Cheapest easy DC motor to survive locked rotor

Have you got any powered remote-operated track switches to spare?

I'd need to ponder the details of the wiring, but it seems to me that one could put a sensor/switch package on each side of the crossing, much like real RR tracks, to operate the switch, then tap the solenoid that normallly switches the track position to move the gate to the up or down position, as approriate.

Early pondering suggests maybe a series of "whisker" or "feeler" type switches wired in parallel poking up through the roadbed leading up to the crossing, so that when the train goes over, the feeler(s) get deflected to make a circuit. Circuit powers track switch solenoid, gate goes down, solenoid holds until train is gone. Once the train is gone and the last of the parallel-wired feeler circuits breaks, the solenoid releases, and the gate goes back to the up position.

Thought about a reflective opto sensor? Easy enough to put 3M reflector tape or gloss/metallic paint on the bottom of the rolling stock.

Wouldn't it be easier to rig limit switches on the arm motor that turn off the motor power at end of travel, rather than figure out a way to cut current and have it sit stalled on a physical stop?

I'd have to sit down with a pencil and figure it out, but there should be a simple and elegant way to open the motor power in 'Up' when it hits the 'Up Limit' and take that switch out of the picture when the 'Down' relay kicks in, all using relay logic. You won't need any sort of braking or hold action if the crossing arm is properly balanced neutral. Probably take a 3PDT or 4PDT relay to reverse motor polarity and select the right limit switch. And you rig the crossing lights so they run unless the arm is in 'Up limit' mode

And if you want to go into r.c.m overkill mode... ;-)

You can use slot opto sensors for the limits, a few TTL gate chips to start and stop the motors, and a 555 or two for timing.

You'd want to add a time delay circuit of some sort so the gate delays down a second or two for the warning lights, then holds down while the crossing is fouled but comes back up automatically after the crossing is clear - if this was a real railroad you could count on track loop detection to see if the crossing was fouled, but not on H.O. And even if you could, it would only see the engine, not the rolling stock - no shorted tracks caused by steel axles and wheels.

And if you space the crossing trigger sensors out for realistic advance time but where they can't see the train the whole time, you might need four train sense switches or more - put two right at the edges of the grade crossing so they'll see the rolling stock if it's running slowly or stops.

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Thanks. The switch is already working fine. Just a stupid contraption from various junk that I had, but it works every time.

I think that sticking a resistor in series is the easiest solution (and the one that I have done after receiving advice and it works).

I want to eventually have some timing, but not now.

Now that my gate works, I need to figure out a way how to make it all apparent to my son, while somewhat proofing it from his destruction (like if he steps on it). He is sometimes not paying attention.

I hope that rolling stock will keep the switch depressed, I have not tried it yet. The engine does it.

I want to screw around with that stuff for several reasons. One is to keep my son interested. Another is to learn about automation in a non threatening setting (ie not a welding CNC setup as a first time project).

Shouldn't matter with DC ones. ...lew...

Yeah, I knew that, or should have, or once did and forgot . In any case, any day that you learn (or relearn) something is a good one.

Ned Simmons

Even better if you can find the right bulb is to use a bulb as the resistor, the current inrush gives the motor higher starting torque and the hot resistance actys as a current limiter.