which (switch)witch is which?

Didn't think I'd taken a photo of this - on film no less!

One quick scan and a digital cleanup later...

About 15 years ago, I had made up a demo control display for the Erin Mills Model Railroad Association using N scale track and turnouts.

The top "Inglenook" was controlled by a single capacitor-discharge circuit (which I thought came from a plan at Rob Paisley's excellent circuitry site, but didn't) that routed power via a diode matrix to a set of Atlas #200 "Snap" relays which, in turn, routed power to a set of Tortoise machines under the plywood. This was slow motion control of three turnouts with sinlge-button route selection. The snap relays had pretty low current draw and virtually no mechanical binding, so a single cap-D was OK. A bonus was the ability to manually slide any snap relay lever and control each turnout separately if required.

The bottom ladder used Peco PL-10 twin-coil solenoids supplied with current from one-per-turnout TTL input capacitor-discharge circuits made from plans at the TracTronics site (see SwitchWitch), also via a diode matrix. Instant and reliable snap-action regardless of how many turnouts move simultaneously, without routing heavy current through the tiny Radio Shack 0.5 Amp momentary N.O. pushbuttons (which would then arc internally and weld themselves 'closed'). Brilliant, low current control circuits for use with something like a Launchpad micro controller? Hint hint...

I added a momentary on-off-on toggle switch to the leftmost TTL input cap-D (on the lower ladder) to show individual (local) control of turnouts in this option as well. The SwitchWitch circuits can be built active-high or active-low to suit your driver output configuration. The toggle merely grounded either input.

The demo board can be seen here sitting on top of my 2.5'x5' N scale portable layout which was made for DCC and two-cab control clinic at the Erin Mills club. For some reason, I have long since disassembled both of these units and scattered the components to the four winds. Probably seemed like a good idea at the time.

A lot of modellers at that point (and probably still now) had trouble "getting" some of the electrical concepts I was talking & handwaving about. In the end, it was easier to build up some working demo units that could be mulled over in real time. Not sure how many people acted on any of the stuff I presented, though.

check, please!

If you decide to use commercial track products for your layout or modules, BEFORE you start laying these on the baseboard and pinning or gluing them down, CHECK the gauge of each and every piece with a proper NMRA (or other regulatory body's) measuring tool.

Seriously.

I have experienced at least a half dozen separate instances where the commercial product's rail are not in gauge, and can't be corrected. The latest instance involved removing a turnout from a ballasted right of way while making a minimum of mess. Not fun.

Every turnout, every crossing, every piece of sectional or flex track needs to be checked before it is installed. Items that are not in gauge need to be returned to their place of purchase as defective. These items are produced in batches and can vary as enviromental changes and mechanical wear occur.

While you're at it, verify the electrical arrangements of each turnout's point & stock rails with a continuity tester. This is especially important in DCC applications where the optimal situation is to have each point rail the same polarity as its adjacent stock rail to prevent shorting when wheelset's back-to-back distance might be a tad tight. I have had two turnouts where the short rail section after the frog had become isolated from the rest of the route (the wire bond underneath was broken) creating a dead spot.

Save yourself some pain and check first.