Model Railway Forum

Running 3.3v LEDS on a LAIS DCC controller function wire. Reading the manual suggests the function connection is the same voltage as the track, does anyone know the size of resistor to take DCC track voltage to 3.3v?

I did have them working for a run before I fried them and they looked great

Thanks

Just use a 1K (1000 ohm) resistor, it'll be near enough. If that's a bit too bright use a higher value.

Decoders normally output 12 volts DC on their function outputs. The Blue wire being the Positive to all other colored function wires which are switched negatives.
Note some mobile decoders offer the option of being able to reduce the function voltage via CV settings, however, this option is not always provided.
As a minimum the LED should have a1K0 (1000 Ohm) series resistor. The actual Ohm value will depend on the brightness required of the lit LED. Higher Ohm values up to 10K or more can reduce LED brightness.