DCC Digital On/Off or Isolating Switch

[csiedmo]

Hello,

 

I would find very useful to have the ability to isolate a section of track on my DCC layout and power it on-request with some sort of digital on/off switch.

The purpose of this is to run a train off-scene and to have it wait there indefinitely (due to it encountering an isolated bit of track).

Then when I want the train to return to the layout, I select a route on the DCC command station, the first element of that route being to switch on the power to the isolated bit on track and the last element of the route being to switch the power off again by which time the loco of the train will have had chance to get through the isolated section.

 

The trouble is, I can't find any such product out there!

 

I can find an unnecessarily complicated and expensive way of doing it, which is that Cobalt Digital point motors have an inbuilt SPDT switch that can be used to isolate a section of track, but there are no turnouts on the layout that would naturally control this, so as I want to have this effect in two places I would have to buy an additional two turnouts and two points motors for effectively no purpose.

 

I've had a look at the ESU SwitchPilot, but it clearly isn't intended to be used for this purpose and whether it could be potentially used for this purpose I cannot tell as I find the instructions totally baffling.

 

Of course I could just run some long wires to a manual on/off switch, but really I want to avoid this as the rest of the layout can be operated 100% from the DCC command station.

 

So does anybody have any suggestions? I find is hard to believe that a simple on/off switch with a decoder doesn't exist!

 

Many thanks,

Ed

[smokebox]

You could have a relay operated from a decoder to isolate a section of track.

[Crosland]

Do you really mean "return" or carry on in the same direction? Returning implies, to me, a change of direction in which case you cannot do it without sending a command to the loco.

 

If you are selecting a route involving that section of track there must surely be some turnouts involved. If it's a simple dedicated oval of track then you could create a "virtual turnout", e.g. a digital Cobalt not actually connected to a turnout.

 

If you have spare outputs on an existing accessory decoder then use one of them to drive a relay or a conventional turnout motor with a frog switch.

 

Another way is to create a "brake on DC" zone, again controlled by a relay or frog switch.

 

Andrew

[AndrewC]

 I select a route on the DCC command station, the first element of that route being to switch on the power to the isolated bit on track and the last element of the route being to switch the power off again by which time the loco of the train will have had chance to get through the isolated section.

 

The trouble is, I can't find any such product out there!

 

I can find an unnecessarily complicated and expensive way of doing it, which is that Cobalt Digital point motors have an inbuilt SPDT switch that can be used to isolate a section of track, but there are no turnouts on the layout that would naturally control this, so as I want to have this effect in two places I would have to buy an additional two turnouts and two points motors for effectively no purpose.

 

 

 

 

 

Many thanks,

Ed

Ok to start with routes don't work that way in any DCC system I've seen. They basically fire off a bunch of stationary decoder commands in order. From the time the first command activates your track until the last one switches it off, would likely be less than 1-2 seconds. I've got a couple of routes on my layout that set 14 points. The whole thing takes only a second.  A better solution to this would be to have a separate switch (point) address just for the block. A cheap stationary decoder capable of handling slow motion motors and sufficient current to lock a small relay is all you need. Switch 10 - left = on, right = off. Of course you will still need manual intervention to change direction on the loco if this track is for an out and back.

 

 There are DCC shuttle devices available that may give you what you need. http://www.digitrains.co.uk/ecommerce/dcc-accessories/general-dcc-accessories/tns001-dcc-train-shuttle.aspx or from CML http://www.cmlelectronics.co.uk/index.php/products-53/sequence-controllers

[Crosland]

Theoretically (!!) one could use a solid-state solution with a TRIAC, but that's not easy for those who haven't the foggiest on what a TRIAC actually is (Andrew knows )

 

I know what one is, I could even, many years ago, have given you the theory of operation, but the closest I have ever been, practically, is a thyristor in a controller circuit from a Babani book, again, many years ago

 

Andrew

[csiedmo]

Thanks for all your replies.

Just to clarify a couple of items:

By "return" I mean that the train is coming back onto the layout by continuing in the same direction in which it was originally traveling, so what it naturally wants to do according to its DCC message.

Yes, there are plenty of turnouts involved in the route, but I studied them all and they cannot be used to control the isolation, as at some point they will end up being switched on as part of other routes and thus ruin the effect.

Its sounding like relays might be the way to go. I'll have to do a bit of reading up on them as I've not encountered them thus far...

 

For AndrewC, you've got me a bit worried here, as it was my understanding that for the ESU ECoS system that I shall be running that I am able to set a substantial delay between firing of each accessory that is in the route. However, if that doesn't work I have Plan-B which is to set the power on as part of the route, and then have a track occupancy feedback module a few inches down the line to activate another "route" which just turns the power off again.

 

Cheers,

[Guest 838rapid]

I fitted a double pole double throw switch on to my control panel.

 

Simple solution as it totally isolates the track,mine is wired so the centre position is wired to the output which allows me to run dc and dcc on my running line.

[AndrewC]

csiedmo, on 15 Sept 2014 - 15:36, said:

Thanks for all your replies.

Just to clarify a couple of items:

 

 

For AndrewC, you've got me a bit worried here, as it was my understanding that for the ESU ECoS system that I shall be running that I am able to set a substantial delay between firing of each accessory that is in the route. However, if that doesn't work I have Plan-B which is to set the power on as part of the route, and then have a track occupancy feedback module a few inches down the line to activate another "route" which just turns the power off again.

