South Downs Railway

Modern Image, Computer Controlled

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Signal Control

Interlocking SIGM20 signals with Traincontroller block signals

Sometimes it is necessary for Traincontroller to force a SIGM20 signal to red. This can be where a train needs to take a route that is blocked by other trains; at crossings for example. The SIGM20 doesn't know that Traincontroller has reserved track, so can't take account of it.

https://www.signatrak.co.uk/product-support/24-signal-controllers/66-sigm20-control-from-traincontroller

The SIGM20 still sets the signal to red/amber/green based in the track ahead. All this change does is to set the signal red for other conditions that haven't yet affected the track ahead, but may do so soon. I suspect that most signals will need this setting eventually, if it is to become safe for a human train driver to drive round the railway.

Ground Dwarf signals

I've finally added dwarf signals at Eastleigh and Portsmouth container yards. In both cases they control exit from the yard tracks to the main line.

The models were kits, from a Chinese source via ebay. You get a plastic mounding and the LEDs; enough for 10 signals for £8 which was excellent value. Superglue holds the LEDs in. I've arranged the LEDs "back to back" so they only have 2 wires. With one polarity the green LED lights; the other way round the red LED lights.

The signals are controlled by SIGM20 boards as usual. The signal heads are programmed as "2 wire searchlight". Because they have no amber aspect, there is no "next signal" number programmed. For the signals at Eastleigh, the next signal should actually be a virtual (among other things to tell you if one of the 3 possible platforms ahead at Petersfield are occupied). Strictly I should add "signal 257 is red" to the "go red when" conditions.

The original plan had been to make some kind of searchlight signal from a red/green bicolour LED and a plastic block. The mouldings for these signal bodies made that ida daft. I've now ordered some 3 aspect versions for a 4 head signal gantry at Portsmouth.

dwarf signals 1

 

dwarf signals 2

Automatic Signal Control

When I was younger, I wanted my model railway to have signals. But not just signals set by hand: I wanted them set automatically as trains went past, when the track ahead had a point set against it etc. The technology just wasn't there 30 years ago.

When I started again into this - about 10 years ago now - I looked into DCC as a way to control trains and realised that now, all of the information to work out a signal aspect was available on the command bus. The idea of automatic signal control started there, but I has to learn LocoNet and DCC first.

There aren't many signals on the railway yet: but there will be. It's a modern image railway, so there will be colour light signals, set automatically as trains move. When a train passes a signal mast, the signal will go red; when the points in the track ahead aren't set correctly, the signal will go red. CML Electronics' SIGM20 does all this, and more.

The SIGM20 is fundamentally a LocoNet device, rather than a DCC device. All the information to work out the signal aspect is on LocoNet. It knows the positions of the points; it knows what track sections are occupied; it knows what other signals are set to. The SIGM20 hoovers up this information, and works out what each signal should be set to.

Each SIGM20 can drive 8 LED signals. The boards will be distributed around the railway, as near as possible to the signal masts.
The new DAC20 extends automatic signal control to semaphore signals too. We may have one or two semaphore signals in the engine shed at Portsmouth, just for fun!

List Of Signals

This is the definitive list of all of the signals on the railway.

