"E. Walter Le Roy" wrote in message
link.net...
| We have a 7 foot water wheel in a mountain stream and would like to hook
up
| an alternator, and light up the fish pond. Can anyone tell me what RPM it
| needs to turn to run one headlamp?
| Thanks
| Walt

About 1500-1700 rpm to get most to "bootstrap" themselves on. You'll
need some source of power to let it think there's a battery there. Any 12V
lead acid battery, even motor cycle or lawn tractor sized, will give it what
it needs. I was trying to figure out if you could use diodes to keep the
battery from driving the load, but it isn't coming to me. I'd have to draw
it out, I guess. I did a project a few years ago for my kids' science fair
project where I drove an alternator with an AC motor and pulled the three
phase out to drive the project. I got 14VAC and with a transformer bumped a
pair of phases up to 50V, which is as high as they let me go anyway. At the
time I just used a wall wart for 12V and had a pushbutton to "start" the
alternator.