2nd Gen Non-Engine/Transmission electrical question

[JWRowe]

Could one of the electrically gifted members give this a try? I am looking to cut down the voltage to a size 1 3/4 LED. I want to hook up several of them to switches (one per switch function) that control my various accessories and I do not know what to use for resistors. I have been told that this size LED operates at or near 2V. The guys behind the counter of the several Radio Shacks that I have been to just look at me with a blank expression. Any help would be appreciated.



Thanks in advance,

John

 

[rfcom]

The value of the resistor will depend on how much current you want to run through the LEDs. The current directly affects the brightness. I would start with 20 mA and adjust from there. The 2V drop sounds right for a T1-3/4 LED. Assuming a nominal 13 volts from your battery supply, we can make the following calculations:



R = (Vb - Vf) / I



Plugging in the numbers, we get 550 ohms. The nearest nominal values are 560 or 510 ohms. Try one of these values and adjust it to adjust the brightness. Don't exceed the max rating of the LED though or you'll burn it out. HTH



Jim

 

[JWRowe]

question

rfcom



Thanks for the reply. Trying to figure this for myself is beyond my capabilities. I will use your info as a starting point. Again, Thanks.



Regards, John

 

[jkern]

radio shack makes 12 volt LEDS. (they already have the current limiting resistor in them with a nice snap bezel mount. i think you can only get them in red though. don't have the number handy, but i have about 15 of them at home... . bought out the three local radio shacks when i found them