mommy daddy daddy daddy love love love you you guys guys guys too too much too too too bad to to hear hear you you have later later tonight I I hope you have you have a fun thanksgiving and and your love family and and your your dad dad love mommy mommy daddy daddy mommy mommy love love you mommy daddy daddy mommy daddy daddy dad daddy daddy love you you deserve deserve deserve deserve you deserve it deserve better love mommy you deserve deserve better love mommy mommy daddy daddy mommy daddy daddy mommy daddy daddy mommy daddy daddy kiss mommy mommy mommy daddy love love you you mommy deserve mommy deserve mommy daddy daddy mommy daddy mommy daddy daddy mommy love mommy love mommy daddy mommy mommy love mommy daddy daddy mommy daddy love kiss mommy mommy mommy mommy love love you you deserve deserve it it mommy it it was was was was good good morning morning love love you mommy daddy mommy daddy daddy mommy mommy daddy daddy mommy love love love mommy you you mommy mommy mommy mommy love mommy mommy daddy daddy mommy daddy kiss kiss mommy kiss kiss me me and and and mommy and kiss kiss kiss daddy mommy daddy daddy mommy mommy daddy mommy mommy mommy daddy daddy mommy daddy kiss kiss kiss kiss kiss hug hug hug hug hug mommy mommy mommy mommy mommy mommy mommy daddy daddy mommy daddy mommy daddy mommy daddy daddy mommy daddy mommy love mommy daddy daddy mommy mommy mommy daddy mommy daddy mommy mommy mommy mommy mommy love love love you love love love daddy mommy daddy daddy love love mommy you you you mommy mommy mommy mommy mommy mommy daddy daddy mommy daddy mommy daddy mommy daddy mommy daddy mommy daddy mommy love love you you mommy you you you you you you you you you you you you you you mommy daddy daddy mommy daddy mommy daddy mommy daddy mommy daddy mommy daddy mommy mommy daddy daddy mommy daddy mommy love mommy love love you love love love you you mommy mommy love love love love love love you you guys guys guys too good good too good good good good good good good good good too too good good good good too good good good good good good morning morning morning morning morning morning love mommy love mommy love love you you you deserve deserve it love love you you mommy mommy daddy daddy mommy mommy daddy daddy mommy daddy love mommy love mommy mommy mommy love daddy mommy mommy daddy daddy mommy mommy mommy love love mommy daddy daddy mommy daddy daddy daddy daddy daddy daddy daddy daddy daddy daddy love love love love you you guys are are are you you you deserve deserve it it it it it it was just a a lot and and and I I hope hope you’re all all all all all all all all all all all all all all yours yours yours yours yours is is is is is is is is is is what what what what do do do with it it it it it it it it it it it it it you like like that that that that that works works works works out better than than me but but I’m still still still still still still still still still still still still still still still still still still still talking talking to to to to to to to to let mommy mommy how you are are we all love mommy mommy daddy daddy mommy daddy mommy daddy love love love love love mommy daddy daddy mommy mommy mommy mommy mommy mommy love love you you deserve better mommy mommy mommy mommy mommy mommy love love
@hla27b
Yeah, in all that ranting I forgot to mention the battery life!
More than 200 hours.
I determined that it wasn't worthwhile to add an auto-off function to this first version, as that would have required an intelligent device to do it properly.
Dave you are amazing man. Thank you soo much for sharing with us your design. I am so happy that here are ppl like yourself who manage to find time to show, explain and put on youtube videos so that we could watch and learn. I am shaking your hand and saying "Thank you Sir, we are glad to have you as our teacher "
This guy is awesome! He had made HUNDREDS of these blogs
Why there is a spider on your face
I have to say this is the best video I've found so far on the channel. Truly a gem of a presentation.
This video is the greatest thing that has ever happened.
It's definitely a great video, but the problem is that nowadays the Chinese will knock off any product despite its patents, and often butcher the design of the original product. It's a nightmare once one has spent countless hours developing, building, debugging, and marketing their product.
@@BillAnt Lmfao...the truth of that statement hurts everytime
@@BillAnt Don't worry about it, because they don't tend to make counterfeit products if it is not sold over thousands,
the circuits like this will not be copied because of feasibility.
