Hand Crank Generator

The hand crank generator makes power when you crank it vigorously. Just plug it into a motor, hold the crank body with your left hand and crank clockwise with your right, and the motor on the output wire will turn. You can also use it anywhere else that a power source is needed -- like to charge up a powerpack.

Sourcing Parts

The Hand Crank Generator is composed of two inexpensive and commonly available components wired together: A generator (a driven DC gear motor) and a 5V power converter module. The generator makes the power, but it does it wildly in a range between 12 - 24 Volts depending on how hard its cranked. The power converter takes that dirty power and conditions it so it always comes out at a relatively clean 5 Volts. You'll find links below, but don't think you need these exact parts: anything electrically equivalent will work.

Hand crank dynamo

A robust hand crank that spits out power in the roughly 12 Volt / 20 Watt range so the step down converter can condition and reduce it to 5V. Something like the link below. These appear to be widely available at low cost on Ebay and many other vendors. Make sure to buy one with a crank, as there doesn't appear to be an easy way to make and attach one short of doing difficult metalwork.

Vendors: - Aliexpress - EBay

DC-DC step down 5v power converter

Something that takes 9-35 Volts of DC input current (with a diode to prevent reverse current flow) and spits out 5 Volts DC relatively regulated. It's nice if it has an indicator light.

Vendors: Aliexpress

Bridge Rectifier

The bridge rectifier takes positive or negative power from the generator and converts it to a single polarity of output. This allows the crank generator to work no matter which way it is cranked.

Vendors: - Mouser

Miscellaneous

• XT30 female connector (which looks like a "plug" and not a "socket") with wires soldered on to make the output cable, or an XT30 patch cable with the male (which looks like a socket) end cut off.
• 2 x 10 cm pieces of stranded wire (14-22 gauge will do), ideally in red and black.
• heat-shrink tubing for generator terminals
• 1.5 inch / 36mm inner diameter x 40mm outer diameter silicon tubing cut to 11 cm lengths. It should just fit around the round motor body on the back of the crank generator, but you can hose clamp it on if it doesn't already fit tightly enough.
• 7 hole length of plumber's strap, to crimp end of tube.
• small bolt that fits through the holes in the plumber's strap (approx. 4mm), nut, and a lock washer. These will keep the tube crimped at one end.

Tools you will need:

• Soldering iron
• wire strippers
• small screwdriver (for power converter terminals)
• heat gun (for heat shrink tubing on generator terminals)
• voltmeter (for testing output of generator)

Assembly Instructions

1. Attach the crank to the body of the generator gear motor. If it didn't come with a bolt that fits the driveshaft hole tightly, a large cotter pin makes a good substitute. Bolts that are too skinny tend to get sheared off.

2. Cut two wires (color doesn't matter) to about 6 cm length. Strip the insulation off of the ends. Solder your wire leads onto the terminals on the back of the hand crank generator. Heat shrink the connection to the terminals to make sure that they don't short against the electronics you will embed in the pipe right next to them.

3. Examine your bridge rectifier. Notice the small + and - symbols printed on one side of the rectifier above the two outside legs. These are the output of the rectifier. We need to solder the positive leg to the input on the power conditioner, and the negative lead to the ground (center) pin. Fold the two inner input legs of the rectifier up over the back of the square rectifier package. Bend the two outer leads of the rectifier inward with a pair of pliers. Place the rectifer on the bottom of the upside-down power converter so that the negative lead is close to the power conditioner's center ground terminal pin, and the positive lead is close to the input terminal pin.

4. Solder the rectifier's + output to the input of the conditioner, and the - output to the ground of the conditioner. Now solder the leads from the back of the generator to the input (wavy line) center leads of the rectifier. Polarity doesn't matter here. But we don't want any of the wires and legs to touch (short circuit) together, so use some electrical tape or heat shrink to insulate them if you think it's possible they might touch.

5. The XT30 output wire gets bent around a lot in the course of use, so we need to provide some strain relief so it won't eventually break. You can try to stick it through a small piece of clear tubing that's only slightly bigger than the wires. If it's too big to fit through, just cut a slit down one side of the clear tube, and then fit it over the output wire. Put your XT30 output lead into the output and ground screw terminals (red for 5V out, black for GND). Polarity does matter here.

6. You can now place the large silicon pipe over the power conditioner and around the back of the generator as well. If it's loose, you may need to use a hose clamp to keep it attached. At this point you can test that everything is working by plugging in a voltmeter to the output terminals of the XT30 and see that it puts out 5V when you crank it.

7. Cut a piece of plumber's strap that's 7 holes long and fold it in half so that the holes align. Place it over the back of the silicon tubing so it holds it closed. Jam a sharp punch or a small phillips head screw driver through two holes to make a path for the bolt.

8. Push the bolt through the strap and the tube and place the nut and lock washer on the other end and tighten. This should form a clamp that holds tightly around the tube providing strain relief for the XT30 output cable. It needs to hold tightly so that when kids pull the output wire, the strain just pulls against the outer tube

9. When complete the generator should look about like this, though a longer wire has some advantages. Make sure that it provides 5 Volts of output when cranked either way.

Desired improvements

For future revisions, here are a some desired improvements.

1. It would be nice if the time to crank up a 5F powerpack was a bit shorter. I'm not sure why this one takes longer than the rev. 1 blue box cranks. Possibly they have better power conditioning circuitry that lest more power through.
2. The rev. 1 cranks also gave a kind of clearer feedback when the powerpack was full, in that the crank would suddenly get easy to turn. You can sometimes feel when the power pack is full with the latest revision one, but it's not as clear for some reason. That intuitive felt feedback is nice though.

Past revisions

Rev. 2a and 2b. A Little too Cheap

2a. Was a clear handheld one with a lightbulb that lit when you spun it. It strips the gears when you crank too fast, feels flimsy, and takes too long to charge a powerpack. And we had to add a diode in to keep the powerpack from back driving it like a motor. It was nice that it was clear though. You can kind of see it in action on this link to a Toot on Amos' Fediverse.

2b. Is a cheap little USB one. About 1/2 of 5 I ordered didn't work, they charge very slowly and broke very quickly. Junk, unfortunately.

Rev. 1. The Blue Box

• Charges quickly and can be set to 5V and many other voltages, which works well but adds risk and complexity. If the kids set it to any higher voltage, it will blow up the component it is plugged into. We put duct tape over the controls and made an XT30 charge wire, and this worked fairly well. But it's much more expensive than later revisions, and also larger, heavier, and seems less robust.
• Note of risk: Using the USB output doesn't confine it to 5 volts, which means if you plug anything USB into it and set the voltage higher than 5, it will probably blow that up too. :(