I have heard that adding a resistor to a freight car axle ?and/or caboose also helps with detection. Train length will dictate the number of resistors needed depending upon block length and applications (signals, grade crossings, etc).
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On Sep 27, 2021, at 9:23 AM, Bill Wilken <bill.wilken@...> wrote:
?
Don,
I know that adding a 5-volt connection to posts 1 and 4 on a BD20
will permit the onboard LED to light or not depending on block
traffic.? I've also read, as you suggest, that it could impact
BD20 sensitivity, but I've never found anything to that effect in
NCE's documentation.? In any event, it's worth a shot.
Thanks for your feedback.
Bill
On 9/27/21 9:10 AM, Don Weigt wrote:
Bill,
There's often confusion between the terms wire, cable, and
pairs. Many people call a multi-conductor cable a "wire", when
it's a group of wires. Also, "speaker wire" is really a pair,
as is "zip cord." They would usually carry the power and the
return; currents in opposite directions, whose magnetic fields
approximately cancel.
The BD20 works by detecting the magnetic field created by
train current going through the wire threaded through the hole
in the detector. That wire becomes part of a transformer. If
you put both the power and return wires through the BD20, the
currents, going in opposite directions, will cancel each
other's magnetic fields. You want only one or the other wires,
not both, wound on the BD20. Perhaps that's your problem? Note
in the wiring diagram it shows only the power feeder wire, not
the return wire, routed through the sensor hole.
Nothing is said about needing a power supply for basic
detection. But, I wonder if one might be needed. I've never
used a BD20, so I don't know. It would hurt nothing to do this
test: Connect a 5V power supply between terminals 1 and 4, as
called out for using the onboard LED or an external
relay.?Make no other changes. With the 5V power on, does the
detector work, and not without it?
Don Weigt
Connecticut
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Don Weigt
Connecticut
