DIY Cheap Variable Power Supply Under 10$

Hello and welcome,

This is an easy Instructable for adjustable power supply that every electrician must have.

The project is under 10$ but you can scrap or scavenge most parts I used.

Caution:

I am not responsible if you hurt yourself or others around you!

Step 1: Things You Need

2 x wood pieces 20 x 12 cm / 7.8 x 4.7 inch (free)

2 x wood pieces 11 x 12 cm / 4.3 x 4.7 inch (free)

LM317 Voltage regulator (1-2$), heatsink is optional

4 x 9 Volt battery connectors or you can use banana plugs but battery connectors are cheaper and you can find them for free by scavenging old batteries. (4$ if you buy banana plugs) (2$ if you buy battery connectors or free)

Switch (1$)

10K potentiometer (2.5$)

LED Voltmeter (optional but it's cheap, 1$ on Ebay)

9-24 Volts power adapter or laptop charger (Free or you can buy it for fairly low price)

30μF electrolytic capacitor (20 cent), 10pF ceramic/film capacitor (10 cent), 1kΩ resistor (10 cent).

Hot glue, duct tape

Some wire to connect all, soldering iron and solder.

Step 2: Cut Wood Pieces and Drill Holes

Layout is optional but I found this one is the most practical one.

I used battery connectors all the time like sockets. (Explanation later)

Step 3: Glue It Together and Fill the Holes

I soldered power adapter to another battery connector so I can plug and unplug it whenever I want.

Make sure you glue it very tight.

Step 4: Electronics

I'm sorry I can't show you the whole proces but here is the easy schematic.

You can solder everything on a board, but I found this is easier for me.

You can now add LED voltmeter and solder it (+ goes in the middle pin, - goes to ground)

LED voltmeter measures 4.5 Volts minimal, have that in mind.

Last step is to glue the back panel.

Step 5: Final Product

You can add up to 30 volts power adapter, but be sure to add a heatsink.

And you can put 9 volt battery and use it like mobile power supply.

This is a little project that takes few hours to make.

I hope you enjoyed, leave a comment below if you have any questions.

Comments

[IamRobert89]

I connected it to 22V power supply (for my cordless drill) and it's not working with 10K variable resistor? Do I need bigger value of resistor or?

[Zhuna87]

How do you know that resistor is a problem? Can you take some pictures of your soldering and post it here so I can check the problem?

[IamRobert89]

It's on breadboard but it's not about my connections because it does regulate to just 15V.. When I disconnect the potentiometer it's about 22V..

[Zhuna87]

Then you should try 1k or 5k potentiometer. See how that works and let me know.

[Zhuna87]

Hello Robert,

Sorry to answer you this late but the problem is your potentiometer.

You must buy potentiometer with more turns, just ask in the store for potentiometer with more turns.

[NoPinky]

Why would you need such a big box? It is all empty inside, isn't it? °_°

[Zhuna87]

I wanted it to look big so I can fulfil free space on my workbench. You can make it however you want, it is your choice. Best regards

[EpicalAgent56]

How can you change the current output? It appears this is only for voltage. Will I have to get a more expensive power board?

[Zhuna87]

For current limiting you will need a different and more complicated circuit. Maybe I will do it in the future. :D

[bpeljto]

I made a prototype and it's working to 12V, can I connect two adapters for more power? btw. Good Job!

[Zhuna87]

Yes you can, connect them in series.

Thank you.