I am pushing ahead with my RS-36 classification/marker light project. I have ordered a supply of bipolar Red/Green common anode (3 lead) LEDs from Mouser. Now I just need to figure out what I need for resistors, and where to place them.
Here is the mouser page with a link to the data sheet for the LED.
I guess my first question is do I need 2 resistors (615- 650 W / 1/2 W) for each LED, or can I use just one on the common anode? I don't anticipate lighting both colors simultaneously,so my gut is telling me one resistor on the common anode should be enough...
I think I did the math right, but feel free to check my work. My DCC track voltage is between 14.5 and 15V, the LEDs are rated 2.0V (red) and 2.2V(green) and draws 20mA
thanks for your help.
Good point about covering my backside...Thanks
Does my math seem correct to you?
Though I am not a rivet counter, I have noticed the light intensity between the red and green is different. I made some single target block signals for our club using two lead red/green LED's and a couple members noted the difference. Not a big deal. If you think it might be an issue, trim one of the resistor values to match the intensity. Usually the LED specs will spell out the light intensity.
Rich
If you ever fall over in public, pick yourself up and say “sorry it’s been a while since I inhabited a body.” And just walk away.
I would start with 1000 ohms (1K.) These are classification lights, and I think you'll find that they will be brighter than you want with 600 ohm resistors. Of course, you'll have the best results by testing once the package arrives.
One of the handiest "tools" I've got is a set of short wires with alligator clips on each end. It makes testing this sort of thing, particularly when playing "Name That Resiistor," much faster. 5 wires, 5 colors, so there's no guessing which clip is which.
It takes an iron man to play with a toy iron horse.
Thanks for all of the guidance. I will likely use a larger resistor, but I wanted to make sure I had my back side covered :)
I am putting together a lamp resistance tester ala this project fron "DCC Projects and applications" I have modified the design to use a small 2 sided fishing lure box (from Wally World) as the case. It will have the tester on one side and the resistors stashed on the other. I still can't figure out why my wife is always shaking her head whenever she sees me at my work bench...