DCC Block Detection and Control

[DigitalGriffin]

There are plenty of block detection units out on the market that can control signal lights for CTC.

Question is, once the train is on a main, and approaches a red signal, how can you get that train to stop automatically? Are there any products which broadcast just a “stop” command for a block?

If I shut down the block power for the next block, and the next block is occupied, then occupancy detection won’t work for the next block (for trains that exceed more than one block)

Lenz has asymetric DCC with their railcom (on Lenz Gold and Silver series decoders) These decoders will have the train automatically stop when a half power rail is found. But this isn’t standardized.

Anybody have any ideas?

[Stevert]

Don,

Since commands are addressed to a particular decoder, there really isn’t such a thing as “a stop command for a block”.

What you need is software that knows what the signal indications are and can also “remember” where a particular train is and it’s direction, based on that block detection, and then issue the appropriate commands to the appropriate decoder. Of course, this requires that your DCC system (and separate signal and occupancy systems, if that’s how you’re set up) has an interface to the computer running that software.

I believe Railroad & Co has that ability, and I also think some folks have written JMRI scripts that will do it.

Steve

[Texas_Zephyr]

Question is, once the train is on a main, and approaches a red signal, how can you get that train to stop automatically?

There are more ways to do this than one can shake a stick at.

Are there any products which broadcast just a “stop” command for a block?

A “block”, I presume you are talking about DC here and just want to turn it off? Or do you just mean the signalling “block”?

If I shut down the block power for the next block, and the next block is occupied, then occupancy detection won’t work for the next block (for trains that exceed more than one block)

That would depened on the type of block occupancy detection being used, and if one had a compensating circuit in it or not (basically like a relay tripped that takes the place of the detected block).

Lenz has asymetric DCC with their railcom (on Lenz Gold and Silver series decoders) These decoders will have the train automatically stop when a half power rail is found. But this isn’t standardized.

Ok now you are talking DCC. Which are you interested in? Totally different scenarios for DC and DCC. On a DCC system one would connect the block detection and shut down the throttle of the locomotive you wanted to stop, not cut power to the block.

Anybody have any ideas?

I’ve got more ideas than one can shake a stick at. There is not enough information here to give any reasonible ideas to accomplish your need. All we know is you want a train to be detected and another train to stop.

1. Is this DC, DCC, DCS, Railcommand, or other.
2. Any preference on type of block detectors.
3. Is there a computer involved.
4. What sort of budget are we dealing with.
5. is this for a roundy round layout or should we consider the blocks independent and in line.
6. Is there one block per signal or multiple.
7. Are trai

[jrbernier]

If the ‘signal’ for the block ahead is ‘red’, then you want the engine to stop before you pass the signal - correct? With DCC(and some transponding) so you can tell when the engine is - it can be done. It will take some JMRI scripts & detection equipment, or similar commercial software. Be willing to invest some $$$ in your project!

Jim Bernier

[DigitalGriffin]

>1. Is this DC, DCC, DCS, Railcommand, or other.

DCC, digitrax system.

>2. Any preference on type of block detectors.

Preferably current sensing so something like Digitrax BDL-168 block detector can be used**.** (This also has connection for signal heads)

>3. Is there a computer involved.

No. The point is to automate it, so the less than computer savy can replace bad “black box” components, and not have to have a programming degree, or buy transponders.

Computers fail, break down, and need changing with layout changes. Although I’m extremely computer savy, most people are not. This has to be a universal easy to use solution.

>4. What sort of budget are we dealing with.

Variable budget. But this is a whole layout conversion from an older relay based DC block based control system. So we are talking couple thousand.

>5. is this for a roundy round layout or should we consider the blocks independent and in line.

Two mainlines and a branchline.

>6. Is there one block per signal or multiple.

One block per signal

>7. Are train cars equipped with resistors on the wheels so a “current” detector can sense them (related to #2 above).

Yes. This is mandatory. Trailing car MUST have a resistance across the wheels of 1000 ohms or less.

>8. Do all this have to be off the shelf parts (as implied) or is there a williness to build custom circuits for oneself.

[Texas_Zephyr]

OK some good information to work with now. I’ll puzzel over it for a while. In the mean time…

Two mainlines

Double track or totally separated mains?

**

7. Are train cars equipped with resistors on the wheels so a “current” detector can sense them** Yes. This is mandatory. Trailing car MUST have a resistance across the wheels of 1000 ohms or less.

Depending on the exact detector selected this resistance might be able to be increased to 10,000. Some of the new detectors are very sensitive. I once calculated that for our clubs main yard current draw for just cars with one 1000 ohm axle each would be something like 4.5 amps.

**

**I do know NMRA RP 9.2.4 has a fail safe mode. And there is a universal “STOP” command that stops everything. I could A/B Relay the block to a booster that is just broadcasting a “STOP” command. But I’m not so fond of this idea as seperate boosters for 36 block sections total = $$$$$$$$.

Unless I am mistaken, even the universal stop command won’t work. To use the stop one would have to have separate COMMAND units on each detection block, not just separate boosters - that is more costly and makes a whole new set of syncronization issues to deal with.

Just skimming through 9.2.4 … hmmm that would be a fairly bizzare unintended way to use that feature.

[CSX_Robert]

…And there is a universal “STOP” command that stops everything. I could A/B Relay the block to a booster that is just broadcasting a “STOP” command. But I’m not so fond of this idea as seperate boosters for 36 block sections total = $$$$$$$$…

You are absolutely right about the universal “STOP” command, short address 0 is the broadcast adddress and sending a stop command to this address will make any NMRA compliant decoder stop, no matter what it’s address is. You do not have to have a seperate booster for each block, however. You have can have one booster broadcasting the stop command and each section switches between your regular booster and the stop booster depending on the signal aspect. Take a look at some of the products available here(including a DCC broadcast stop signal generator, although you can also configure the programming outputs of a DCS100 for this) : DCC BitSwitch

[CSX_Robert]

I forgot to mention the brakedist.pdf that shows how to setup a brake district using a DCS100 and one additional boster.

[DigitalGriffin]

Robert, thanks for the heads up.

The ballast bulbs look like Joe Fugate’s automotive bulb solution for short detection/protection. I was wondering how they were going to keep from shorting out between blocks (when a metal wheel/truck crosses sections with different voltages)

Looks like I have two viable solutions now to present! Either DC or DCC braking section via DCS100 + additional booster.