SIGM20DCC addrLocationVirtual
1 201 Portsmouth platform 1 exit signal  
1 202 Portsmouth platform 2 exit signal  
1 203 Portsmouth platform 3 exit signal  
1 204 Portsmouth platform 4 exit signal  
1 205 Portsmouth GR1 exit  
1 206 Portsmouth GR2 exit  
1 207 Portsmouth spur on entry to Portsmouth  
1 208 Portsmouth GR3 exit  
1 209 Virtual at diverging junction in Portsmouth ladder. Yes
1 210 Virtual in Portsmouth loop at diverging junction Yes
2 217 Main line ORANGE signal before Portsmouth loop junction  
2 218 Portsmouth reverse loop 1 exit signal  
2 219 Portsmouth reverse loop 2 exit signal  
2 220 Portsmouth reverse loop 3 exit signal  
2 221 Main line GREEN at foot of Butser hill  
2 222 Main line ORANGE at foot of Butser hill  
2 223 Virtual in Portsmouth approach Yes
2 224 Virtual in Portsmouth approach Yes
2 225 Virtual at diverging junction in Portsmouth ladder. Yes
3 233 Main line ORANGE storage track 4 exit under Eastleigh  
3 234 Main line ORANGE storage track 3 exit under Eastleigh  
3 235 Main line GREEN storage track 1 exit under Eastleigh  
3 236 Main line GREEN storage track 2 exit under Eastleigh  
3 237 Eastleigh stand 2 exit to main line  
3 238 Main line GREEN at junction for Petersfield loop  
3 239 Reverse loop exit to main line at Petersfield Loop  
3 240 Unused  
3 241 Virtual at diverging junction in Portsmouth loop Y
3 242 Virtual to entry to ORANGE storage roads under Eastleigh Y
4 249 Main line GREEN at junction for Portsmouth spur  
4 250 Portsmouth spur at entry to GREEN main line  
4 251 Eastleigh stand 1 exit to main line  
4 252 Petersfield platform 1 exit  
4 253 Petersfield platform 5 exit, ORANGE  
4 254 Petersfield platform 4 exit, ORANGE  
4 255 Main line ORANGE at diverging junction to Portsmouth spur Y
4 256 Main line ORANGE at diverging junction to Eastleigh Y
4 257 Main line GREEN at diverging junction into Petersfield Y
4 258 Main line GREEN at diverging junction into Petersfield Y
5 265 Petersfield platform 2 exit, GREEN  
5 266 Petersfield platform 3 exit, GREEN  
5 267 Fiddle yard ORANGE line 1 exit  
5 268 Fiddle yard ORANGE line 2 exit  
5 269 Fiddle yard ORANGE line 3 exit  
5 270 Fiddle yard ORANGE line 4 exit  
5 271 Fiddle yard ORANGE line 5 exit  
5 273 Diverging junction on main line ORANGE at entry to Petersfield Y
5 274 Entry road to Eastleigh, diverging jn at double slip to track 1,2 Y
6 281 Fiddle yard GREEN line 1 exit  
6 282 Fiddle yard GREEN line 2 exit  
6 283 Fiddle yard GREEN line 3 exit  
6 284 Fiddle yard GREEN line 4 exit  
6 285 Fiddle yard GREEN line 5 exit  
6 286 Diverging junction on main line GREEN into fiddle yard Y
6 287 Diverging junction on main line GREEN into fiddle yard Y
6 288 Diverging junction on main line GREEN into fiddle yard Y
6 289 Diverging junction on main line GREEN into fiddle yard Y
7 297 Main line GREEN at diverging junction to Clanfield  
7 298 Main line ORANGE at Clanfield junction  
7 299 Clanfield platform 3 exit  
7 300 Clanfield platform 2 exit  
7 301 Clanfield platform 1 exit  
7 302 Diverging junction on main line ORANGE into fiddle yard Y
7 303 Diverging junction on main line ORANGE into fiddle yard Y
7 304 Diverging junction on main line ORANGE into fiddle yard Y
7 305 Diverging junction on main line ORANGE into fiddle yard Y
7 306 Diverging junction on main line ORANGE into fiddle yard Y
8 313 Orange fiddle yard track 1 centre  
8 314 Orange fiddle yard track 2 centre  
8 315 Green fiddle yard track 1 centre  
8 316 Green fiddle yard track 2 centre  
8 317 Petersfield reverse loop behind fiddle yard  

 

 

SIGM20 serial numbers:

SIGM20 serial number location
1 8 Portsmouth
2 7 panel under Portsmouth
3 6 panel under Eastleigh
4 5 panel under Eastleigh
5 64 fiddle yard
6 65 fiddle yard
7 277 Clanfield

Fiddle Yard Signals

The first section signalled is the fiddle yard. The fiddle yard isn't a scenic section, so the signals don't have to look that part. Instead there are small signals inserted into the baseboard. Small signals made from 3mm red/amber/green LEDs have been assembled using veroboard, and mounted into the baseboard to the left of each track.

baseboard_signals

fiddleyard_signals

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20 October 2019

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