Thanks Randy, as always
Any of them will work with a reverse loop. Just follow the same wiring concept as the main tracks except the the source of all power for each section in the reverse loop must come from the output of the autoreverser.
How those dectectors work is that the loop of wire through the transformer induces a copy of the DCC signal on its secondary. In every schematic of one fo those I've seen, the output is then rectified by a diode before hitting the rest of the circuit. Unless you are using address 00 to run a DC loco, the DCC signal is symmetrical, so it makes not one bit of difference if it is reversed by the autoreverser when the train exists the loop, there still will be an induced voltage in the transformer of that detector and as long as there is a load to cause current to flow, it will report occupied.
Just make sure the detector is installed AFTER the AR1 - the AR1 itself draws a slight current to power itself and it would show the block occupied at all times if the detector was before the reverser. SO - bus wires to AR1 input, AR1 output, one wire to the 'common' rail, one wire through the detector transformer and to the other rail.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
After considering all of your valuable comments/advise (thanks especially to Randy (what else is new) and Dwayne) I am now going to use the Team Digital BlocD8. I can return my Digitrax BD4 for credit at LHS. But of course I now have an additional question: Is the NCE version of block detection (BD20-one track/section detector) useable in a reverse loop managed by a Digitrax AR-1? My project is 8 track yard (so BlocD8) and a reverse loop (so I need only one more dector and the NCE seems to have decent reputation and is inexpensive). If the NCE won't work, what will? Again, only need for one dection zone. As always, as someone who is less than a year into DCC, I truly appreciate all the advise from all.
Thanks Randy. To be absolutely clear, I am actually not intending to have detection in the helix (only one train at a time at it is visable enough and once in the helix it will continue to either end of the helix) but rather in each of the tracks of the staging yard just as an additional help if visual it an issue once installed. Just simple LED's on a panel. Thanks to all again, I appreciate the advise from everyone.
Randy:
I'm sorry if I wasn't clear. None of my detected sections are consecutive. Every time the train moves into or out of a detected section it is moving out of or into an undetected section. I do not see any difference in the speed or power of the train.
Dave
Lackawanna Route of the Phoebe Snow
The difference would be between detected sections and undetected sections, not adjacent detected sections. The OP seems to only want to monitor progress through his helix. The BDL168 has never had an issue with supersonic decoders, but it also lacks a generic output connection to light LEDs (unless you extend the test ports on it), which is what the OP wants rather than feeding into Loconet and drive some sort of indication with either a Loconet output device or a JMRI panel.
As I said earlier, I use the BDL168. I see absolutely no change of any kind as trains move into and out of the detected sections. I do not get any false detections.
Mr. Tophias,
I have a distrust of impedance elements placed into a circuit. In my mind (experienced industrial controls engineer) the best sensor systems are those that are non-intrusive. As well, the connections to the detection element are themselves potential reliability risks. Thus my deference to detection based on current transformers like the BlocD8 or the BOD-8.
Finally, the voltage drop experienced by the locomotive on the track is going to be the sum of all drops to that point: bus wire, detection elements, intermediate connections, feeder wires and finally the rail itself. The exact 'right' solution for yours or any installation will depend on all these elements, too.
Have a great Christmas.Dwayne A
The BD4 will have about a .7V drop through any sections it's connected to - one standard silicon diode drop. It is usually recommended that the voltage all over the layotu not vary by more than about .5V so the variations aren't visible. Dropping voltage in the helix - that's kind of exactly where you DON'T want it. I'd test it out, perhaps on a long straight section (off the layout) where you have an undetected section, then a detected section int he middle, then an undetected section, see if the speed change is visible as the loco goes from undetected to detected and then back out again. ANd also you can see if you are getting any false detection caused by the high frequency drive in the decoders.
I wouldn;t trade my Digitrax system for anything, but I don't particularly liek their decoders or their occupancy systems. The SE8C for signals though, is a nice deal.
