Sunday, 8 January 2017

Really Simple Block Wiring

If there's one thing I struggle with greatly in this hobby, it is wiring. No sooner does the soldering iron come out than my wife invariably grabs the car keys and head to the shops, and I generally find myself quitting the hobby 14 times within the next hour! So this post isn't designed to enlighten the minds of the DCC savvy circuit breaking, record making masters of electrical wizardry. It is purely for the simple DC modellers, like myself, who struggle when it comes to the thought of which wire goes where and would like to master the basic concept of creating an isolated block of track that is controlled by a simple switch. Because, let's be honest, we all have to start somewhere before we stretch our imaginations to the next level.

As you can see by the above diagram that I drew up on a piece of paper, all I wanted to do was create an small set of isolated blocks of track on my staging shelf, that by means of throwing a simple switch would cut the power to one locomotive at a time. I could then throw a switch to the other track to make that track live and bring a different locomotive into view on my bookshelf layout. The problem was, whenever I Googled anything like DC block wiring for a model railroad, the result was a series of diagrams popping up on my screen that resembled the wiring schematics of a Collins Class submarine. Thankfully, model railway wiring and I have reached a peaceful truce. I call it the KISS treaty, short for keep it simple stupid. So this little project had a simple outcome, that simply works.

Visiting my local Jaycar Electronics store, I purchased 5 toggle switches with the simple on/off lever frame, making sure that they were the version that had the on/off marked boldly in red and black. Not only do they look better in my opinion, but eliminating which way was on from which way was off made it a lot easier for me to understand what I was doing. These switches are known as SPST, or single pole single throw switches, and a good run down explaining the differences between SPST, SPDT and DPDT can be found on the website Sparkfun.

The single throw switch simply acts as a current break for the positive wire that feeds from the control pack to the rail. The block of track that will be isolated is of course defined from where you use a plastic insulator join (or carefully cut gap in the track) as shown in the above drawing, or between two insulated breaks in the rail if creating a block section on a continuous stretch of track. The negative wire is then connected to the negative rail, bypassing the toggle switch altogether. On is on, off is off, and a better explanation of how it works can be found on the website Learning About Electronics. The term common rail wiring simply means that the negative wire power feed is already connected to the negative rail (providing a common rail and negative grounding). So wiring a toggle switch using common rail wiring will only require the positive wire feed into the toggle switch and a positive wire out of the toggle switch to the positive rail. I still connected the negative wire to each section I was wanting to isolate simply because of the joins on each track where my staging shelf connected with my layout.

Mounting the toggle switches the front of my lower staging shelf kept each one within easy reach.

Between the upper and lower levels of my layout, I wanted to create 5 isolated blocks of track, 2 for each siding on the lower staging shelf, 2 for each siding on the upper staging shelf and 1 for the main platform road at the station on the upper level. So to keep the toggle switches reachable from a single operator's point-of-view, I drilled 5 holes centered at the front of the lower level staging shelf, wide enough for the body of each toggle switch to sit up level with the surface of my staging shelf.

Underneath the layout, the positive wires went in at one end of the switch and out on the other to the track above.

The wires to each switch are connected from underneath my layout. As you can see in the above photo, the single positive (red) wire has a join that connects with 2 wires that lead to the positive 'in' on both toggle switches. Each switch then has a positive 'out' wire that leads through the holes drilled to the left of picture to the two tracks above on my staging shelf. One is joined the positive rail on track A, the other is joined to the positive rail on track B. On the other hand, the negative (yellow) wire has a join that connects with 2 wires that bypass the toggle switches altogether, they lead directly through the holes drilled to the left of picture to the negative rail on track A and the negative rail on track B. It doesn't matter which negative wire connects with which negative rail above, as they both join beneath the layout and become the same wire below that feeds back to the control pack.

These simple on/off switches will control each block of track I wish to isolate.

The toggle switches I purchased from Jaycar are positioned in place from underneath the layout and secured above by a screw-on washer that tensions down on the face plate. The 9 mm plywood base on my staging shelf proved too thick however for the small clearance on the thread between the washer and face plate, so I had to make a backing plate using some scrap 3 mm MDF board. I then covered the MDF board using some leftover adhesive vinyl wrap, keeping with the same steel checker-plate pattern that I used on the back panels of my layout. I glued the backing plate in place using some craft glue and then tensioned the washers on the toggle switches until the whole assembly was held firmly in position.

Mounting the switches neatly didn't detract from the overall appearance of my layout's staging shelf.

The finished panel looks stylish, but is really, really simple. The simple switches provide simple operation on a simple block wiring section of staging tracks. The two toggle switches to the right control the two tracks on the bottom level, while the other 3 toggle switches are sitting in place ready to be wired up to the 3 isolated block sections that will be located on my upper level extension. Once I have named each track location, I will add a small nameplate beneath each toggle switch to give the simple panel the feel of a signal box.

While I am still no expert at model railway wiring, sitting down to write a how-to article such as this really makes the lessons I've learned stick. For those that argue that DC control should be referred to as Dinosaur Control in this digital age of model railroading, this simple block wiring technique has stood the test of time in this hobby. With Philden now wired and ready to handle the coming-and-going of two different trains on an up-and-back layout, I feel a lot more confident that this simple project will add a lot more visual operating fun to a small layout such as mine. Now all I have to do is send in my exhibition applications and see how my new layout handles some model railway show appearances this year.

See also; Let's wire this up


  1. Phillip
    Not really relevant to this particular post but I'm wondering whether you would be able to publish a track plan (rough pencil drawing would be fine) of both levels of your layout. Your photos show most detail I guess but an actual diagram would be great. Thanks Peter

    1. Good suggestion Peter. I've been putting it off, and putting it off some more, thinking that if the track plan drawing wasn't as nicely illustrated as what appears in Great Model Railroads magazine, then no-one would want to see it. But, if everyone is fine with one of my own hand drawings such as above, then at your request I'll draw one up in the very near future. At least it will give everyone a good overview of just how much modelling space you can fit into a condensed bookshelf layout. Stay tuned!

    2. Thanks Phillip

      I'll look forward to it. Peter


Thanks for taking the time to visit Philden. I hope you'll book a return ticket soon. Cheers, Phil