Autobraking?

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#1
Hi, I've found some references to an autobraking feature in DCC and I was wonder if that's still something that's used. It appears to be something that comes from Lenz. I've seen some references suggesting that it never took off. But, I'm curious about it. It would be really handy at the end of spurs, sidings and near the edge of my layout.

I've been looking into it and I'm not really finding much information. It doesn't look that involved, but if it's not something that's likely supported, then it's not worth doing.
 

tootnkumin

Well-Known Member
Staff member
#2
I vaguely remember something from when first looking into DCC that used (I think) a section of DC track to trigger a stopping function in a train about to cross into the next power district to protect a train stopped in that next power district ( DCC layout divided up into similar blocks as DC with power boosters for each district, so that a short circuit in one didn't shut down the whole layout ), because, as you probably know, a DCC decodered engine will keep on going until commanded to do otherwise, while there's power to the tracks. I think it also relied on the decoder being programmed to not recognising DC as a power source. (hang on, while I get my bullet proof vest on)
 
#3
I vaguely remember something from when first looking into DCC that used (I think) a section of DC track to trigger a stopping function in a train about to cross into the next power district to protect a train stopped in that next power district ( DCC layout divided up into similar blocks as DC with power boosters for each district, so that a short circuit in one didn't shut down the whole layout ), because, as you probably know, a DCC decodered engine will keep on going until commanded to do otherwise, while there's power to the tracks. I think it also relied on the decoder being programmed to not recognising DC as a power source. (hang on, while I get my bullet proof vest on)
From what I saw in a YouTube video, the section of track is insulated from the rest of the track and diodes are used to halt half of the signal. When the train hits that section it interprets the situation as stop, and slows to a stop.

The wiring for it doesn't seem that hard, it's a total of 5 resisters and a switched used to bypass that when you want to go. Doesn't seem that hard to do, I'm just not sure if this is something people still do.

 

trailrider

Well-Known Member
#5
On my previous (DC only) layout, I had a block that was wired with a bunch of different resistors in the power circuit. I had a rotary selector switch on my control panel that could decrease the power, causing a locomotive or "motor" (diesel locomotive) to slow down on the downgrade. Haven't done that on my current layout. Some of the DCC decoders have a back-EMF function that will slow the train down somewhat. I generally just use the throttle control to do that, if necessary.
 
#6
Frank

There are three ways of doing this in DCC:-

1. Brake signal insertion unit. These are made by a few different manufacturers including Lenz. You switch the section of track to use the brake inserter instead of the DCC track supply, and the train will slow using its predefined inertia settings to smooth stop just as if you had set the controller to stop. This will work with any NMRA compliant decoder and is therefore universal, but can take a lot of effort to implement in terms of wiring.

2. Brake on DC. For this you just supply DC of the polarity in reverse to which the train is going and suitably equipped and configured decoders will slow the train to a smooth stop just as with the brake signal inserter above. Wiring is much the same as with a brake signal inserter, but you just need to supply DC instead. It is not universal and does require suitably equipped decoders such as those from ESU.

3. Asymmetric Braking. This is primarily a Lenz solution but suitable decoders are available from other manufacturers such as TCS, Zimo and Hornby as well. It is by far the easiest to implement because you just need to put a simple Lenz BM1 module in line with the track feed to one rail in the braking section. BM1 modules are easily made from five diodes for a few pennies, but you do need the trains to have suitable decoders fitted. One big advantage of this method is that you retain full control of the train while in the braking section able to reverse out, control lights and sound (including the horn to wake the signalman), and even override the braking using a function button if required.

The first two methods are rarely used because of the complexity of wiring and limited functionality, but asymmetric braking is often used when people have a fleet of trains fitted with suitable decoders, especially in Europe where Lenz and Zimo decoders are widely used.
 
#7
Thanks for the info.

I may well go this route as I've only got one DCC loco at the present, so even if it doesn't work with it, that's not a big buy in. I looked at the BM1 and the BM2, that BM2 is a bit more complicated and expensive, but it's kind of cool that it has that slow down section before finally stopping.
 
#10
I have a yard detection device that can be used to automatically stop the train in a yard, siding, etc. It also uses a panel LED to show its occupied and a push button switch to allow it to leave.
 





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