Voltlog #82 - DIY Adjustable Analog DC Electronic Load

[@raymondheath7668]

I bounced back and forth between the small ones all the way up to the 10 amp kits and finally decided on the 10 A. Now I wish I had found your meter before I designed my front panel!

[@mnovo]

At first I wasn't sure I liked the blue project box and preferred the plastic one. Now after seeing it in this vid, the quality looks pretty good for the price. Your skills are also improving. Dremmel did not jump around as much as on the plastics. The extra height for the PC heat sink is the top seller for this project. Nice work!

[@voltlog]

thanks! also the harder metal sheet of this enclosure helps keep the dremmel disk on track.

[@mnovo]

@@voltlog do you know if the RD6006 will fit in that enclosue without modification?

[@f.m.a5928]

Nice video.sir you said that above 60w add more MOSFET but how to connect them ..in parallel or ..?and on same heat sink?

[@standishgeezer]

Great job! Always like your very thorough explanation of the build and your tips (such as the pinout on 10 turn pots - that one caught me out some time ago).

[@voltlog]

Yup, these tips can help allot! Thank you for watching!

[@JackZimmermann]

Very nice build! I really like the matching color of the LCD and the case.

[@tonbovee5351]

great job Voltlog, Tx again . I learned a lot from this video I just installed a temp switch my unit is fail safe now . 80 C. added a second mosfet ! (You need to match them, I added a series resistor for each to divide the load better. This increases the fail save situation as well Silicone glue is great stuff.I did not know this type of glue. I took the larger tube. I suggest keep it in the fridge for storage and it lasts! This DC load is easy to modify and so easy to use. Got 2. Keep it going

[@voltlog]

thanks for the tip!

[@nomadic_rider42]

Nice build, @VoltLog. I always use regular screw for newly bored holes, once it screws/unscrews without a problem, I switch it to standoffs (even plastic ones).

[@voltlog]

thank you for the tip!

[@ufohunter3688]

I love your videos. Your narration is unscripted, but flows beautifully. Your camera work is excellent. You have done it right my friend. gj. +1

[@voltlog]

thank you!

[@MindFlareRetro]

Great project. Can you simply trim the length of the post on the 10-turn pot so the knob mounts flush with the enclosure?

[@voltlog]

It's actually useful in this case that it sticks out, because it's easier to grab & spin it, because the front panel is a bit recessed. However you could trim it if you would like to do so.

[@MindFlareRetro]

Ah, yes, I see what you mean. I really like this project - might give it a go myself. Oh, I did find the metal case a bit cheaper from another supplier if anyone is interested, goo.gl/qamH8K.

[@ericvandeee]

Great video!!!! I want to build one myself but i will need more amps i can draw, so just ad mosfets in parrallel and upgrade you cooling????

[@felixcat4346]

Hi, very nice build. I would have been nice to see what the board circuitry does since there are a few ic's on the board. If memory serves, one is an op amp. Removing the mosfet and connecting it to the heat sink is a great idea and leaves the door open to increasing the draw by adding more mosfets. But why mount the heatsink and mosfet upsidedown?

[@voltlog]

I have added a link in the description with the reverse engineered schematic (By Adrian Carstea, a subscriber). With these kinds of projects where I assembled different parts that were not really meant to go together I have to find an optimal solution. In This case the heatsink is not mounted upside down, that is the correct position it should sit, with the fins pointing up.

[@DeeegerD]

Being upside down helps to dissipate the heat as the electrons fall out ;)

[@felixcat4346]

Thanks for the schematic link. Why did you replace the heat sink that comes with the kit? The choice of this type of panel meter almost doubles the cost of this economy project. The cheapie ebay volt/amp meter is a better choice. For those who are following along with this video, be aware removing the mosfet from this board is not for the faint of heart.

[@voltlog]

What heatsink? There is no heatsink with the kit. If possible it would be better to leave the mosfet on the board (shorter high current path), in my case it was not possible.

[@felixcat4346]

My kit came with a small cheap heatsink attached to the mosfet. I assume the kit was designed to the appropriate spec with that heatsink included for a 10amp load. I also noticed that the current shunt has room to put a third one, making it a total of 3. If that is the case it looks like the whole thing could possibly handle up to 30 amps. I believe this might be accomplished using just the one mosfet and some cooling.

