INSTRUCTIONS FOR THE IRDASC-3
The IRDASC-3 consists of an infra red train detection circuit and an electronic circuit to provide signal block working. Relay contacts are provided for signal operation and track isolation. One side of the circuit board is fitted with the electronic components the other side has an infra red emitter and detector.
The basic operation of the IRDASC only requires 2 wires to connect the power supply, three wires to the signal and one wire linking each IRDASC.
The signals are normally at red. There is a train detector at A (IRDOT-1 for example), an IRDASC at B wired to signal 1 and an IRDASC at C wired to signal 2. Assume the signals are initially all at red. A train travelling from the left will first be detected by the train detector at A. A wire connecting A to B will tell the IRDASC at B that a train is entering the block section and signal 1 will change to clear (green) As the train passes signal 1 it will reach the IRDASC at B. The IRDASC at B will detect the train and know that it is leaving the block section and so set signal 1 to red. Simultaneously it will tell the IRDASC at C via a wire that a train is entering its block section and so the IRDASC at C will set its signal to clear (green) until it detects the train when the IRDASC (at C) will return the signal to danger (red).
This chain of signals can be extended, each extra signal requiring an extra IRDASC to control it. If an oval circuit is signalled then the first and last IRDASC are connected together and there is no need for a train detector at position A. Alternatively if the first signal is a starter signal it can be set to green by a push button switch instead of the train detector at A.
This describes the simplest operation. More complex operation is possible. Operating the override/interlock terminal causes the signal to stay at red even though a train is within the block section. Removing the operation of this terminal returns the signal to normal operation. Uses for this input are; connection to a switch to allow the signal to stay at red for trains stopping at stations etc. Connection to a point operated contact to force the signal to remain at red whilst the point is wrongly set. Connection to an output terminal from the IRDASC in the next block section to force the signal to stay at red whilst a train is in the next block section.
START UP
When power is first switched on the units do not know if the trains are in there section or not. This could lead to trains becoming trapped on isolated sections. To overcome this there is a start up time during which signals are all switched to green and therefore all isolation sections are made live. To show the start up time is occuring the TIS_LED flashes.
During this time if a train is detected the unit signals along line TES and switches its signal to red.
If a train is detected entering a section (ie TES terminal is activated) then relay will go to red stopping train in isolation section for remainder of start up time.
POSITIONING THE IRDASCs
Position each IRDASC slightly past the signal it is to control remembering that when the train reaches this IRDASC the signal will return to danger and the track section will then become isolated. Ie allow space for the engine to leave the isolation section before reaching the IRDASC.
INSTALLATION
Drill a small pilot hole between the sleepers where the infra red detectors are to be fitted. Drill an 8mm hole from beneath the baseboard using the pilot hole as a guide. (Mark the 8mm drill bit with tape so that the depth of the hole is slightly less than the thickness of the baseboard.) File or cut away the small amount of baseboard remaining between the sleepers. Provided the infra red emitter and detector are very close or touching the sleepers the unit will work with the sleepers over the edges of the infra red devices. Gaps between the hole and infra red devices can be filled with modelling materials after the wiring has been tested. The unit works with the normal sleeper spacing of Z gauge and all larger gauges.
WIRING THE IRDASC (cross reference to numbering of previous IRDASC-3 version shown in brackets)
The screw terminals are numbered on the infra red side of the board.
+ Power +12 volts input or AC (1)
A Relay contact: track isolation common (3)
B Relay contact: signal common (2)
C Not used
D Relay contact: to signal green (5)
V0 Power 0 volts or AC (6)
e Relay contact: signal red (4)
f Relay contact to track isolation (7)
g REVERSE RUNNING: input (8)
h TRAIN ENTERING SECTION: input (9)
i OVERRIDE/INTERLOCK: input (10)
j TRAIN DETECTED: output (11)
k TRAIN IN SECTION: output (open collector transistor) (12)
l TRAIN IN SECTION: output to LED only (13)
m TRAIN DETECTED LED output to LED only
CONNECTION TO POWER SUPPLY
The IRDASCs can be powered from either 16 volts AC or 12 volts DC. If using DC the positive side of the power supply is connected to all the + terminals and the negative side to all the V0terminals.
If using an AC power source be careful to connect all the + terminals to one terminal of the power source and all the V0 terminals to the other. "crossing over" the connections will result in each IRDASC working individually but connections from one IRDASC to the other failing to work.
After wiring check the unit is detecting trains correctly by running rolling stock over it. As the rolling stock passes over the IRDASC the train detected LED on the IRDASC should light. (see later for details) With no rolling stock over the IRDASC the LED should not light. If the LED is permanently lit check it operates correctly when the IRDASC is removed from the baseboard. The cause of the problem will be found to be either reflection from sleepers (solved by slight repositioning of the IRDASC or moving it closer to the sleepers) or reflection from overhead bridge or tunnel ceilings. Solved by painting matt black or fixing a piece of foam or felt (which are very poor infra red reflectors) to the tunnel ceiling.
