21st century technology

Having given up with DCC many years ago, I should really know better than to combine modern technology with 1950s state-of-the-art!

BUT - technology has its uses - the shuttle track being a prime example. Trouble is, it's very complicated, what was a simple shuttle control unit has been modified again and again to make it work as it currently does.

For starters, the signal in the main station is just a bit too far away from where the train stops and starts. The programming within the controller turns the signal green for only five seconds and this is not adjustable so SPADs occur. I overcame this by adding a home-made delaying PCB (as used for the automated signals elsewhere).

Then there's the points at the terminus station. It was suggested that it would be great if they could be automated, and I found a way to do it by taking a feed from the shuttle signal - a transistor is wired to the green signal LED, this provides current return for a relay, which operates another pulsing relay (one pulse turns on, one pulse turns off) which then operates the original pcb for the points controller.

Then there's the track isolation, the shuttle has to be completely electrically separate from the rest of the track system, no common return, so to manually operate the tracks (so that I can use the siding) I had to add yet another relay control system to switch out the live and return when the shuttle module is operated. 

All of the above means that there is now a fairly complicated amount of electrical components under the boards just to make two locos run up and down in rotation.

I wasn't looking for a solution as so far, this hasn't really been a problem but after doing some research on how to motorise a standard Dublo turntable (still working on it) I came across several mentions of something called "Arduino".

I've always been intrigued by things like the Raspberry PI and often wondered what they actually do and what people use them for. After learning that they can control devices and require only basic programming skills (years of owning a ZX Spectrum and also using MS Visual Basic!) I decided to splash out a whole £4.00 for this:

After about an hour of reading tutorials online, I'd found a basic program that made the internal LED on its circuit board blink and realised that the basics of the blink program were all I needed to create a shuttle program of my own.

By pairing this with a relay board I can control track polarity, signals and points just by using simple on/off commands and delay times. The first version of the program I managed to figure out in about an hour, just need the relay bank to begin testing. I should now be able to adjust the journey times, waiting times and of course the signal aspect timings. Once the program is sent to the device via PC and USB cable, it's stored within the unit and just needs a 12v supply. It's also possible to control the speed of the loco, so smooth acceleration and deceleration may also be possible in future.

This will mean that the shuttle operation will be via two separate PCBs, one containing the program data and one with all the relays and transistors. It'll make fault-finding much simpler and separate the more delicate programming aspect from the relay controls. In its current format, if a short circuit occurs then the whole shuttle unit shuts down. Sooner or later there is a risk of damaging the unit due to the high current consumption of the locos. Later on I can also look into using variable speed control for starting and stopping the trains more smoothly. 

Clearly there are many more possibilities for integrating these into the layout. The signalling could be operated using one of these and I could then vary the timings and even design it so that the timing doesn't commence until the train has passed the last of the three sensors on the inner loop.

I could even automate the upper loop...