New to this site and I need some help to how to find the current

Thread Starter

Kevinscouch

Joined Jun 23, 2020
14
My source voltage is 12 volts. LED forward voltage is 3 volts and the forward current is 20 mA. I can do the math to get the resistor values and the wattage values for the resistors. However I try, I do not know how to find the current that the array draws. I have tried Ohm's law and Watt's but I just can not come up with the array drawing 100mA from the source. Would be thankful for any and all help. This information was put into the LED.linear1.org website.
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Last edited by a moderator:

ericgibbs

Joined Jan 29, 2010
10,208
hi Kevin,
Welcome to AAC,
Each string draws 20mA and there are 5 strings, so 5 *20mA =100mA
Is this what you are asking.?
E

Update:
3 * 3Volt LED's = 9V drop across the LED's , leaving a 3V drop across the 150R. I= 3V/150R = 20mA.

1 * 3Volt LED's = 3V drop across the LED's , leaving a 9V drop across the 470R. I= 9V/470R = ~20mA.
 

Thread Starter

Kevinscouch

Joined Jun 23, 2020
14
Thanks so much Eric. I don't know how I could be so silly. It has been a long time since I have sat down and worked the math on a circuit.
 
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