CONNECTIONS TO SIGNALS
Each signal is switched by a double throw relay contact this can be treated in exactly the same as wiring to a (single pole changeover) switch. Note that this allows the signals to either be powered from the same supply as the IRDASC or from a separate power supply as the contacts are electrically separate from the irdascs supply. Terminal B is the common. Ie either B and d are connected (green) or B and e are connected (red)
BULB SIGNALS
The left hand diagram shows the bulbs powered by the same supply as the IRDASC the right hand diagram shows a separate supply.
LED SIGNALS
The wiring is the same as for bulb signals but current limiting resistors must be provided and the LEDs must be powered with the correct polarity. Either 2 (LEDs back to back Patronics signals for example) or 3 wire (positive or negative leg of LED commoned) signals can be used. The diagram shows a common negative signal which uses the same supply as the irdasc. The diode is only necessary if the supply is AC.
SEMAPHORE SIGNALS
The IRDASCs have been used to operate semaphore signals by using the relay contacts to operate slow motion point motors. The relay contacts can also be used to power home made solenoids or a relay with an armature adapted to move the semaphore signal. Another possibility is to use memory wire.
Check for correct operation of the signal as follows: The signal should initially be at red. Touch a piece of wire between terminal 0V and terminal h. A click will be heard as the relay switches over and the signal should change to green. Operate the IRDASCs infra red detector by passing rolling stock or your hand over it. Again a faint click will be heard and the signal will change back to red.
DISTANT SIGNALS
No extra IRDASCs are required. Wire the (distant) amber bulb in parallel with the green (home) bulb and the red bulbs in parallel with each other.
WIRING "TRAIN ENTERING SECTION"
Assuming left to right running then the train detected output (terminal J) is wired to the train entering section input (terminal h). If an IRDOT-1 is used for the train detector at the start of a block section then terminal 2 of the IRDOT is wired to terminal h. If a pushbutton switch is used this is wired to apply 0 (connection to terminal OV) volts onto terminal h when the pushbutton is pressed.
The effect of the push button being pressed or a train passing over the IRDOT-1 or previous IRDASC is to change the signal to green. A pushbutton switch may be useful for the starter signal out of a bay platform.
WIRING EXTRA FEATURES OF THE IRDASC
OVERRIDE/INTERLOCK (terminal i)
When 0 volts* is connected to this input it prevents the signal changing to green (and also keeps the section before the signal isolated). Although the signal will remain at red whilst the 0 volts is connected the IRDASC still remembers a train is in the section and as soon as the 0 volts is removed the signal will change to green.
* "0 volts" is defined as the voltage at terminal V0 of all the units. All inputs operate when connected to "0 volts" and do not operate when there is no connection. Hence for purposes of experimenting with the effect of the inputs and verifying the correct operation of the IRDASCs a piece of wire can be connected to terminal 6 and touched onto the inputs.
The outputs switch to 0 volts when they operate. When they are not operating they are open circuit (electrically disconnected). This allows as many outputs and switches as required to be connected to the same input.
Uses of the Override/Interlock input are:
To keep the signal at red for stopping at a station.
Interlocking with points. i.e signal is at red and track isolated if points setting would derail the train.
Both the above are accomplished by wiring a switch or point operated contact to put 0 volts onto the Override/Interlock input when the signal is required to remain at red (with a train in the block section). Releasing the switch or changing the point removes the 0 volts so changing the signal to green when a train has been stopped in the block section.
Stopping trains running into an occupied block section ahead. This is done by connecting a wire from the IRDASC Train in section terminal (k) of the next block section to the O/I terminal (i). See above.
The IRDASC can be made to operate as an automatic station stop by using it with the dual timer.
The diagram shows the override operated by a switch on the right hand IRDASC.
TRAIN IN SECTION (TERMINAL K)
This terminal switches to 0 volts when the block section is occupied. It can be wired to the Override /Interlock terminal of the previous IRDASC (terminal I). Suppose the block section is occupied then as a train moves into the previous block section the signal will stay at red (and the track in front of the signal will be isolated) because of the 0 Volt (from the TIS terminal) linked to the Override/Interlock input.
Where there is a junction it is possible to wire several override/ interrupt terminals to the same TRAIN IN SECTION terminal. Diodes may be necessary to prevent unwanted electrical connections where point contacts are also used.
TRACK ISOLATION SECTION
The IRDASC 3 has relay contacts from terminal A and f for connection to a short isolated section of track in front of the signal to stop locomotives at the signal. When the signal is at green these terminals are connected together by the IRDASCs relay, when at red they are disconnected thus isolating the section of track.
Remember that the IRDASC 3 must be positioned far enough past the signal so that the engine is clear of the isolating section before reaching the IRDASC. Otherwise as the signal returns to red the train will be stranded on the isolation section.
A wire is shown bridging across the isolation section so that tracks either side of the isolation section are always live.
If trains are to run in the opposite direction to that signalled then the signals will be at red and the trains will be unable to cross the isolation section. This can be overcome by the use of a diode. (shown in the diagram). A 3 amp diode is recommended. The diode is not required if the trains always run in the direction signalled. Feedback controllers will not work with diodes, if they are to be used either have a switch for each isolation section, or a more sophisticated solution would be to have a relay for each isolation section and have the relays switched by a direction detector board