Hello,
I'm somewhat new to electronics and wiring, so bear with me. I'm trying to wire up a power supply to a dpdt switch that controls a tortoise switch machine and 2 bi-color LEDs. The goal is that when I flip the dpdt, the tortoise moves, and the LED's flip color from green/red to red/green to indicate route for main/diverging.
Here is a diagram of what I'm thinking of trying, and I wanted to see if this is the right way to do it? Are resistors needed? Thanks for any feedback.
<Paging Rich for his handy diagram>
There's a much easier way, using bi-color LEDs that only have 2 leads, and no resistors required. The LEDs are simply wired in series witht he wire going to the Tortoise. Depending on which way the LEDs are connected, one will be red and the other green, or both could be the same color (ie, one on the control panel and one as a signal next to the actual turnout).
You have the DPDT switch wired correctly to work the Tortoise, so my text drawing will be the wires goign to the Tortoise:
(switch)-----<LED>-----<LED>----------(tortoise)-----------(switch)
You want 2 lead bicolor LEDs, not 3 lead ones.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
greg previously provided this diagram.
gregc
Alton Junction
Just as a note (it's described in many other threads): the two-lead devices work because a LED is not just light-emitting, it is a diode. Therefore if you have two of them in opposite polarity molded into the same housing, one will conduct one way, and vice versa. (Incidentally you can get a range of yellow and orange by applying different kinds of AC across the device...)
You may still need a resistor (only one) in circuit to suit the LED cores. That will be clear in Rich's circuit. Remember that not only simple, clean DC may go through this or any circuit reliably all the time...
If I use a 2-lead, bi-color LED, then the LED is bi-directional? When current goes one way it is green, when it goes the other way it is red? In this case, it's not really a "one-way" diode?
Thanks
WHat's inside the case of the 2 lead bicolor LED is what's shown in Rich's diagram - 2 individual LEDs wired back to back. So yes, they still are and act exactly like a diode - current only flows in one direction. But when it flows one way, it can go through one of the LEDs and that one lights up, the other does not. Reverse the polarity, and it flows through the second diode, and not the first any more.
rrinker WHat's inside the case of the 2 lead bicolor LED is what's shown in Rich's diagram - 2 individual LEDs wired back to back. So yes, they still are and act exactly like a diode - current only flows in one direction. But when it flows one way, it can go through one of the LEDs and that one lights up, the other does not. Reverse the polarity, and it flows through the second diode, and not the first any more. --Randy
Got it. Thanks for that explanation.
Our club ran the Tortoise at 9 vdc. A little slower. LED still ok. I had been working with LED's since 1972.
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.