# Resister value calulation

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#### Mr KAR

##### New Member
Hi in my design i am using 24 volt 8 amps relay.I that circuit to check the relay status iplan to add one led. I want to know that value of that rsister and how to calculate.

Can anyone help to solve this issue.

#### birdman0_o

##### Active Member
[24V - (2 to 3 V)]/20mA = Resistor.
Where do you plan on putting the led, will it be a basic on/off indicator?

#### Mr KAR

##### New Member
thanks i want to check relay is active or not so that i plan to add led.

yes basic on/off indicator

#### birdman0_o

##### Active Member
Yea what I said will work. Just put it in parallel with the other circuitry the relay is turning on.

#### Mr KAR

##### New Member
Thanks. I choose Forward volt 2.3v. So your Calculation shows 1.1k.

#### birdman0_o

##### Active Member
The foward voltage will depend on your specific led, you can find it in the datasheet. 1.1K sounds right for the value you have chosen.

#### Mr KAR

##### New Member
ya thanks in my datasheet shows forward voltage 2.3.

Thanks for youe help

#### crutschow

##### Well-Known Member
Yea what I said will work. Just put it in parallel with the other circuitry the relay is turning on.
If you put the LED and resistor across the relay coil instead of the contact load, you can have any value of voltage or type (AC or DC) on the relay contacts without it affecting the LED circuit operation.

#### birdman0_o

##### Active Member
I can't picture this Carl, do you have a schematic handy?

#### Mr KAR

##### New Member
Relay contact rating is 8A @ 250VAC/30VDC(NO):8A @ 250VAC; 4A @ 30VDC(NC)

I don't have any schematic.

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