Lego USB Charger




About: Working wireless-ly.

This project describes how to build a hand crank Lego usb charger with parts from a Mindstorms kit and Radio Shack.

The charger uses a Lego motor to generate current which is passed through a voltage regulator and then to the usb port.

It would make a great stocking stuffer for anyone who uses devices that charge via usb. If you are getting it for a person who likes to build their own things, just collect all the parts put them in a ziplock, and put that in the stocking. Then when they want to build it you can show them this instructable.

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Step 1: Building the Lego Base

Follow the photos for details on how to build the base.

Some of the photos include the wired up electronics, ill explain that in the next step.

Step 2: The Electronics

The 3 parts needed for this step are:
- Short lego wire, cut the block piece off one end and strip about a centimeter of the wire off
- +5V Fixed-Voltage Regulator 7805
- Female usb port

Plug the lego wire onto the motor as shown in the photos, test out which wire is positive by connecting the stripped wires to a multimeter and cranking the motor. Wire the positive end to pin 1 (input) on the voltage regulator. Wire pin 3 (output) to pin 1 on the usb port (if staring into the socket while the contacts on the inside are facing down, pin one is the farthest to the left). Wire pin 4 on the usb socket, and pin 2 on the voltage regulator to the negative lego wire.

Step 3: Ad Ons

It is easy to create devices (ex: flashlights) that can be plugged into the motor or the usb port to provide power. For this project I enabled collaboration, so if anyone has any ideas for ad ons let me know and you can put them in.

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    70 Discussions


    4 years ago on Introduction

    ok could you make a video on this and show a top view of the connections between the regulatorss and the usb port it help

    Raptor Z

    7 years ago on Introduction

    in my opinion its not worth it, as the motor costs 20-30 dollars, and you can buy a small dynamo hand charger for 3 dollars.


    9 years ago on Step 2

    do you know which side of the lego wire is positive and negative? O and Radioshack carries the 7805 voltage regulator, i got it pretty easily.

    1 reply

    Reply 8 years ago on Step 2

    Since the motor can be turned either way, I think the polarity can change. The next question is would this still work if a tiny rectifier bridge was added - like this one - It would drop a few volts mind...


    9 years ago on Introduction

    its so simple yet so good i dont no what to rate him


    10 years ago on Step 3

    Couldn't u use another motor attached to the crank in order to charge something instead of standing there for an hour cranking? Would work just as well, instead of tiring your arm out =)

    1 reply

    Reply 9 years ago on Introduction

     Then what is the use?
    Find a power source, convert it to movement and then convert it back to power?
    All you're gonna do is lose power on the way (goes to heat by friction). 

    I've seen projects on instructables to charge USB devices using normal batteries (AA, AAA, 9V). Might be a better solution if you don't want to do some effort for the power. 

    This is a nice thing to have with you if you run out of power without any batteries or other power source nearby. 


    10 years ago on Introduction

    could this thing be used as a usb driven motor?
    so i can control my legos?


    Reply 10 years ago on Introduction

    it's just an electromotor. Normally you put electricity in it and rotation comes out, but he uses it as rotation in -> electricity out


    10 years ago on Step 2

    do you need a voltage regulator


    12 years ago on Introduction

    the worst of it is trying to find the right piece of junk to get the +5 volt regulator....i don't have a radio shack round ere'....:(....but still beautiful idea and i love it :D

    1 reply

    Reply 11 years ago on Introduction

    Every old computer power supply and most other digital electronics will have 7805 regulator in them.