Our club layout has a few block detectors scattered around. They're made by Integrated Signal Systems. Does any one have a instruction booklet for these? I want to know how they're supposed to be installed. It looks like the fellow who installed them put them in one feeder to the block, but left the bus alone.
I've observed an interesting behavior where the signal in front of an approaching train changes before the train crosses in to the next block. There's a good 15-18 inches before the signal when it changes.
The parts of the signal system I'm referring to are here:
Charles Davis wrote in news: firstname.lastname@example.org:
The electrical block starts immediately under the signal bridge and continues through a turnout to single track before stopping at a second turnout continuing on to double track. (The double track reduces to single track to go through a tunnel.)
Where the signal changes, there's still 12-18" to the gap.
The behavior you're describing points pretty clearly to either shorted blocks, a sneaky current path that closes based on turnout position, or something conductive making intermittent contact with the rails.
It's rather irritating that they don't have the full manuals for the detectors on their site. Not even a part number so you could find it somewhere else. I was able to find in their catalog that they are dcc compatible - some of these kind of systems aren't, so you're in good shape there.
From the picture, it looks like these go in-line to one rail of the track - they're not induction based like the team digital or digitrax detectors. That means you need to have a very solid break on both ends - make sure one end or the other hasn't expanded together against the adjacent blocks. You also cannot share feeders - check if someone maybe patched in a power feed hooked to your detector's rail input for some other block. Sloppy stuff happens, especially when 'it doesn't matter'.
Another thing to check for is any sneakage from your turnouts - make sure the power routing is working properly and there's no chance that the non-switched leg of the turnout is supplying power to your detection block (or the block you're leaving). That one rail needs to be 100% isolated from everything else, 100% of the time. Sometimes accomplishing this can be brain-seizure inducingly difficult.
Good luck with this - it can be a pain to solve, especially when turnouts are involved. I have a lot of turnout and signal automation on my layout, and it tooks months to work all the kinks out.
Bet you are looking at the wrong gap. Remember, what is being detected is the occurrence of an electrical load. Dummy locos on the head end don't trigger detection, which set of wheels is drawing power has a bearing [Particularly with steam, where you may have 8 - 12" of loco before the tender wheels start picking up from the other rail.]
You may be seeing the time delay associated with the circuitry responding.
Ideally, *all* rolling stock should present a 'load': dummy locos, freight cars, etc. should have metal wheelsets (with one wheel insulated). Solder either a small 1/8 Watt carbon film or 'chip' resistor (either can be had cheaply in quanty from
from wheel to wheel. The value (resistance) of the resistor depends on the sensitivety level of the detector. The value should be choosen to not present a significant drain on the track power (and the current should be low enough not to cook the resistor!), but be enough to trigger the detector. Each piece of rolling stock should have 2 wheelsets with a resistor, one at each extreme end of the rolling stock.
Start by taking a 1K ohm resistor and running the leads down the track. See where the signal changes. My bets are that there is a gap at that point on one rail. That rail will be the one that the detector is attached to. The circuit is the modified Twin-T design using diodes instead of transistors and it detects current flow to the track on one lead. The power leads don't matter as to which is attached to the track, normally with these circuits, and the IC is a quad comparater chip that detects the voltage across the diodes and converts it into a signal when there is aomething drawing current on the track. The circuit design has been around with minor changes in resistor values since the early '70s. The Twin-T design has been around since the '50s.
pv+ email@example.com (PV) wrote in news:tNudnX0EzoJC43rUnZ2dnUVZ firstname.lastname@example.org:
The detected feeder is the last feeder before the signal bridge gaps, so it seems like the next detector is detecting something before it should. (Some sort of sneaky current path or capacitive effect from having the wires so close?)
I'm going to give them a call tomorrow, and see if I can get anyone to answer the phone. It looks like after their move they just gave up doing business.
Please expand on the part about not being able to share feeders. Is it ok to go from the bus, through the detector to the rail, and then have the next block go from the same bus through another detector to another block?
Do all feeders for the block need to pass through the detector (essentially splitting the bus--series), or will everything work ok with the detector in parallel to the other feeders?
Wouldn't double gapping the divergent rail side and feeding the turnout from the bus solve the isolation problem?
