Azatrax D2T-3W User manual

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 wor s: 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 '
● Bloc ing 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

● Alternating action with direction sensing: Moves the
points to the opposite position when a train approaches the
points end of the turnout Trains will automatically
alternate between taking the main line and the branch line.
The two IR sensor pairs are placed on the track leading to the
turnout points The D2T changes the points position only
when sensor pair #1 is triggered before sensor pair #2
To enable alternating action with direction sensing, connect a resistor of
3,000 (3k) to 10,000 (10k) ohms from S1 to C as shown.
Push buttons for manual operation may also be connected to 'S1' and 'S2', see above
● Alternating action, external trigger: Moves the points to the opposite position in
response to an external switch or detector circuit Connect terminals 'S1' and 'S2' together,
then connect to an external momentary switch or detector circuit (such as an Azatrax
MRD1) as shown here The switch should be “normally open ”
Closing the contact will move the turnout points to the opposite position (from main line to branch line, or from branch
line to main line) The switch must be released (opened) for at least four seconds before the D2T will respond to another
contact closure This is to avoid inadvertent points movement while a train is moving through the turnout
● Derail prevention at a cross-over: Two turnouts can make a 'cross-over' that allows a train on one track to cross over to
the other track If a train takes the cross-over and the operator neglects to set the turnout points back to the main lines
(straight-through), then if the next train approaches from the opposite direction it is at risk of derailing on the turnout points
Preventing this type of derailment is similar to
preventing derailments at a standard single turnout,
except that at a cross-over, both IR sensor pairs
will set the two turnouts to the main line (straight-
through) position Setting the points to the cross-
over position must be done manually with a push button connected to
terminals 'S2' and 'C ' See “Manual operation” on the previous page
To enable derail prevention at a cross-over, connect a resistor of
3,000 (3k) to 10,000 (10k) ohms from BL to C as shown.
The two switch machines are connected in parallel to the D2T 'M1' and 'M2' terminals They will operate simultaneously,
therefor the power supply must have sufficient power capacity to operate two switch machines at the same time.
Install the sensors
Each sensor pair may be installed in one of two ways - 'Across the Track' or 'Reflective ' Choose locations according to how
you will use the detector -- see 'Operation Options' on pages 1 & 2 Sensor leads may be extended up to 26 ft (8 meters)
with similar twisted pair wire Wire from telephone or 'Cat 5' computer cable works well
Across the Track sensing: The IR LED is positioned horizontally on one side of the track(s), and its IR receiver is placed
on the opposite side A train is detected when it blocks the light path between the LED and
receiver The distance between the LED and its receiver can be up to 18 in (46 cm) With
careful alignment longer distances can be achieved
Tip #1 - If mounting the sensors vertically as shown here, slide the plastic tubes away from the
sensor then carefully bend the leads to a right angle The leads are somewhat brittle, bending
them more than two or three times may cause a break
Tip #2 - Locate the receiver so it faces away from bright lights or sunny windows Sensors can be concealed by scenery or
structures
Always turn off power before making or changing connections !
© 2016-2018 Azatrax.com D2T-3W turnout control (3-wire switch machines) installation guide pg. 2 of 4