@@myetis1990 < I'm not talking about about small run products, but in general. Feasibility? Anything is feasible, it's just a matter of return on investment. I've read that in a particular Chinese city there are actual factories which only do counterfeit products. They have reverse engineering departments, along with China's lax intellectual property laws, they can operate just like any other factory. It's sad but true.
@@BillAnt Chinese can give only corona
I took a crack at deciphering the uCurrent schematic but a few things were leaving me scratching my head. This explains everything so clearly. In the first 25 minutes of this video I've gained so much knowledge.
From urban dictionary:
schmick
1. I say this in Australia to mean anything sick, cool, tight or excellent.
Usually the item is new, shiny, fresh and mad bling-bling style.
One of the best videos on electronics design. Incredibly detailed and informative.
Ten years late to the show, but love the content. Was trained in electrical engineering and took a different path, but wanted to get back in as a hobby. This was exactly what I was looking to walk me through the thought process. Love it!
When you talk about contact resistance needing to be taken into consideration takes me back to in tech school how we took "ideal"components most of the time but even "simple"pieces of equipment you have to be very precise.like taking even say the resistance of conductors or stray capacitance into consideration.enjoyed the presentation.
51 minutes of the best product/process presentation I've ever seen! thanks for sharing.
Brilliant engineer. Spares no details and that’s important to understanding how it works
@xspoonedx
Interesting question.
If you have the LED operate the other way around and have it only come on when the battery is low, then if you go to turn the unit on and the battery is completely flat, then it won't come on and you'll think your product can be used. So in this case (with no power LED), it's better to have it the other way around so you can check the battery is OK before you use it. So you could say it's more important to know that battery is OK, than know if it's flat!
I'm 3 minuets into this things and I can already tell you've knocked this one out of the ball park. I'm going to grab a beer and some popcorn and enjoy my next hour of engineering bliss.
Cheers.
George Graves
I watched this over the last two nights with my 4 year old inventor son, for his bedtime story :) To his credit he was really listening for the first 10 minutes of each 25 minute night... and he loves the way you say "banana" Dave. I really enjoyed the video and all of the information. Thanks for taking the time to put it together!
Dave, I just saw this great video! Better than a book! Better than a seminar! Better than college courses! You have inspired me to follow through on an idea I have DaveCadded. When done the finished product will be much better because of your generosity. THANK YOU AND KUDOS TO YOU!
I'm incredibly impressed. These should be selling by the truckload. It's elegant, compact, functional, ergonomic, producible, and economical! You just proved that simple is better. Your attention to detail shows the importance of creative skills that many engineers lack. Most engineers likely forget about how the product feels when they get too caught up in the circuit. Yeah, their circuit might be good, but it looks and feels like garbage.
Your best video yet Dave, length was perfect for such a complex topic. Please keep up the longer format from time to time, don't wait another year for one!
Cheers!
This is such an interesting video.
I love seeing how you develop that circuit and the thoughts and considerations that go into the product.
I stopped watching TV a long time ago and started watching videos like yours.
@BitEntropy No, the LED does not switch on if you move the switch quickly enough, a nice side benefit. It's easier to move the switch all the way to one side than centre it, so it's easier to switch it off.
Just wanted to say, love the videos man. I've been an electronics hobbyist since my teens (Amateur Radio operator since age 14 and I dabble in guitar amp and effect design/repair as well). I finally took the plunge and enrolled in a BS Electrical Engineering program this year. After 7 years of working security all over the world I'm definitely ready for a career change haha
I have several similar channels I follow but the wit, sarcasm, and humor you bring to the videos definitely make this the most enjoyable to watch. Not to take away from the value of the other channels but some can have a very dry delivery of the knowledge.
Great channel, and keep it up.
-KC9FJE
Both this comment and this channel have aged well. Cheers!
I would've thought 'reverse LED's' would 'suck' light as opposed to emitting light!
David Perkins not really. That's what black LEDs are for!
@@balahaasdf2219 What's the opposite of an LED? A DED.
Dark Emmitting Diode.
DED!
Thank Big Clive for that :D
Solar panels?
