Introduction: Build Your Own Variable Lab Bench Power Supply

Picture of Build Your Own Variable Lab Bench Power Supply

In this project I will show you how I combined a LTC3780, which is a powerful 130W Step Up/Step Down converter, with a 12V 5A power supply to create an adjustable lab bench power supply (0.8V-29.4V || 0.3A-6A). The performance is quite good in comparison with other models which cost around the same. Let's get started !

Step 1: Watch the Video !

The video gives you all the information you need to build this correctly. But I will also present you a parts list and more pictures for convenience.

Step 2: Order Your Parts !

Picture of Order Your Parts !

Here is the parts list with example sellers:


1x LTC 3780:

1x 12V 5A Power Supply:

1x AC Input:

1x AC Switch:

1x Voltage/Current Display:

2x Binding post:

1x 200kΩ Potentiometer:

1x 500kΩ Potentiometer:

2x Knobs:

1x LTC 3780:

1x 12V 5A Power Supply:

1x AC Input:

1x AC Switch:

1x Voltage/Current Display:

2x Binding post:

1x 200kΩ Potentiometer:

1x 500kΩ Potentiometer:

2x Knobs:

1x LTC 3780: -

1x 12V 5A Power Supply:

1x AC Input:

1x AC Switch:

1x Voltage/Current Display:

2x Binding post:

1x 200kΩ Potentiometer:

1x 500kΩ Potentiometer:

2x Knobs:

1x LTC 3780: -

1x 12V 5A Power Supply:

1x AC Input:

1x AC Switch:

1x Voltage/Current Display:

2x Binding post:

1x 200kΩ Potentiometer:

1x 500kΩ Potentiometer:

2x Knobs:

Step 3: Build It !

Picture of Build It !

Here are some picture which should hopefully help you to build your own supply. And be careful when working with mains voltage !

Step 4: Success !

Picture of Success !

You did it! Now you have successfully built your own variable lab bench power supply!

Feel free to check out my Youtube channel for more awesome projects:

You can also follow me on Facebook, Twitter and Google+ for news about upcoming projects and behind the scenes information:


DeckardC (author)2016-12-14

Hello guys, can someone tell me if linear/algorithmic pots matters ? Also could a 250k pot rather than 200k work fine?

el8805 (author)DeckardC2017-12-04

It does not matter what type of potentiometer you get but I think it is easier to use a linear potentiometer because you don't need a screwdriver but those tend to be more expensive. Also a 250k can work but the output will be lower than 30v.

krzdan (author)DeckardC2017-11-24

A 200K pot on the current sense lets you set the max current limit to about 13 amps. Rather than a 200K (or worse, 250K) pot, I'd use a 100K pot in series with a 100K resistor, so that the max current limit would be adjustable from ~160mA to around 6 or 7 amps (guesstimating, here...)

A logarithmic-taper pot would give you more / fine adjustment at the low end of that current limit range, and more coarse adjustment at the high end of the current limit.

Note: the LTC3780 is pretty noisy, so add some extra low-ESR bulk bypass cap(s) on the output. That's what I did on mine, powered from an old ATX PSU that I had laying around, ultimately giving me +5, +/-12, +3.3 and the variable LTC3780 output. Makes for a real handy bench supply.

totally_screwed (author)DeckardC2017-08-07

Linear, because the trimpots will be linear.

types140 (author)DeckardC2017-01-20

I'm also interested in this question! Till yet i didn't find a 200k pot in my preferred shop :-( only 250k pots ...

JamieC142 (author)types1402017-02-06

i'm also interested in that question i can't find any on lightinthebox/ bangood

AntonioS113 (author)2017-10-18


Please tell me, what happens if I connect the ”+” and ”-” output wires? Is there a fuse that burns out? Do I need to install a fuse, and where exactly do I connect the fuse holder and the fuse itself? And the power of the fuse?

Thank you

AndrewA201 (author)2017-10-15

LTC3780 just blinks on and off immediately.. When I first got it it worked after turning undervoltage, fault led went off. Now it just cycles on off and gets hot. It must be pulling too much current for the power supply? :( lots of work and disappointing.

abuhafss (author)2017-10-11

Can LTC3780 be replaced with following module?

buddahnature (author)2017-09-28

my LTC 3780 cam without the fuse on the input side - just an empty fuse socket :(

can anyone tell me the spec for that fuse please?

I think it is 15 A SMD Fuse

bar007 (author)2017-09-21

I would like to know if i can connect two modules in parallel to reach higher output current. Thanks.

GellertK (author)2015-07-30

Hi all !

Most likely it's a stupid question... but.

Why do you need a current adjustment ?

I mean, the thing you power up should draw as much as it need, no ?

Thanks for you'r answers !

totally_screwed (author)GellertK2017-08-08

"Why do you need a current adjustment?" Because some loads will draw more current than is good for them. LEDs are an example.

