DinoFab ~~ Stepper Motor Powered Bike Light - Build your own power source with a stepper motor and your bicycle!

Stepper Motor Powered Bike Light

In this project you won't find some sort of "free energy"... but you will find converted energy in the form of electricity that can power an LED light system on a bicycle, all from a re-purposed stepper motor!

Let's start with a list of supplies you'll need for this project:

First there's the stepper motor. Most older printers will have one or two stepper motors inside them. How do you know if it's a stepper motor? It will have 4, 5 or 6 wires coming out of it. They usually have some kind of gear or drive wheel on one end. It doesn't need to be big to produce the amount of electricity we need. Smaller is actually better in this case.
READ>>More about generating electricity with stepper motors<<READ

Rubber drive wheel. You will need some kind of rubber wheel to mount on the stepper motor, unless it has one. I found that the rubber grommet selection at the hardware store proved to be a good place to find a suitable wheel. You'll want one larger than the diameter of the motor. This will allow the motor to be mounted near the wheel with the rubber drive wheel touching the bicycle wheel's rim. See photos 1, 2 & 3 below. The hole in the center of this wheel should be small enough so as to be pressed on to the existing gear that's on the stepper motor and epoxied in place.

LEDs. 1 white, 1 red. 2 Optional yellow side markers. I used large 10mm diameter LEDs on my bike for this project. These are high intensity with a narrow field of view so they appear very bright to oncoming traffic. See Photos 4 & 5.

4 feet of small gage insulated wire. I used some wire from the laser printer that I got the stepper motors from. An added benefit was the plug for the stepper motor was already wired on!

Small hose clamps. These will be used to clamp the motor mount to the bike frame.

Misc. bits of metal and other hardware. Since I don't know just what stepper motor you will end up using, I can't tell you exactly how to mount it, just give you some ideas here and the basic location criteria. You'll need some sheet metal that you can fabricate into a right angle bracket that will be clamped to the front fork, or perhaps one of the rear seat stays. You'll also need some small machine screws, nuts and washers to mount the motor to the angle bracket. Finally you'll need some springs of various lengths to put tension on the motor so that it makes contact with the spinning bicycle wheel. See photo 3.
I'll assume you have a soldering iron and solder and know how to use them.

We begin this project by mounting the drive wheel to the stepper motor. This can be done with some 5 minute epoxy. Make sure you don't get extra epoxy on the motor shaft! Keep everything as clean and free of extra epoxy as you can. See photo 1 for my example.

The next step is perhaps where your engineering skills will get a good workout. Mounting the motor to the bicycle fork.
Criteria:
1. It has to be able to pivot and it must touch the rim in a manner so as to allow it to be spun by the friction of the rim in motion.
2. It will need to be spring loaded on it's mount so that it is being tensioned into the rim.
3. It has to be sturdy enough to accommodate bumps and shakes. Remember, your mounting a fairly good chunk of mass on this thing and it has to be stable while riding.

Once you get the motor mounted in place, the wiring is quite simple. Since we're dealing with AC voltage here, we can connect the LEDs any way we want. Polarity doesn't matter in this project, but I still prefer to connect the shorter lead, the cathode, to my chassis ground. To do this, I simply drilled a small hole in the bike fork and installed a machine screw. I attached the common coil wire from the stepper motor to this screw. See photo 1.
This allowed me to run just one wire to each light and simply ground the negative lead of the LEDs to the bike frame. See photo 6.

NOTE: Since the different color lights have a different operating voltages, they need to be connected to separate coils. Since you read the link above I'll assume you know that there's a common wire, or set of wires, and the other wires are the ones that supply the AC voltage for this application. Just connect the red LEDs anode to one coil wire, the white to a second coil wire etc.

I used 5 minute epoxy to mount the lights to metal tabs which were attached to the brake mount bolts. This is where reflector brackets usually mount so if you have them on your bike, by all means try to utilize them as a mounting point for your LEDs. The metal bracket can be used as a ground for the LEDs.

I used some spare cymbal washers ( I'm also a drummer) as reflectors for my lights. Very Robo-chic. :)

Make sure the motor spins easily and that the rim of your bike is true and not too out of round. All of that will add to the stress on the motor mount. You will observe that the spring tension on the motor mount will keep the drive wheel in contact with the rim as it spins so a bit of wobble in the wheel is ok.

When you go out for a test ride, be aware of where you're going! It's very easy to get caught up in reveling in your success as you stare at the pretty lights and plow into a curb!

Have fun building your bike light system. You'll enjoy many hours of safe illuminated night riding and the energy source is YOU! Enjoy your lights and the "free energy" . (wink)

Click on a photo below to view large version.


Photo # 1 Motor mount	Photo # 2 Stepper motor and rubber wheel	Photo # 3 Motor mount spring


Photo # 4 Front lights. I added side markers.	Photo # 5 Rear light.	Photo # 6 Light wiring detail.