PRR Chartiers Branch: Hazel Mine - Electronics
This section covers the electrical work I have done to make the layout operate. The first section covers how I installed the Circuitron Tortoise switch machines to control the turnouts on the layout. I have used these on everyone of my layouts, and I am happy with their performance. Since switching to battery-powered locomotives, I have had to find an alternate method of toggling their position. This is done via a small circuit, which I have covered on this page.
On my previous layout, I had a small pushbutton and one bi-color LED to toggle and indicate the position of the turnout, respectively. The aforementioned circuits were used and I really like them. The miniature pushbuttons I used on that layout didn't stand up to the operating, and occasionally my shirt sleeve would snag one, and so several had broken buttons. Having one LED that showed both red and green worked OK. However, it still made it a bit hard to determine which direction the turnout was thrown. Also, if I would ever have anyone operate on my layout in the future who happened to be color-blind, the single-LED approach wouldn't work. So, for this layout I am going to use two LEDs. The green LED will be positioned such that it indicates the through, or straight line, and the red LED will indicate the divergent route. The LEDs will be positioned to the left or right of the pushbutton, to indicate the direction of the turnout.
To make the three parts look the same all throughout the layout, I decided to make a simple template out of some leftover plywood. I marked a line on the top of the layout that was in line with the location of the throwbar. I made a vertical line on the drilling template that is to be lined-up with the line on the layout. I then marked-off and drilled the holes for the pushbutton and the two LEDs. The pushbutton lines up with the throwbar, and the two LEDs are in the direction of the turnout. By flipping this drilling template over, I can have the holes going in the other direction.
I used a drywall square to mark a line on the edge of the layout in line with the throwbar.
Here you can see the template in action, lining up with a turnout that is right at the front of the layout.
I then positioned the template with each of the lines and drilled pilot holes using the template. This photo shows two turnouts that are close-by each other and in opposite directions.
Next, I disassembled the modules of the layout, so that I could work on them underneath.
With the module stood on its edge, I drilled out the holes for the LED holders that I am going to use.
I used a Forstner drill bit to make the larger holes for the pushbutton. These have a body that measures just under 7/8ths of an inch, so I used a 7/8" bit.
I then drilled a hole in between the headstock ties of the throwbar. In the past I had made the Tortoise actuating rod come up in the printed-circuit board tie, in the middle between the rails. The problem with that approach is that it is always visible. So, this time around I drilled the hole outside of the turnout in between the headstock ties, with the intent of placing a non-operating model of a turnout controller on top of the headstock ties, thereby hiding the actuating rod. Update: it turns out that the force required to move code 100 rails (the first time I've used those, and I don't use hinged rails for turnouts) was too much for the PC ties, so I switched back to having the actuating rod come up through a hole in the PC tie in the center between the rails, which is what most people do.
External Reference:
Using a couple of straightedges, I transferred the relative angle of the throwbar, from the top of the layout to the back, so that I could install the Tortoises under the layout at the same angle. Note that I made the hole bigger in the bottom of the layout, so that there is more room for the actuating rods to move.
For my previous layout, I built these circuits, I mentioned at the top of this article, to control the Tortoises via a pushbutton interface. Each board holds four independent circuits, so that it can, independently, control up to four Tortoise switch machines. I only need two for this module. However, I didn't want to try to route wires back and forth between modules. I have three of these circuit boards, so I can put one in each module. Having two extras on this module may come in handy in the future, if I want to add some animation to the module. Note that there are a bunch of extra wires on this circuit board, because I cut it out of the previous layout when I demolished it, and hadn't bothered to remove the various wires. You will notice further below that it is a lot cleaner.
I connected one of the wires from the circuit board to the Tortoise. I am using wire holders to make the installation cleaner, and also to keep the wires from being grabbed when the module is carried to be moved.
Back in 2002, I built this huge, stand-alone helix for my, then, N-scale layout. I built detection circuits to allow me to monitor the progress of trains going up and down the double-tracked helix. I had bought these 3mm LEDs and their holders to report the position of trains on the outside shell of the helix. They all had red LEDs in them, so I carefully removed the red LEDs from some of the holders and replaced them with green 3mm LEDs. I wound up not using the hardware for these holders (shown on the right), because the front fascia of my modules is quite thick.
I soldered sections of wire to the legs of the LEDs, and then installed them into the module. Due to the module's thickness, I wound up using various glues to hold the holders in position. It seems to be very sturdy, but I can always add more glue over time.
I could then hook up the LEDs' wires together. An LED's red wire connects to the other's black wire. This causes one to light up when the current flows in one direction, and the other when the current goes in the opposite direction. The output of those wires goes to the Tortoises.
As much as I like the idea of using batteries to run the layout, they wouldn't last long with the overhead LED lights I have, so those are powered by a 12-volt power supply. So, for the Tortoises, I decided to go ahead and tap into that existing wiring. The Tortoises don't consume much power at all, so they should all be able to be powered by that one power supply. So, I routed two bus wires from the circuit boards to the back of the module where the 12-volt wires are available. This bus wire is also available for any future lights, animation, and/or sound modules I may install on this module.
I could then install the pushbuttons to complete the whole installation. It took some effort, but I was able to use the hardware that comes with the pushbuttons to tighten them into position.
External Reference:
And here is the final look of the front fascia of this module (rotated 90-degrees, of course). See the link for the buttons that I installed. I really like them. They have a solid feel to them. Yet, the push is smooth. Reviewers have indicated that they feel like elevator buttons, and they do. The chrome look matches that of the LEDs' holders.
This is with the power plugged in. One thing I noticed was that on my previous layout when I used the bi-colored LED, the LED would turn off while the Tortoise was in motion, which was always a bit disconcerting. With using two separate LEDs, the LEDs switch immediately.
Here is a photo of the completed LED, switch, and Tortoise installation of the middle module.