Also as was mentioned in the video, if one makes a mistake, a fault current could flow, destroying a component. Restricting the current helps limit the damage.

totally_screwed (author)GellertK2017-08-07

Why do you need a current adjustment ?

Because a number of types of loads (a load is anything that you might want to power from this), rely upon a current limit. Example: LEDs

Leds need a current limit otherwise the current will rise to a level at which they will be destroyed.

ChuckG24 (author)GellertK2016-10-17

In my case, I will use this to locate a short to ground on laptop mainboards. Set the voltage to the rail requirement, and slowly bring up current. The will make a component that is shorting to ground heat up, making it identifiable. Or in some cases, the bad component will blow. In the event it's a short inside the board, at least there will be a hot spot. Unfortunately, the laptop power supply shuts itself off when there is a short to ground on the board. Making it difficult to locate the problem area. Using this bench supply, will hopefully come in handy.

PaulG78 (author)GellertK2015-11-15

Your building a prototype of somthing and don't want to burn up the components with to much current. In the event you made a mistake.

Testas.T (author)GellertK2015-08-11

You need to adjust current when you charging batteries. If you will charge them with 5A batteries could heat up or explode. I hope i answered your question.

fanuch (author)GellertK2015-08-08

What if you wanted to simulate a circuit where 5Amps aren't available? e.g. a 9V battery or a button cell battery

SamTheAnon (author)2016-11-04

One of the parts are obsolete now, no ones selling them anymore. :(

"One of the parts are obsolete now, no ones selling them anymore." - It would be helpful if you mentioned which one is obsolete.

IvanŠ187 (author)2016-10-26

Will this power supply be good for this?
It is 12V and 7.2A
This is from a old ps2(fat version)

Please be very careful. That looks like an open switch-mode power supply. In an open switch-mode power supply, Dangerous mains voltages will be accessible and if you touch the wrong place you could receive a fatal electric shock. Please be very careful. I think you'd be much safer using an enclosed power supply as suggested in the instructable. The very-same voltages are present, but should stay safely enclosed within the casing.

Iqbal Samin (author)IvanŠ1872016-12-11

It should work, but be careful!

badpakb made it! (author)2017-01-08

LCT 3780 :-)

Arduineer (author)badpakb2017-01-15

You have to be careful, some sellers send the version without the aluminium backplate although the pictures are with the aluminium heatsink.

If so, complain, because what they sent isn't what was offered. If you pay by PayPal you should be able to get a refund.

DanielHutchinson200 (author)2017-05-19

ordered everything just can't wait to try it out. how can I change the pots to the ones I ordered without damaging the circuit as some people have above please Some help cheers

Use a solder sucker and or desolder braid. It's probably best to reflow the solder pads with lead-solder first as the lead-free type can present problems.

JustinW186 (author)2017-06-17

Will this -->

work, it doesn't have a heat-sink underneath but there seem to be heat-sinks on top. Will there be any problems?

I rather suspect that you may need a fan for the version with the small heatsinks, especially if you're dissipating more power. I found at least three variants, there may be more.

watmd (author)2017-07-10

Hello, I just finish it, all the same as this instructables, but the ltc3780 fault LED lit up and the volt meter show 0.3volt fix, can't adjust the voltage. I check the power supply voltage is12v. It can drive my 12v LED and my 12v motor. When I try laptop power suply which is 20v the ltc3780 work normally. How can I fix it.

FedericoC35 (author)watmd2017-07-24

Same thing here except that it's stuck at 2.5v

ArgleB (author)FedericoC352017-07-27

Try reducing the overvoltage control multiple turns until the fault light goes out. Mine arrived and when I powered it up to test it read 000 volts. I contacted the ebay seller who sent me this link to a docx file that I will repeat here in the broken english that it was typed in.


Battery undervoltage protection adjustment method: (12V lead-acid battery set 10V undervoltage protection, turn off the output as an example)
Input voltage stabilized power supply adjust to 10V, adjust the undervoltage protection potentiometer (clockwise increases, counterclockwise decreases), until the fault indicator light (red light), which is set up successfully; so the battery discharge to 10V, will automatically cut off the power supply to protect the battery from being damaged.
Note: if it is not battery powered, you can't set it up;

output voltage adjustment method: input power supply (voltage is higher than the undervoltage protection value), the red light is not bright, the blue light is on, is connected to the output of the multimeter, adjust the output voltage potentiometer clockwise increase, counterclockwise),until the required voltage
Note: normally the red light is not on, the blue light is on, otherwise, for the fault, the input is under voltage protection, the output over-current protection, the output short-circuit protection, please remove the trouble and re power.

output current adjustment method: (12V input 12V charging battery, charge current 5A as an example)
Input connect the 12V power supply, output and connect the ammeter (red pen connected to the output is positive, black pen then negative, direct short-circuit output. Recommended with more than 15A ammeter, to prevent burning insurance), adjust the constant current potentiometer (clockwise, Hour to reduce), until the ammeter shows the required value of 5A, remove the ammeter, connected to the battery can be normal charge.
Note: If used for constant voltage equipment, only need to set the maximum output current.

