Don't remember, but 470 ohms 1/2 or 1/3 watts plain carbon should do.

Depends on max allowable current for the LED and its rated voltage.

Lets assume max 16 volts.
LED voltage 2.3 volts and 0.030 amps (30 mA):
(16 - 2.3) / 0.03 =  457 ohms.

470 ohms is a standard value (390 ohms is next lower value, which might be better).
Assuming max battery voltage of 13 volts and LED voltage of 2.3 volts:
(13 - 2.3) / 0.030 =  357 ohms.

P = I * I * R =  0.030 * 0.030 * 470 =  0.42 watts.
P = I * I * R =  0.030 * 0.030 * 390 =  0.35 watts.

The above examples should give you enough info to recalculate once you have the LED specs.
The resistor is used to limit the current through the LED. The higher the resistor value (ohms) the less current.

Finn

paul wrote:

Thank you very much for the info, Finn....sounds even simpler than a diode and a relay. Do you have any information regarding the resistor? (type, resistance, bought at Radio Shack, etc)?   Thanks again.  Paul Conner

----- Original Message -----

From: Finn Lassen

To: Rotary motors in aircraft

Sent: Sunday, August 29, 2004 2:01 PM

Subject: [FlyRotary] Re: alternator connections

Has not been true for me. LED and resistor in series only has been working well from day 1.
I beleive my Mitsubishi is the stock RX-7 alternator.

Finn