Full Version: Stub terminal safety in DCC
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With DC we could protect a stub terminal by cutiing a rail and wiring in a diode to halt a loco but allow it to reverse out automatically.
As DCC runs on AC a diode would not control such a circuit. Has anyone any ideas on circuitry to achieve the same protection . I want to arrange a shelf layout fo DCC and can see some potentially loco fatal situations for stub ends ( inattention, distraction, unexpected acceleration or merely using speed control in the wrong direction).
My irst thought was to use a block control switch to isolate the last section, and reset it to closed to reverse the loco out, but this seems a bit too crude operationally.
A second thought is to use an LDR to bias a transistor to control a NC relay. An RC circuit could slowly repower the relay to restore power to the stub section, giving time for the operator to reset the DCC controller to where it is wanted.

If any one hs any ideas or circuits to achieve protection, I would love to hear them. Cheers
Very simply, put one N.O pushutton in series with that section. the loco will stop in that section unless the pb is held down. Just a safety override button.

Of course, this is down and dirty, has no logic, won't allow only reverse, does not care about turnout position, etc.

My $0.02
Thanks Cid
It is neater than the toggle switch idea I had. The test racks are on the workbench at present, but I have already seen how it s possible to over run the end of the track!!

Paul
I drilled a small hole at the end between the rails and plugged a big black nail in when in operation. May be to simple?
Isn't one problem with a switched dead section that when power comes back the loco will continue the way it was? Will a direction reverse apply if the loco isn't receiving signals?
David
I think you are right, I was expecting to reverse the loco before restoring power, but I can see that it would not receive anything.
I suppose we could get round that by having the length of the section long enough to give time to restore power and send the DCC signal before the loce ran too far forward. My other idea of using a relay and recharge circiut would suffer from the same disadvantage you point out.

Paul
Reinhard
See comment fom Davd and reply. I'm using buffer stops on the test bench and think I will have to instal them on the layout, same as your nail.

Paul
I was registered, but some time back... so I am new again, I guess.

And a month late to this party, but thought I would toss in a correction.

When the DCC control station sends a command to a loco to move, it includes the direction. So, even if the loco is on an unpowered section of track, as soon as it gets power it will go in the last direction selected. In other words you can change the direction on the controller whether or not the loco is getting power at the time. The loco doesn't remember the last command it got when it wasn't powered, it will be looking for a new one.