INSTRUCTIONS FOR IRDOT-3D
Reminder- to prevent accidental damage please make sure the power is not
connected when you make or alter any of the wiring connections
INSTALLATION: The unit is screwed to the underside of the baseboard with the infra red emitter and detector
located in a hole between the sleepers.
It is easiest to install the units after the track is laid. Drill a
small pilot hole between the sleepers. Fit an 8mm drill bit
marked with tape for slightly less than the base board
thickness. Drill from underneath the baseboard following
the pilot hole. Cut or file the small amount of baseboard
material left between the sleepers. Install the unit, and then
fill the remainder of the hole with modelling material. Blue
tack will hold the units in place temporarily.
When fitted to Z or N gauge track the gap between sleepers will be less than the diameter of the infra red detector
and emitter. However, the modules work well provided they are adjusted to fit close to the sleepers. This
positioning prevents reflections off the sleepers causing detection.
The modules will also operate on their side placed alongside the track. For thick baseboards and restricted space
we can supply units with the emitter and detector fixed to wires up to 18 inches long.
+
OPERATION: When the IRDOT-3D
detects a train it lights a red LED and
A
operates a double pole relay. The IRDOT is
B
supplied with a 5mm diameter red LED
C
connected to the correct screw terminals.
e f g h i
l m
D
This provides an aid while installing the
0V
IRDOT to check for reflections off
obstructions. After installation the LED is wired to the control panel. The double pole relay is effectively the same
as 2 spdt switches. The diagrams below show how the
C
C
relay contacts correspond to terminals.
A
A
POWER SUPPLY
f
f
The diagram shows how to connect a number of
IRDOTs to the same power supply. As the current
D
D
consumption is low many units can be powered by the
B
same supply. The supply should be from 12 to 16 B
e
e
volts. The units work with either AC or DC. If DC is
used the positive connection of the power should
not detecting
detecting
connect to every "+"terminal . If AC is used it is
important to be consistent and connect all the "+" terminals to the same power supply terminal.
+
power
supply
A
B
C
D
+
e f
0V
lm
A
B
C
D
+
e f
0V
l m
A
B
C
D
e f
l m
0V
HIDDEN SIDINGS AND LOOPS: The infra red may reflect off low tunnel ceilings causing a permanent
detection. The sensitivity of the unit can be lowered in the following ways. Paint the tunnel ceiling matt black to
reduce the reflected infrared. Bend apart the infra red emitter and detector.
If any rolling stock is not detected by the units white self adhesive labels can be stuck to the underside of the
rolling stock to increase the infra red reflected.
INCREASING INFRA RED RANGE The rubber heat shrink covering the emitter and detector may be trimmed
back to increase the range. Do not expose the infra red detector as this will allow the infra red to travel straight
from emitter to detector giving false detection.
LED WIRING
The IRDOT3 is supplied with the red (detect) LED fitted long leg to m short leg to l. This LED will light when a
train is detected. A second LED may be fitted long leg to l short leg to m. This will light when not detecting. If a
number of IRDOT3s are used each with a single LED these can be wired with long leg to l short leg to "0V".The
advantage to this is that "0V" is a common connection thus nearly halving the number of wires needed. The lower
2 diagrams show how to wire to both 2 leg and 3 leg bi-colour LEDs..
+
+
A
B
C
D
0V
A
B
C
D
0V
e f
lm
e f
+
+
A
B
C
D
0V
A
B
C
D
0V
e f
l m
l m
e f
l m
DELAY TIMES
As supplied the unit has a 3 second delay. Ie it detects a train immediately but remains detected for 3 seconds after
the train has left.
By connecting wires from the g, h, and i terminals longer delays are obtained.
Delay
3sec
6sec
9sec
12sec
15sec
18sec
21sec
24sec
g
x
x
x
x
h
x
x
x
x
i
x
x
x
x
- indicates no connection
x indicates connection
+
A
B
C
D
e f g h i
l m
0V
Above right is an example of 18 second delay wiring:
EXTENDED LEAD VERSION
Units attached to the emitter and detector with wires are used in the same way. Both emitter and detector are fitted
into a single hole between the sleepers. A small piece of foam can be used to wedge them in place from the
underside of the hole. Some people also find it helpful to fix the emitter and detector together with a piece of
insulation tape or sellotape. The emitter and detector may also be used at the side of the track.
Alternatively they can be used to form a beam pointing at one another. The train breaks the beam thus reversing
the LED indication. The operation becomes no train = beam across track = red led lit. Train blocking beam = red
led unlit. The red led may be fitted as shown for the green led to restore operation to red led lit=train detected.
The emitter wire may be extended (this is located closest to the edge of the board) and a beam length of 5 to 6 feet
will work.
Automatic storage for a row of trains: IRDOT-3D units can be used to store a queue of trains automatically
moving trains up into empty sections. The IRDOT-3Ds also provide LED indication of the occupied sections.
The diagram shows 3 storage sections 1, 2, and 3 separated by isolation breaks. Each section has an IRDOT-3D
positioned at X (no delay and only one relay pole is required at 3 so either an IRDOT-3D or IRDOT-2D or
IRDOT-2 can be used at this position). Electrical connections from the isolated sections are through the IRDOT3Ds relay contacts back to the controller. When no train is over the IRDOT-3D the relay contacts A and C or B
and D are connected powering sections of the track. (Relay contacts A, B, C, D refer to the numbering of the
terminals of the IRDOT-3D). Further track sections may be added to the left.
Suppose a train moves from the left into section 3. Power will be connected onto the track through the relay
e
contacts until the front of the train is detected by the IRDOT-3D. The relay will then open. If there is no train in
section 2 the track in section 3 will still be connected to the controller through section 2s B and D relay contacts.
When a train is in section 2 the train in section 3 will be isolated and will stop when it is detected by the IRDOT in
section 3. When the train leaves section 2 the train in section 3 will move up into the next empty section. A train
moving into section 1 will be isolated and stopped when detected. The push button switch "PB" is used to connect
power to the track. The switch should be a "push to make" type.
Operating 2 aspect signals with the IRDOT-3D
The IRDOT-3D can be used to operate a 2 aspect signal, either bulb or LED. If you want similar operation to
semaphore signals (where the signal is normally at red until the train approaches and the signal then changes to
green until the train passes) then fit the IRDOT-3D before the signal at the point on the track where you want the
signal to change to green.
+
power
for
red
signals
A
B
C
D
0V
e f g h i
l m
green
The diagram shows the wiring to the signals. The signals may share the IRDOT-3D power supply or they can use a
separate supply. Terminals A, C and f act in exactly the same way as a changeover switch. (SPDT). The common
wire from the signal goes straight to the power supply. Red and green go to C and f terminals and terminal A (the
common of the switch) is wired to the power supply to complete the circuit. Resistors supplied by the signal
manufacturer must be used.
The timing delay of the IRDOT-3D needs to be adjusted so that the signal remains at red until the train has passed.
Heathcote Electronics, 1 Haydock Close, Cheadle, Staffs, ST10 1UE TEL/FAX 01538 756800
Email: cah@heathcote-electronics.co.uk web site www.heathcote.electronics.co.uk