[@louamadio7249]

Excellent dialog and video production. Just yesterday I was looking at the CC kit you used. Have you checked the performance sub 100mA? What MOSFET comes with the kit? WRT the meter mod, I did something similar. I did not cut the R10 trace but instead removed M7 diode and connected the cathode side to the spare screw terminal.

[@voltlog]

It's been a long time since I worked on this project, I haven't checked stability under 100mA but I remember it could go below 100mA.

[@androidservice1533]

Hi. And why not connect v_sense (r10) to a free Load + pin? So that the wires do not stick out of the panel? ) I made a similar alteration. To do this, remove the MOSFET and turn on the power directly to the stabilizer z1 from a separate power source. The measuring part was not touched. (It's about the PZEM-031 Panel Meter)

[@chrismoen5853]

Excellent and very clear discussion. Now I have your great advice on how to build this unit.

[@voltlog]

Thank you!

[@oz2hns]

Hi, I built this a year ago, and it just works perfectly. The built-in box is drawn in onshape and laser cut.

[@voltlog]

Glad to hear that.

[@DeeegerD]

Another nice video but this DC load is very reminiscent of #38 ;) One day (some day soon I hope) I would like to design one that has PC logging, uC controlled of course, with constant resistance, power, current and the ability to run it with different wave forms. Meanwhile I have the one you showed in #38 which does a decent job but lacks logging.

[@voltlog]

thank you for watching! Sometimes I would like to have a twin, I would work on the hardware he would work on the software, this way we could bring projects to life :-)

[@surgingcircuits6955]

Well done. Did you consider holes in the cabinet to allow air flow and heat escape?

[@voltlog]

The enclosure comes with slots on the sides. I haven't considered additional holes.

[@codebeard]

Nice project. Is there a reason you didn't have a sense wire for the load negative?

[@voltlog]

main reason because I think (haven't thoroughly checked) the ADC/MCU GND is connected to the common ground on the PCB so I wouldn't have a point where to connect it. Second reason is because the voltage measurement is accurate enough as it is, less than 100mV error, which is enough for me, I won't be doing any precision voltage measurement with this dummy load, there is no need for higher precision.

[@FlyingShotsman]

There's a simple modification you could make that would greatly improve the accuracy and usefulness of the panel meter on your DC load. Install an additional input on the front of the instrument with a SPDT switch to select between internal (at the banana jack) or external voltage sense. Imagine that you're testing a power supply at 5A. There will be significant voltage drop in the test leads to your DC load. In this case, you would want the voltage to be sensed at the output terminals of the power supply under test, not at the DC load's input terminal.

[@TheRadioShop]

Very nice project. Thanks for showing this. Just may build me one of these. Good job!

[@voltlog]

thank you! I hope to see one on your channel.

[@bap8guy]

I ordered the PZEM031, but got a ver 4.0 and yours was 1.0. They are very different. Looks like R1 & R2 go to -load terminal and R10 is connected to R9 & R11. I know it is not likely you have a ver 4.0, but just in case you do, can you comment on which trace(s) to cut?

[@voltlog]

I don't have a ver 4.0, can't help you.

[@mjoebar]

also I ordered the PZEM031, but got a ver 4.0, have you found the solution?

[@TheFunkman]

Very nice project. I have one observation. I didn't see any way to get airflow through your heatsink/fan assy. You need to have fresh air entering on the right and exhaust on the left.

[@KrX3D]

hi, are those eagle files how to drill the holes in the case somewhere available?

[@fellpower]

Yeah, bring all that resistence to the mosfet (the connector and the wires) - it will burn very nice sometimes ^^

[@Elberto71]

careful using those gloves when using a drill press, a work friend lost a finger recently when the glove got caught up in the drill bit.

[@voltlog]

thanks, I will be careful!

[@tonbovee5486]

hi, Tx for the diagram. Do you know what is the function of the IC 1A LM393N?

[@voltlog]

According to Adrian, the guy who did the reverse engineering "When no load is applied between V+ and V- the non inverting input of the comparator is below one diode than inverting input, so is pulling down the non inverting input of the op amp" and i think he is right.

