$2 Cassette Box Cellphone/USB Charger




About: I've had many different jobs in my life, but I've discovered my passion: Mental Health Counseling. However, that doesn't keep me from still being a technogeek!

I love the Mintyboost power supply/charger Instructables, but wanted to look for something a little readily available that doesn't see much use anymore and that was a little easier to customize. Going through a few stores of odds and ends, I came across an old cassette tape collection, and there it was! I tossed in a $1.69 Radio Shack 7805 5 volt regulator (they have virtually every type of protection built in, including thermal overload, spiking, reverse polarity, etc.), and came up with this! It's easy, fast, and a great little charger that you can use with just about any DC power source to charge your cellphone, or, with a little extra effort, your USB! A big thanks to JDurban for his advice on this project!

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Step 1: The Regulator

You couldn't ask for an easier part. It requires no additional components to work, and you only have to solder to three pins. The DC power leads attach to pins 1 and 2 (2 is the common ground for both input and output), and pins 2 and 3 for the output... what could be simpler?

Step 2: The Simple Version

The simplest means of setting up and using this regulator is to simply take the cellphone connector wire from a broken wall charger and solder the red(positive) lead to pin 3, and the black/white(negative) lead to pin 2 (ground). You can then cut the end off of any used DC wall wart (make sure that the milliamps is AT LEAST the same, or more than what's listed on your original cellphone wall wart), and solder the positive wire to pin 1, and the negative wire to pin 2.

I went ahead and used an old leftover female USB port (leftover from a motherboard add-on) instead of wiring directly into my cellphone wire, as I had a USB charger adapter readily available. I also used alligator clips which would allow me to attach any available DC power power supply, including batteries, instead of wiring directly to a DC wall wart.

Here you can see that I'm actually charging my cellphone from a 9 volt battery! 4-6 AAs also work, and even a cordless drill battery...

Step 3: A Heatsink Is a Good Idea...

Now, one word of caution... if you plan on hooking this onto something like a 12 volt car battery or anything with serious amps, you'll definitely want a heat sink attached to the regulator. I drilled a small hole in the bottom and ran a bolt through alternating small and large washers on the underside of the case to make a "fanned" heatsink, then placed two small washers inside to hold the regulator up off the plastic case, and then the nut to tighten everything in place. It works well without getting too hot, even with a 2-3 amp, 12 volt power supply.

Step 4: Hot Rod It!

I took it a step further by adding an LED with a 1K ohm resistor attached to the positive LED pin, and soldered the LED to pins 2 and 3 of the regulator. This would serve as a nice indicator light to show that I had the polarity correct on the alligator clips before plugging anything into the USb port, which I also mounted inside the cassette case. I finished the whole thing off by making a custom case cover in Photoshop and printing it out on a sheet of photo inkjet paper, which I then cut down and glued to the top!

Step 5: Hooking Up to Any DC Wall Supply

It's pretty easy to hook up the clips to a DC power adapter simply by using a paper clip, needle, etc. for the center and then clipping the other lead to the body as seen in this picture.

Step 6: Charging USB Devices...

I've tested this with several USB devices, including MP3 players, and it works great! I'm not guaranteeing this will work with everything, as some devices might use the lower amp 3 volt signal present in a full USB to computer interface. I could even use it on my USB powered Mutant Furby!

Step 7: UH OH!!!

What's this? A guest appearance by a large hammer? I wonder what's about to happen? I guess you'll have to watch the video and see! ;)

Please vote up if you like this Instructable, and any comments, suggestions, etc., are welcome and appreciated!

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    27 Discussions


    10 years ago on Introduction

    I got a voltage regulator but the guy didn't know what the hell he was selling so i had to guess. I'm fairly certain i got the right one but it still doesn't work. i also got 2 green 2.6v LED's if that helps. the one I'm using now is a yellow one. I dont know what it takes. i got it from and old PC. Can anyone either tell me whats wrong with it or give me any pics. That would be a great help. Thanks. Untitled.jpg

    6 replies

    I kind of quit for a while but I still have the regulator and plenty of 9v batterys. I think I could make one now but have been busy lately with other things like trying to figure out if I should make a small ammonium nitrate & molasas bomb and set it off out in the country or go through the tedios task of turning it into sodium nitrate and then mixing it with sugar to make a smoke bomb. Also want to make something special for my girlfriend since valentines day is comming up. But after I'm done with thoughs things, I'll give it a shot again lol. ( I don't have a phone to test on anymore though so I'll try to borrow the mp3 that I gave my gf a while back.)  I'll let you guys know how it turns out. =)

    You have a problem in your schematic!!!

    The negative goes to the 2nd pin and out in the same pin(kinda need to have solder skill) 1st is positive in and 3rd is positive out!!!

    nah cause were I live, it's kinda hard to get that stuff and I don't like to buy over net. (havn't done it yet lol) But you did give me an idea. I could try to make a heart pillow that can recharge anything that a USB will plug into. I could even make it into an instructable. =) And I know what your'e thinking, we already have alot. But IF I do, do this. Then I will be detailed and give a readable schematic, unlike when I first tried to learn. =)


    10 years ago on Introduction

    Never connect LED in series with voltage regulator.It will reduce input current to the LM7805 and LED may destroy.


    11 years ago on Introduction

    looks nice and simple! but I'm a bit confused (probably due to the mix of blurry pictures, and my lack of knowledge in electronics). If I wanted to be able to plug a usb device into it, I would simple go battery to regulator to usb? that sounds too easy!