I just noticed an LED on my control panel that was not lit.
All of the LED's on the control panel are 2 leg, and each LED has a resistor wired on one side. The legs of the LED connect to the center posts of a DPDT switch which is powered by a DC transformer.
The green color is not lighting but when I flip the DPDT switch, the red color is lighting. That surprised me. I assume that the LED made contact with the power source somewhere on the leg above the resistor. If it did, wouldn't the entire LED blow so that there would be no light, green or red?
Rich
Alton Junction
Depends on which polarity it got without the resistor. Only the one in the conducting direction would blow with no current limiting, the one currently reversed would not blow out.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
rrinker Depends on which polarity it got without the resistor. Only the one in the conducting direction would blow with no current limiting, the one currently reversed would not blow out. --Randy
I'll be darned. I never knew that.
Thanks, Randy.
Think of a BiColor LED as two LEDs in one case. One can "burn out" and the other still be good.
Exactly. Buy a red and green LED and wire them back to back - boom, bicolor LED. At least the type that only have 2 wires. There are 3 wire types, where one is a common, one wire is the red, and the other wire is for the green. These kind you can't use for the typical inline with the Tortoise motor type of thing. And if you search a site like Mouser or Digikey, you'll find that red and green aren't the only color combinations you can get.