Any of the typically mentioned top dealers will have the NCE products, and most should carry Team Digital as well.
thanks to all so far for your input. I was looking at the NCE bd20 as well but decided on the Digitrax BD4 because of Digtrax reputation and my Super Chief system. Dwayne (and/or anyone), are you saying that there is a significant voltage drop using the BD4? What are the real world ramifications? I have only purchaed one of the BD4's so if I had to sacrifice that unit I could get over it. I will consider the Team Digital product. Suggession on best vendor to buy from? Thanks all.
Sir,
I used the Team Digital BlocD8 for exactly the same purpose; display of occupancy of hidden track. The device can drive LEDs directly and/or report occupancy to LocoNet. Easy to install and configure - actually it worked out of the box with no intervention.
http://www.teamdigital1.com/prod_catalogue/blocd8_product/blocd8.html
Good luck. Keep your stick on the ice.Dwayne A
NP01 ... a helix and 8 hidden tracks you gave alar greenhouse empire ...
... a helix and 8 hidden tracks you gave alar greenhouse empire ...
whoa! Apple autocorrect!! I meant "you have a reasonably large empire" ...
Colorado Front Range Railroad: http://www.coloradofrontrangerr.com/
Echo concerns about the BD-4.
Is your layout DC or DCC? It seems to me that with a helix and 8 hidden tracks you gave alar greenhouse empire that a BDL168 with Loconet and 8 more channels might be OK.
I have a BDL 168 and I am very pleased with it.
NP.
I use NCE BD-20's. They can be used to operate a small relay or to light an LED. They work independently of your command station and will work with DC or DCC.
Actually, it's pretty much the exact same thing as 1/4 of a BDL-168, minus the Loconet interface part. Same diode drop detection technology.
'Supersonic' is Digtrax's term for high frequency motor drive. NCE calls is Silent Running, others have different terms. Almost every decoder today has this, the cheapy DCC motor only decoder used by Bachmann is one fo the few that doesn't - non-supersonic decoders frequently have an audible buzz in the motor, particualrly at slower speeds.
Now, they are saying it doesn;t play well - this has been reported for multiple older devices on various Digtrax lists. Perhaps it's true - but the older BDL-162 is anotherone that supposedly will not work with supersonic decoders - friend of mine has one on his layout to detect the tracks in his trolley loop, all his decoders are 'supersonic' and it works perfectly fine. Well, it had issues with JMRI - false detections, which is the main issue reported. Say the trolley was in block 1, block 1 would shouw occupied, but so would maybe block 9 and block 12. He switched to RR&Co for the automation and - it works absolutely perfectly fine! 4 trolleys run along the line, never running into any ahead of them.
SO, do they work, or do they not? If you already have the device, I wouldn;t toss it. If you haven't purchased anything yet - there are better options. I don;t like any of the diode drop detectors from anyone, they put a voltage drop on the track, and if you want to have sections that don;t have detection, you need to put a set of diodes in to keep the voltage equal in all sections. Better are the detectors that use transformers. Several of those can easily drive an LED or two right off the detector circuit, nothign extra (besides a power source for the LEDs) needed. NCE and Team Digital are two to look at.
I have no experience with the BD4, but I use the BDL168 and it works great.
I do know that the BD4 does not connect to Loconet. Any Loconet has to be made through another component. It is older technology than the BDL168.
I'm about to build a 8 track hidden staging yard with reverse loop under my layout (built the helix last year) and plan on using BD4's to indicate block occupancy by sending signal to LED's in a panel. I asked Digitrax if the BD4 can be used alone for this (their web kept mentioning connecting to other Digitrax components to connect to the LocoNet). Their reply was yes, but that it doesn't play well with "Supersonic" decoders. 3 questions please: what exactly is a supersonic decoder? Who (QSI, Soundtraxx, etc.) makes them? Anyone using the BD4 as I intend and what are your thoughts/experience? Thanks all.