Install sensor signals

Guiding light Chris Leigh has an illuminating experience installing automatic signals.

Back in the days when I had my Hornby-dublo train set, my dad bought me a two-aspect colour-light signal. I already had a couple of semaphores, one of which was electrically operated, but the colour light was so much more exciting, especially if you turned off the lights and played trains in the dark! When my brother was driving, it was great fun to throw the signal to red at the last second and see how far he would SPAD (signal passed at danger)! Since then, signals have not figured much on my layouts. ‘Black Dog Halt’ had the solitary Chippenham home signal, controlled by the fiddle-yard operator, and it simply held the train until he had a space for it in the fiddle-yard. The train driver had control of a whistle or horn to remind him if he forgot to pull off the signal! On my Canadian layout I have a three-aspect signal in which each of the aspects can show green, amber and red from a single LED, to give the umpteen permutations necessary for the North American system. I had to get my brother-in-law to build the switch unit that operates it. I’ve never gone beyond a single signal on any of my layouts, largely because electronics and electrical wiring is outside my area of expertise, and I had little prospect of making them work properly.

LIGHT FANTASTIC

However, when Train-tech offered me the chance to try out its new sensor signals, the only suitable test-bed was my ‘Polwyddelan’ layout. The prospect of having working signals alongside the buffer stop lights and station lamps really appealed although, in reality, it is unlikely that a modern single-track branch would have such signalling. The sensor signal does just as its name implies. Its default position is to display green, but the moment a train passes over the tiny light sensor, the signal turns to red, just as it would on the real railway. It will default back to green after a set time period but, if it’s linked to a second signal, it will remain red until the second signal is passed and then, if it is a three-aspect signal, cycle through amber to green after a preset interval. What really appealed to me is the ease of installation, particularly on a DCC layout, although it is not significantly more difficult on analogue. There is minimal wiring to be done, and you can add such extras as a manual override, mimic displays on your control panel, or add additional signals without disrupting what you’ve already installed. There are a couple of important considerations to bear in mind, however. The signal needs to be accurately positioned so that the light sensor detects the passing train and is not affected by strong light from elsewhere, and there must be good, reliable power connection. On DCC, the power connection is from the track, while analogue users will solder power connection to the signal.

RETRO-FIT

I did face one small disadvantage. My layout is nearing completion. In order to fit the signals in appropriate locations, I would need to modify small areas of scenery, so the first job was to find locations that would cause minimum disruption to finished work. The two locations were obvious, one at the platform end and the other close to the fiddleyard entrance. This had the advantage that both signals would be on the same baseboard section, so there would be no need for more inter-baseboard wiring. The signal at the platform end would be teetering on the edge of an embankment, so it would be necessary to install a small concrete plinth for it to stand on. This could be purely cosmetic, and fitted after the signal was installed, tested and working correctly.