Signals

[Mem-160]

I am going to be scratchbuilding a few signals, and re lighting some old ones, preferably all with bicolor LEDs. Is there any benefits or disadvantages with 3 leg or 2 leg bi polar LED's?

Thanks,

- Mark

[ApproachMedium]

2 leg ones use polarity to make red or green, and pulse back and fourth to make amber color which usually requires a special controller or circuit. In my honest opinion, now with 4 leg 3 color surface mount LEDs there is really no need to go with the two leg bi polar units unless you are trying to conserve signal system controller outputs. The 3 leg bi-color LEDs (one leg green, one red, both on makes amber) usually need an adjustment pot for one of the two colors because the signal will look either too red or too green when trying to do the amber color. This is the simplest LED to use however when trying to be conservative about signal system controller outputs and requires the least amount of additional hardware.

A friend of mine at the Lehigh and Keystone valley model railroad club in Bethlehem PA has been using 4 leg 3 color surface mount units glued in the back of searchlight heads and they are amazing. The color output is fantastic, and the look is very realistic once you add a lense over the LED vs. the older style LEDs where what you saw sticking out of the signal was the LED. Check out their FB page, my buddy constantly posts photos of their various signal projects that are based on Reading, Lehigh valley, CNJ and some PRR signal practices.