Introduction: Bike Generator
Third Prize in the
Discover Green Science Fair for a Better Planet
Runner Up in the
Park Tool Bike Month
The is my first attempt at a bike generator and I have made many improvements to the project. Check out my new instructable BikeGen for the new generator which recharges 2 AA batteries and powers the lights. BikeGen can also be used to recharge you cell phone or Ipod
I made this friction drive bike generator to power my head light and tail light. I got the idea and a lot of the info for this project from another great instructable personal powerPlant
I recently bought a bike to commute to work and around town and figured for safety's sake I'd get a light set. This is the light I got, Planet Bike 1200, but there are many options for bike lights. There are many instructables on bike lights too. My lights are both 3V, two AA's in the head light and 2 AAA's in the tail light, and the box said the head light will work for 4 hours and the tail light for 20 hours in blinking mode. While this is respectable it still requires some attention. I got this bike for its simplicity, single speed means I can just hop on and go, but replacing batteries gets expensive and complicates things to much. By adding the generator I can power the lights while riding.
Thanks to instrutables member aaronscottaugustinhotmail.com a schematic of the circuit is also available.
Step 1: Gather the Parts
Your going to need a few things if you want to build a bike generator. Here's what they are:
1x Stepper Motor - I got mine from a printer I got at goodwill for $3
8x Diodes - I used 1N914/4148 from Radio Shack #276-1122, the personal powerPlant used 1N4001, Radio Shack #276-1101
1x Adjustable Voltage Regulator - LM317T, Radio Shack #276-1778
1x Project Box w/PC Board - Radio Shack #270-283
2x Resistors -Radio Shack #271-003 You'll need the 150 Ohm and the 220 Ohm
1x Heatsink - Radio Shack #276-1363
1x Battery Connector - Radio Shack #23-445
18-20 gage solid wire
You don't have to get everything from the Shack but I find its easier and roughly the same cost as say Jameco or Digi-Key once you pay shipping.
1x Bike Reflector bracket - I took this off my bike when I put the lights on.
1/2" Aluminum Angle Stock - Both Home Depot and Lowes have this usually in the hardware section or order it from McMaster-Carr #88805K41, You'll need a piece roughly 6in long
Small nuts and bolts - I used the screws from the printer and some other hardware I had, #10-32 machine screws and bolts would be good
Small rubber wheel - This attaches to the stepper motor and rubs against the wheel as it spins. I used a Tamiya 70145 narrow tire because it was what I had.
Dremel - This isn't completely necessary but makes things a whole lot easier
Drill and drill bits
Screw Drivers, wrenches, allan keys - for the hardware
Solderless Breadboard - Radio Shack #276-003 I used this to test the circuit before soldering everything to the PC Board
Step 2: Make the Circuit
Now lets make the circuit. Its a good idea to test everything before you start soldering it all together, so I built the whole circuit on the solderless bread board first. I started with the motor connector and the diodes. I desoldered the connector from the circuit board of the printer. Placing the diodes in this orientation changes, or rectifies, the the AC current coming form the motor to DC current that the lights can use. The stepper motor has two coils in it and you need to make sure each coil is wired to one set of the diode groups. To find out which wires from the motor are connected to the same coil you just need to check for continuity between the leads. Two of the wires are connected to the first coil and two of them are connected to the second coil.
Once the circuit was built on the solderless bread board I tested it. The motor produced up to 30 volts while riding the bike normally. It is a 24volt stepper so this seems reasonable. With the voltage regulator installed the output was a constant 3.10volts. This was the plan. The resistors control the output voltage and the 150 and 220 Ohm resistors were chosen to get 3.08volts. Check out this LM317 Voltage Calculator to see how it was wired up.
Now it just need soldered to the PC board. I used small gage solder to make all the connections. It heats up faster and allows for better connections that only bridge where you want them to.
The .pdf's show how everything is connected to the PC Board. The curved lines are the wires shown in some of the pictures and the short black straight lines are were you need to make the solder bridges.
Step 3: Motor Mount
The motor mount was made from the 1/2" aluminum angle and the reflector bracket. Holes were drilled in the aluminum to mount the motor first. Then one side of the angle was cut out to make room for the wheel. The wheel was attached by wrapping electrical tape around the motor's shaft until there was enough to allow the wheel to be forced over the tape. This method works for now but will probably need upgraded in the future.
Once the motor and wheel were attached to the aluminum I found a suitable place on the frame to mount everything. I mounted mine to the seat tube. My bike is a 61cm frame so the area where the generator is mounted is fairly large compared to smaller frame bikes. Just find the best location on your bike to mount the generator.
After I found a good location I marked the aluminum bracket, with the reflector bracket in place, so that it could be cut to size. Then drilled holes in the bracket and the aluminum and mounted the whole thing to the bike.
I then finished everything off by attaching the project box to the aluminum mount with two 1/2" standoffs.
Step 4: Hook Everything Up
Now all thats needed is to hook it up to the head light. I just pushed the wire ends behind the battery terminals on the head light, then drilled a hole in the light to run the wires through. The wires were then connected to the battery connector. I used this because I wanted to be able to disconnect the the head light quickly. The project box will need slots or holes for the wires for the light and the motor.
Once everything is on go out and ride!
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