Reflective sensing: Trains are detected when light from the IR LED is
reflected off a train and sensed by the IR receiver Typically the sensors
are mounted in two #12 (3/16 inch or 4 8mm) holes drilled in the roadbed
as shown here Vertical installation works for S, O and larger scales as
long as there is no structure above the track such as a bridge
Angling the IR LED and receiver toward each other is best for N and HO
scale where trains are close to the rail head, and in places where an
object above the track might otherwise cause false detections Angle the
IR LED and its receiver so their centerlines intersect at the height of the
bottom of your rolling stock
Tip #3 - You can ballast your track after sensors are installed Cover each sensor with a bit of transparent tape Apply
ballast When the glue has dried, use a dental pick or similar tool to remove ballast from the sensors An opening of only 1
or 2 mm is required
Connect the sensors to the D2T circuit board
Connect sensor pair 1: How you connect the IR LED and its receiver to the D2T module determines whether Detector #1
operates in 'Across the Track' or 'Reflective' mode Strip the end of the sensor wire Firmly push down the square button on
the terminal block and insert the wire at a 45º angle Release the button and tug on the wire to verify it is secure
Sensor pair #1, Across-the-trac mode Sensor pair #1, Reflective mode
Add connections for sensor pair 2: Detector #2 can operate in the same mode as Detector #1, or in a different mode
Note that when both sensor pairs are wired to the D2T, there will be two white or yellow wires in terminals 'R' and 'X '
Additional wire may be spliced to the sensor leads if needed Use similar twisted pair wire for total length up to 25 ft (7 5m)
Sensor pair #2, Across-the-trac mode Sensor pair #2, Reflective mode
Connect power to the D2T-3W circuit: 12 to 16 volts AC or DC works well with most switch machines If one side of
the power supply is connected to a layout 'common' or 'ground,' connect it to terminal 'P2' Connect the 'hot' side to 'P1 '
When power is turned on, the D2T checks whether the IR LEDs are connected or not
● If IR LED #1 is connected, then the green on-board LED #1 will flash three times
● If IR LED #2 is connected, then the red on-board LED #2 will flash three times
● If no IR LEDs are connected, the on-board LEDs will flash four times in unison
On-board LEDs: A green and a red LED show the status of the sensors and the turnout position
If the turnout points are positioned for the main track, the green #1 LED will be on
If the turnout points are positioned for the branch track, the red #2 LED will be on
A flashing green #1 LED indicates that IR sensor pair #1 is detecting a train or other object
A flashing red #2 LED indicates that IR sensor pair #2 is detecting a train or other object
Adjust the sensors / troubleshooting:
With no trains in either detection zone, the green and red LEDs on the D2T should not be flashing If either LED is flashing,
correct the false sensing condition
© 2016-2018 Azatrax.com D2T-3W turnout control (3-wire switch machines) installation guide pg. 3 of 4

To fix false sensing for Across-the-Track mode:
1 Verify that the sensor pair is wired correctly
2 Make sure the IR LED and its receiver are pointed at each other, and nothing is between them
3 Shade the receiver from bright lights, and point it away from windows or other strong light sources
4 Change the nearby room light from incandescent to a fluorescent or LED bulb if possible
To fix false sensing for Reflective mode:
1 Verify that the sensor pair is wired correctly
2 Pull the IR LED and receiver a bit deeper into the roadbed
3 Infrared light may be 'leaking' through the roadbed material from the IR LED to the receiver Push a metal shim, such as
the tip of a hobby knife blade, vertically into the roadbed between the IR LED and receiver
4 Is there an object above the sensor, such as a bridge, or an upper layout level? Mount the IR LED and its receiver at a
shallower angle, or paint the overhead object black Or use across-the-track sensing
Both detectors now off? Good, now test for train detection Place a locomotive or car in the detection zone of IR sensor
pair #1 The on-board green LED #1 should flash If the red LED #2 also flashes, re-adjust IR sensor pair #2 for false
detection (see above) If the green LED does not flash, correct sensor pair #1 for a false clear condition
To fix a false clear indication for Across-the-track mode:
1 Verify that the sensor pair is wired correctly
2 Adjust the sensor height so the train is fully blocking the light path from the IR LED to its receiver
To fix a false clear indication for Reflective mode:
1 Verify that the sensor pair is wired correctly
2 Adjust the sensors higher or lower in the roadbed
3 A bright light source above and to the side of the track may be saturating the IR receiver Try pulling the receiver deeper
into the roadbed or create shade with scenery or a structure Change the nearby light to a fluorescent or LED bulb
Test with several types of rolling stock and adjust the sensors as needed
Remove the train from IR sensor #1's detection zone, make sure the green LED stops flashing
Place a train in IR sensor #2's detection zone The on-board red LED should flash If the green LED also flashes,
adjust IR sensor pair #1 for false detection (see above) If the red
LED does not flash, adjust sensor pair #2 for a false clear condition
(same as above for sensor pair #1)
Connect the switch machine
Twin-coil machines are driven by one brief pulse of current
The switch machine connects to D2T-3W terminals M1, M2 & M3
If the points move in the wrong direction, swap the wires at M1 & M3
Do not connect to other buttons or circuits.
Do not connect 'M2' to a layout 'common' or 'ground.'
On-board relay contacts: A single pole (SPST) relay is connected to terminals Y1 and YC, and a second SPST relay is
connected to terminals Y2 and YC
Y1 connects to YC when the turnout is lined to the main track
Y2 connects to YC when the turnout is line to the branch track The relay contacts are
rated 3 amps, 30 volts max
Example - power routing to trac sidings.
Example – signal control.
If using LED signals, use a DC power supply with
proper +/- polarity and resistors according
to the signal manufacturer's recommendations.
© 2016-2018 Azatrax.com D2T-3W turnout control (3-wire switch machines) installation guide pg. 4 of 4
switch machine
M1
M2
M3
red
common
green
connect to the D2T- W only
M1
M2
M3
connect to the D2T- W only