# Relay Coil Rating

Thread Starter

#### vindicate

Joined Jul 9, 2009
158
I was looking at a 5v coil relay to switch 120VAC. The nominal current was listed as 200mA. So is nominal current the max current it needs? The minimum current it needs? Or what? How does that work? Does it draw what it needs?

Could I give it 6 or 7 volts but with a resistor inline to limit the current?

#### KMoffett

Joined Dec 19, 2007
2,918
Can you post a link to that particular relay?

Ken

#### beenthere

Joined Apr 20, 2004
15,819
Just place a diode like a 1N4000 in series to drop the excess - for 7 volts use 2. Relays are not sensitive to overvoltages, but the coil will heat and possibly fail.

#### mik3

Joined Feb 4, 2008
4,843
Yes, it will draw 200mA.

You can use a resistor with an appropriate value to limit the current if you drive it with higher voltages.

Thread Starter

#### vindicate

Joined Jul 9, 2009
158
Yes, it will draw 200mA.

You can use a resistor with an appropriate value to limit the current if you drive it with higher voltages.
So with the 5v 200mA example I gave I could use a 10v supply and a 25 ohm resistor rated for 1watt?

#### mik3

Joined Feb 4, 2008
4,843
So with the 5v 200mA example I gave I could use a 10v supply and a 25 ohm resistor rated for 1watt?
Yes you can!

Thread Starter

#### vindicate

Joined Jul 9, 2009
158
Yes you can!
Excellent. Thanks you.

Last question. Pull In Voltage. It's listed at 75% or less of nominal voltage. So If I have a 5V coil, could I technically power it with 4V and it would work fine?

#### mik3

Joined Feb 4, 2008
4,843
Excellent. Thanks you.

Last question. Pull In Voltage. It's listed at 75% or less of nominal voltage. So If I have a 5V coil, could I technically power it with 4V and it would work fine?
Yes you can but it is better to power it with the nominal voltage.

Thread Starter

#### vindicate

Joined Jul 9, 2009
158
Yes you can but it is better to power it with the nominal voltage.
Alright, thanks for everything

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