Let me start by saying I'm not new to DCC, but new to track occupancy detection. I have a pretty sizable layout (main line run 200ft, and 12 track yard) and know that I will be using track occupancy detection in coordination with RR&Co software to monitor all mainline and yard tracks. I believe I will need three detection zones per block (two short ones on the ends and then the main body of the siding). Here's my question. If I understand the BDL168 manual, the 16 outputs provide the power to the tracks, however, I know I plan to have stretches of track (20 ft or more) that will have many more feeders than the one that would come from the BDL. So can I have feeders coming from my main bus as I normally would and just have one from the BDL for each section I want to have detection in? I hope that makes sense.
Thanks,
John
Hi John,
I believe I will need three detection zones per block (two short ones on the ends and then the main body of the siding). For blocks where you expect trains to be stopping it is good practice to have a "slow down" zone and a "stop" zone. The "stop" zone is very short, 6" for N-scale, 1' for HO, etc. Whereas the "slow down" section might be 6' to 10' long. If you are only going to run in one direction around the track you actually only need two zones per block. If you are running in both directions then you are correct. Three zones will be ideal: a short one at each end with a long "slow down" zone in between.
the 16 outputs provide the power to the tracks. Correct
I plan to have stretches of track (20 ft or more). Keep your zone wires in heavy gauge and supply a feeder wire every 5' - 6' in HO if the track belongs to the same zone.
So can I have feeders coming from my main bus ? Yes, you can have feeders that by-pass the BDL and power sections that don't require detection at all. Keep them in heavy gauge for as long as possible. Remember to only do this for blocks where you won't need to know that something is on the track.
If you're looking to economise on cost AND you're going with the three zones per block, consider by-passing the "slow down" sections between the two "stop" sections. For example, if one of the "stop" sections on a siding is occupied it might be resonable to assume that the whole siding is occupied. In such a case you can skip detection for the long zone in the siding and rely on the two ends.
On the other hand, if you're going to shunt freight in sidings and have locos moving around sidings with prototypical detail then not only will you want to detect the length of the siding, but you might also want to split it into 2 or 3 more zones so that you can load the siding with 2, 3, or 4 locos.
Hope all this helps.
Cheers
The_Ghan
Thanks for your quick reply Ghan. Just one last clarification question.
Are you saying that it is not recommended to have both general bus feeders and a single detection feeder on the same stretch of track? My goal here would be to insure adequate track power every few feet but have a single sensor somewhere in the mix to indicate occupancy for the whole track. obviously this would be a single ungapped section of trackage.
John,
If you run one wire from the track to the BDL168 and another wire from the same block of track to the booster the BDL168 will not show that track occupied because the direct wire will shunt the circuit. You can, however run a single (call it a bus) wire from one terminal on the BDL168 with several feeders to that one block of track.
Also if your locos are set up properly RR&Co can accurately stop the loco using only one block, but it will take some fine tuning.
Regards,
Dave
From Mt Pleasant, Utah, the home of the Hill Valley and Thistle Railroad where the Buffalo still roam and a Droid runs the trains
You know sometimes the obvious just isn't obvious until someone points it out. DUH!!! Thanks Dave. Of course I should run it as its own mini-bus. Why didn't I think of that.
And I have read that RR&Co will allow such things as shifted braking and stops and I will likely use them in testing before I finally decide which route is best. That method would certainly cut down on the number for detection sections required, and we know the BDL's aren't cheap.
Thanks for your tips guys and happy railroading.
Are you saying that it is not recommended to have both general bus feeders and a single detection feeder on the same stretch of track? Correct. For each zone ALL feeds come from EITHER the BDL or the Booster. You can't mix them.
My goal here would be to insure adequate track power every few feet but have a single sensor somewhere in the mix to indicate occupancy for the whole track. obviously this would be a single ungapped section of trackage. That's not how it works. Occupancy detection works by detecting current drawn through the circuit so if you share BDL and booster feeds on the same section of track you will by-pass the BDL and occupancy will not be detected. You can run a heavy gauge wire from the BDL for each zone. At #16 to #12 gauge, these wires might be 20' to 30' in length. Each can "follow" one section of track under the layout and have 6" feeders at, for example #20 gauge, every 3' to 6'.
A few questions:
1. Have you already bought the BDL?
2. What are the physical dimensions of your layout?
3. Are you planning to use transponding now or ever?
4. Have you looked at using breakout boards rather than the edge connector and soldering? It will save you the time of soldering, cutting short wires, and wiring up a terminal block. Check it out here: http://acculites.com/index.php?main_page=index&cPath=40_77
Especially if you've already wired the layout, detectors that use remotely mounted coils are easier to retrofit to add detection - you cut the bus at the boundaries of each detection section, and then jumper it to a new bus line (only have to do this for one rail) with the jumper passing through the current sense coil.
In either case, ALL feeders in each detection section must get their power via the detection ahrdware. This does not mean running 10 feeders from one section back to the BDL168, it means making a 'sub bus' connecting all those feeders then a SINGLE line from the sub bus to the BDL.
The only thing that can be downstream of the BDL is the track. If you have any UP5's wired tot he rails, they need to be disconnected, anything drawing track power in the detection section will result in the section appearing to always be occupied.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
Thank you all for the suggestions. I have not yet purchased the BDL's. I currently have the entire yard laid and about 60 feet of mainline. I am in the process of mounting switch machines in the yard. I have bus wires run for the entire layout except the yard area and fortunately, I have only done a few feeder taps to the bus for testing so this is a perfect time to consider the best way to partition the bus sections to take advantage of the BDL to give me the proper output.
