Monday, August 29, 2011

Tech: under-layout wiring, switch motors, & switch controls.

Yeah, it's been a while. I've been messing with other projects lately and the layout has been neglected. This weekend I went back to it and finished wiring up the Prince segment and thought I'd share some of the electrical work involved.

Due to prior positive experiences with Circuitron Tortoise switch machines, I chose to use them on this layout. Yes, I'm sure there are cheaper options than a Tortoise... but they work well, seem reliable, and are versatile. They can drive more than one turnout and they have a built-in DPDT switch to handle frog power for the Atlas C55 track. Circuitron makes a remote mount kit that when paired with an extra cable and actuator will operate two switches with one motor (such as for a crossover).

A switch motor is useless without a way of controlling it. I wanted to have the option for both local control via a fascia-mounted pushbutton and to allow for remote operation either via handheld throttle or by a dispatcher using a CTC panel or comparable computer interface. With this, the list of options gets pretty slim. I am using the Digitrax DS64 for the task.

The 3'x16' Prince WV segment has a total of 11 track switches, 8 of which are arranged as crossovers. That means 4 crossovers and 3 other switches for a total of 7 Tortoises and two DS64s in this segment. Each Tortoise has a PCB sticking out with 8 solder pads. Two to drive the unit and the other six are the DPDT switch that is thrown as the motor drives the turnout. For a crossover, all 8 terminals are used. When you start adding in feeders (for blocks, since I've planned ahead for detection and signaling), bus wires, frog power wires, and ancillary things like the pushbuttons on the fascia and LocoNet wiring, it adds up. There's a lot of wire under this layout and more is to come. Fortunately, some spiral wrap helps a lot as you see below.


The big wire at the back is 12 gauge stranded for bus wire. Green wires are frog feeders and red and black are usually track power. These are 22 gauge solid. The yellow and orange pair you see above goes to one of the pushbuttons on the fascia, they're peeled off the 4-conductor ribbon packaged by Model Power. The other two (red and brown) feed power to the Tortoise motor.

Below is the DS64 and its wiring:


Loconet cable on the DS64 is not currently connected - I'm using track power for both power and data to the DS64 for now. The six-space terminal block next to it is for block feeders. The side with no wires in this photo will be connected to a detection circuit in the future, but for now I've tied all blocks into the main bus wire at the back edge of the layout.

More to come later on the DCC system and the plan for power management as well as the plan and construction of Quinnimont.