Electrical schoolwork...

[Louis-Alain RICHARD]

Hi there,

If I were to install some red 3V LEDs to backlight the numerous switches
around the instrument panel of my 1983 urQuattro, what is the resistance
value I must introduce to this circuit to lower the 12V to something more
acceptable?

Resistance value of the LEDs: 150 000 ohms 
Ideal voltage at the LEDs: between 2.5V and 3V.
Electrical voltage at the switches: 13.6V, permanent, switched by the
ignition, not the IP rheostat.

My electrical knowledge is so far away (20+ years), I don't remember anymore
how to compute series resistance in a simple circuit like this!

Please light me... and my car!

Louis-Alain
1983 Quattro
85-D-900463