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Do I Need to Add a Resistor to a Relay Circuit

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tmort

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I want to use a 5V relay to switch a 12 volt light circuit on.

I know how to wire the relay except I have a question. My relay will be open with the coil is energized and closed when the coil is de-energized. I'm wondering if I should add a resistor the coil part of the circuit to limit the amount of current passing through the coil. The circuit will be a battery operated circuit and I want to minimize battery drainage. Also, if it is advantageous to add a resistor, should I add it to the positive or negative side of the coil.

TIA
 

A relay actuates on current, not voltage. You will need to supply
the pull-in current min value. If you have an excess voltage
you could drop some across a resistor. But more appropriate
would be to find a relay whose coil current, for rated / required
contact current, is a minimum.

As a rule, for low to medium load currents a transistor
(MOSFET) low side switch is going to be much more efficient.
 

I'm not familiar with MOSFETs. Can you elaborate a little on what a low side MOSFET is and what I should look for. My 5V signal is about 200 mA and the 12V load is about 1A.
 

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