# Calculate how to size a resistor for following circuit?

Have a DC supply that varies from 48-54VDC that is supplying a relay that works between 12-48VDC. We have a 475 ohm resistor in series to drop the voltage but we continually keep blowing up the electronic relay.
We are now looking at connecting a zener Diode (39V 1W) and keep the series resistor. Will we need...
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Have a DC supply that varies from 48-54VDC that is supplying a relay that works between 12-48VDC. We have a 475 ohm resistor in series to drop the voltage but we continually keep blowing up the electronic relay.

We are now looking at connecting a zener Diode (39V 1W) and keep the series resistor. Will we need to change the size of the resistor?

Could someone show me how to calculate this?

We are now looking at connecting a zener Diode (39V 1W) and keep the series resistor. Will we need to change the size of the resistor?

Could someone show me how to calculate this?

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