# grade crossing signal trigger - suggestions wanted



## zr1rob (May 27, 2020)

I purchased a grade crossing setup that uses an IR emitter/receiver unit for the trigger. Unfortunately for me, it is always triggering in sunlight, but works fine indoors. I suspect that the receiver is looking for light in the near visible range, while sunlight is providing plenty of far IR creating problems. Does anyone have another way? Magnets might work but I don't want to put magnets on every axle. Photocells across the tracks might work, but the receiver probably would be affected the same way as I have now. So maybe a mechanical means?


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## Greg Elmassian (Jan 3, 2008)

Small tubes on emitter and receiver to point only at each other, shield from sunlight


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## zr1rob (May 27, 2020)

Greg Elmassian said:


> Small tubes on emitter and receiver to point only at each other, shield from sunlight


thanks greg. Actually, this is the IR sensor setup where the emitter and receiver are side by side pointing in the same direction, so normally off. they are meant to be under the track between the ties pointing up so when a train passes over them, the emitter's beam is reflected down towards the receiver and it turns on. The circuit relies on a normally open sensor, so the photobeam method won't work.. I've thought about reed switches, but they would only be momentary unless there are DPST reed switches. They could be triggered by the loco, and a magnet on the caboose. That might work if there are DPST switches. Any more reasonable ideas? This one sounds kludgy.


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## toddalin (Jan 4, 2008)

I use the reed switches to trigger 555 chips that power the relay. Then you can set the time the relay stays open with a pot.

You can also do this using a track gap using the "Tortoise Bump Accident Sentinental System" (Bump A.S.S.) that needs no reed switches and will trigger from any engine, lighted car, or car with metal wheels. I do this for my crossing where two trains would normally collide. But to everyone's amazement, they alway stop short of a collision and the second train to approach will wait for the first to clear the crossing before proceeding.


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## zr1rob (May 27, 2020)

Hey Todd, thanks - good suggestion. I use battery power but how about using an ambient light detector, like one that turns off/on a night light?


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## Greg Elmassian (Jan 3, 2008)

so transmiter and receiver side by side, something comes close by and the IR reflects off it.

So, put a tube on the receiver, so it only receives the reflection, not sunlight. Should only need to be long enough so the receiver does not get direct sun. 

Worth trying.

Greg


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## toddalin (Jan 4, 2008)

Actually, all one needs to do is make sure that there is always shade on the sensor. This could be from a trackside structure or even overhead foilage.


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## dougiel (Jun 3, 2008)

Does the sensor looks like the picture below ?. This is manufactured by Sharp. If it is similar try putting a small capacitor across the power feed close to the sensor. They are susceptible to dips in the voltage caused by the frequency of the IR light. Dougiel


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