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Model rail block detector to drive relay

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The bridge just provides a two-diode voltage drop regardless of polarity. That sets the voltage fed to the opto.

Ok. So here's how I think the module works.

As long as there is a signal being received at its input, via the track rails (it doesn't matter if the input signal is bi-polar or uni-polar), the output will be ON causing the module output voltage to be low. This would be the normal "Track Unoccupied" condition.

If a train comes along and shunts the track, the input signal is blocked, the module input signal is lost, and the module output then goes high.
This is the "Track Occupied" condition.

An assumption for both of the above conditions is that the module output is pulled up.
 
I understand the track detector that’s not what I want to know
Back to my original post I want to know how and if I can trigger a timer relay with it
 
I think the resistor is 330 ohm.
The resistor is 33 ohm, same as the diagram I posted - the last number on standard smd resistors is the 'multipler'.

The hook up diagram (post #9) looks right, but before you do that - power up the timer module without anything else connected and measure across LL Trig and ground to see if there is any voltage there.

If there is, then you won't need the 4.7k resistor.
 
Thanks for that. When I contacted megapoints controllers and asked whether a timer relay could be attached to the output of the current based block detector I was told.

“It is designed to drive open collector inputs.”

That is what I don’t understand
 
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