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Cheap timer circuit


Mr chapman
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Hello. My friend has tasked me with fitting a train tech level crossing. As per the instructions it can be wired to a sensor or an on off switch. My friend tells me the sensor is not cheap. I have fitted a push to make switch on his panel that controls the barrier lights but obviously you have to hold it down. I'm after a cheap little do-dad that will sit between the push to make and power supply so that when pushed it will run the circuit for a few seconds and turn off again. Something based around a 555 timer perhaps? It's been a while... And I don't know what is available these days. 

 

Any help would be wizard.

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Clearly a 555 timer will do this,  just search for a few examples of wiring arrangements.     eg, this one-shot example: 
https://www.dummies.com/article/technology/electronics/general-electronics/electronics-components-555-timer-chip-in-monostable-one-shot-mode-179881/

 

There are numerous other devices which would do the same, including various things with Ardunio's and the like (but overkill for the job), and there may be ready-built circuits from Amazon/Ebay/China.    

 

 

 

Of course, if you have to buy some components, pay postage, faff with some prototyping, and a few hours doing it,  it could be cheaper to just buy the manufacturer's detector.   Whereas if you have a cabinet full of odds and sods of electronics parts and some spare time, it might be a fun thing to build.   

 

 

 

- Nigel

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There is a MERG pocket money project that does what you want:

https://www.merg.org.uk/download/chapter/27

Part 17 describes a signal timer operated from a LDR sensor.  You could keep the sensor or replace it with your switch, and use the output to drive the traintech device instead of signal LEDs.

Paul.

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