Hi, We just put together a basic "pedal power" demonstration bike, using a belt on the rear wheel as a large pulley and a small pulley on the alternator mounted behind the seat... we figure that with the current gearing, we have it spinning at around 3500 rpm....
somewhat similar design to this site:
http://www.c-realevents.demon.co.uk/altgen/altpedgen.htm
anyways, the alternator we are using is off of an older watercooled vw, it has an attached voltage regulator.... We would like to charge a 12v battery with it for a stereo/ etc for demonstrations...
The alternator + voltage regulator has 2 contacts (attached together, (+)), the casing is hooked to ground, and it has a 3rd wire that I believe is for a charge warning light...)
When we pedal with just the + and - contacts hooked to a battery, it doesn't put out a charge, so we tried the internet and came across the above mentioned site, below is a direct link to their wiring diagram...
http://www.c-realevents.demon.co.uk/altgen/hrcircdiag.GIF
I could not completley understand what the circuit on the above mentioned link is doing, and tried to replicate it, but couldn't find any resistors that were even close to the ones they are using (or the right size light bulb)....
Is my thinking correct that they are just using resistors to regulate the "difficulty" of pedaling?
I understand that in order for the alternator to start charging, the field coil must be energized.... However, I am not quite shure how to go about that with the resources we have avaliable (scrounging parts, etc)... I tried running a small power supply (12v) to the (+) contacts on the alternator, and this did not start charging at ~14v...
I also tried using a light bulb (12v, 5w) in the same manner as the circuit above describes (from charge warning terminal through bulb to (+) terminal)... what difference would using the 24v 3w bulb they describe make? (it seems to me this would just change the speed the alternator cuts in at...?
Well anyway, we would greatly appreciate any help in simplifying or explaining these concepts or any errors in our thinking.... By the way, the alternator was working when we pulled it from the car..
Thanks for your help!