At 04:06 PM 7/9/01 -0500, you wrote:

>rated at 380mA and thus should not be all that loaded with 80mA. So the coil
>current is likely to be even higher. Ok, so we need a bigger transistor, and
>the saturation voltage won't quite be negligible. But still, that seems like
>a lot more current than specified.

If you have current to burn, as in the original question, you can just put
a resistor in series, reducing the nominal coil voltage (after things settle
out) to nominal under nominal input conditions. Use the next lowest relay if
the voltage isn't close enough.

Too low voltage and you can reduce the life of the relay, or it may fail to
pull in properly under low line conditions and high ambient temperature.
Too high and the coil gets too hot, meaning failures or shortened life
under high ambient temperature conditions. The coil resistance increases
with temperature, so there is a bit of self-regulation.

>Looking in a DigiKey catalog, i notice some Omron relays have a %of rated
>voltage for continuous operation. This goes from 110% to 200% Guess you can
>do it with some relays more reliably than others?

You have to look at the temperature derating and maximum Ta compared to the
actual maximum Ta for your application. More sensitive low power relays
tend to be more forgiving of high coil voltage (200% voltage = 400% power
and about 4 times the temperature rise).

Best regards,
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