Resister value calulation - Electronic Circuits Projects Diagrams Free

Mr KAR · 20th October 2009, 07:43 PM

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 · 20th October 2009, 07:48 PM

[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 · 20th October 2009, 07:52 PM

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

yes basic on/off indicator

birdman0_o · 20th October 2009, 08:30 PM

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

Mr KAR · 20th October 2009, 08:35 PM

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

birdman0_o · 20th October 2009, 08:46 PM

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 · 20th October 2009, 09:47 PM

ya thanks in my datasheet shows forward voltage 2.3.

Thanks for youe help

crutschow · 20th October 2009, 09:59 PM

Quote:

Originally Posted by birdman0_o

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 · 20th October 2009, 10:02 PM

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

Mr KAR · 20th October 2009, 10:09 PM

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

I don't have any schematic.

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20th October 2009, 07:43 PM	#1
Mr KAR	Resister value calulation 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.

20th October 2009, 07:48 PM	#2
birdman0_o	[24V - (2 to 3 V)]/20mA = Resistor. Where do you plan on putting the led, will it be a basic on/off indicator? __________________ Mike My website: www.ElectroBird.net

20th October 2009, 07:52 PM	#3
Mr KAR	thanks i want to check relay is active or not so that i plan to add led. yes basic on/off indicator

20th October 2009, 08:30 PM	#4
birdman0_o	Yea what I said will work. Just put it in parallel with the other circuitry the relay is turning on. __________________ Mike My website: www.ElectroBird.net

20th October 2009, 08:35 PM	#5
Mr KAR	Thanks. I choose Forward volt 2.3v. So your Calculation shows 1.1k.

20th October 2009, 08:46 PM	#6
birdman0_o	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. __________________ Mike My website: www.ElectroBird.net

20th October 2009, 09:47 PM	#7
Mr KAR	ya thanks in my datasheet shows forward voltage 2.3. Thanks for youe help

20th October 2009, 10:02 PM	#9
birdman0_o	I can't picture this Carl, do you have a schematic handy? __________________ Mike My website: www.ElectroBird.net

20th October 2009, 10:09 PM	#10
Mr KAR	Relay contact rating is 8A @ 250VAC/30VDC(NO):8A @ 250VAC; 4A @ 30VDC(NC) I don't have any schematic.