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  • Need Help with Electrical Schematic

    Transformer.jpg I'm having trouble figuring out how to wire these parts to work correctly. What I want is when the switch is OFF for the RED LED to light. And when the switch is ON for the GREEN LED to light.
    Can someone help me draw the lines for what connects to where? Help is greatly appreciated!

  • #2
    Transformer 2.jpg Does this look correct?

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    • #3
      Most people would want the lights to switch automatically when the track power went between on and off. In that case another relay is needed that would be activated by the track power relay. If you just want to manually switch between red and green a relay is not needed if you use a center off switch. If you used a regular on/off switch you would also need a SPDT relay. There is another hitch here. The red and green LEDs operate at different voltages, full track voltage would burn out both types immediately. Red LEDs operate at 2 volts and green LEDs operate at 3 volts.
      Some years ago I added a track call system to my track and just for kicks I included red and green LEDs in that. I chose to have a separate 12 volt power supply for the lights, rather than get power from the track power supply since that might be adjusted to different voltage values. The LEDs would have burned out at 12 volts so I included dropping resistors for those. Later I switched to a computer based system, but the original one is still in place as a backup.
      Look here: https://drive.google.com/open?id=0Bz...I4OWU1MWZkMzI4
      The correct values for the dropping resistors were not included in the article, there are online calculators for sizing the dropping resistors like this one: http://ledcalc.com/

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      • #4
        Most people would want the lights to switch automatically when the track power went between on and off. In that case another relay is needed that would be activated by the track power relay. If you just want to manually switch between red and green a relay is not needed if you use a center off switch. If you used a regular on/off switch you would also need a SPDT relay. There is another hitch here. The red and green LEDs operate at different voltages, full track voltage would burn out both types immediately. Red LEDs operate at 2.2 volts and green LEDs operate at 3.5 volts.
        Some years ago I added a track call system to my track and just for kicks I included red and green LEDs in that. I chose to have a separate 12 volt power supply for the lights, rather than get power from the track power supply since that might be adjusted to different voltage values. The LEDs would have burned out at 12 volts so I included dropping resistors for those. Later I switched to a computer based system, but the original one is still in place as a backup.
        Look here: https://drive.google.com/open?id=0Bz...I4OWU1MWZkMzI4
        The correct values for the dropping resistors were not included in the article, there are online calculators for sizing the dropping resistors like this one: http://ledcalc.com/
        You would also need to look up how many amps each type uses, for red LEDs 20 milliamps is a common value and for green LEDs 30 milliamps should work.
        Last edited by RichD; 08-07-2019, 10:02 AM.

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        • #5
          Rich, thanks for your input but you didn't even touch on answering my question! haha - whether the wiring of the circuit is correct. It is for those that want to know

          This system is only for street lamps on the layout, and need to be completely independent of the power on the track. It's fed 3V from a buck converter voltage regulator that's tied to the main track power. I know the LEDs are different voltages, I can easily replace the Red one when it burns out, not a problem! What's not in the diagram is a DPST Switch that will provide power to the lighting circuit and act as a Mains for the streetlights. The system will only be on when we want to run cars "at night".

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          • #6
            I did not fully understand what you were trying to do, if it was me I would skip the relay and use a center off switch like so:


            Otherwise your schematic would work if you added the correct resistors.
            Last edited by RichD; 08-09-2019, 06:45 AM.

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            • #7
              Thanks Rich, no worries! I already had the switch and the relay, so buying more parts wasn't an option. The "mains" DPST switch between the circuit and the power will break both positive and negative for good measure. No resistors needed because I'm only feeding 3v from the regulator transformer - which I might drop to 2.8 actually. It's a really trick device that works like a charm!

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