You actually can use a reversed LED as a light sensor, with some careful filtering and amplifying. But obviously it's inferior to proper light sensors (e.g. LDR, PT, PM).
That was a really interesting and nice video. Don't hold back on these please, I loved it. Goes to show that getting exactly the right components (not overkill or underestimated) takes so much more than actually thinking of the circuit and simulating/testing it. Thanks for the tips!
I had bought an electronic blanket from a second hand store. It worked great I thought. It only used 8 watts. I thought "wow they have cone a long way. 8 watts nice.' then it broke a few years later. I went to buy another one to find out that I could not replace it. Every blanket I got was at least 150 watts. Devistated I didn't know what to do. I live in my RV. And to have an electric blanket that I could use for 3 or 4 days on my batteries was I wonderful thing. To use one that eats up 150 watts they would be dead in no time. 1 to 2 hours. The one I bought from the second hand store was clearly defective. But for me, it couldn't have been better. I need to find a way to bring a new blanket from 150 watts to 8 to 15 watts. So many of us love in RVs. And then there are the penny Pinchers. This would be a great thing to bring to market. Who needs 150 watts? That gets so warm it's uncomfortable. Can I just add a resister to the board somewhere to bring that down? Please help. And if you can't, can you point me in the right direction?
11 years ago. Quality looks so good. Better than most I see now
I will be honest. At 33:20ish you blew my mind.
Dave's been doing pcb board design "forever", so no big surprise there... however it's still a nice product ;)
Why?
Easily Dave's best video as of 2016
when you said the product was included in the 2009 catalogue, I thought you might have been taking a trip down memory lane, until I noticed this video is almost 11 years old. great standard of video for the time, and today!
Dave, it's one of Your older videos. After few dozen of projects, i have to tell You that You opened my eyes and showed me how to do stuff. I'm so glad and thankful... I want to buy You a coffee and meet in 4 eyes :) Maybe one day i'll visit Australia. I hope to do so.
Man this channel has been going for a long time. What an amazing resource for a novice! Thanks mate!
10 years old video and yet lots to learn from, thank you.
Thanks Dave.
You have inspired me to design my own dual power / microprocessor controlled lab power supply. I don't really intend to sell it, but thought it might be a great challenge and something to concentrate on, after work and on weekends.
About 75% there... as of today.
EE Student
Fantastic work, I enjoyed hearing about the design process. That red PCB looks so good, I never suspected that was what it was.
This video deserves millions of views. Huge thanks for this video Dave.
@oehrlein49
I use PCBcart, cheap and plenty of options.
No special deals for Altium Designer unless you are a student. Otherwise it's $3900/year or $5K outright for the PCB version. That's less than half the price it used to be.
Never seen the third pos/neg power supply system before. Really interesting.
That DP3T switch throughout the first 15 minutes is really bugging me when it could just be a SP3T switch instead.
No it can't
@@hansdietrich83 In all cases, every pole of the (ganged) switch is connected through to itself, unless it needs to function in a non-ganged configuration, and then I admit I don't know what the purpose of the circuit is. If they are truly ganged, this means an optimization can take place. If you used the poles of the switch to select which input resistance you need, into a common input node to the op-amp, then yes it CAN be reduced to a single pole triple throw switch. Simpler design means less prone to failure. I think Dave would agree.
@@byugrad1024 I have it the same way. I thought it was for precise measurement of contact resistance.
There is an alternative configuration that Dave neglected to show which only uses 2 banana jacks, and a single SP3T switch. Wire the 3 poles of the switch to each resistor to ground. Wire the common from the SP3T to the input banana jack, as well as the op amp input.
A subtle little thing... If I were to use AA/AAA's for this project I might've used three batteries instead of two, to avoid wasting battery power and having to switch batteries more often than needed. (2.6V/2=1.3V/cell vs 2.6V/2=0.87V/cell) Of course you'd have to consider battery impedance and such.
Which brings me to something I'd like you to speak about when seeing this: The black art of bypass capacitors, which would probably deserve an episode on its own merits.
Out of stock is my biggest enemy.
@dc100GHz
I used Altium Designer and got the boards made by PCBcart. Next to impossible to make your own silkscreened and solder masked boards.
