"Greg Mayman" bravely wrote to "Mike Ross" (05 Sep 03  08:30:00)
 --- on the heady topic of "VEHICLE LED'S"

 -=> Mike Ross said to Wayne Chirnside
 -=> about "VEHICLE LED'S" on 09-02-03  21:36.....

 MR> Consider that 1mph is about 1.5ft/sec and a wheel periphery measures
 MR> about 7 ft, then 1 revolution/sec = 4.75mph, so 20mph is only about
 MR> 4.2 rps or 252 rpm. A 60 hz generator needs turn at 3600rpm! Luckily

 GM> What has 60Hz got to do with it? The bulbs aren't that sensitive
 GM> to frequency. They will work from DC up to megaHertz.

True the bulb doesn't care but it matters to the power generation. It
has to do with the magnetizing self-inductance. The output voltage will
drop as less lines of force are cut each second and the magnetizing
impedance rises. An a.c. generator will not produce DC and does cutoff
at a low frequency. You can feel that effect in how the generator steel
pole piece tends to line up with the magnetic poles. It's like the
effect in a stepper motor.

If you connect the dynamo output to an audio preamp, you can hear the
lines of force clicking as you gently move the rotor very slightly. I
forget what this clicking effect is called. You can also hear it with an
electric guitar going through a fuzz box. When the strings are gently
moved one can hear that magnetic clicking effect.

 Mike
 ****

... A fail-safe circuit will destroy others.
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