Hmm ... the atlas snap switch machine should be powered by an AC supply. The Common supply is DC? If you are running DC, the snap switch acts like a short (after the first microsend when you are applying the pulse). And that might mean your power supply voltage drops a lot. It maybe triggering the op-amp in the crossing, which otherwise is stuck thinking the lights are always shining on the optical detectors.
Separately from this issue, you need to make sure the switch is getting correct power, or you will fry it or the power supply or both.
NP
I'll through in guess. So, the switch machine and the crossing unit are both powered by an older power pack, maybe try seperating them, and run just the crossing unit with the power pack, just to see if it works as it should, the same with the switch machine. Also, maybe do a continuity test on the crossing unit, by itself, and then with the wires you used to connect it to the power pack, attached to the crossing unit, to make sure your wiring is good.
It seems like you need to seperate things, and get each one working the way it should, kind of like divide and conquer.
Maybe your old power pack is throwing out random power surges.
OK, done guessing for now!
Mike.
My You Tube
Welcome to the forum.
I would urge you to edit the title of your first post to something that will catch people's eyes, like Optical Crossing Malfunction. Vague titles are often, not in your case, but often accompanied with a minimal description of the details. Those threads follow a guessing game pattern where we try to guess what scale, what electrical system, which loco manufacturer. A couple pages later the OP tells us about the reversing loop. Eventually people lose interest in looking at posts like that.
A better title will get the attention of people who had a similar problem and be searchable in the future. It will also bring in the electrical gurus of the forum who, unlike myself, are full of electrical solutions and opinions.
Best of luck
Henry
COB Potomac & Northern
Shenandoah Valley
The sensors are the type that sit between the rails and look up, going off when the light is covered from the passing train, so there is no alignment to worry about. And if they were dirty or covered, the unit should be activated.
My guess is that the optical sensors are the problem. It’s hard to trouble shoot without seeing a picture or diagram but that seems like a place to start based on your description. Have you tried cleaning them? Did they become misaligned?
Here's my situation: I have an old crossing unit that has two signal lights, a bell unit and two optical sensors that all run to a common box. It's an older unit from Model Power or Bachmann or some other low-cost provider and I've had it for years. It stopped working last year, but I couldn't figure out why. Power is getting to the box, but I gave up as I just figured something in the circuitry gave out.
But yesterday when I was working on replacing a dwarf signal that is operated through an atlas snap relay and snap switch, the thing suddenly sprang to life! The bells and lights all worked, but it wasn't operating off the optical sensors, because no matter what I did, it wouldn't shut off. But when I pressed the snap switch again (I think that's what it's called - it's one of the old school turnout buttons that throws a turnout with a quick burst), it shut off! The unit will sometimes come on and sometimes turn off when the switch is pressed, but it's really random.
The ONLY place the wiring for the snap switch and the crossing unit touch is directly at the powerpack -- both are wired to the AC accessory screws. That's it. I'm guessing that maybe the power surge from the switch is activating the crossing unit? Does that yield any clues as to what might be wrong with the crossing unit? I had given it up as dead and was leaving it as a nonfunctioning crossing, but it obviously can still function when it wants to, but currently, I have no control over when it goes on and off.
All guesses appreciated!