Advice required

[chris m01]

Here's one for the electrics guys. I want to be able to switch power off and on to a section of track. I use a train engineer and have a remopte switch accessory with a spare output.

I've worked out the following diagram to give me a latching circuit fed from the switch accessory. It works - I've tested it using a controller in place of the switch accessory. Now my question. I will be using the switch accesory to power a relay rather than a point motor. I don't think this will be a problem for the electronics in the unit but I would just like other people's opinion. Must say I trhink this will be a nice easy way to switch power off and on - just press button E on the TE.

 

[ntpntpntp]

I'm not familiar with how the Aristo accessory unit works, but my first reaction was that 3 relays seems excessive - couldn't you use a single latching relay? Then you wouldn't be driving relay coils continuously to maintain the latch. eg:

http://www.maplin.co.uk/2a-miniature-dpdt-latchingrelay-37529

(Granted the above is only rated at 2 amps but it's just an example)

 

[Neil Robinson]

Hi Chris.
I'm a bit puzzled by your diagram. As I see it once relay C is energised it can't be turned off by the switch unit.
However I have no experience of the TE switch unit and you claim your system works.
What I would like to suggest you conform to standard practice and fit the relay coils with parallel reversed diodes to short out any induced reverse voltage that may damage any electronics.

Edit, if you're using halfwave rectified power the above may need further investigation.

 

[Tony]

Chris ive just used an Lgb points motor with a aux switch on the end that normaly switches a signal, a lot less wiring

Tony

 

[chris m01]

Sorry Neil - diagram was incorrect - here is the corrected one

 

[chris m01]

Chris ive just used an Lgb points motor with a aux switch on the end that normaly switches a signal, a lot less wiring

Tony

Yes I thought of that but I want to do two sections.
Your way will cost over £80 from Dragon, mine will cost £20 from Maplin (or cheaper on line) and I get the pleasure of having made the circuit!

 

[chris m01]

I'm not familiar with how the Aristo accessory unit works, but my first reaction was that 3 relays seems excessive - couldn't you use a single latching relay? Then you wouldn't be driving relay coils continuously to maintain the latch. eg:

http://www.maplin.co.uk/2a-miniature-dpdt-latchingrelay-37529

(Granted the above is only rated at 2 amps but it's just an example)

Thought of a latching relay but I don't think it would work. The switch unit gives out a short burst of 12 volts or so with current flowing one way when the button is pressed. The next time the button is pressed the current flows for a few seconds in the other direction and so on.

 

[ntpntpntp]

Thought of a latching relay but I don't think it would work. The switch unit gives out a short burst of 12 volts or so with current flowing one way when the button is pressed. The next time the button is pressed the current flows for a few seconds in the other direction and so on.

If the latching relay coil requires dc, no problem - just feed the accessory switch output through a bridge rectifier before the relay.

Assuming that the Maplin relay I linked to would do the job, then I guess you're looking at around £5-ish for the relay and rectifier. I reckon I'd give it a go for that sort of outlay.

 

[chris m01]

Sorry Nick - wasn't thinking - your suggestion is a good one. I guess that as I had three ordinary relays in the spares box I was thinking in these terms only. I might well get myself a latching one.

The other thing I was a little concerned about is whether feeding a relay coil is any different to feeding a point motor from the switch accessory point of view. I can't see it will cause any problem but I've already shown my lack of knowledge on electrics.

 

[ntpntpntp]

The other thing I was a little concerned about is whether feeding a relay coil is any different to feeding a point motor from the switch accessory point of view. I can't see it will cause any problem ...

Neither can I (see a problem). As I said, for a fiver-ish it's worth a go.

 

[chris m01]

Nick
Did you see that I have gone for the Helmsman controller - thanks for pointing me in that direction.

 

[ntpntpntp]

Nick
Did you see that I have gone for the Helmsman controller - thanks for pointing me in that direction.

Yep. Looks like a decent bit of kit, and something I'd consider if I ran analogue and needed a tethered controller. Hope it serves you well.