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Circuit for Wheel Sensor to Throw Point


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I'm looking for some guidance on an electronic circuit. What I want to do is use a wheel sensor, like a modified Tomix TCS 5558 Plug-In Sensor, but have the contact finger that the wheel flange touches throw a point (track switch). I have a few concerns. One concern is that the high-amperage pulse drawn by the point motor may pit the sensor finger (and maybe the wheel). The other concern is that every passing wheel (2 to 8 on a tram) after the first one will result in additional unwanted pulses to the point motor. Is there some simple circuit, like a capacitor discharge circuit or a power transistor/relay circuit, that could keep the contact finger from having to handle the full current, and also be designed to prevent subsequent firings for 5-10 seconds? I would run this off a 12V DC supply. I'm not sufficiently knowledgeable to size components on my own, so a circuit with component values included would be best. Thanks!


Rich K.

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yes I think you would want a cap discharge circuit that’s tripped by the momentary closure and then a timer that would not let it fire for a set time. This could be done with a 555 timer circuit and length set by a variable resistor. I kind of remember a 555 circuit that did just this for doing servos on a rr crossing using the old minitrix wheel switches. Might do some searching on 555 and rr crossings.


i can search some tonight.



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