Can I power 5 Volt relay coil with 24 volts with the proper series resistor?
I assume this will work. Should i be looking for a resistor that will reduce the current to what the realy coil is looking for? Or should I be looking at reducing the over all power (watts)
Example. 5volt relay coil @ 120 Ohms = 42ma or 210 milliwatts
If I was to drive the same coil from 24 volts should I be looking to limit the current to 42ma or the total power to about 200 milliwatts?
Current limited to .042 @ 24Volts
24 Volts / .042amps = .571 ohms - (120 coil resistance) = about 450 ohm resistor. But the power draw will be about 1 watt!!
Power limited to about 200 milliwatts:
.200 (watts) / 24vdc = about .008 milliamps (is that enough current??)
24/.008 = 3000 Ohms - (120 Ohm Coil Res) = 2.7K resistor.
How should I be looking at this?
Thanks!
Bob