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.
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)
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.