DIY Hacks & How To’s: Pocket Sized Power Supply

In this episode of DIY Hacks & How To’s, Jason Poel Smith build a simple, pocket-sized device for testing battery-powered electronics on the go–perfect for making sure you garage sale buys actually work. Read all about it on MAKE and get instruction for the full project:

Go here to the project on Instructables:


Marco Mardegan says:

Where is the protection?

Nikidoesitright says:

i double dare you to try it 😉
would be the better way imho.
measure output volume and mark with a sharpy, a lot easier to make and to use.

partysean says:

Put it in a altoids tin

Sam Archibald says:

You could make a cool case with this project!

Jima Tohno says:

AFAIK you can. Notice how the resistor array is hooked up to the voltage regulator. The resistors aren’t what carries the output voltage, the resistor array’s job is only to act as a voltage divider to adjust how much power the regulator will output.

Merk Marley says:

Lol packo jeans

arsyad aris says:

can you help me to make a voice recorder

aLaNiSsAk320 says:

I wish he showed a better Tutorial on this

Jima Tohno says:

Either way, it has the same outcome. I don’t see any advantages on that. I think his method is even better simply because you can use any switch to increase or decrease voltage. (which with a 1 switch per voltage mode, you might accidentally toggle a 9 volt switch on a 3 volt device.)

PvPbomber009 says:

very nice

thomas hardin says:

That’s it!
I’m raiding the RadioShack!!!

NetrixCze says:

Can i use potentiometer???


nice try more videos

GeneralPepe says:

this is going to dissipate a lot of power when dropping 9 volts to 1.5 , that’s nearly 8 volts that it has to dissipate. I suggest a small heatsink

ChintamiAtmanegoro says:

and how about mini multimeter ? it really helpfull

magicbuskey says:

Very nice! Thanks!

Spikey DaPikey says:

So damn cool !!

Sirus says:

Yup, but the voltage would be a little bit off.Shouldn’t make much difference with battery powered stuff.

Michael Angel says:

I think although alot of you guys have some really great ideas for improvements, but most small electronic devices uses max 9v. Also, I think you’re missing the point…IT’S A QUICK CHECKER!!!…but if you need more power on hand, connect two 9v in parallel and that should do the trick…wouldn’t recommend using a Li-Po without a fuse circuit, because if the failure is with the electronic component, then it along with your handy-dandy checker will go up in flames…quickly

lukx31tutoriais says:

This charge cell phone?

Stinky Cheese says:

It doesn’t power the device long enough to see if it works in many cases because a 9V battery isn’t capable of enough current for many things that use AA or larger cells.

lksk 99 says:

Can i use electrolytic capacitors instead of ceramic?

48Dacman says:

Instead of using an array of resistors that you switch on until you ratchet the voltage down enough, why not use an array of different resistors that will give you an exact voltage based on a switch by switch basis? Combined will a joule thief, seems to me this would be a more consistent way. Any electronic engineers wanna fact check me on that?

frozen2kx says:

Cool, I’ll make one ASAP

Mysteria9 says:

“it was already broken…” =D

Maximilian Hans says:

Nice gadget, thanks for sharing.

MaxGecko says:

I know you listed 7-270 ohm resistors, can i use 7-220ohm 1/4w resistors instead?

Jeff Herman says:

lol I noticed that too. I think the last time I saw Paco Jeans and the last time I saw a Simon were about the same time.

jaffar syria says:

no pal the lm317 provides 1amp of direct current

Tim Watson says:

Surprised you did not put an LED power indicator on it.

Centi Zen says:

The LM317 works, but if you are using it in any application where you need real battery life it is a bad decsion. It is a very inefficient way to transform power, discarding much of the battery power it is converting as heat.

A DC/DC buck convertor usually has efficiencies of 95% or greater. The LM317 works as long as you aren’t counting mAh, but when you need all the power you can get a LM317 is not the best choice.

Todd na says:

I love this project, It may look like easy project but it good for the experimenter.

Cristian Barberena says:


I Stole Your Sandwich When You Looked Away says:

Does this still work in 2016….. A lot has changed

Marco Mardegan says:

Two caps aren’t the protections, they are in the circuit for levelling the voltage and give instant power to the load.

You need at least a diode and a resistor to make sure you can’t broke your circuit and, when you switch off the unit, the charge in the capacitor can flow in the opposite way so you can damage the voltage regulator… but i prefer a switching converter.

Sorry for my english, bye.

Ron Harper says:

A LOT more simple method is to simply get a clip connector for a 9 volt battery, put alligator clips on the ends of the bare wires or just hold the bare wires to the device + & – (It wont shock you, & if it does just a Very little tickle). Clip the 9 volt battery to its end, The alligator clips to the device & Presto. This will work for any device that takes Any regular battery : AAA, AA, A, C, CC, DD, D & such or 9 volt just to test it. Don’t touch the wire ends together as it could short the battery out. ALSO, You can use a regular 6 volt lantern (flashlight) battery to power a regular car radio to test it, or in a pinch with bad weather. just run two pieces of wire one each from + & – on the battery to the + & – on the car radio. It’ll run the radio for a few hours if its a good battery. I’ve done all of these many times over many years with No problems. No need to complicate things.

Breeanna Freeman says:

well he does shop in a thrift store

theultimaterockr says:

How old are those jeans????

TheAppleman352 says:

Yes this looks easy but this took me so long to actually make this in my shop at school

Joshua Unitt says:

there’s two filter caps on either end of the regulator, that’s generally about all you need for this kind of power supply

Mustafa Khan says:


Kyle Bergevain says:

looks like that would fit inside an altoids tin

Centi Zen says:

Getting the pot to the precise resistance would be a challenge. You would have an unreliable power supply.

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