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Model Railroad Infrared Train Detection
If something can be activated with a button, it can be automated with a train detector!
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Infrared ('IR') Train Detectors
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Coded pulsed infrared proximity sensors for detecting model trains on the track.
- Pulsing (modulation) allows the detector to ignore ambient lighting.
- Coded pulsing allows each detector to ignore the IR signals of other nearby detectors.
- May be used as a reflective detector (sensors in the roadbed) or as an interrupt detector (detector looks across the track).
- Sensors can be used with the room lights on or off, they do not require overhead light sources.
- No rail gaps required, no modifications to rolling stock.
- On-board LEDs to aid with installation.
- Relay contact triggers crossing signals, trackside signals, panel lights or action accessories.
- Infrared detectors also available as an Arduino shield.
Other methods of model train detection
• MRD1-V (variable delay)
installation instructions [pdf]
• About relay contact ratings
How to:
• Install the IR sensors
• Connect to a green/red LED signal
• Connect to Digitrax LocoNet™ decoder
• Connect to Märklin s88 decoder
Continuous mode drop-out delay:
how long the detector remains 'on'
after the train clears the sensor.
In this video Rob McCrain shows how to connect an MRD1-V to simple
two-LED
trackside signals.
• MRD1-NV (non variable delay)
installation instructions [pdf]
• How to install the IR sensors
Activation 'After Departure'
Need to activate a layout accessory after a train departs from a particular location?
The MRD1-V-AD version will do this for you.
You adjust how long the circuit waits before turning on the accessory, from 1/2 to 20 seconds after the end of the train leaves the sensor.
You select whether the accessory is energized momentarily (1/2 second) or continuously.
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MRD1 - Single & Simple
- Single position detector, senses a train at one point on the track.
- Includes optical sensors with 2-ft. wire leads.
- When activated, the on-board relay contact closes. You connect your circuit to this relay contact, it functions as an on/off switch for your circuit.
- Output contact rated for 3 amps.
- To control higher currents, use with an auxiliary power relay
- Compact size: 1.7 x 1.5 x 0.7 in.
- Power required: 8 to 16 volts AC or DC, 40 milliamps.
The MRD1 is available in two versions, MRD1-V and MRD1-NV, described below:
MRD1-V variable delay version
Using the on-board delay control, you select one of two operating modes:
Turn the delay control counter-clockwise from center to put the MRD1-V in
one-shot mode.
In one-shot mode the arrival of a train activates the detector, closing the relay contact. An internal timer immediately starts ticking, and when it reaches its limit it de-activates the detector, opening the relay contact.
The detector always activates for the same length of time, whether the train is still on the sensor or not.
You set the activation duration with the delay control. Turn it fully counter clockwise for the minimum 1/3 second 'on' time. Turn it back toward center for longer 'on' time, up to 14 seconds.
Turn the delay control clockwise from center to put the MRD1-V in
continuous mode.
In continuous mode the arrival of a train activates the detector, closing the relay contact. As long as the train is on the sensor, the relay contact stays closed ('on').
After the train clears the sensor the detector stays active for a short time, called a
'drop-out delay.'
After the drop-out delay has elapsed, then the relay contact opens (turns 'off').
You set the drop-out delay time with the delay control. Turn it fully clockwise to select the minimum 1/3 second drop-out delay. Turn it back toward center to select a longer drop-out delay, up to 14 seconds.
MRD1-NV non-variable (fixed) delay version
Single detector, as above, that always operates in continuous mode with a 'drop-out' delay fixed at one second.
MRD1-V-AD variable delay that activates
After Departure
Single detector, as above, that activates an accessory after the end of the train clears the IR sensor.
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The D6X HexDetex™ has auxiliary outputs to trigger a signal or relay, up to 0.35 amp.
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In this video
Doug Hodgdon of Model Railroad Academy shows how the HexDetex and some LEDs can warn you when a train is nearing the end of
a hidden track.
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D6X HexDetex™ with four or six pre-wired infrared sensor sets
Select the number of IR sensors and their wire length.
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- Four sensor sets for crossing signal control where only four sensors are needed.
Two sensor sets with 2-ft (60cm) wire length.
Two sensor sets with 6-ft (180cm) wire length.