Your videos are simply timeless
Could you do another one of these?
You could event move the 100 ohms opamp output protection resistor into the feedback loop to let the feedback compensate for its voltage drop
cls that's smart
Wow. I am so happy I found your vidcast Dave. Brilliant stuff.
Spot on, Dave! Your vids are an inspiration to us DIY electronics pirates all around the world!
About 45:xx I was thinking "how do you test the outputs" and the following discussed how to test for interference. Would be interested in seeing more about verifying the outputs to be correct.
No Batteriser for a 2032 battery (yet) :)
37:53 when I realise that the thing is bright red instead of the normal phenolic cacky brown, and it's like that on purpose not cause you cheaped out on the solder mask.. The joys of being colourblind :P
I don't believe you need a low-offset op-amp for the gain stage. You can simply null out the offset by zeroing the DVM when no current is applied :)
I find the real problem is how to design the front panel and how to imagine switches that can operate deep inside the boxed housing electronics. I think it becomes a mechanical engineering problem which strays from all the effort and excitement of realising the design. What's needed is that front end design handled by some computer process so that the electronic engineering is separated from it's commercial realisation but is automated if the design is taken to fruition by paying the cost.
Fairly brilliant that. Dave you are tops.
@gameboygenius - If you were using AAs your idea of using 3 would allow use of NiCads/NiMHs (whereas a 2 battery design wouldn't (only 2.4v). I like this versatility.
But rechargeables aren't ideal for an occasionally used low-drain piece of test equipment due to internal discharge, so accommodating rechargeables isn't as big an issue.
Although generally I like using an even number of AAs as they come in 2s and you don't have one left over when you need to change them.
2.65V cutoff - Dave, looks like Batteriser (the one you debunked) would be something to use with your design.
@GeorgeGraves
Thanks.
Hey, your comment got posted 3 times and got flagged as spam by RUclips! Yet another youtube new comment system screw-up?
Your approach to subject is lucid and spot on. But I have one point to make. Can you not design chopper stabilized amplifier to combat voltage drift? Whenever we measure low voltage this drift is comparable to input voltage being measured.
Dave, You're a Genius! This is a super video. Greetings from Ohio, USA.
Great video! I really enjoyed, just one thing what about regulations to sell it internationally?
Well done and well explained. ,,👍🏻🥰
absolutely brilliant video, really helped. My only question (from a noobie perspective) does the 100 ohm resistor that provides overload protection affect the final readings? Surely they will in series with the 3 resistors you can choose from? Many thanks!
David Mason Solo la afecta en un 0.0001%. El MAX4239 entrega su tensión sobre el divisor formado por el resistor de 100 ohm y la impedancia de entrada del voltímetro, que es del orden de los 10 Mohm. Por lo tanto el 99.999% de la tensión que entrega el MAX4239 es leída por el multímetro.
Thank you Kokou2be
OMG, I'm impresssed, 50 mins of a great material, using PCB as the front panel - great idea!
Really an amazing and enlightening session ! Thanks a lot !
Thank you for such a great tutorial.
I wish I saw this job long before.
One thing I wonder about PCB layout, is there any countermeasure or consideration for precision measurement (opamp stage)?
The second thing is how should protection be for overcurrent?
thank you dave for this great "how to" video !
very inspiring
Brilliant. I truly admire inventors anden of science.
99k is hard to find, but resistor divider networks are very cheap and far more precise than matching ±0.1%.
Great post! Clever design tricks!
Would it have been practical to include overload protection for the input resistors and what would you have used? Maybe diodes?
Surely, the low battery LED should be off and turn on (red, error) when low? Otherwise it's a drain?
A pitty that Dave did not respond on your legitimate remark. A "battery low" indication would show during measurements that the battery voltage came to low and not only when switching to power on, where the battery would come from a no load, recovered mode.
Actually wouldn't it be possible to build this with an opamp working as transimpedance amplifier? That should (theoretically) lower the shunt resistance to zero and the shunt resistance was the main driver behind this project right?
Hey @EEVblog Dave, do you do any 3D printing for your jiffy boxes?
