It looks pretty slow here in the halls of CR4. Everyone must be working remotely, that COVID thing I suppose.
Since we’re not too busy I’ll start another discussion about a model train electrical issue.
O Gauge 3 rail train. On 3 rail, the outside rails are neutral and are connected common in all power districts and blocks. That is to say, all outside rails on the layout are connected. The center rail is the hot, places where a track controlled by transformer ‘A’ intersects a track controlled by transformer ‘B’ are built to isolate the center rails.
I run everything in analog: analog here means a transformer is used to provide 0-18 VAC to the track, train speed is controlled by varying the voltage. Standard train bell sounds can be activated by a pulse of DC positive, whistle with pulse of DC negative. These pulses are generated by the transformer, controlled by two separate buttons. Some engines have enhanced features (crew chatter, headlight on/off, open coupler to disconnect cars... ) that are controlled by combinations of horn/bell button presses. Most important to this discussion, engine direction is controlled by an onboard component called a Reversing Unit (RU). With an approx 1 second interruption of ALL power the RU will cycle the locomotive to the next of three states (forward/neutral/reverse) in a loop.
We previously discussed ways to deenergize the track in derail event. That was pretty straightforward, this is the really sticky part.
Imagine two parallel tracks (tracks 1 and 2). Each track has a separate transformer, this allows independent train control. A track crossover allows a train to change from track 2 to track 1, center rails on tracks 1 and 2 are isolated at this crossover.
A train traveling on track 2, engine crosses from track 2 to 1 without incident, a couple more cars pass over no trouble, and then a dented wheel flange causes the next car to derail. Sparks pop out (this causes a fault that cuts power to track 2), car jumps off the track, and (because the engine, now on track 1, continues under power) drags next car off the track, then another, more sparks, cars are being dragged on their sides until track 1 transformer handle is twisted to zero.
SO... the question: How might we cut power to ALL tracks in a derail event? Previously covered in another thread is a faster way for the system to respond to a track fault, now how to get that response (or some as yet undefined trigger) to cut power to multiple tracks AS SOON AS DERAIL IS DETECTED. In this example two tracks are involved, but many layouts have 4, 5, maybe 6. I currently run three tracks, and getting ready for another reset.
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