Problem with using a signal to isolate a siding from the main line

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playmofire

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I'm not quite as desperate as the Forum title suggests, but advice would be very much appreciated.

I am, at long last, getting round to creating a (small) permanent layout (a separate thread will be started for this).

The layout is a simple oval with two inner sidings and exit from a siding is controlled by a signal - signal at clear, train can leave, signal at stop, train stationary. I am using the LGB 50960 semaphore signal.

The instructions for wiring the signal said that by bridging the 2nd and 5th terminals in the isolating rail with a diode appropriately wired, a train could enter the siding against the signal, i.e. the signal at stop.

I wired things up like this and a test on a straight piece of track with a siding coming off it worked perfectly. Train on siding, signal at stop, train would not move when controller applied. Signal at go, controller applied, train could leave siding.

Working the other way, signal at stop, train could enter the siding from the main line and pass the signal.

However, when I came to set the signal and siding up on the oval layout, when a train was on the siding and another train was running on the oval clockwise all was well, but when I reversed the train on the oval, the train on the siding also reversed because current was passing through the diode in the isolating rail!

The electric motor controlling the point into the siding has an auxiliary switch and so I thought that if I wired this through the isolating rail in the signal in place of the diode it might solve the problem, but it didn't. I tried various ways of wiring the auxiliary switch through the signal's isolating rail but without success.

Does anyone have any experience or ideas on this, please? I know one answer would be to remove the diode and wire up the siding through an on/off switch to make it live when wanting to put a train into the siding, but an automatic system would be preferred.
 
I would need to draw out the logic table for this, but I think you need the switch and a diode in series across the gap..

PhilP.
 
the problem is, when you reverse trains in the loop, you switch plus and minus rails against each other. - with the result, that your diode connects the (now) wrong rail.
the only way i can imagine, to keep that signal function working, would be to interrupt both rails between loop and signal, giving that parts its own control-block.
 
playmofire said:
The electric motor controlling the point into the siding has an auxiliary switch and so I thought that if I wired this through the isolating rail in the signal in place of the diode it might solve the problem, but it didn't. I tried various ways of wiring the auxiliary switch through the signal's isolating rail but without success
Click to expand...

You need to use the auxiliary switch on the point motor to completely switch of power to the siding while that point is set to the mainline.... that means that you switch off all power to the siding. EPL can do this but it is not really a plug and play sort of thing,.... you may need another isolating track section to make it work in a simple manner.

There are two 1015U single rail isolating tracks in a standard 50960 pack, so you could use the second 1015U with the gap on the opposite rail to what you have set up for the signal switching function. Alternatively you could use 1015T track section which has gaps on both rails.

I'll work up a diagram a bit later when I have time.
 
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Software is completely correct, but a cheeper option may be a couple of Massoth Isolating clamps utilizing the screws to put in power after the isolation break.
 
playmofire said:
It stops the problem of reversing a loco in the main line also reversing the loco on the siding, but it also stops me running a loco into the siding when the signal is set to stop.
Click to expand...

if you remove the diode and you control the signal and the points with the same electrical switch, the siding will only be powered when the point is open and the signal is set to halt. this will allow you to run trains into the siding as you describe as there will be no situation where the points are open and the siding is unpowered.

Also bear in mind that you can isolate the locomotives in the sidings using the cab switch (sometimes it's behind the smokebox door) if this makes your operation easier.
 
maybe i'm wrong, but...

you could by using the additional switch on the signalmotor to toggle the direction of the current, to go in and out of the siding.
but then what? leaving the siding, somewhere you would run into a place, where your loco will short everything out. when one axle is on current like the siding needs, and the other axle is on the reverse current of the main loop.
to evade that, you would need to throw in some reeds and a section like in a reversing loop - but then any train on the loop would suddenly go in the wrong direction.
i don't see a way to solve that.
 
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