Background. There are 8 Servos for 11 sets of points across 4 boards, 4ft x 14in and a small section of infill. They will get dismantled [and mantled] regularly, so means of operating the points from a control box had to be found, with a minimum of connectors. Richard of DCC Concepts, suggested his Alpha Encoder would provide Signals for the Servo boards and Alpha Mimic could also use the Signals to indicate the routes set on the Control Panel. So I left the show, with a couple of boxes in my bag and wondering quite what I had taken on??
I have a couple of reasons for the Servo choice, firstly I did r/c planes for a goodly number of years, so familiarity is quite high up there, secondly, I wanted to place as many as possible on the top of the boards, so they had to be small enough to go under platforms. Thirdly there are quite a few bracing walls under the boards and Servos easily be manipulated around / through them. I like the Cobalts, they are very efficient, self-contained and easy to use, so they were definitely also in the choice zone.
Testing the Assembly. Each SPDT switch connects to 3 labelled contacts to reverse the polarity of the feed [see the first picture - far lower left of the larger board - number one switch connected]. The Alpha Encoder then produces a Fwd / Rev signal for Accessory [servo] number 1. The signal is passed to the Controller Handset from the black socket, on the left hand edge of the board, along the black curly cable which is also providing the power supply for the Alpha Encoder. The Servo could then be controlled from either the SPDT switch or the controller handset, both work just as well. Those same DCC Signals are read by the Alpha Mimic Board, from 2 wires connected to the DCC Bus Wire. There is one dual colour LED for each direction which could be selected at each set of Points. It then changes the dual Red / Green LEDs to indicate which routes have been selected, matching the direction of the Points.
At the top of the same picture there is a small black PCB, with a little green light. The 2 wires at the top left of this board carry both power and the digital signals into the board, from the controller handset. It will identify which Servo is being addressed and send Fwd / Rev to the relevant one [1, 2, 3 or 4] along the 4 red wires connected along the lower right-hand edge. The 5th [orange] wire is the common return. The larger board at the right-hand side of the picture sends to the appropriate Servo being addressed, as can be seen in the second picture [only 1 & 4 are connected for initial test purposes]. This board also controls, throw angle, direction and speed that each Servo arm moves. The next 4 Servos will be connected to a second similar board system, with Servos addressed 5, 6, 7 & 8.
The third picture shows the inside of the box, with wiring nearly complete, only 3 more SPDT switches to add ...
... and the last picture looks at the face of the Control & Mimic box, with completed wiring. Last job now, to tidy the wiring.
Actually the wiring is very much more simple than the impression given by the wiring in the pictures. Each Alpha board can be thought of as 12 separate circuits built onto one breadboard, together with some clever electronics, which you don't have to even look at, let alone touch! Each circuit has an SPDT switch wired to 3 push fit connectors [labelled L C R] - Right, well that's it, an Encoder taken care of, done, finished.
For the Mimic lights, each LED is already connected to a plug, which fits into a socket on the board, one for the left Points selection and the other for right [1L 1R - 2L 2R - 3L 3R - ... ] and so on. - Err, well, that's it, the Mimics taken care of, done, finished.
For the next circuit, just go to the next set of connectors and follow the above pattern. In truth the wiring is absurdly simple, if you complete one circuit at a time. It took a lot less time than making the box. The choice of Alpha RGB ribbon wire made life easier, as an aside comment, so much tidier – imagine what the inside of the Control Box would have looked like with single strand wire!!.
Come to mention it, if you chose the right size SPDT switches, you don't even have to solder the 3 wire ribbon to the switch, you could have screw connections there too. I just liked the smaller switches and solder just requires a proper routine. It isn't pretty, but it stuck, so if you don't like "ugly" look away now!
For a working test of all 8 Servos, switches and Mimic LEDs, the link might take us there, but this is a first for the video, for me.