Hi All, thought I knew how to wire up signals but have hit a snag. I have purchased some led red/green signals and find that the power is through the earth, and the red/green work on power. My question is, how the heck to I wire these through a SPDT toggle switch??? These appear to be the opposite of the normal led signal wiring. Any help will be greatly appreciated.
If you mean they use a common anode configuration then wire power ground to the common terminal of the switch and the ground/cathode to each of the switched outputs. Then wire the + power directly to the common anode lead on the signal. Make sure to have a proper voltage drop resistor in line if you are using voltage greater than what the LEDs are rated.
Hi John, Normally the Anode side (long lead) of a LED is positive. To use a SPDT toggle switch, I'd connect the positive input to the center terminal on the DPDT, connect the positive lead from one LED to one of the outside terminals on the SPDT, connect the positive lead from the other LED to the opposite outside terminal on the SPDT and tie all the negatives together. If this is the method you used and it did not work, flip the positive and negative wires on your power supply and see if that lights the lights. Also be sure you are using the correct voltage for the LED's, too much current / voltage will burn them out in a flash.
RICH is spot on right. QUESTION: Is this a two color LED? Some LED's are made that if you send current one direction through the inputs, it goes to RED, if you reverse the current and sent it the other way, the LED goes to GREEN or other color. How many leads are on the LED? Two or three? If there are THREE leads one will be a ground and the other TWO are for power. One for RED and one for GREEN. They are tied together internally to the common [ground] lead. Use a multi meter and SMALL power supply to test which is which. Go light on VOLTAGE till you find out. They can make a QUICK snap that tells you, that you are going to get a NEW LED! Check the pack the LED or the LED itself for maximum voltage allowed. Usually on the LED or package.
I have some bi-color common anode LED's on my layout to indicate turnout positions and have a drawing in my media. DualLED by nscalestation posted Aug 7, 2021 at 9:44 AM The reason that there are two different values of resistor is that on some LED's one color may appear brighter than the other so I was trying to even them out. If that is not an issue then just one resistor can be used on the common side.
Sweet! Glad it made sense enough for you to work with it. Brad's (nscalestation) drawing is the perfect illustration for what I was explaining so worth keeping that in your information arsenal as well.
That diagram is nice, but it will never work. The current is flowing uphill (must have been drawn by a physicist.) That'll back the toilets up into the warp drive!
What's worse; when I printed it out so I could turn it upside down to make it work, the whole diagram disappeared!!!
