Using a single Railcom on multiple track sections

[Heinz57]

Hi all,

 

I'm considering the use of Railcom for the tracks within the main shed on my Gresty Bridge layout. The shed is around four feet long with two tracks and can hold up to eight locos.

 

I'd like to use Railcom to display the DCC addresses of each loco in the shed. But I'd like to avoid purchasing eight of these devices. My question is, would it be possible to use a single railcom device for four sections, but still retain power so lighting and sound doesn't cut out?

 

Here is a diagram to sort of describe what I mean...

 

 

As I say, when the display is on one section I'd still like to retain power to the other three so sound and lights will stay on. This may require some sort of clever eletronics. Has anyone got any thoughts?

 

Cheers,

 

Matt

[WIMorrison]

If it possible then it will be dependent upon the ability of the display to read and display multiple decoder IDs at the same time.

 

What display do you plan to use?

 

FYI, I can do this easily (and do) but I am using a computer to read and display this data

[Nigelcliffe]

I'm assuming this is a simple display, like the Lenz LRC120.    I think it could work, needs an appropriate change-over switching between the display and "non-display normal DCC".  

 

I'd approach it like this ( Theoretical,  I've not tried it, someone will have to experiment! ): 
Single-pole change over relays, one per section, with each relay switching between normal track supply and the display connection.  

A rotary switch which can select one of the relays, leaving the other relays in the "normal track supply" state. 

 

Relays are fairly cheap on pre=assembled boards from Amazon and Ebay. They come in fours and eights (and other sizes).  Will need either 12v or 5v DC to power the relay boards (depending on voltage of board purchased), at a push this could come by rectifying the DCC track power, but separate DC power is better. 
Rotary switches are usually 12 positions.  A standard 12-way single pole rotary switch will come with shaft end-stops which can limit it to 8 (or 4 if preferred) positions.

 

 

But the hardware and a system which can display the lot, as Iain describes, might be better.

 

 

Or, the low-tech solution low-cost option is fridge magnets.  Write the number of each loco on a fridge magnet.  Have a metal sheet behind the track plan, and move the right magnet to where the loco is parked. 

 

 

 

[Heinz57]

Thanks chaps,

 

I was thinking of using the Lenz LRC120 display. Obviously this has a single display. So I'm wondering if there is a posibility to use a rotary switch or something to switch between track sections. So say its currently reading and displaying section 1, I then move the switch and its now reading and displaying section 2 and so on. Is this possible?

 

Cheers

[WIMorrison]

Absolutely possible, but a bit of a nightmare with the wiring

[Nigelcliffe]

Rotary switch on its own, as Iain says, possible, but messy.    Rotary switch plus relays, is simpler, neater wiring.

 

Switch on its own, I can think of two approaches:

a - expensive, but usable result on single switch.  One multi-wafer rotary switch.  Needs 8 wafers, and at least 8 positions, for the eight loco blocks (one wafer per block).  In 7 of eight positions, each wafer connects to normal supply.  In the 8th position (different position on each wafer), the wafer connects via the LRC120.    Multi-wafer switches are expensive (quick glance at Farnell, and I estimated the parts at over £60).  And its a lot of wires/connections to make.   

b - cheaper, far less easy to use.  Three of three-pole, four position rotary switches (these are standard items).  The total of nine poles means there are up to nine blocks (one pole to one block).  On switch one, the positions are "off", block1, block2, block3, switch two is "off", block4, block 5, block 6,  and switch three is "off, block7, block8, block9.   To use it, two of the switches must be at "off", the third can be either "off" or a block of choice.    I think this is an operating mess.  Getting it "wrong" won't be a disaster, just the LRC won't read anything if two occupied blocks are connected at same time.  

 

 

 

[Heinz57]

Thanks for your help. Do you have any infomation on the extra componentry I might need and perhaps a wiring diagram so I can understand what you mean?

 

Thanks

[Nigelcliffe]

31 minutes ago, Heinz57 said:

Thanks for your help. Do you have any infomation on the extra componentry I might need and perhaps a wiring diagram so I can understand what you mean?

 

Thanks

 

Which solution ?   Relays plus one Rotary Switch  ?  A Multilayer Wafer Switch ?  Three Rotary Switches ?

 

The wiring for each, whilst similar in concept, is different. 

 

- Nigel

[Heinz57]

Relays plus one rotary switch, to read four sections please

 

Cheers

 

M

[Nigelcliffe]

As I said, this is theoretical, so needs to be tried out to prove it.  I am pretty confident it will work.

 

 

 

The image shows a typical bought 4-relay module.  They're cheap on Ebay or Amazon.  8-relay versions also available, or you could use two 4-relay units to swap all eight positions.  The diagram is for a 5v relay board, so 5v supply (old phone charger or old USB charger ? ).  You can also get 12v boards, so a 12v DC supply. 

 

From the top:  a typical rotary switch - in this case, a 12-position single pole.  It will have a tab washer on the shaft (under the fixing nut) which sets how many positions are in use.  Set it to allow four, or five if wanting an "all off" position. 

The purply-black wire (0v/ GND) goes to the centre pin on the switch.  Four wires (green) come from the outer pins to each of the four inputs (IN1 to IN4 on relay board) - I'm assuming the board has the Inputs to GND to operate them, most are supplied this way.  
Wires also branch from VCC to a 5v DC supply, and from 0v/GND to the 0v of the DC supply. 

You can buy, cheaply, pre-made ribbons of cable with "dupont" connectors on the ends, much the quickest way to attach to the pins on the board shown,  cut the other ends for soldering to the switches and power supply. 

With just the above connected, the rotary switch will connect one of the relays depending on switch position.  You'll see the LED Indicators (IN1 to IN4) light in turn, and also hear each relay click over.

 

 

At the bottom, blue outputs 1 to 4 go to your track sections in the shed.  The "normally connected" (ie. connects when relay not powered) goes to the normal DCC feed  (red in your diagram in the first posting, sorry should have matched the colours!).  The "normally open" (ie. connects when relay is powered) goes to the out wire from the LRC120  (orange in your first diagram posting).   

With one relay operating, it swaps power to the track for one section from the direct DCC to going via the LRC120,  but all others remain on direct DCC.

 

 

 

 

[Heinz57]

Perfect, awesome, thanks for that! To be fair that wiring on that doesn't look that complicated

 

As you say though some sort of experiment would have to happen to try it out.

 

Cheers

 

BTW, don't worry about the colours of your diagram not matching mine. You were kind enough to post the diagram so thats all what matters. I can cross reference that from the written infomation you provided with it. Thats enough for me to figure it out!

Edited June 13, 2020 by Heinz57