NCE’s EB3 connection for a remote
indication.
The EB3
has 3 optoisolator transistors on board, one per channel, to allow for a remote
indication of a “short” condition of the appropriate channel. The EB3 will normally
be located under the layout or else where, but the operating power district
will certainly in many cases be no where near the EB3. This remote indicator
LED, appropriately located, possibly on the facia of the layout, near the power
district, will indicate the operating state of the EB3. A steady LED indication
will mean a short in the power district.
NCE has
provided a pair of pads, one round pad that is connected to the on board
voltage reducing resistor and one square pad. The optoisolator IC has the
capacity to switch a current, maximum of 50 mAs on and off, at a maximum of 40
volts. This voltage has to be supplied by an external power source to supply a
LED. Hook up as shown with the LED connected between the supply positive and
the round pad. The square pad is connected to the supply negative. The NPN
transistor in the optoisolator IC chip is a low current switch.
The
opto isolator with the 470 ohm resistor is designed to operate a LED that is
supplied with a 12 volt “extra” power supply.
You
could also use a 12 volt 15 to 40 mAs incandescent lamp, but you will have to
remove the 470 ohm resistor and insert a link in its place. You would have to
use a 12 volt wall wart.
The
auxiliary 12volt power supply could be a separate 12 volt “wall wart” or the 12
volts that is running in the cab bus, supplied from the Command Station/Booster
or a wall wart power supply, that would be easily accessible from any part of
the layout. The current draw on the cab bus would only be 15 – 30mAs for the
LED indicator, only when there is a short. The rest of the EB3’s circuits are
completely isolated by the optoisolator IC.
To
operate a larger light than a LED then an additional circuit will have to be
added.
Using a 12 volt 5 to 27 watt lamp as a
remote indicator.
See the
article about some EB3’s not
resetting when using sound locos where a 12 volt 5 to 27 watt lamp is
used as a “bypass” lamp connected in parallel to enable the EB3 to reset. This
lamp can be located in the local area that the EB3 is controlling and would
serve as a very visual indication of a short if located strategically on the
layout facia or in a line side building.
The
bypass lamp ONLY illuminates when the EB3 has tripped, indicating a short in
that power district. Using this method, the district that has a short, the
power has NOT been disconnected as with the normal operation of the EB3 but the
current to the short has been reduced, depending upon the wattage of the lamp.
A 10 watt lamp would reduce the current to the short to about .75 Amps. This
will not damage any thing on the layout.
A fair
few EB3 and Tony’s Power Shield users are using this procedure so that their
circuit breakers automatically reset correctly when using sound locos.
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