Block detection: what to do about the "odd blocks"

[NP01]

I am interested in saving sections on my BDL 168. I really don't need block detection for every piece of track on the layout - those industry sidings etc can be undetected. Can I wire them directly to the Rail A and Rail B of the booster? Or should I group them all onto one of the blocks of the BDL168?

NP. 

[mfm37]

It's your choice. The grouping could always be changed later

[rrinker]

 If you group them, and have a car with resistor wheels sitting on the siding, the the whole block would report occupied even though no trains were on the main. This is probably NOT what you want. If you bypass a detection section in the BDL168, you might want to put a pair of 1N5401 diodes wired back to back (antiparallel) to one another so the voltage drop to the rails not going through the BDL168 is the same as the voltage drop to the rails that are connected to detection sections.

 That's why my preferred system of detection is the current trransformer type, no voltage drops, so no compensation needed for detected vs undetected stretches.

 What tyically would be done is that the turnout connecting an industrial area to the main would be wired to report the block occupied if the points are lined for the sidings - you can do that simply by using the switch machine contacts to connect a resistor across the rails when the points are lined for the siding. That way you'll get signal indications at either end of the block with the switch so another train doesn;t come barraling along and run into the open points. The rest of the instrial trackage and any other switches would not be monitored in any way and be under control of the local crew operating there.

                   --Randy

 

[NP01]

Thanks Randy. 

Re: your second point, you are saying connect say a 10K shunt across the rails each time the points are set to the industrial siding with the AUX contacts on the tortoise? Ok ... But that would still consume a channel on the BDL168, something I am trying to conserve at $20 per block. I could just set SSL to show a Red each time the turnout is set to the siding. No? 

Your first point: so it is still possible to wire some of your track to Rail A and Rail B of the booster when other parts are through the BDL168. Just compensate for voltage drops with back to back Schottkey diodes. Got it. 

Ok now talk more about this current transformer method? I.e. did you implement with a BDL168 or with something else? I like it only because it keeps signal path separate from power path ... Just for neatness of design ... But don't know where to find the components. 

NP. 

[jrbernier]

NP,

  What Randy is saying is to wire the aux contact on the Tortoise to shunt the live mainline block IF the turnout is reversed.  This will knock down the signals on each end of the block(safety feature).  This will not use any more BDL168 blocks.

  You will want to isolate the spur as you do not want a box car sitting at the feed mill to light up the signal system.  As Randy mentioned, you will have a small voltage drop between the spur and the mainline - and will need to address that as Randy mentioned.

Jim

[Renegade1c]

RRcirkits makes a block detector that uses current transformer. You can get them either directly from RRcirkits or from Tony's train exchange. I use it for block detection on my layout. You will need a TC-64 as well which allows it to communticate with Loconet.

I prefer this type of block detection because it does not have the voltage drop that the BDL-168 do in their design. I used 10Kohm resistors on 2 axles of each car and the BOD-8 are sensitive enough to pick up just one axle. A BOD-8 will handle 8 blocks. Although it is a little more expensive than the BLD-168 I think it it is easier to setup  and you don't have to worry about voltage drop.

As far as wiring sidings, you should isolate them from the detected blocks and feed them directly from the power bus, bypassing the BDL-168.. there is no point in wasting detection sections on spurs and industrial tracks.