Sensor for signal bridge.

Check this out.

Build Files For 2-3 Aspect Signal Actuator; Common Anode LEDs; Video Added

Not sure what the 20 VAC LED's are about, you're talking about something like Evan's Designs LED's?  The project listed above uses bare LED's.

I’m just letting you know what it’s set up to accept as I’m sure it will affect what can run them.  The bulbs can be powered directly from track power.

Well, the design I posted probably won't work for that one, sorry.

Probably not.  But it was interesting.  I don’t think that design had a sensor🤷🏻‍♂️

The sensor isn't difficult, you need something that drives the bulbs.  It's a lot easier with bare LED's, then there are a number of possibilities.

I used 2 Z stuff DZ 1075's to activate My MTH signal bridge, but I believe the light progression is in the MTH electronics.

These folks have sensors for everything and are very reasonable. I can trigger a double track crossing from any direction for $40, http://www.azatrax.com/

John Parsons at Azatrax is also very helpful  and answers emails promptly if you have any questions.

@davidbross posted:

I have a plasticville signal bridge set up to run led lights at 20v ac.   I’m looking for a photo sensor or some other sensor to activate lights from green to Red to yellow and back to green.

Let's take your voltage requirement at face-value.  If you are trying to steer 20V AC to 3 independent loads using a single trigger and the commonly used R-Y-G timed-yellow method, I think you need to use relays.  That is, all the off-the-shelf 3-aspect electronic modules I'm aware of drive DC loads.

That said, if you're willing to cobble together some eBay modules Lego-style, I think it could be done without soldering.  It would be like the following which is discussed in greater detail in this OGR thread.

The simplest sensor would be an insulated rail you cut into the track right below the signal bridge.  Or you could buy or wire up a photo sensor; the simplest and most reliable would be where you shoot an LED across the track(s) to a photo detector.  When the beam is interrupted by a passing train this provides the trigger just as the wheel axles would do across an insulated trigger rail.

Maybe you would like this IR signal controller:  https://www.azatrax.com/block-signal-circuit.html

I used I TADS from MTH but as Rick said I think the controls are inside my MTH Pennsy. bridges.

I thought LED's had to run off DC current? Nick

@rockstars1989 posted:

I thought LED's had to run off DC current? Nick

Clearly, the LED's in question have a diode and resistor in series with the LED.

The resistor and diode are soldered in the wire lead. They could be cut off to give me bare led if that helps get a driver board and sensor combo that works.

If you don't need to drive 20V AC bulbs, then you don't need relays and should be able to find off-the-shelf controllers capable of driving low-voltage LEDs (DC).  eBay seller "wehonest" has a wide variety of signaling electronics.  If I understand the instructions of this module, it includes an infrared/optical occupancy detector as well as the ability to drive a 3-aspect LED signal head with the timed-yellow delay: