Howdy all,
Last night I finished soldering all of the wiring to my N scale layout and should be finished hooking it all up tonight (after a trip to “the ‘Shack’”). I have isolated the layout into “Detection Sections” for future use, but had some questions.
If you have a section that is longer than the 3’ reach of a single booster wire from the buss to the track and have to use two on the same section, could the currency dectector be only hooked into one section and still work?
Thanks
Chuck
Chuck,
In a word, no. All the current for a given track detection section has to go through the detector.
My suggestion would be to branch off the buss with another length of the same gauge wire, and detect that. Then, connect the two feeders downstream of that detector.
What you would end up with is this:
Buss–> Buss extension with detector–> Feeders to track.
HTH,
Steve
I guess I could also do the following:
Buss —> same gauge as buss to detector ----> same gauge as buss, detector to short section of smaller gauge wire.
Correct?
Chuck
I’m going to disagree with Chuck. If I understand the OP’s question, he has a signalling block that is of such length that he has more than one fedder running to it from the track bus. The question is does he need to have a block detector located on each feeder? The answer should be, No.
First, think in DC terms. You have a multi-block layout. If, for each block you run two pair of feeder wires to the rails, one at the beginning of the block and one at the end of the block, you wouldn’t run each set to a separate toggle switch to be able to turn on or off the block. You would run each pair to the same toggle switch so you can turn off the power completely.
It is somewhat similar in DCC with current block detectors. The detector senses the draw of current from a loco, resistor wheels, lights etc, in the block. Since the current draw is occurring throughout the block, only one detector is required for each block. The detector outputs are what will control the signal. I’d guess that on extremely long blocks there may be a need to have more than one detector, but that would be rare. There maybe a case where because of the length of the block a train maybe in the beginning of the block and the block detector is located at the end of the block and maybe not sense the current draw, but my first solution for that would be to try and located the detector in the middle of the block or to increase the detector’s sensitivity by increasing the windings through the detector.
jktrains,
You would never need two decoders, even for an extremely long block.
Regards,
Edmunds
I wouldn’t think so, but there may be the odd exception where it may occur. Think of the quarter test for determining if the system can detect a short. The same concept probably would apply for signaling, but that would be an extremely long block.
JKTRAINS,
I think you missed the point of my question. I have a section on the layout that basically has a feeder at each end. I was wondering if it would work to tie one of the two feeders through a detector and just attached the other set to the buss. If I did this would it still detect even though only one set of feeders goes through the dectector with the other set just feeding from the main power buss.
From the other comments it would seem as if I should just use the same gauge as the buss to power the detector and then run the buss gauge wire from the detectors to the existing feeder wires. I cannot tie the feeders both directly to the detector as the run would be over 3’ long on the small gauge wire.
Chuck
I guess the first point for clarification is exactly what device are you using for a detector? Each electrical block for signal purposes must have the following:
Regardless of the number power feeders you have going from the track bus to the rail, you only need one detector. The detector will detect if the block is occupied and the detector will change the signal indication. It makes no difference if the train is at the beginning or the end of the block, it is still occupied, and the detector will sense that occupancy throughout the entire block.
Maybe it’s better explained another way. Say you already have built your layout and wired it for DCC as one big block with feeders to each section of track/rail on the layout. Now you want to add signaling. You can go around the layout and cut gaps on one side of the track, say the north rail. and divide the layout into signaling blocks. Now you need to add detectors, like a BD-20a, which has the feeder wire wrap through the current sensing transformer on the detector. The more wraps you use, the more sensitive the detector is. You can simply add a power feeder with the detector to the north rail in each signaling block. You don’t need to remove the existing power feeds or try to install them on the existing power feeds, just add them to the existing wiring. The detector, like a BD-20a, is electrically isolated from the DCC wiring. It is not powered by the track bus, it only sense a change in the flow of current through the feeder wire wrap through it.
You can use a smaller gauge wire for your power feeders. For example, if your track bus is 18ga you can use 22ga for the power feeds. The short distance
I don’t mean to be so blunt or to offend you, but you are wrong.
The correct wire scheme would be closest to the first post.
--------------- /-------------
I_______---------------------
-------------
I hope that diagram is understandable, I’ve been try’n for a half hour to upload a BitMap drawing and can’t.
Basically, you run a buss, from buss to detector, from detector to track(with as many feeders as you need for that block, but ALL current to a given block MUST run through the detector.
And you would NEVER use more than one detector per block when using this method of “block occupency detection”. By definition you are detecting ANYTHING occupying that “block”, with that O
To further expand on this, the terms used to describe a wires use does not dictate its gauge. In the case of your N scale layout, any run of up to 20 feet long would be handled by a “Buss” size of 12 gauge, but could be only 14 gauge if under, say, 15 feet. If on the other end, your “feeders” need to be more than 12 inches long, run a 16 gauge wire from your detector to where your “feeder” comes through the layout and splice your 16 gauge “feeder” to your existing 22 gauge(?) “feeders” that are now only a small gauge for a very short distance.
So as an example:
Buss=12 ga. - carries all current to all parts of layout
Sub-Buss=14 ga. - carries current from Buss to Detectors
Primary-Feeder=16 Ga. - carries current from Detector to Secondary Feeder
Secondary-Feeder=22 Ga. - carries current from Primary-Feeder to Track
Chuck.
No expert here, however from what I gather the detector reads a voltage bias created when the loco enters an isolated block. If this is so it seems to me the detector would work. I read about optical detectors that use a light beam, don’t have the site handy tho.
I don’t see how 2 or 5 feeders would alter a voltage bias.
Maybe I don’t understand the situation here or your using a different type of detector.
Jules
Jules,
Optical Detectors are great for hidden staging, or yard tracks, or maybe even a stub siding of short length, but, I would think, they may not “see” a train throughout an entire “block”, and might then say a track is clear when it is actually not? Curious as I am not familiar with there use other than for “sighting” down a staging or yard track.
Also, I think you missed a key part of the OP. He was asking if ALL feeders for a given block must run through the detectoer for that block, or could he wire (2) feeders to the block with only one of them going “through” the detector. The answer is, yes ALL feeders must run throught the detector for that particular block for it to operate correctly.
Voltage bias is a steady voltage applied to an cathode to allow it to be altered both positive and negative by a signal.
Block detectors measure current flow.
I agree with KingConrail’s answer.