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The IRDOT-1D is for situations where you wish to see the train as a single detection rather than have the outputs switching on and off as individual wagons and carriages cross due to the gap between them. The IRDOT-1D has the same operation as the IRDOT-1 both detect the train immediately but the IRDOT-1D has a 4 second delay before indicating the train has left and so the IRDOT-1D's LED will remain lit and terminal 2 will remain switched during these gaps due to the 4 second delay.

The constant output can simplify the design of computer software and home made signalling and control systems.

The IRDOT-1D could be used to automatically trigger some of our other boards when the train has reached a certain location however it usually has no advantage over the IRDOT-1 as only the initial detection matters. Examples are the SA series of boards Timer, Simple Shuttle, IRDASC-1, 2, 3 and DSS. The difference between the IRDOT-1 and IRDOT-1D is that when a train passes over the IRDOT-1 it will usually detect each wagon individually due to the gaps between wagons (it is very unreliable to depend on only the couplings to reflect the infra red) whilst the IRDOT-1D will have a single detection for the whole train as the delay will be timing during the gaps and reset on every new detection.


The IRDOT-1D uses infrared to detect trains. When it detects a train it lights an LED and gives an output for activating other controls. The LED may be mounted on a control panel. It is simple to wire, requiring 2 wires for power and 2 wires for the LED.

The standard version has the infra red detector and emitter soldered to the reverse side of the circuit board. They extend 22mm. The IRDOT-1D has the infra red emitter and detector attached to the circuit boards by 18 inch long wires. This is to allow the board to be used in locations where it cannot fit directly under the track for example where there are baseboard supports in the way or where the track is raised on a viaduct etc.


As the IRDOT-1D can operate in tunnels and detect all types of rolling stock it is very suitable for train positioning and indicating track occupation in hidden sidings and loops. It is usually best to position the IRDOT-1D at the end of the loop where the front of the train is to stop. Once the "train detected" LED lights the train can be stopped. The IRDOT-1D operates in both light and in the dark.


This is as detailed below, but full instructions are supplied with the IRDOT-1.

Terminal 1 Connects to the positive terminal of the power supply

Terminal 2 Electronic switch (open collector transistor) for connection to our other units such as SA8.

Terminal 3 11 volts output used for relays and undetected LEDs

Terminal 4 Not used

Terminal 5 Connects to the long leg of the LED

Terminal 6 Connects to the negative power supply and short leg of LED

The wiring is as detailed below, but full instructions are supplied with the IRDOT-1D.

LED Illumination

Shows how an IRDOT-1D operates a red detect and green undetect LED

To indicate when a train is detected a LED is connected to terminals 5 and 6. We supply the IRDOT-1D with a 5mm diameter red screwed to these terminals. The IRDOT-1D can also operate a seperate LED which lights when no train is detected (green in the diagram) or a bicolour LED. The Bicolour LED displays green when a train is not present and red when a train is detected. Note that if the IRDOT-1D is being used to operate our other boards terminal 2 will be used and so will not be available for a green train not detected LED or for a bicolour LED. If this is a problem the IRDOT-3 can be used instead.

Power supply

shows how 3 irdot-1ds are connected to the same power supply

The IRDOT-1D can be powered from 12 to 16 Volts either AC or DC. The diagram shows how 3 IRDOT-1Ds are powered from the same power supply.


How to connect an IRDOT-1D to a relayTerminal2, the electronic switch output of the IRDOT-1D will operate many types of relay. A relay of any voltage can be switched subject to a maximum coil current of 100 ma. If the relays coil voltage is 12 volts, it can use the same supply as the IRDOT-1. When operating a relay this way the power supply must be smoothed 12 volt D.C. If an AC or unsmoothed DC supply is used the relay will "chatter" ie switch on and off rapidly at the mains electricity frequency.

Connection to Digitrax DS54 stationary decoder:

The Digitrax stationary decoder requires an input that changes from less than 6v DC to greater than 6v DC. This can be provided from terminal 5 of the IRDOT-1. Use a separate power supply for the IRDOTs. Connect the 0v DC of both the IRDOT and Digitrax power supply together. Remove the LED from the terminal and link terminal 5 to the Digitrax input. An LED train occupation indication can be provided by linking from terminal 2 to the short leg of the LED, then wiring a resistor from the long leg of the LED to terminal 3.

For more information about how infra red detection works and installation tips: See How infra red detection works



Voltage 12 to 16 volts, AC or DC

Maximum current consumption 25 m A


Length x Width 3 .45 x 1.2 Inches

Board to highest component

Height of infrared components 22mm