FedericoC35 (author)ArgleB2017-07-28

That didn't solve it, in fact, the board was fried because I powered it without potentiometers and that shorted the ltc. So I bought another one and this time everything worked, but I wasn't satisfied because the pots were not accurate and they were 400k ohm instead of 500k, so the maxmimum voltage was 23v. So I quickly resoldered the original pots and it worked, only that the wire was soldered so badly it went off and shorted the board. It is very disappointing since on a 24€ board with all those features I would have expected to be a protection even for that... Do you think that I can ask for a replacement or get a refund? I really don't want to spend another 24€ on that because all the components together costed 47€, and buying two extra boards would add 48€, which is a lot considering that I can buy a high quality one with that much money

ArgleB (author)2017-07-27

Does anyone have any idea why I have no current adjustment? It shows the draw but I cannot adjust it with the pot, even when under a load. :(

oxikort (author)2017-07-13

My version, fan is with temperature control...

Mário Césard1 (author)2017-06-27

GreatScott!, I have a doubt and I can't find an answer. :/

The thing is... The voltage/current display shows what the load draws, right? So, if you power it up without connecting it to anything, it would show the voltage and zero amps.

So... How to limit the current that way? Do you use something as load to do that? If so, what do you use?

Thanks a lot!

You should not need a load or anything fancy. You just need to set the voltage at its minimum then short the output terminals with some thick wire and set the current limit pot while reading the display. If you don't want to do the method above, you can also implement a momentary switch, with a high current capability, that shorts the output so that you can set the current to your hearts content. :)

Oh... I see! Thanks a lot! :D

For now I'm going to use a DPH 3205 that I bought. It has everything in it, even a display. But, when I need something more powerfull, I'm going to do that. :)

Again, thanks a lot!

speedboxx (author)2017-06-18

Just built mine from an old cheap ATX power supply. I'm using the 5V rails to power this regulator instead of the 12V as I noticed the output voltage was more stable this way (not sure if it's because of the LTC3780 or because of the cheap psu).

The only annoying thing is that those cheapo eBay amp/meter units are horribly inaccurate even after adjustment. The volt reading is inaccurate by about +/- 0.5V at the lower and upper ranges. The current reading is even's literally off by several factors and the potentiometer adjustment does not make much of a difference. Anyone else have this problem, or did I maybe just get a bad meter?

DanielHutchinson200 (author)2017-05-19

ordered everything just can't wait to try it out. how can I change the pots to the ones I ordered without damaging the circuit as some people have above and ended up breaking the tracks on the board and having to buy a new one . also if use a plastic ABS project box do I need to figure a way to earth the ac input to the box or will it be fine with it being plastic Ie. non-conductive please Some help.
cheers Daniel

yes, u can use plastic case or acrylic sheet to make the profile for power supply. I'm using the acrylic sheet to make one.

sharpe351 made it! (author)2016-06-21

I'm building this with a twist. I'm using the computer power supply as the supply for the whole thing also using the power ports from the computer for static 12v, 5v, & 3.3v with a variable output for the other part. the case I've used is a bit too small, but I'm making it work.

MattTuck (author)sharpe3512017-05-23

I was thinking of making the same tweak!!!!

principle (author)2016-01-06

Ok so I tried a different technique which should be safer if you're worried about unsoldering the pot. The board seems very sensitive to heat so...

Take some standard headers like so male or female does not matter. These pin headers have the same pin pitch as the pot and can be easily and quickly soldered to the bottom of the board. Just tack them to the pads that are already there. This is much easier than unsoldering the pot. Now take a sharp knife and cut the legs of the pot that's on the board (carefully) take your time try not to stress it.

You now have one pot removed and one header in place waiting for the new pot, just solder the wires to your new pot then plug them into the header, solder on a header connector.

The header pins are not 100% necessary but i find them convenient. You can then swap out the pot later on for say a multi turn pot or a pot and stepped resistor ladder, or whatever else you come up with and you won't have to solder to the board again.

Thanks scott for the instructable I hope you don't mind me offering a suggestion

JonathanM221 (author)principle2017-04-25

Good thinking batman, i just ordered some as i must have messed around with the board some how when unsoldering the original pots!!

Ocelotsden (author)2017-02-22

For the pots, It looks like pin 2 goes to the center pad on the board where the old pots were. Does it matter which pads pins 1 & 3 go to on the board?

Iqbal Samin (author)Ocelotsden2017-03-27

It doesn't matter, it determines which way you have to rotate (clockwise/counter clockwise) to increase your voltage/current.

You can swap them to change the direction.

ayman hussien (author)2017-02-11

how can i prevent backflow?

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