Ghan, to answer your questions:
1. Have you already bought the BDL? Not yet
2. What are the physical dimensions of your layout? It's an around the room shelf layout taking up all the walls of my basement. Average shelf width is 14" and entire loop length is about 190~200'. Then of course I have the yard area in my storage area of the basement. It has 11 yard tracks with an engine bypass/ drill track.
3. Are you planning to use transponding now or ever? Not planning on transponding at this time.
4. Have you looked at using breakout boards rather than the edge connector and soldering? It will save you the time of soldering, cutting short wires, and wiring up a terminal block. Check it out here: http://acculites.com/index.php?main_page=index&cPath=40_77 I will be checking those out. Anything that makes wiring connections easier is a good thing in my book.
Thanks everyone!
What switch machines did you go for and how do you plan to power them? The reason I ask is because I made the mistake of going with cheap snap machines which require something like the DS64 as I want to use LocoNet. Meanwhile, I want to use signalling, so I bought an SE8C. After reading up on the SE8C I learned that not only can it control up to 32 signal heads, but also:
2. power up to 8 Circuitron Tortoise motors or semaphore signals; and
3. has connections for switches to control turnouts; and
4. has 8 inputs for occupancy detection. However, you need to either purchase BD4s or build your own occupancy detection circuits, which is pretty easy to do actually. I've decided to use the inputs to detect turnout position electronically, ie: not rely on the position of the motor or electrical switch. I'm still working on that myself ATM.
Back on topic ... just make sure the BDL168 might not be the best component for the job ... depending on what other things you might like to automate on your layout.
Hey Ghan,
I have the circuitron tortoises for all my switches. I will have to check out the manual on the SE8C because I must admit that I didn't realize it was that powerful. I don't think using BD4's or making similar should be a problem. It looks like there's a good bit of info on the remote sensing diode construction and if the SE8C has half as many detection inputs as a BDL and still can control 32 signal heads and trigger my switches I would be silly not to consider it. Thanks for throwing out another option!
Firstly produce a drawing of your layout with all the sections clearly identified. Then mark the ones that you want detection and/or transponding on. Where you have groups of 3 or 4 BD4s linked to a SE8C might be the best option. BTW, the DS64 can also connect to one BD4 for occupancy detection. If you have a yard with 12 or more sections requiring detection then go for the BDL.
Here's another sneaky thing: although the RX4s are primarily used for transponding, they are also occupancy detectors. If it detects something then the track must be occupied, right? Ergo, a BDL168 has it's 16 occupancy detection sections plus 8 transpond sections = the ability to detect occupancy over 24 separate sections. The caveat here is you must us Digitrax decoders with Transponding enabled.
I use transponding and stick with Digitrax decoders. Here's how I wire up:
1. a platform siding with short/long/short sections: the feeders to all three sections pass through the same RX, but only the two shorts go to separate points on the BDL, the feeder to the long section goes straight to the booster. The RX will detect the transponder but neither of the shorts will detect occupancy. Therefore the train is in the middle section.
2. a shunting siding with short/long/short/long/short/long/short (ie: the siding is split into thirds to help accurately stop a loco in the same position for switching and run-arounds): all four shorts go through one RX to four separate points on the BDL. A single feed from the booster also goes through the RX, and then splits to serve the three long sections. Combine several of these setups and you can automate some pretty serious freight movements (I need the hand of "God" to uncouple the wagons though ). Note: if you wanted to get really complicated and operate to locos on the same siding you might split the wiring between two RXs as all of the long sections detect as simply "somewhere in that block" .... complicated but I hope it makes sense.
Finally, did you know a range of companies make Digitrax compatible products? I've already mentioned Acculites, but there is also these companies making LocoNet compatible DCC products:
2. http://www.cmlelectronics.co.uk/ I particularly like (but haven't used) the DTM30 panel animator. I do have a DAC10, though ... works perfectly and is simple to wire up;
3. DCC Specialties have circuit breakers and auto reversers;
4. http://rrcirkits.com/
5. Tam Valley Depot;
6. Team Digital;
7. https://www.uhlenbrock.de/intern/index.htm ... makers of one of the best controllers you'll ever find.
I'd like to explain more but the "Minister of Home Affairs" is calling me to dinner so I'll leave you to look up the relevant websites. But check out this stuff before committing. It is all LocoNet and Digitrax compatible and all part of the Digitrax world of DCC.
Nige'
I don;t think you can fake it out and use the 8 RX's as an extra 8 detection sections, well, not without a lot of oddball programming in JMRI, because the way they work is that the Zone and transponding information is combined so that you can tell Loco XXX is in Block YYY. I suppose you could alter the logic to read a transponding message as a block occupied message, but unless you have transponding decoders in every car, it is more a point detection that zone detection - you'll know when the loco leaves the block but half the train could still be standing in there and it would show clear is just based on the RX's output.
I don't know about JMRI.
The process is explained briefly in the Digitrax transponding application note: http://www.digitrax.com/static/apps/products/detection-signaling/bdl168/documents/transponding%20bdl16xrx4%20app%20note_1.pdf