I suppose it can't hurt, but the more turns you put through the coil, the LESS current flow it takes to trip the detector. A couple of turns and you can detect a DRY finger across the rails.
Is the BD20 that gives the false reading anywhere near the bus that feeds the block that incorrectly activates it? Or even, right below the track? Or close to a common bus where the feeder that goes through the BD20 taps off? If the BD20 is too close to where the feeder joins the bus, as opposed to closer to where the feeder goes through the roadbed and connects to the rail, you can easily pick up the current flow through the bus even though that wire doesn;t go through the donut hole.
What about the gaps - are they made with insulated joiners, or did you just saw through the rails? If you just cut the rails, did you put small scraps of styrene in place to keep the gap from closing up?
Try swapping BD20s, see if the problem is in the same block (which indicates a wiring issue) or if it follows the BD20 (which indicates that one BD20 may be defective).
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
If it were me, I would at least try a second wrap of wire around the donut on the BD20. Since a second wrap of wire increases the signal requirement on Block 3, it may eliminate the flicker on Block 2. Stranger things have happened with the BD20.
Rich
Alton Junction
Hi Wolfe,
Thanks for your suggestions, I checked the gaps and checked with multi meter but all appears good. I moved the BD20 to the other side of the track which seamed to improve the situation. Now I have about 4 inches of block 3 where block 2 displays. I did find an extra track feeder wire which I removed and that solved the flicker situation. I will keep at it to try nail this last bit.
thanks again , Paul
Hi Randy, thanks for your suggestions, no the ballast isn’t wet, the BD20 wires not pararrel and are not long runs or even any where near each other. It’s a bit funny. On the weekend my son and I checked everything again and found a feeder wire I had missed. But no change. We decided to move the BD20 to the other track line. Which fixed most of the problem. Now we have about 4 inches of track line where the block 2 will light up the detector. I guess that it is better than the whole block lighting up.
Thanks again
Paul
rrinker Are you mixing it up with a BD4? The BD20 is a current transformer detector from NCE, it doesn't have 10 pins on its connector. There's no system ground, it's electrically isolated from the track power - a superior type of detector, like the RR-CirKits BOD-8. No voltage drop is the primary advantage. And I've always felt the centralized nature of the BDL-168 defeats the point of keeping bus runs short. --Randy
Are you mixing it up with a BD4? The BD20 is a current transformer detector from NCE, it doesn't have 10 pins on its connector. There's no system ground, it's electrically isolated from the track power - a superior type of detector, like the RR-CirKits BOD-8. No voltage drop is the primary advantage. And I've always felt the centralized nature of the BDL-168 defeats the point of keeping bus runs short.
Don - Specializing in layout DC->DCC conversions
Modeling C&O transition era and steel industries There's Nothing Like Big Steam!
Perhaps there is a track capacitance issue. Here's a description:
https://sites.google.com/site/markgurries/home/dcc-general-best-practices/wiring-planing/wire-properties/track-wire-capacitance/example-calculations
Do you have pin 10 properly grounded to the system ground with an appropriately sized wire? and Pin 8 to the ground on the DS64 or equiv? Could it be a floating ground issue?
If you have metal wheels, the power from block one, goes into block two as the wheels cross the gap. Hence the flicker.I don't know how you are exactly wired up, but a capacitor on the signal wire would help mitigate some of the noise.Scratch that, I forgot you can't do that with a BD20.
Except he's getting indications on non-occupied blocks. Making the detector MORE sensitive isn't going to hekp there. I still say it's wires run too closely in parallel, or even bundled together.Or the loop through the detector is too close to the main bus.
richhotrain I have several BD20s on my layout to trigger crossing signals. They work well. If the current detection is insufficient, do a second wrap of the wire through the loop. Rich
I have several BD20s on my layout to trigger crossing signals. They work well. If the current detection is insufficient, do a second wrap of the wire through the loop.
Re: BD20
Me and my "gang" usually loop the wire through the coil four or five times, so as to get detection.
Thus implying once-through may be inadequate.
Ed
Lets get some more info to isolate the problem better. This sounds like an issue with a short. Not so much the particular manufacturer. The BD20 is probably picking up that short. Does it do the same when a loco is in other blocks? Is block two still effected? Or other blocks. I find with expansion and contraction gaps close permanently over even short periods. Might have to recut those gaps. Or a small piece of conductive material found its way in. Check solder connections too. there could be a small solder whisp jumping a connection almost unnoticable. Doesnt hurt to invest in an ohms meter. Nothing fancy. Or the age old light bulb with alligator clips to find a short or exactly where a dead spot is and the cause. So start with gaps and connections.
Wolfie
ps. A piece of .10 or . o styrene super glued into the joint will keep the insolation. You could do what the prototype does and mark the block with yellow or white paint
A pessimist sees a dark tunnel
An optimist sees the light at the end of the tunnel
A realist sees a frieght train
An engineer sees three idiots standing on the tracks stairing blankly in space
Ballast still wet? That will cause enough current flow to trip the BD20. The other issue would be if you have any of the wires paralleled - either the block feeds, the track bus wires, or the outputs of the BD20. You can get inducded current from one wire to another with long parallel runs if they are too close.
PMorrie Hi all, not sure what to do. I have installed block detectors BD20 on my 12 blocks, when I put LOCO on block 3 , block 2 flickers on and off some times. All blocks have been isolated with only one feeder to each block going thought the BD20. It’s like there is a low current bleed through the ballast. Is that possible? I did put a trim pot on block 2 but that didn’t fix the problem. Any suggestions would be appreciate. Paul
Hi all,
not sure what to do. I have installed block detectors BD20 on my 12 blocks, when I put LOCO on block 3 , block 2 flickers on and off some times. All blocks have been isolated with only one feeder to each block going thought the BD20. It’s like there is a low current bleed through the ballast. Is that possible? I did put a trim pot on block 2 but that didn’t fix the problem. Any suggestions would be appreciate.
I'm not up to NCE products, I use Digitrax, but here is a link to the pdf manual for the BD20, if you don't already have it.
https://www.dccconcepts.com/wp-content/uploads/2016/02/NCE-BD20-Manual.pdf
Mike.
EDIT: Yea, like what Henry just said.
My You Tube
I would think current leak through ballast would be very unlikely, especially if your other 11 blocks are good. Double check your feeders and gaps is all I can think of. Fortunately for you, there are people here way smarter than I am.
Henry
COB Potomac & Northern
Shenandoah Valley