Train Detection with Mutliple Sensors

[Junctionmad]

If the layout is DCC you are committed to a lot of expense with regard to train detection.

 

 

​actually DCC is cheaper as you have a constant voltage/variable current  to detect , the back to back diode method is very simple , for example , DCV with its sometimes quite low voltages and reversing  track  currents are much more awkward to deal with 

 

 

If the layout is analogue 12v DC, then you don´t need to BUY ANY system off the shelf. A simple but effective train detection system can be made using a few DPDT relays (available in MAPLIN stores around 5 pounds each). Each relay is connected to a very short (1 inch long) dead section cut in the negative rail. Any vehicle with pick ups such as locomotives or vehicles with lights in, passing over the dead section completes the ciurcuit for the relay, and can firstly operate the signals as well as lighting up LED´s on a control panel track display.

 

 you dont have a fixed negative rail, secondly at low speeds , the relay being in series with the motor will most likely not operate , you will also get a notable reduction in voltage affecting motor speed, the relay will only be powered when circuit feed track voltage into the dead section and  say with diesels the other bogies are essentially shorting out the relay!!!!

 

and you are creating a 1 " dead zone, not a good idea, 

 

Ive never seen a DC detection system like you describe in operation 

 

note a DCC single channel detector is about £1.50 in parts  

 

 

A second switch on each relay is used to latch the relay in the ON position, holding a signal at red for example, until the train passes the next signal up the line where the 2nd relay then releases the 1str relay, allowing the previous signal to change to Yellow.

 

yes but  correct operation of three or four aspect Track circuit block signalling is a lot more complex and best implemented these days in software rather then loads of wiring and relays and stuff

 

 

 

In other words you can have signal control, and train detection for basically the cost of a DPDT relay !!!!! Using analogue 12v DC of course.

 

I very much doubt it 

[The Stationmaster]

3 aspect signalling is extremely simple with relays as - standing aside the matter of junction indicators or trailing junctions - each signal only needs two sets of changeover contacts and that gives you absolutely correctly operating aspect sequences.  Full track circuit block of course obviously requires some sort of train detection but there is no problem in using that to drive either indications or signal operating relays if that is what you wish to do.

 

It all depends exactly what you want to do and, in some respects, how you want to do it, as well as what kit you happen to have at your disposal.

[Junctionmad]

3 aspect signalling is extremely simple with relays as - standing aside the matter of junction indicators or trailing junctions - each signal only needs two sets of changeover contacts and that gives you absolutely correctly operating aspect sequences.  Full track circuit block of course obviously requires some sort of train detection but there is no problem in using that to drive either indications or signal operating relays if that is what you wish to do.

 

It all depends exactly what you want to do and, in some respects, how you want to do it, as well as what kit you happen to have at your disposal.

Yes I accept if all you want is a simple track circuit block 3 aspect , you can use the two changeover wiring. Well detailed here http://www.brian-lambert.co.uk/Electrical%20page%202.html#Signalling

 

I however , remain of the view that operational comphrehensive train on track detection. Is not a trivial undertaking. , especially if you'd like your detection to also act as TCB interlocking