hooking up leds to 12v or what???

[delta88]

In reading down about the translucent microswitch led thingy I would like to get pink microswitch buttons and light them up...i am going to use a keyboard or joypad hack for this project so i will power the leds from the pc power supply...........any ways long story longer I canneot remember how to hook leds up without blowing them....i.e. resistor wise...the whole shibang..
thanks

[ErikRuud]

LED/Resistor info.

http://www.7volts.com/led_resistor.htm

http://ourworld.compuserve.com/homepages/Bill_Bowden/led.htm

General LED Info for the curious:
http://ledmuseum.home.att.net/

[aramis]

I haven't dealt w/ LED's in a long time, but here is what I remember....  

I would use the 5V instead of the 12V of the PC power supply. Then, throw a 1/4W resistor in series with the LED so you don't burn it out. (Remind me...don't normal LED's run on just 2-3V DC?) You may have to experiment w/ different resistor values to try to get the brightness just right, but start w/ a 1K or so. IIRC, led's are current driven, not voltage driven so just remember the ol' V=IR formula. Depending on the number of led's (and total resistance) you might have to keep an eye on the total current draw from your +5V supply.


There are some super-bright BLUE led's available that run on 5V...they are like $5 each, but might look pretty cool, depending on the button color.

[JMDickson]

Minimum voltage varies by the LED color and design, but all requre under 5 volts.  You should be able to run most from 12v, but you will need a higher ohm resistor.

ir/red 1.2-1.5v
green 1.5-2v
blue/uv 3.5-4v