North American Turbocoupe Organization



jeff korn pls
Shannon Clark Offline
Member
#1
I have a 1.7 volt led I want to hook up. What size resistor do I need to run it off of 12 volts. Im building a "shift light " for the TC.
11's in a TC.........Soon
Currently 12.002 @114.77
11's next year I promise!
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Joe F Offline
Posting Freak
#2
To run the LED safely at about 25mA of current, here's how to figure it:

Resistor Value = (source voltage - LED voltage) / LED current

Resistor wattage = (source voltage - LED voltage) ^ 2 / Resistor Value

So: (13.8 - 1.7) / .025 = 484, so use a 470 ohm resistor (I used 13.8 volts because that's the "normal" auto operating voltage).

Wattage: (13.8 - 1.7) ^ 2 / 470 = .311 watts, so use at least a 1/2 watt resistor.

Simple ohms law, E=IR and P=IE. HTH and educates a little.

P.S. Moved to electrical forum.
JR's Place - My '87 Turbocoupe
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Shannon Clark Offline
Member
#3
Thanks for the info but I wanted to get going on this project. I ended up buying a 194 Aotomotive socket LED.
11's in a TC.........Soon
Currently 12.002 @114.77
11's next year I promise!
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