My group and I have finished our junkyard generator. Here is an overview of what we did (click on the images below to go to bigger versions of them):
The frame was initially made out of steel. Sherman did a good job with this (I will try to get a picture of it to put here.) We quickly discovered that the magnets in the generator had too much of an attraction to the frame and made spinning the axle very difficult. Chad then made the frame out of wood.
You might be wondering what some of this stuff is. The red and black wiring is to connect the generator to the 2 light bulb sockets. We weren’t planning on using both light bulb sockets at the same time, but had both of them so we could use whichever is more convenient. However, the generator was able to light up two light bulbs (one in each socket) anyway! The light bulbs we use are 6.3 V, 150 mA. The one on the board is nice to use because it is front-and-center, but the one at the end of the wire is easier to hold up for presentation purposes. The black and red wires are connected to the magnet wire that is wound around the big gray-colored cylinder at the top of the board.
The gray cylinder is actually the air duct for a computer case fan. I had it laying around, and it was the perfect size to house our 2 magnets. The wire is wound around this, and covered in electrical tape so we don’t accidentally scratch the wire and short the coils (this would be BAD!)
The metal rod is the axle for the generator (the part you spin to get the magnets rotating.) It looks like there is a big blob of electrical tape in the middle of the road, and it is! However, there are actually some magnets underneath that tape. On the right end of the rod is a caster wheel to make spinning the rod easier.
Now for some close-up pictures with more detail and more explanation…
Here is a close-up of the cylinder, magnet wire, and the connections with the higher-gauge wire. We used higher gauge wire to connect to the light bulb sockets simply because it would not break as easily as the magnet wire. There was a little extra length of the red magnet wire, so it is taped down to the base. In this picture, you can see a little bit of the red and green magnet wire on the cylinder underneath the tape. The 2 wrappings are wound in the same direction, and connected in series. We did not count the wrappings, but there is 200 feet of red magnet wire and 75 feet of green magnet wire (from Radio Shack.) The circumference of the cylinder is about (80 mm) x (2) x (PI) = 503 mm. This equates to about a total of about 165 wrappings combined. Winding the wire can be boring. Forrest wound our wire, and I think he did it while watching a movie. I would definitely recommend having something (like a movie) going on so to keep you entertained if you are winding wire.
The lower-gauge wire (i.e., thicker wire) is screwed down and has a knot tied in it so that the fragile magnet wire doesn’t get pulled on and broken.
You can see the magnets on the rod that are covered in tape. The magnets are actually pretty strong. We obtained them from some broken shake-powered flashlights. They stay on the rod pretty well by themselves, but when got the rod spinning REALLY FAST they would tend to fly off towards someone’s head. So we taped them on. This would not be a good long-term solution.
The light bulb sockets conveniently had holes that small screws could fit in. I removed a small portion of the wire insulation, added some solder to the wire to give it some strength, and screwed the socket to the board so that the connections were covering the exposed wire. There is another socket at the end of the wire (not pictured.)
I drilled some holes in the rod (for bolts) and secured a caster wheel to it. The caster wheel is there so that we can press it against a bicycle tire, spin the bicycle tire, and achieve some pretty high RPMs on the generator (due to the bike-to-generator gearing ratio.) You can see from this picture that I used my Dremel to roughen up the surface of the caster wheel so that it would grip the bicycle tire better.
Using a 1-speed BMX-style bike, we were able to produce a frequency of about 36 to 37 Hz (or about 2200 RPM.) This speed lit up our 6.3 V, 150 mA light bulb fairly well.
The generator works well for being made out of junk (hence the name “Junkyard Generator.”) We spent a total of $8 on this: $5 for the wire and $3 for the bulbs and sockets. We should be able to easily get an A on this project unless our bulb breaks or we bomb our presentation on Wednesday.
I thought the next 2 pictures were kind of cool. They are close-ups of the light bulb. The red effect was made by using my hand to partly cover the flash on my camera (the generator light bulb isn’t lit up):