I have recently purchased several Tomar color light mast signals. Each signal has one head with three lights: red-yellow-green. The lights are LEDs. There are four wires coming out of the base of the signal: blue-red-yellow-green. The blue is the common anode (+), while the other wires are the cathodes (-) for each LED. Where in the circuit do I place the current limiting resistor(s)? Tomar states that a 390 ohm resistor can be used for these LEDs, but their wiring diagram shows resistors on every wire, which I have never seen before. Do I place one resistor on the common cathode wire (blue wire) or one resistor on each of the anode wires (red-yellow-green wires)? Thanks, Jamie
I'll assume the signals are wired common anode (your description was inconsistent). In any case, if only one LED is to be lit at a time, you can do it either way. One drawback of placing a single resistor in the common anode lead is that the individual LEDs might not be of uniform brightness when lit. Try it, and if it is an issue, go with separate resistors in each cathode lead and adjust the values of each to suit.
This may not answer your question. But this vendor has some interesting products to activate your signals. I am using the infa red signal animators. They work very well. http://logicrailtech.com/index.htm