 

Cheers,

Ok, wasn't sure what system you are running. I guess its down to how much time you need to clear the section and how much delay you can add. Is the ECoS capable of setting the delay per switch command or only for the whole route? you may find that having to wait 10 seconds or so for the whole route to align will become tiresome. Also what happens if you run the loco in at a slower speed? If say at 50% it takes 5 seconds to clear the block, and you run it in at 25%, the route will complete before the loco escapes.

 

Using block detection may be a better way to go. How about a block occupancy on either end that shuts off power to a centre section. That would allow it to run bi-directionally and independent of loco speed. Again, this would require a stationary decoder to power a relay or some other device which controls the power on/off of the centre block. This could be done with a single Cobalt digital wired under the layout. The motor switching on/off the track section via its ancillary switch. You wouldn't need to actually attach it to a point. £20 + 2 block detectors to solve the problems.

[csiedmo]

Is the ECoS capable of setting the delay per switch command or only for the whole route?

 

I believe that the delay is per command, but I'm only going off the literature as I'm still at the planning stage and the ECoS hasn't left its box yet.

However, I agree with you that block detection is going to work a lot better, so I think I'm going to go down that road.

It's going to be a double track main line with no wrong line working allowed, so I don't need to worry about bi-directional running.

Do I assume correctly that the DCC Concepts AD1 although meant to be a cobalt decoder is in reality just an accessory decoder that I could use to power a relay? Or would you recommend a different product? I don't really know what I'm doing when it comes to decoders and relays and what works with what.

[AndrewC]

You could use the AD1 with a relay, or you could use H-DCP-CB1D which is a cobalt motor with the AD1 attached. That literally gives you an on off switch attached to a stationary decoder. Just mount it and let the motor freewheel. Use the accessory switches that are normally used for frog polarity as the on/off for the isolating section.  

[csiedmo]

Ah, now I understand

Thanks Andrew!

[Ron Ron Ron]

Andrew's suggestion of a "Brake on Dc", or if your decoders support it, using an "asymmetric braking' module, would seem to be a very simple way of achieving your aim.

 

 

.

[TWG]

...I've had a look at the ESU SwitchPilot, but it clearly isn't intended to be used for this purpose and whether it could be potentially used for this purpose I cannot tell as I find the instructions totally baffling........

 

......So does anybody have any suggestions? I find is hard to believe that a simple on/off switch with a decoder doesn't exist!

 

Many thanks,

Ed

 

We seem to some extent to be making difficulties where there are none.  There are various decoders that incorporate relays or circuits that give an on/off or switchover function.  Look at the LDT SA-DEC4.  There are others that can be set up either to give a pulse for a solenoid or to switch a constant current.  The Switch Pilot can do this.  See page 7 of the current instructions.  There is a small switch marked k93 and k94; set it to 94 for constant output (the designations come from the early days of Maeklin digital).  The outputs cannot be set individually, so, if you have no use for the other 3, you would do better to look at the Uhlenbrock 67500 or 67600.

[Crosland]

We seem to some extent to be making difficulties where there are none.  There are various decoders that incorporate relays or circuits that give an on/off or switchover function.  Look at the LDT SA-DEC4.  There are others that can be set up either to give a pulse for a solenoid or to switch a constant current.  The Switch Pilot can do this.  See page 7 of the current instructions.  There is a small switch marked k93 and k94; set it to 94 for constant output (the designations come from the early days of Maeklin digital).  The outputs cannot be set individually, so, if you have no use for the other 3, you would do better to look at the Uhlenbrock 67500 or 67600.

 

An accessory decoder such as the switch pilot is not suitable for switching the track supply. You still need a relay.

 

Andrew

[TWG]

Yes, Andrew is quite right about the Switchpilot (you would need the Switchpilot Extension).  Apologies for not thinking things through.  However the Uhlenbrock devices are suitable, as they have no connection between the input current and the output.  They contain a relay and the description on the website specifically suggests using them to switch track supply.  The LDT device contains 4 relays and also appears to be suitable.  I have a Viessmann decoder,  which I use as on/off switches, feeding lights and accessories from different supplies; you can hear the relays clicking as they change (I can't recommend it as Viessmann prices, once very reasonable, are now absurdly high).  There are probably others.

[csiedmo]

Thanks guys,

I'm wanting to isolate on two different tracks, so I had started to look at the NCE Dual-Relay (two independent relays on the same board) attached to a NCE Switch-It decoder (which will decode two devices), which was coming out at about £28.

The Uhlenbrook 67600 that TWG mentions, I understand to be 2 decoders/switches combined into one cased device (I wish I was more fluent in German-English), so is a lot "nicer" than the NCE products and about five quid cheaper!

So that's the new favourite!

Thanks again!

Ed

[TWG]

 

.

The Uhlenbrook 67600 that TWG mentions, I understand to be 2 decoders/switches combined into one cased device (I wish I was more fluent in German-English), so is a lot "nicer" than the NCE products and about five quid cheaper!

 

The Uhlenbrock 67500 has 2 single pole changeover contacts that work together, the 67600 has 2 separate contacts with different DCC addresses.  While Uhlenbrock do not have an English version of the website, they do have good  English translations of the instructions for their products.  You can find these under Downloads, then click on Handbuecher, then on English.  If you have any further questions, phone the UK importers, A&H Models, who are good in my experience.