INSTRUCTIONS FOR THE IRDOT-P
Reminder- to prevent accidental damage please make sure the power is not connected when you are making or altering any of the wiring connections
The IRDOT-P detects trains by reflection of infrared. It has a 10 amp rated relay for switching up to 4 solenoid (PECO Hornby, or SEEP) point motors. As soon as a train is detected the relay contacts close for approx. 1 second then reopen. The relay contacts will not close again whilst the train remains detected. When the train leaves there is a dead time of approx. 4 seconds before the contacts can operate again. These two measures are to ensure that the point motor cannot be continually energised which may damage it. The relay contacts are accessible on the "R" terminals. A faint double click can be heard when the relay contacts operate.
Whilst a train is detected the red LED is lit. The LED is wired, long leg to "led" terminal short leg to "VO" terminal. The IRDOT-P is supplied with the LED fixed in this position. After installation the LED can be wired to a control panel. The LED must be wired the correct way round or it may be damaged. Note the LED's current limiting resistor is built into the IRDOT-P board.
The LED flashes very rapidly after a detection to indicate the "dead time" during which the IRDOT-P will not switch the points or operate the “P” terminal.
Terminal "P" provides a pulse of 0 volts at the same time the relay contacts close. Its purpose is to activate other units. Examples of other units activated by the "P" terminal when the IRDOT-P detects a train are:
The latching relay board (for reverse loops).
The Dual Timer, SA6 or SA6-B for storage sidings.
The SA1 or SA3 shuttle when the IRDOT-P is used to add sidings at the end of the line.
Terminal "I" is used to stop the "R" and "P" terminals operating. To do this it is connected to "0 volts". (I.e. it is connected to terminal "V0" or the same voltage as "V0". Either a switch, relay contact or any terminal on our units which switches to 0 volts can be used. Uses for the "I" terminal include switching from automatic to manual point operation and preventing the points changing when trains leave storage sidings.
Terminals "+" and "VO" are for connecting to a power supply. The IRDOT-P is powered from 12 to 16 volts AC or DC. The IRDOT-P only requires a small current so a number can be powered from the same supply. Positive connects to "+" negative to "V0".
INSTALLING THE IRDOT-P
It is easiest to install the IRDOT-P after the track has been laid. A small pilot hole is drilled between the sleepers. This hole is used to guide an 8-mm drill from underneath the baseboard. The drill is marked with tape for to give a depth slightly less than the baseboard thickness. The small amount of baseboard material left is then filed from between the sleepers.
When fitted to Z or N gauge track the gap between the sleepers will be less than the diameter of the infra red detector and emitter. However the modules work well provided the infra red emitter and detector are adjusted to fit against the underside of the sleepers. This positioning is necessary to prevent reflection off the sleepers causing detection. The adjustment is easily made with cardboard packing between the baseboard and the IRDOT-P. The IRDOT-P can be held temporarily in place with "blue tack" or similar. Connect to the power supply and check the LED only lights when an object is over the infra red detector and emitter. If the LED lights continuously adjust the IRDOT-Ps position.
WIRING TO THE POINT MOTORS
The IRDOT-P is wired so that when the relay contacts of the IRDOT-P close a pulse of electricity flows to the point motor. This is exactly the same as wiring to a passing contact switch. Either a transformer or a capacitor discharge unit can be used to power the points. An example of operating two points with two IRDOT-Ps is shown.
STORAGE SIDINGS
One IRDOT-P is required for each storage loop. For abrupt stops and starts a single Dual Timer is also required. See catalogue for wiring details.
For storage loops with a gradual slowing and acceleration a single SA6 or SA6B plus a single IRDOT-1 is also required. See SA6 instructions for wiring details.
REVERSE LOOPS
For a train running between 2 reverse loops position the IRDOT-Ps where the train is reaching the point to leave the reverse loop. Using the wiring shown each IRDOT-P sets both points to leave the reverse loop it is on, and to set the point for the other reverse loop. The "P" terminals can be fed into the "R" and "S" terminals of the latching relay board to change the polarity of the track automatically.
WIRING A STORAGE SIDING WITH 3 LOOPS
The diagram only shows the wiring associated with the point motors, refer to the Dual Timer or SA6 instructions for the other wiring. The small upright rectangles represent the 4 point motors. The centre (common) connection of all 4 point motors is connected to one terminal of the point motors power supply. The other connection of the points power supply runs to one "R" terminal of every IRDOT-P. When a train is first detected by the IRDOT-P the two R terminals will connect for 1 second. This causes the other "R" terminal to become "live". This "R" terminal is connected to the point motors to cause the points to change for the next track.
When a train arrives in loop 1 two point motors will operate to change the points to loop2. A train arriving in loop 2 will change two points to set the track for loop 3. A train arriving in loop 3 changes 4 points to return to the initial setting for loop1. As 4 point motors are switched together a capacitor discharge unit may be needed to supply enough current.
Heathcote Electronics, 1 Haydock Close, Cheadle, Staffs, ST10 1UE
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