Using the wrong style dual color LEDs on your turnout control panel with tortoises

You done did it. You ordered some dual color LEDs for your switching control panel, You wanted 2 legged ones, that glow red in one direction and green in the other direction. By mistake, you ordered 3 legged common cathode 2 color LEDs. Oops! but you can still make use of them, if you also have or can get many diodes like 1N914s. Looking at the diagram attached, take two of the 3 legged LEDs and wire 1st's green lead to the 2nd's common cathode. And the 2nd's green lead to the 1st's common cathode. Now take a 1N814 diode and connect its cathode to the 1st LED's red anode lead. And the diode's anode connects to the 1st LED's common cathode. Do the same with the 2nd LED using a 2nd 1N914. Now you can put this circuit in series with the Tortoise coil, and with the. tortoise thrown one direction, the 1st LED should glow red, and the 2nd green. And throw the tortoise the other way and the 1st LED should now be green and the 2nd red.

You could use optocouplers in place of one of the 1N914 diodes. The optocoupler output in turn connects to a Sentry board and then to your layout computer. Why not just use a switch contact in the Tortoise you ask. I found that those are really unreliable.

And if you did get the correct bipolar color LEDs you can still use an optocoupler, just have a 1N914 diode across the optocoupler's LED diode, wired backwards in parallel so the opposite direction current can still light the appropriate LEDs and operate the tortoise.

To get a better visual understanding of this, think of the diodes and LED symbols as arrows. And follow in one direction the current flow. You should pass thru a green part of one LED, and the red part of the other LED, and then the 1N914 diode. Flip the current direction and you should be able to visualize the LED colors flipping to the other colors.

A turnout control control panel Dennis built with both types of red-green LEDs I installed. They do look the same. And the wiring in back. Hot melt glue keeps the LEDs and their holders from falling out of the masonite board.