Great advice ! did you make a video about the decisions made when you decided to make the Gold version ? that would be so useful to have you thoughts on the products evolution.
Double Pole 3 Way Gang Switch :)
Seriously, This guys the Boss.
Thanks Dave
Year 2023. Love u Dave!
Masterclass!
Why aren't tutors this good?
how can I amplify(or multiply by a constant) a DC voltage in the mV range by a factor of 100 ?! any suggestion?
Op amp
can you put the switch on the another side of that 3 resistor..in that case you do not need double switch
one more thing you can use op-amp if current usage less like 10 ma (max output of current of opamp)
you can use tl431 its even cheaper and current is upto 100ma
and can use a transistor to increase current
Excellent video Dave, instead of fortuitous one may even say "elementary my dear Watson". Love the look of the end product, where can I buy one here in Australia?
This is a great idea, but you would think multimeter companies would just add in smaller loads and an amplification stage in their meters. Is there any reason why this isn't already incorporated in most multimeters? Assuming all DC measurements, I don't see why not. Maybe power?
Thanks Dave, I learn so fast from you, like Number 5 from Short Circuit
It's 2022 & this video helping me a lot.
Thank u man.
U r legend 👌
If you could make the PCB quick to open by using a hinge or a magnet etc. then you would be able to store banana cables in the box to connect the output to your DVM. Or leave it as is and secure a spare battery in there. Or slap some googly eyes on it and "Bob's your uncle".
Wow Dave
51 minutes and you didn't waste a second. I couldn't fill 51 minutes in front of the camera.
One question, how long does the battery last? Say if you forget it switched on?
Hi Dave. I'm curious, how much real time did this design actually take (approx)? Thank you. Great video.
yep, good design, from start to end, I like how you used PCB as front panel
Hi Dave, great vid!
What about agreements to sell in other countries? like Europe...
Or anyone interested in Designs in general..
As products of universal inherent quantization "computation".., default time-timing designs, ..of course the elemental mechanisms are of total importance. Functional Devices focus attention on what, how and why.
what a great video!
only got one question - what did you use to power the LMV321?
cheers :)
I know this is old, but I thought I'd reply as I didn't see anyone comment on this. Really what he's doing is providing a 1.5V DC offset to the input of the MAX3249 to allow negative input current measurements, so all opamps are supplied with 3V and 0V from the battery, referenced from the battery. The CMRR of the Opamp takes care of the offset voltage.
Nice product... but why don't the multimeter companies build that functionality straight into the meter? Forgive me if there is a really obvious reason I'm missing.
So, I think I will just do a "parametric" search for multimeters that have the same or better current range as Daive's Device here.
Stellar work here by Daive. An engineer can create for $10 what any person in a garage would need $100 to make.
Has the article link expired? It's returning a 503 error at the moment. Is there a copy anywhere? :)
EEVblog Fantastic Videos Thank you for them all
Really love this video. So much to learn. So well explained. Thanks thanks thanks
And why you need a voltage follower at ground ? To be able to get any current between +Ve or -Ve and ground ?
You need it so the ground will stay stable "whatever" impedance you connect to it. If you don't put any voltage follower, the ground you created will swift away from the average of the positive and negative power nodes. The resistance at the output of the voltage follower is used to limit the current driven by the node. So you typically want an op-amp that drifts low current so there's no voltage growing at the sides of the resistor.
It has to do with output impedance. A voltage divider, as you learn, cannot output much current before the voltage begins to sag. A LOT. (more technically the output impedance is defined as voltage over current, or change in voltage over change in current. It defines how much the output voltage will sag if some amount of current is drawn from it.) The voltage follower or _buffer_ will have a non-changing input impedance thats nearly infinite (no current draw almost) and the output is essentially regulated so that unless more than many dozens of milliamps are drawn, the output voltage will remain exactly the same. In other words, the output of the buffer will not change with respect to the current drawn so the output impedance is nearly zero. (until you overload the op amp obviously.)
I would always limit the bandwidth with a feedback capacitor on something like this.
You Sir, are a genius.
no, he is a shill.
Why do you say that?
this is very beautiful for one man to accomplish . i loved it . genius .