[@tonbovee5486]

Tx I will use this board to drive several Fets , it will be more fail-safe at higher voltages.

[@him481]

Nice project. Have you stopped working on the dark load project?

[@voltlog]

I haven't done any work on the software for a very long time, so you could say I stopped working before I even got it fully working. But I have ordered a rev B of the PCB's just this month. I have made a couple of improvements on the hardware. It would be ideal if someone would like to join the project and help with the software for the STM32.

[@principecristiano]

you recommend this assembly, aliexpres ZPB30A1 60w 13 euros, which voltage handles this source Aoshike DC 1V-100V Constant Current Source Electronic Load Board 75W 0-10A Power Tester ZPB30A1 9.99A 60W 30V Does the one you ride on the video work more voltage?

[@jonvannatto]

Any comment on recent news on Eagle moving to a paid subscription model? Moving to KiCad or sticking with Eagle?

[@voltlog]

I was planing to start working in KiCad for a long time ago, now I seem to have an additional reason to do that.

[@mauriceb]

How accurate can you adjust the load ? Down in the 10mA ?

[@voltlog]

I can adjust in steps of 5mA with easily achievable fine movements.

[@felixcat4346]

You don't need to use a 10 turn pot to acheive accuracy on this thing. If you have a 10k pot on hand it will work just fine. You also don't need to use the expensive panel meter shown here, just a 5 usd ebay cheapy volt amp meter, a used computer atx power supply case with the fan built in, and you got yourself a dummy load for less than 15 usd. When you want to dissapate more amps, start adding more of the same mosfets, and another current shunt or two.

[@yannis92preloude]

Hi. das any one now what is the lowest voltage that the meter display can go.

[@jlegen]

I usually hate having the power switch at the back! 😉 But that's a nice little project, thanks for showing us...

[@voltlog]

Thank you!

[@tengelgeer]

Damn, again I bought all kinds of stuff during/because of your video. Damn eBay addiction :p

[@voltlog]

don't worry you are among similar addicted people here :-)

[@eddyfontaineyoutu100]

Hi !, In the mean time, i build mine using the same parts you selected and hacking the V+ sense input like you described. I am really satisfied with it ! Thanks for sharing ! 👍👍👍

[@voltlog]

Nice to hear that! :-)

[@Hugatry]

Another great dummy load video! That panel meter looks great with nice layout and decent precision. If it had (m)Ah instead of Wh, I would have ordered one straight away... Anyway, awesome project!

[@voltlog]

thanks! I wished the panel meter had mAh instead as well..

[@fredlllll]

usually people use isolating heat transfer pads, cause the back of the mosfet is connected to the circuit, is this one isolated?

[@voltlog]

the mosfet is electrically connected to the heatsink but I have nothing else connected to the heatsink or the enclosure so it's not a problem

[@fredlllll]

well the mosfet is rated 100V isnt it? wouldnt like to touch the case when there are 100V DC on it

[@voltlog]

That's the reason I've "limited" my model to just 60VDC, to keep things safe.. If you are building one yourself, it's pretty easy to add one of those silicone thermal pads, but they do increase the thermal resistance when compared to thermal paste.

[@fredlllll]

when being barefoot in my lab in summer i can already feel 30V tingle, dont want to touch 60V :P

[@felixcat4346]

Some of these kits come with heatsinks and a sil pad which will isolate them from the heatsink. Of course using this sil pad thingy will reduce heat dissapation. The best practice would be to keep the heat sink away from the case.

[@gamerpaddy]

can you use multiple mosfets in parallel?

[@voltlog]

yes you can but you need to ensure equal loading with some 0.1 resistors.

[@gamerpaddy]

Thanks, just ordered a board to fiddle around. + Subbed, good channel you got there.

[@MrBrymstond]

I believe I would have applied the Thermostat on top of the plastic part of the mosfet not allowing any conductive thermal paste or cream to touch the conductive parts of the mosfet if it's supposed to be isolated and maybe it would also act more accurately as a bonus. Just a thought.

[@voltlog]

there wasn't enough clearance between the bottom of the enclosure and the mosfet to attach the thermal switch there.

[@jstro-hobbytech]

Do you still use the load?

