andrew12345678 said:I have ordered 3 16F88 so i will be definately using a PIC.
I guess i'll have to test the magnets and if they arent strong enough i can mount them closer. Good thing you reminded me about the inverse square law, i'll need that for end of year exams![]()
Microchip is actually very good at handing out free samples of their chips. You'll need a non-yahoo/hotmail/etc. email account, though:
http://sample.microchip.com/Default.aspx?testCookies=true
Also, I've found that reed switches work well (perhaps even better), and they in general cost less than an Hall effect sensors.
As for LED brightness, I would get the brightest you can find. Then you can run them at lower currents to save on battery power.
Figure out a way to mount the batteries as close to the wheel center as possible. I rode 40 mi. with a bicycle pov on my back wheel, and I definitely had to work harder to pedal it. I also didn't distribute the batteries evenly around the wheel, so there was an imbalance which was very noticeable at higher speeds.
Finally, consider using AAA's instead of AA's. They are 1/2 the weight but still have 1200 mAH which probably will be enough to power you through the entire race - it all depends on your LEDs.