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The IRDOT-3 is an infra red train detector with built in double pole contacts and outputs to operate LEDs to indicate both detection and non detection. Either two separate LEDs can be used or either a 2 or 3 legged bicolour LED. The LEDs may be mounted on a control panel. It is simple to wire, requiring 2 wires for power and 2 wires for the LED.

contact arrangement of the IRDOT3 infra red detector

When the IRDOT-3 detects a train it lights a red LED and operates a double pole contact. The IRDOT-3 is supplied with a 5mm diameter red LED.  This provides an aid while installing the IRDOT-3 to check for reflections off obstructions.  After installation the LED is wired to the control panel. The diagrams on the right show how the contacts join to the terminals.


These are rated for currents up to 5 Amps. There arrangement is shown in the diagram.

LED wiring

A second (green) LED may be fitted long leg to k short leg to l (see diagram). This will light when not detecting. If a number of IRDOT-3s are used each with a single LED these can be wired with the long leg to terminal l and the short leg to the 0V terminal. The advantage to this is that 0V is a common connection thus nearly halving the number of wires needed. The diagrams also show how to wire to both 2 leg and 3 leg bi-colour LEDs.


The IRDOT-1D can be powered from 12 to 16 Volts either AC or DC.


For information about infra red detection and installation tips see:

How infra red detection works



Voltage 12 to 16 volts, AC or DC

Maximum current consumption

SIZE Length x Width 122 x 30Millimetres 4 .6 x 1.2 Inches

Height ( Board to highest component) 20mm 0.6 Inch

Height of infrared components 22mm 0.9Inch