Portable, Variable Power Supply




About: I've always liked pulling things apart - it's the putting back together again that I have some issues with.

I’ve been using a bread board a lot lately to build electronic projects and wanted to come up with a small, portable power supply. After a bit of rummaging through my spare parts I managed to find all of the bits needed to build one!

This is a simple project but has been invaluable in powering my circuit projects. You only need a handful of parts and some basic soldering skills to make your own and if you tinker with circuits and electronics, you’ll find this little, portable power supply come in handy.

The power can vary from 2 volts to 25 volts and has a potentiometer to allow you to change the voltage easily. I also wanted to be able to change the ends of the testing wires for different projects so also added banana plugs to be able to swap and change.

Step 1: Parts and Tools


1. 9v Battery Holder – eBay

2. 9V Battery

3. 10K Potentiometer – eBay

4. Voltage meter – eBay

5. Bread Board Jumper Wires – eBay

6. Voltage Regulator - eBay or eBay

7. Banana Plug Socket Jack Connectors – eBay

8. Alligator Test Lead Clips – eBay

9. Hook Clip Test Probe – eBay

10. Banana Plug Multimeters Probe – eBay

11. Small piece of scrap plastic.


1. Hot Glue

2. Soldering Iron

3. Wire Cutters

4. Super Glue

Step 2: Removing the Potentiometer

The first thing that you need to do is to remove the 10k pot from the voltage regulator. The reason being this is too small to easily change the voltage so adding a larger one makes the job easier.


1. Place the pot into a vice, pliers or anything else that will hold it for you.

2. Heat-up the solder points with a soldering iron and wiggle the pot loose. You might have to try and do one side first and then the other to enable to get it out.

3. Once it’s out, clean-up the solder points and get ready to add the new 10 K Pot

Step 3: Adding the New Poteniometer


1. Place the legs of the pot in the holes of where the original pot sat. You will probably have solder blocking them so you will need to re-heat the solder point

2. Heat the solder points with a soldering iron and push the pot into place. Make sure that the legs are lined-up to the holes in the circuit board correctly.

3. Add some more solder so it is secure and cut the excess legs coming out of the holes.

Step 4: Adding the Banana Plugs

To be able to add the plugs I had to add some extra plastic to the 9v battery case.


1. Cut and shape a piece of scrap plastic. It should be strong enough to not bend when putting the plugs into the female connectors.

2. Drill a couple of small holes into the ends of the plastic and secure the banana plugs into each one.

3. Next rough up the areas of the plastic so the super glue gets a better hold on it. Add some super glue and attach the plastic to the back end of the battery case. Make sure that the banana plugs are orientated correctly by placing the regulator on top of the case and lining up the positive solder point to the red plug and the same with the negative.

Step 5: Adding the Voltage Meter

To be able to know how much voltage is being supplied by the regulator, you need to add a voltage meter. If you managed to get your hands on a regulator which already have a voltage meter, then move to the next step


1. The wires from the voltage meter can be attached to the banana plugs. To do this first unscrew the tops of the banana plugs.

2. Cut the wires on the meter top length and wrap the wires round the metal section of the plugs.

3. Replace the tops onto the banana plugs.

4. Lastly, glue down the meter with some hot glue.

Step 6: The Battery Case

The next thing to do is to add some power to the regulator.


1. Hot glue the regulator on the battery case. It should be attached to the bottom of the battery case (where the switch is located).

2. Trim the wires on the battery holder and solder them onto the corresponding solder points.

Step 7: Attaching the Banana Plugs to the Regulator


1. Solder a red wire to the positive solder point on the regulator and attach this to the red banana plug

2. Do the same thing for the negative wire.

3. Lastly, add a battery and test to make sure everything is working as it should.

Step 8: How to Use the Power Supply

Using the power supply is pretty simple. To change the voltage you just adjust the poteniometer on the regulator. The voltage level will change on the meter as you tun the pot.

Having a range of connectors will help attach the power supply to different applications. I also added a couple of banana plug ends to some jumper wires so I could also use it on a bread board.

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    25 Discussions


    Answer 4 months ago

    If you Mean to charge one then yes. Don’t know if it would be a viable replacement for the battery in a cell phone


    Tip 7 months ago

    Just a quick tip, if you cover the voltage meter with a piece of plastic from a translucent plastic folder they are much easier to read (I saw that little tip on youtube) in all lighting conditions and angles.


    Question 1 year ago on Step 7

    Wait, what? Can you dial up the voltage above the 9v input voltage?

    1 answer

    Answer 7 months ago

    I'm pretty new to electronics but was reading about these a few days ago. So say you have a circuit that runs on 5v but you only have a 9v power supply, you can use the buck/boost to step down (not sure that's the correct term) the 9v supply to 5v . The really crazy thing is that as your battery depletes and goes below 5v, the buck/boost will then switch and step up (again, not sure about the terminology) the voltage so that your circuit will always get 5v. It will do this with whatever input voltage it gets until the battery is completely spent. I gotta do a bit more research on these which is kinda how I found this page. You can get the buck (step down) and boost (step up) as separate components or you can just get the buck/boost. I guess it depends on your project which one you go for. How crazy is that!?


    9 months ago

    I just able to find the voltage regulator with 1 inductor. Im thinking it wont work, will it?


    Question 1 year ago

    So I tried to make this. I got everything on the list except the potentiometer becasue it doesn't ship to my country (US). I replaced it with this one, but it was too big to fit in the board, so I soldered wires from the three leads into the board. Other than that, everything's the same. This being said, what I made doesn't work, the meter oesnt light up and it just kind of makes a high pitched sound. Is there something wrong with the potentiometer I used? Or did I damage something along the way?

    1 answer

    Answer 1 year ago

    Hey there,

    The Pot looks fine to me. Maybe the solder points on the board are touching where the pot was joined to the board?. Check and make sure that they are clean and no solder has joined them together. Also check and make sure that you have the pot soldered on the correct orientation. Maybe de-solder the pot and turn it around.

    Do you have another module? If so, I would first attached the voltage meter (attach the positive section of the voltage meter to the positive output on the module and do the same for the negative point). Don't remove the pot and see whether the voltage meter is working ok and it is measuring the output. If that works, then carefully remove the pot on the module and re-solder a larger one in the correct position


    Question 1 year ago

    Does your buck converter becomes hot?

    Myone just goes nuts as soon as I turn on the switch

    2 answers

    Answer 1 year ago

    Hi there,

    The input voltage is usually from 5v to 25v so 9v shouldn't cause the module to overheat. You may have a dodgy one.


    Question 1 year ago on Introduction

    Nice project. How do you get up to 25v output using a 9v source and a step down voltage regulator?

    3 answers

    Answer 1 year ago

    most of those cheap ebay devices are either buck or boost and they have only one standard inductor. the Buck/boost has two inductors. That's how you recognize the difference. the two inductors are connected by a capacitor. the first inductor makes a boost and transfers energy to the second inductor similar to the operation of a flyback p/s. thats the simplified explanation.


    Answer 1 year ago

    +1 question.

    I think lonesoulsurfer pointed to the wrong eBay url..

    Lonesoulsurfer's module has Two inductors while the url has a Single inductor !


    Question 1 year ago on Step 8

    In Parts

    6. Voltage Regulator ( typo )

    I think that you lonesoulsurfer pointed to the wrong eBay URL.

    That module is a step down voltage regulator

    Yours has Two inductors while the eBay URL has a Single inductor !

    1 answer

    Answer 1 year ago

    Thanks for the heads up. I’m away at the moment but will fix it soon.