- Six sensor sets, all with 2-ft (60cm) wire length.
Use when all detection zones are close together.
- Six sensor sets, two with 2-ft (60cm) wire length
and four with 6-ft (180cm) wire length.
Use when detection zones are widely separated, or
for crossing signal control where six sensors per track are needed.
- No IR sensors included.
For users who will use their own IR sensors.
You can splice up to 26 feet (8 meters) of additional wire to the sensor leads if a longer reach is needed.
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• Installation instructions [pdf]
• More installation tips and examples
How to:
• Connect to green/red LED signals
• Connect to Digitrax LocoNet™ decoder
• Connect to Märklin s88 decoder
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MRD8, Eight Channel Detector
- Senses model trains at eight places on the track.
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Solid state relay outputs for electrical isolation and maximum system compatibility.
- Eight on-board LEDs for easy setup.
- Quick-connect terminal blocks.
- 10-pin ribbon cable connector compatible with RR-CirKits LocoNet Control Point (LNCP)™, Tower Controller (TC-64)™ and similar interface boards.
- Power required: 8 to 16 volts AC or DC, 40 milliamps.
LocoNet Control Point and Tower Controller are trademarks of RR-CirKits, Waxhaw, NC
- Standard MRD8 - each output relay stays closed as long as a train is on its sensor, and remains closed for one second after the train clears the sensor (1 second drop-out delay).
- Momentary MRD8 - each output relay closes for 1/2 second then opens, and will not close again until after the train clears the sensor and the next train arrives.
Useful for actuating latching relays.
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Standard MRD8 with eight pre-wired infrared sensor sets
Output relays stay closed as long as a train is on the sensor, plus one second drop-out delay.
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Select the number of IR sensors and their wire length.
One sensor set = one IR LED + one IR phototransistor receiver.
Sensor sets have wire leads pre-attached. Available lengths are 2 ft (60 cm) and 6 ft (180 cm).
You can splice up to 26 feet (8 meters) of additional wire to the sensor leads if a longer reach is needed.
Choose "without sensors" if you plan to use your own infrared LEDs and phototransistors.
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Momentary MRD8 with eight pre-wired infrared sensor sets
Output relays close for 1/2 second when train arrives at the sensor.
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Select the number of IR sensors and their wire length.
One sensor set = one IR LED + one IR phototransistor receiver.
Sensor sets have wire leads pre-attached. Available lengths are 2 ft (60 cm) and 6 ft (180 cm).
You can splice up to 26 feet (8 meters) of additional wire to the sensor leads if a longer reach is needed.
Choose "without sensors" if you plan to use your own infrared LEDs and phototransistors.
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• Extra sensor sets for use with MRD1, MRD8, D2T or D6X detector circuits above
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Two sensor sets can be wired to one detector when used in across-the-track configuration. For details [ click here ]
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Order extra sensor sets. One set includes one IR LED and one IR phototransistor.
Does not include a detector circuit.
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DBD2, Dual Block Occupancy Detector for DCC
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• Installation guide [pdf]
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- Senses current flow to two track blocks.
- Sensitive enough to detect one 10k ohm resistor.
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Separate solid state relay output (SPDT) for each block,
- Now with Normally Open and Normally Closed contacts for both blocks, very easy to connect green/red block occupancy signals.
- Complete electrical isolation
- Maximum system compatibility
- Solid state relays are 'bounce-free'
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Each relay can switch up to 350 milliamps
(0.35 amp) AC or DC.
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Current-sensing coils cause no voltage loss to the track.
- Sense coils can be placed up to 12 ft (4 m) from the circuit board, right at the power feed to the track block.
- No need to re-route your track wiring.
- Separate sensitivity adjustment for each block.
- On-board LEDs for easy setup.
- Power required: 9 to 16 volts AC or DC, 25 milliamps.
The DCC bus may be used as a power source if less than 17 volts.
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Sense coil connection choice:
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One DBD2 kit:
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Pkg of three DBD2 kits:
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Plain coils, you solder your own wire to the coils
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Coils pre-wired with 3 ft (1 m) wire leads
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Each coil on a solderless quick-connect terminal block
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© copyright 2009-2023 Azatrax LLC, Longmont, Colorado
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