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The IRDOT-P board has 3 screw terminals at one end and 4 at the other. It provides automatic switching of points.

The IRDOT-P allows the movement of trains to switch points automatically. Infrared detection is used to switch from one to six points (operated by solenoid point motors such as PECO or SEEP) when a train reaches a specific part of the track.  Uses are automatic storage sidings, points on reverse loops, trailing points and complicated routes.

IRDOT-P terminals

Terminals R and R1 are wired to the solenoid point motor. Other terminals provide conection to a train detected LED indication and inhibit to stop the point motor being switched

V0 and + these terminals are used to connect power to the IRDOT-P.  The IRDOT-P may be powered from 12 to 16 volts AC or DC.  This supply is separate from the one used for the point motors.

P on first detecting a train, this terminal switches to 0 Volts for approx. 1 second.  Its purpose is to activate other units such as the Dual Timer, latching  relays, SA1 shuttle and SA6 when the IRDOT-P detects a train.

R and R1 These two terminals are used to connect power to the point motor.  When the IRDOT-P first detects a train the R and R1 terminals are connected together for approximately 1 second.   Whether the train stops over the IRDOT-P or continues to move the point motor is only powered for 1 second and will not close again until the train leaves and a new train arrives.  There is also a dead time of approx. 4 seconds after the train leaves before the detection of a new train will cause the R and R1 terminals to operate again.  The 1 second timing and the dead time prevent the point motor from damage by being continually powered.  The IRDOT-P makes this connection between the "R" terminals with its internal relay contacts.  The relay contacts are of 10 amp capacity allowing at least six point motors to be switched.  Using a relay keeps the IRDOT-P power supply and the point motors power electrically separate.  The terminals act as an automatically operated momentary contact.  The diagram shows two point motors controlled by two IRDOT-Ps. The common connections of the point motor are all wired straight back to the point motors power supply.  When the top IRDOT-P detects its "R" terminals will be temporarily connected giving a burst of power to the left hand connection of both point motors, switching the points left.  When the bottom IRDOT-P detects it will switch both point motors right.

Two IRDOT-P switch 2 point motors. This arrangement can allow a train to alternate between two different routes

LED: this lights an LED (supplied fitted) when the IRDOT-P detects a train.  Long leg of the LED to "LED" short leg to "-".  This LED is useful during installation.  It can be wired to the control panel if required. The LED also indicates when the dead time is being timed by flashing rapidly.

I (inhibit) stops the R, R1 and P terminals operating when it is connected to 0 volts. The train detected LED still lights when "I" is used.  A switch, SA6, IRDOT, Dual Time Delay board, relay, or Train Direction Detector can be used to operate 'I'.  This terminal is used to automatically stop the IRDOT-P from operating the point when a train is in a certain place or travelling in a certain direction.  "I" is also used if it is required to change from automatic to manual point operation.

Trailing points

This is the simplest installation. The IRDOT-P is arranged so that trailing points are always correctly set.  If required they can be set manually for the facing direction.

Complicated routes

A train can travel along alternative routes by locating 2 IRDOT-Ps each before the point to switch it ready for exiting and switch another facing poinr ro change the trains route

An example of how two IRDOT-Ps can make a train alternate between two different routes is shown. In this arrangement the train will alternate between doing one lap of the outer then a lap of the inner ovals. The IRDOT-P at B switches point 1 for the outer oval and point 2 for the inner.  The IRDOT-P at A switches point 1 for the inner oval and point 2 for the outer.  The effect of this is for the train to make alternate laps around the outer and inner lines.  This idea can be extended to more complex arrangements.

Automatic storage sidings

click here for information

Sidings at the end of shuttles

 click for information about SA1 (gradual braking) shuttle with sidings and  click for information about Simple Shuttle with (sudden stops) sidings

Changing to manual control

One switch is used to connect all the "I" terminals to 0 volts (terminal "0V").  When the switch operates, the IRDOT-Ps no longer control the points.  A manual point switch is wired to the two "R" terminals.

Slow motion point motors

We can supply the IRDOT-P modified to close its relay for approximately 20 seconds.  This allows sufficient time to operate slow motion point motors. However if the point does not have the point blades held over with a spring it is better if the slow motion point motors are continuously powered. This can be achieved by using the IRDOT-Ps to switch latching relay boards. The DPDT contacts of the latching relay boards can then be used to reverse the polarity to the point motors.

Solenoid point motors

Many solenoid point motors need a large current for a short time.  If the current continuously flowed through the solenoid then it might overheat and burn out.  When the IRDOT-P detects a train it closes its relay contacts for approx. 1 second.  After this time the relay contacts always reopen.  Even if a train stops over the IRDOT-P the contacts will only power the point for 1 second.  This time allows the required burst of current to flow to energise the point motors solenoid.  Capacitor discharge units can be used with IRDOT-Ps; these may be essential if the IRDOT-P switches several points.


Voltage12 to 16 volts, AC or DC current consumption 45 mA

Switched current The IRDOT-P contacts are rated to switch currents up to 10Amps

SIZE   Millimetres Length x Width 4  5/16Inches  x  1  3/16 Inches 110 Millimetre  x  31 Millimetre