Thanks. I powered up the signals tonight and everyone was impressed. Next week, they'll be hooked up to the 12V bus permanently.
I was talking about someone patching into the wire leading from the detector to your detection rail. I've never used these units, so I can't tell you whether a voltage drop (which shouldn't be dramatic anyway unless you're using too-thin wire) on the booster side could cause you trouble. If you can do a home-run back to your booster's distribution panel, by all means try it! It lets you eliminate another possibility.
You really should connect all feeders to the block to the rail side of the detector. But, not doing that would probably cause false negatives, not positives. Generally, detection blocks are short enough that you can pull the other feeds anyway, at least temporarily. Try it and see if the problem goes away.
Unless something has fallen into the turnout and is making intermittent contact, I'd say yes. It's good practice to isolate any turnout involved with detection for this reason. Note however that different manufacturers (or even different lines from the same manufacturer - Peco, I'm glaring at YOU) do things differently, and sometimes you have to fiddle with the rail breaks to get everything to behave. When I'm doing a detection block involving turnouts, I try to end the block at the turnout itself, briding power as needed. Having the block travel through the turnout can drive you crazy, and you might also get chatter effects on a detector without good debouncing.
My "signaling system" is mostly just showing turnout positions and is there for visual interest - I haven't done any fancy CTC stuff with it yet. But even then, it really adds something. *
It depends what you're doing. if you want block occupancy detection, you're right - if the rear of the train has no load you'll show as a vacant block as soon as the engine gets off.
If you're using block entry as a trigger for some event (an automated turnout throw, for example), you can get away without adding dummy loads. I've never had a lot of luck with resistance wheels - either the value is too high and they don't register, or they work fine, but interfere with other things, like automatic reversing sections. *
There have been a lot of block detector makers over the years. The circuit is public knowledge. Normally with this type of detector, the detector is in series with the South Rail (which is the common rail in common rail systems) and the North Rail is the rail that is fed the power for the train for speed and direction. If you're running seperate rails with seperate power supplies, you need to isolate the power for the detectors also as they WILL "trigger" or even destroy themselves if you start tying things together. YOU HAVE TO BE RUNNING COMMON RAIL POWER FOR THE DETECTOR TO WORK!!! It also helps if the whole trackage is setup with detectors as this will keep the train speeds constant over the whole layout. Anyplace that you have a detector will be seeing 0.6 to 1V lower voltage.
pv+ email@example.com (PV) wrote in news:1LSdnSMtifylT3XUnZ2dnUVZ firstname.lastname@example.org:
That makes quite a bit of sense. If something else is between the detector and track, it'll be detected too. A home-run would be difficult, but splitting the bus wouldn't. It'd be a great place to add a diagnostic toggle, too.
We've gotten a few false negatives. Low current draw locomotives didn't seem to trip the detector. (It doesn't trip when I've got the headlight on but the locomotive isn't moving. It would be great for approach-based grade crossing circuits.)
It looks like we'll have one block that ends after a turnout, with another one inside the block. The turnouts are Tortoise powered, so I'd think any boucing would be limited to when the turnout was moving.
Most of what we need to do is ABS, and that's really easy to do. Some parts of the main line are single tracked and blind, so it requires the operator to walk ahead of their train to make sure the way's clear.
No you don't. A double-isolated block is fine - just make sure you connect the ground part of the detector correctly. That said, you never really NEED to double-isolate unless you're in a reversing section anyway.
The detectors Puckdropper is using have a very low voltage drop (.06v) if I read the specs right. These aren't your father's T-detectors.
On my layout, I use team digital's current sensing detectors - you just pass a feeder wire through a hole in the detector, and it works. The downside is you need to power them seperately, but I run that alongside the detector's signal wire to a controller.
With this stuff and JMRI, you can do all sorts of automation and sensing on your layout. *
The detectors are compatible with DCC. One wire from the DCC station needs to be attached to the ground power wire for the power of the signal detector power supply. That is the common side of the power. It is, in the common rail system called the South Rail. Multiple DCC power stations means that you need a seperate detector power supply for each of hte DCC power stations. Either that or you need to connect one side of the DCC power stations to each other.