Installation Guide
Azatrax Dual IR Train Detector
D2T-3W for 3-wire turnout control
What it is:
The D2T-3W is a two-channel model train detector using advanced infrared
('IR') technology. It can detect model trains at two different locations on the layout and
activate a turnout (track switch) if the turnout is actuated with a 3-wire switch machine.
Three-wire (or 'twin-coil') switch machines include those made by
Atlas
,
Bachmann
,
Peco
,
Kemtron
and others.
To control a turnout equipped with a 2-wire switch machine, use a D2T-2W circuit.
Kit contents:
★
Circuit board
★
Two infrared light-emitting diodes (IR LEDs) with orange & white wire leads
★
Two IR receivers with green & yellow wire leads
★
Four plastic mounting tubes. The tubes are for protection of the sensor leads and to provide mounting support. They are
not essential for detector operation and may be shortened or removed entirely to best fit your situation. Use caution, do
not damage the leads.
★
4,700 ohm (4.7k) resistor to select alternating action or cross-over mode.
How it works:
Trains are detected by infrared (IR) light, invisible to the human eye. There are two sensing elements at
each track location - an IR LED light source paired with an IR receiver.
The turnout can be controlled manually by connecting push buttons to the D2T.
Green and red LEDs on the D2T show the status of the detectors and the position of the turnout points.
Operation Options
●
Derail prevention, single turnout control:
The two IR sensor pairs
are installed to detect trains approaching the frog end of a turnout (track
switch). Sensor pair #1 is placed on the 'main' track (green). When a
train triggers this sensor pair, the turnout points (the movable rails at the
end opposite the frog) will align for the main track.
Sensor pair #2 is placed on the 'branch' track (red). Triggering sensor pair #2 will align the turnout for the branch track.
Safety lockout:
If a second train approaches the turnout while the first train is still on its sensor, the D2T will keep the
turnout points aligned for the first train.
The D2T waits until the first sensor has been clear for four seconds,
then it will
align the points for the second train. The first train must move fast enough so its last car
clears the points within four seconds after it clears its sensor.
The safety lockout duration can be shortened to 1/2 second by connecting a resistor with a
value between 3000 and 10,000 ohms, to terminals 'S2' and 'C.'
●
Blocking the automatic control:
To positively prevent
the D2T from moving the points while a train is on the
points, an external detector such as an Azatrax MRD1 can be
located at the turnout points.
Connect the external detector's output so it connects D2T
terminal 'BL' to terminal 'C.'
As long as 'BL' is connected to 'C', the D2T will not move the points in response to its
IR sensors.
The D2T will, however, move the points in response to manual push buttons.
●
Manual operation (optional):
To have manual operation of the turnout, connect two push buttons as shown here.
Use push buttons that are “momentary, normally open.”
Pressing the button connected to 'S1' will align the turnout for the main track, pressing
the button connected to 'S2' aligns the turnout to the branch track.
© 2016-2018 Azatrax.com
D2T-3W turnout control (3-wire switch machines) installation guide
pg. 1 of 4
D2T-3W
1K
1F
X
R
2K
2F
BL
S1
S2
C
P1
P2
Y1
YC
Y2
M1
M2
LED 1
LED 2
M3
