Build Your Own Variable Lab Bench Power Supply

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Introduction: Build Your Own Variable Lab Bench Power Supply

About: Awesome Electronics Tutorials, Projects and How To´s

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 !

Here is the parts list with example sellers:

Ebay:

1x LTC 3780: http://rover.ebay.com/rover/1/711-53200-19255-0/1?...

1x 12V 5A Power Supply: http://rover.ebay.com/rover/1/711-53200-19255-0/1?...

1x AC Input: http://rover.ebay.com/rover/1/711-53200-19255-0/1?...

1x AC Switch: http://rover.ebay.com/rover/1/711-53200-19255-0/1?...

1x Voltage/Current Display: http://rover.ebay.com/rover/1/711-53200-19255-0/1?...

2x Binding post: http://rover.ebay.com/rover/1/711-53200-19255-0/1?...

1x 200kΩ Potentiometer: http://rover.ebay.com/rover/1/711-53200-19255-0/1?...

1x 500kΩ Potentiometer: http://rover.ebay.com/rover/1/711-53200-19255-0/1?...

2x Knobs: http://rover.ebay.com/rover/1/711-53200-19255-0/1?...

Amazon.com:

1x LTC 3780: http://amzn.to/1DMl7G4

1x 12V 5A Power Supply: http://amzn.to/1DMlfp5

1x AC Input: http://amzn.to/1DMlgJI

1x AC Switch: http://amzn.to/1DMliRZ

1x Voltage/Current Display: http://amzn.to/1c9uGK1

2x Binding post: http://amzn.to/1GRcw9X

1x 200kΩ Potentiometer: http://amzn.to/1JJFlbK

1x 500kΩ Potentiometer: http://amzn.to/1E6t89w

2x Knobs: http://amzn.to/1JigGYH

Amazon.de:

1x LTC 3780: -

1x 12V 5A Power Supply: http://amzn.to/1FIc4vK

1x AC Input: http://amzn.to/1FIc7b5

1x AC Switch: http://amzn.to/1FIceDs

1x Voltage/Current Display: http://amzn.to/1AwUnt8

2x Binding post: http://amzn.to/1ENKLzo

1x 200kΩ Potentiometer: http://amzn.to/1ENKQmP

1x 500kΩ Potentiometer: http://amzn.to/1AwUEfD

2x Knobs: http://amzn.to/1FIcuCC

Amazon.co.uk:

1x LTC 3780: -

1x 12V 5A Power Supply: http://amzn.to/1FId7fh

1x AC Input: http://amzn.to/1R1lRl9

1x AC Switch: http://amzn.to/1AwWsoT

1x Voltage/Current Display: http://amzn.to/1AwWFsa

2x Binding post: http://amzn.to/1ENM3uh

1x 200kΩ Potentiometer: http://amzn.to/1FIdAyb

1x 500kΩ Potentiometer: http://amzn.to/1FIdBSx

2x Knobs: http://amzn.to/1AwXvoY

Step 3: 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 !

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:

http://www.youtube.com/user/greatscottlab

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

https://twitter.com/GreatScottLab

https://www.facebook.com/greatscottlab

10 People Made This Project!

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user

We have a be nice policy.
Please be positive and constructive.

Tips

Above 80W the LTC3780 inverter need more cooling so I recommend adding some more heat sink and a fan. I also recommend adding a 130W fuse for over power protection, in my case I don't have a 130W fuse and the closest thing I have is a 125W fuse so that's fine too.

3 Questions

Does anyone know where the enclosure was obtained from?

How do you know to solder the pins on the external potentiometers correctly to the pads on the ltc3780?

182 Comments

In the parts list he has two different types of potentiometers but he never specifies which one goes where in the video. Does anybody know where each goes?

2 replies

The 500 KOhm goes to the Voltage control it is the one on the far left (in other terms the one closer to the output terminal) I hope this helps

the potentiometers on the board wich you remove are marked with the same values. current control is 200k and voltage control is 500k


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

1 reply

WELL YOU WOULD NEED TWO OF BOTH THE HV PSU AND THE LV PSU. THEN YOU WOULD CONNECT THE OUTPUTS OF THE LV PSUs IN PARALLEL.

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 !

7 replies

Its to prevent over current draw and damaging stuff

"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.

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.

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.

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.

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.

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

How much does everything cost in total?

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

4 replies

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.

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.

Linear, because the trimpots will be linear.

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