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Meindert Sprang
 
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Default Need help with electronics circuit

"Norm Freedman" wrote in message
om...
Thanks for all the suggestions.

This is really a simple application. I have no trim tab indicators.
All I really need to know is if they are fully retracted or extended.
When that happens, the motor current goes from about 8 amps to about
15 amps. Most of the time, the circuit is off. I just thought this
would be a simple way to tell, using a waterproof LED.


The most simple approach is to use a reed contact. You simply wind the power
wire to the motor around the reed contact (a glass tube and the current
though the coiled wire will produc a magnetic field that closes the reed
contact. The number of turns needed depends on the sensitivity and size of
the reed contact but can be determined by experiment. The goal is to find
the ideal number of turns that does not close the contact at 8 amps, but
does so at 15 amps. This solution gives no voltage drop or heat loss. And
the obvious: you switch the LED with the reed contact :-)

Meindert