MAKE | 0 – 24 Volt, 2 Amp Bench Top Power Supply

By Michael Colombo
Category: Workshop, Electronics
Difficulty: Moderate

Hobbyist electronics projects need robust, reliable power supplies for prototyping and testing. I learned how to build this circuit from the Basic Analog Circuits class at ITP taught by Eric Rosenthal, but took it several steps further in building a solid enclosure and integrating a voltage meter. Now it lives on my desk, ready to power most small projects I’m working on.

You’ll see example shots of point-to-point wiring of components to perfboard while following a schematic for this power supply. A wood enclosure is built, and Adafruit’s Mini Volt Meter, V_out posts, and a potentiometer are mounted in the final product.

Parts List:

One 3×5" perfboard
LM317 variable voltage regulator
BR805D Bridge Rectifier
Heat Sink
120 VAC to 24 VDC transformer (mine is part number LP-575)
Power cable
Two 1000 microfarad capacitors
One 0.1 microfarad capacitor
One 1 microfarad capacitor
One 100 ohm resistor
One 5k ohm variable resistor
One 1N4002 diode
1/2" plywood
1/8" wood or MDF
six half inch wood screws
8 1/2" long x 1/8" wide nuts and bolts
Plastic knob
Mini volt meter from Adafruit Industries

Steps

Step #1:

Solder the positive and negative (red and black) leads from the transformer to the power cable. Twist the threaded wires together and use a liberal amount of solder, completely covering all connections. Finish with heat shrink tubing or electrical tape.
Apply thermal compound to LM317 and screw into heat sink.
Wire all components to the perfboard. There are a couple of ways to go about this: some find it's easier to put all the components into the holes first and bend the wires so they stay in place, then solder everything together. I like to go step by step, following each part of the schematic individually to verify that I have every connection correct.
You'll be using point-to-point wiring on the back of the perfboard. Make sure that all your connections are separated, and use insulated wires if you have to cross over any connections you've already made.
Make sure to solder leads onto your potentiometer for easy mounting to the enclosure later on. Also be sure to short out the middle pin to an adjacent pin on the pot, so it functions as a variable resistor and not a voltage divider.
Solder long leads to two header pins on your positive and negative output for easy mounting to the enclosure later on.

9 Responses to 0 – 24 Volt, 2 Amp Bench Top Power Supply

Colombo on October 17th, 2011 at 3:36 pm said:

It was supplied by my institution, probably bought in bulk. But you can use any transformer that has similar specs – judging from a recent user comment you’d probably want to go with one that’s lower amperage so you don’t accidentally burn out the LM317.

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Colombo on October 21st, 2011 at 2:13 am said:

Sorry I’m not exactly sure what you mean…did you find different part numbers from JameCo? What do you wish to edit?

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Colombo on October 21st, 2011 at 2:14 am said:

I think you could test it with a 9 volt to see if the LM317 is doing its job – though someone may need to verify this for me…

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Joseph on October 21st, 2011 at 9:35 pm said:

I mean just adding links to Jameco products
(Note I am not affiliated with Jameco. I just opened their catalog first.)

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Joseph on October 21st, 2011 at 9:36 pm said:

This should be fine, BUT you will not be able to get a full 24v.
Just 1.5v-9v about.

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Colombo on October 24th, 2011 at 2:28 pm said:

Great to hear you’ve improved upon the original design! Once you’re finished please post links to photos, or put them in the Makezine flickr pool.

- The best place for a fuse is probably right after the bridge rectifier on the positive lead, before it goes through the rest of the circuit.

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Eric Marcoullier on October 25th, 2011 at 9:06 pm said:

Did you ever find the Jameco part numbers? I can’t find a suitable transformer but I’m not sure if I’m looking correctly

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pranker225 on June 9th, 2012 at 12:53 pm said:

go here:

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Doug Strickland on November 13th, 2012 at 3:54 pm said:

@John – You can still use the transformer mentioned in the project (Jameco Part no. 112513) because it is rated for both primary voltages. Here’s from the datasheet:

Primary Voltage: 115/230VAC @ 50-60Hz
Secondary Voltage: 24VAC @ 2A

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