alt.energy.homepower

-> Stepper motor has two pairs of wires (a pair reads about 50 ohms).
-> These go to the ~ ~ terminals on the bridge rectifier. The two +
-> terminals go to the cap. The - terminals and the other end of the cap
-> go to ground. That's your 12V power supply for your cf lamp.

I'm sceptical about this circuit. If you just have the cap, it will
charge up to the input voltage, then take no more current, so the motor
will not act as a brake. If you put a neon lamp across it, the lamp
will "strike" at some voltage and discharge the capacitor down to some
lower voltage, then repeat. The braking effect will be periodic, and
the energy will be dissipated in the neon, which won't take much
without burning out.

Much better, make a circuit with a zener diode, a power transistor, and
a couple of resistors, one of which should be capable of dissipating as
much power as needed. Call that one R1. Connect the + side of the zener
and one end of R1 to the + output from the bridge rectifier. Connect
the other end of R1 to the collector of the transistor (assumed NPN).
Connect the - end of the zener to the base of the transistor and to one
end of the other resistor (R2). Connect the emitter of the transistor and
the other end of R2 to the - side of the bridge.

Values? R2 should be biggish. Maybe 10K. R1 should be smaller, maybe
100 ohms. The zener voltage should match the voltage output by the
bridge when the windmill is turning at the desired maximum speed.

When the mill is turning slower than the maximum, no current will flow
through the zener and the transistor will be cut-off. No current will
flow, so there will be no braking effect. When the maximum speed is
reached, the zener will conduct, the transistor will turn on, and
current will flow through R1, dissipating energy. The mill's speed will
stay very constant.

That's how I'd do it, but then I'm much more familiar and comfortable
with electronics than hydraulics. Other people will have different
preferences.

dow