# wiring multiple leds - pc modding

Discussion in 'Electronic Basics' started by [email protected], May 18, 2005.

1. ### Guest

hi
i wish to wire 6 (or x number) of the same led, using a psu - 12v line.
Most probaly it will be an orange led, thought i should say that as
i've read that the actual colour will effect the resistors ..is that so
?
So simply whats the best way .... ?

2. ### John BokmaGuest

wrote:
find out the Vforward and Iforward for the LEDs you are going to use

(12 - x * Vf)
R = -------------
If

3. ### Guest

thanks.....one thing though
could you elaberate on Vforward and Iforward ((If Vf)?!

4. ### Bob MonsenGuest

Put them all end-to-end (in series) and put a 1k resistor in series too.
That should light them up with 3.6mA. If you want them brighter, use a
lower value resistor, but too low will cause them to fail. The lowest
you probably want to go is 220 ohms.

5. ### John BokmaGuest

wrote:
Those values are given in a datasheet. Vf is different for LEDs with
different colours. If is often around 20 mA, but look it up.

E.g. http://www.lsdiodes.com/5mm/5mmorange.htm

Vf = 1.7
If = 20 mA

( 12 - 6 * 1.7 ) / 0.02 A = 90 Ohm.

So use a 100 Ohm resistor in this case.

6. ### John BokmaGuest

Hence: look up Vf and If, and *calculate*