[@voltlog]

No because I have better electronic loads in my lab currently but this thing served it's purpose in the beginnings.

[@luisbulek65]

Good job, Sir.

[@DavidWatts]

This was great mate. Who needs a fail safe anyway :-)

[@voltlog]

thanks!

[@dormstories]

Where did you source the panel meter from?

[@voltlog]

Links for all the items are in the description of the video.

[@michaelpiotrowicz6100]

You need to turn the tap backwards regularly to break the chips when cutting a thread. Even with aluminium you should hear a click.

[@voltlog]

yup, I figured that later from other peoples comments. It was my first time using a tap.

[@YouAllKnowBob]

Nice affordable project! Thank you.

[@voltlog]

thank you for watching!

[@stephanc7192]

Thank you very much for the schematic.

[@voltlog]

no problem, thank you for watching!

[@stephanc7192]

I looked at the schematic and built the current sensing op-amp (OB1B) in a test circuit. I like the differential sensing technique used on this board. Initially, I had a small problem with the circuit as shown. I was wondering if the bottom of R8 should be connected to GND and not V-, or perhaps V- and GND are connected together? Then I realized that a negative rail is created with the D1. Clever! Kind regards PS: A great thanks to Adrian Carstea for the schematic. Does he have a channel?

[@rubenuspv]

Very nice project!, the only thing I'll do different it's to leave the fan on the wall of the box.

[@voltlog]

Now I think that would have been better, because the way I installed it, allot of the hot air stays trapped inside the enclosure.

[@FlyingShotsman]

This is easily fixed with some thin plastic or cardboard to form a sealed baffle around the fan and heatsink. Make sure that all air from the exhaust side of the fan is forced through the heatsink and can only exit out the side of the enclosure.

[@johncherry108]

Nice project, explained clearly.

[@voltlog]

thanks!

[@RobinCernyMitSuffix]

hm... I actually have exactly the same Panelmeter laying around and didn't had an good Idea... Now I have one :D Actually I was also thinking about to modify the Meter like you did, but didn't had the time to think more about it :/ Thanks for your work! And your Video (:

[@voltlog]

thank you for watching!

[@esuohdica]

Nice useful video once again thanks!

[@MauroSedrani]

+VoltLog Great job!

[@voltlog]

Thanks!

[@squalazzo]

very well done :) i think i'll do 1 for myself :) oh, correct the box link, add "box" to the description, otherwise you have car wheels :) the KSD9700 NO Thermal Switch link is wrong, too

[@voltlog]

Thanks, I fixed the links!

[@squalazzo]

VoltLog the box one still points to car wheel rims... m.ebay.com/sch/i.html?cmd=SKW&_pgn=1&_nkw=170mm+x+130mm+x+75mm+metal

[@voltlog]

I have tried fixing it once again by adding an extra keyword in the search, please check.

[@radekhn]

I see the last link pointing to right enclosure. Also thanks for presenting nice project.

[@jameshauser1507]

Nice video. Nice project.

[@voltlog]

thanks!

[@ovalwingnut]

Good times.... good times :)

[@tablatronix]

great build

[@voltlog]

thank you :-)

[@randycarter2001]

Be very careful when testing batteries. Your project as shown doesn't have a backup disconnect. You can never rely on semiconductors alone to shut off the current flow. Batteries are never off.

[@iceberg789]

i have the same power bank i guess.

[@voltlog]

pretty good as a stand, right?

[@Александр-я6л6э]

Вот валенок! За эти деньги можно готовый и более крутой просто купить!

[@technolabcreation]

nice one::))

[@Graham1904]

You could half of the time in building it and spend some time on how the module actually works as you did not do a user review of it previous....!!!

[@MrMac5150]

Nice

[@voltlog]

thank you!

[@apollorobb]

Horrible thermal management !! Kids dont do it this way

[@juliusvalentinas]

Very bad idea to use thermal switch that is under 230VAC, the case is wired to live AC. You need to use insulated one ! That much thermal paste in not desirable, as if it squeezes on the pins there can be a short circuit if the paste is conductive.

[@voltlog]

I don't think you watched the video entirely..

[@blackbrayn]

first?!

[@voltlog]

the one!