Reed Switches for auto-reversal

[MikeEK]

I'm considering setting up train auto-reversal on a stand alone track stretch (N scale). I thought about using Simple Shuttle with a reed switch - but which one?  I am not sure whether it needs a Normally Open or a Normally Closed type of reed switch? Any specific recommendations will be really welcome.

[Jeremy Cumberland]

What flavour of Simple Shuttle? The current version of Block Signalling SS1 Simple Shuttle just requires an isolated joiner at each end and a separate 12 volt supply.

https://blocksignalling.co.uk/Shuttles/SS1

Documentation: https://blocksignalling.co.uk/pdfs/27FFF1J.pdf

 

A previous version was powered from the controller (provided it was set above a certain voltage) and used a diode across each of the isolated joints.

 

You could make your own with a pair of normally open reed switches and a dual coil DPDT latching relay (10 pin, not the single coil 8 pin version), but this wouldn't have the delay timer of the SS1.

 

I take it you're talking about DC.

Edited July 28, 2023 by Jeremy Cumberland

[MikeEK]

Thanks that's most helpful. 

Edited July 29, 2023 by MikeEK
removing the factual error in my first draft

[cliff park]

A diode and a reed switch are poles apart. A reed switch is a mechanical switch operated by a magnet, it is about the size of a cigarette. A diode is an electronic device which allows current to flow in one direction only, and blocks it the other way. It looks very much like a resistor without the coloured bands lol

[MikeEK]

Thanks for the clarification. It does seem the latest SSI with diodes included will be the easiest solution to my requirement.

[Colin_McLeod]

Much smaller than a cigarette.  On a previous  layout I had signals operated by reed switches and they were in a glass cylinder approx 20mm long by 2mm diameter and fitted between the rails.

[Jeremy Cumberland]

No reed switch is required. The circuit doesn't really detect the train. The dead sections at each end do two things. They stop the train, and the interruption to the circuit also drops the latching relay coil. The diodes are there so that when power is restored in the opposite direction, the train is no longer isolated.

 

Use a 1N4001 diode at each end, bridging across the insulated joint. The ends with the bands need to face the same way (both to the left or both to the right), but you will need to test which way is correct.

This isn't at all difficult to do, and diodes are very cheap. But you are right that the newer version makes it easier.

Edited July 29, 2023 by Jeremy Cumberland
Correction

[meil]

14 hours ago, Jeremy Cumberland said:

What flavour of Simple Shuttle? The current version of Block Signalling SS1 Simple Shuttle just requires an isolated joiner at each end and a separate 12 volt supply.

https://blocksignalling.co.uk/Shuttles/SS1

Documentation: https://blocksignalling.co.uk/pdfs/27FFF1J.pdf

 

The MERG version (PMK 4) does exactly the same thing for £2.50.

Edited July 29, 2023 by meil

[RAF96]

Gaugemaster SS1 is a DC shuttle.

Edit - GM has an old article on-site showing how to use this on a DCC track.

Edited July 30, 2023 by RAF96

[WIMorrison]

11 hours ago, meil said:

The MERG version (PMK 4) does exactly the same thing for £2.50.

 

You forget the £29 joining fee and subsequently £24 ongoing annual fee 🤣

[kevinlms]

On 29/07/2023 at 04:05, MikeEK said:

I'm considering setting up train auto-reversal on a stand alone track stretch (N scale). I thought about using Simple Shuttle with a reed switch - but which one?  I am not sure whether it needs a Normally Open or a Normally Closed type of reed switch? Any specific recommendations will be really welcome.

A reed switch is almost always a very low current device, which is unsuitable for directly controlling a motor (even an N gauge one), so something else such as a relay is required, so switch larger currents and to provide a reversing function (if required).