Re: Feeds for detection blocks

Mark Gurries

On Feb 26, 2016, at 12:48 PM, sgrzegorzewski@... [WiringForDCC] <WiringForDCC@...> wrote:

I will be using a BDL168 detector and will have a PM42 feeding into it from the booster.  The zone common will be rail A (red) coming out of the BDL168, and the detection common will be the rail B (black) coming out of the BDL168 also.  My question pertains to long blocks (6 to 8 ft).  

Definition of block length, long or short, of a given block is relative to the typical train length your running.

Looking at the BDL168 manual dated 2013 that names of the wires and the color do not match.  We need to work from a common drawing.  I am using the 2013 version of the BDL168 manual as listed on the Digitrax Website.

i will attempt to answer you question based on Figure 1 and using the wire colors shown.

I will likely need a second connection to the zone common (red).  

With the exception of the PS14 connection, all wires running long distances to or from a PM42 or BDL168 that carry track power must be heavy gauge.  The problem people encounter is that large gauge wires do not fit on the connectors.  A common solution to deal with the wire gauge problem is to mount a terminal block next to the BDL-168.   The terminal block makes it easy to transition between different gauge wires.  You can actually pre-build the BDL168 on a piece of plywood along with the terminal block and pre-wire the BDL-168 to the terminal block with small gauge wire.  That way when you install it, all you doing is working with the large gauge wires.

Looking at the BDL168 manual dated 2013, the:

1)  red wire is the “Detection Common” wire.  This heavy gauge wire should be run under the track.  You should have multiple smaller gauge track feeders connecting the heavy gauge detection common to the rail that is powered by the same given booster.  It should not be a single connection.

2) gray/black wire is a “Zone Common” wire which is also supposed to be a heavy gauge wire.   When the heavy gauge zone common wire reaches the BDL-168, it can be broken up into 4 very short smaller gauge wires such that each Zone input, A,B,C and D will each have a connection with a wire that fits the connector.

3) blue wires are the “Detection Section" wires.  The long run from the BDL168 to the track again needs to be heavy gauge since they will carry the train current.   Since heavy gauge wire cannot be directly connected to the terminals of the BDL-168, again you will have to use a short length of smaller gauge wire to complete the connection between the heavy wire and the BDL-168.  For each heavy gauge detection section wire you should have multiple smaller gauge track feeders connecting it to the sections of physical rail that represent the detection section.  It should not be a single connection.

Must I make the second connection to the long block from the same output of the BDL168 feed or can I connect it to the rail A bus that comes out of the PM42? 

PM42 must be placed after the booster but BEFORE the BDL168.    The same concept of having a terminal strip to adapt wire gauge local to the PM42 to deal with the change in wire gauge also applies.

GRAY/BLACK WIRE:  You need to run the Zone common Gray wire from the booster to the PM42 RAIL A input connection.  Then from the Track A output, run the Gray wire out to BDL168 Zone connections A, B, C and D.  This assume you want all 16 detections zone powered by the same booster.

RED WIRE:  You need to run the Detection common red wire from the booster to the PM42 RAIL B input connection.  Then from the Track B output, run the red wire out to the rail to complete the detection common connection.

Best Regards,

Mark Gurries
Electrical Engineer
DCC Website & NMRA DCC Clinics:

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