Id like to include a signal prior to a Bascule Bridge. Red Light when it cycles up and green when its down. Has anyone wired a semaphore or block signal to do that? Thanks!
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I would guess this can be done with a relay if you can find a way to activate the relay when the bridge is up.
My local Train Museum has done this. I'm pretty sure a relay of some type was used as necrails mentioned above. When the bridge is up, the light changes and power is cut to a block of the track to keep the train from running off the rails.
The simplest could be a mercury tilt switch mounted under the bridge.
Brendan
My thought is to use a 151 Semaphore. Connect the light to constant power (i am going to put an LED bulb in to keep heat and amperage down). I should be able to run a hot lead from the motor of the bridge (ill have to figure out which terminal) to the coil of the semaphore. When the motor is running, track power is cut, the semaphore is down with the red lens lit up. Once the motor stops power is cut to the flag, it raises, the green lens is lit, and track power is restored. Sounds like a plan, let see how many snags i hit, lol.
Google:
"micro switch"
"limit switch"
"cherry switch"
They are all members of the same family. There are approx a million variations, and one will certainly do what you need done, without relays or magic. Mount one at the open end of the bridge crossing, so that the switch is operated when the bridge is down, and released when the bridge is what we call "off-normal" or open. The contacts will be robust enough to operate the semaphore or block signal.
The switch can also operate a relay that will cut off power to the approaching track sections, to stop a train from doing a dive into the river.
