IRDASC Signal Controllers
The IRDASCs are infrared train detectors and automatic 2 aspect signal controllers combined on one circuit board. The Infrared detector works in the same way as the IRDOT.
There are three versions of the IRDASC. IRDASC-1 is for operating LED signals, IRDASC-2 switches the signal with relay contacts; these contacts can operate bulb or LED signals. IRDASC-3 has a double pole relay for operating both the signal and isolating the track in front of the signal.
How the IRDASC operates
There is a train detector (IRDOT-1 for example) at A, an IRDASC at B wired to signal 1 and an IRDASC at C wired to signal 2. The signals are initially at red. The detector at A will first detect a train travelling from the left. A wire connecting A to B will tell the IRDASC at B that the train is entering the block section. This causes Signal 1 to change to clear. After the train passes signal 1 it reaches the IRDASC at B. When the IRDASC at B detects the train it sets signal 1 back to red. Simultaneously it will "tell" the IRDASC at C via a wire that a train is entering its block section. This makes the IRDASC at C set its signal to green. When the IRDASC at C detects the train it returns signal 2 to red.
This chain of signals can be extended indefinitely. Each additional signal will use an extra IRDASC to control it. When signalling an oval, wire the first and last IRDASC together and omit the train detector at A. If the first signal is a starter signal a push button switch can be used to set the signal to clear when the train is due to depart. The IRDASCs can be used to form block sections. When used in this way the signals only change to green for approaching trains when the next block section is clear.
Installation
Each IRDASC is positioned past the signal where the train is required to return the signal to red. The IRDASC is fitted beneath the baseboard in the same way as the IRDOT. It is supplied fitted with a "train detected" LED so the correct operation of the infrared train detector can be checked. All three types of IRDASC can be used together. Follow the link if you wish to see the terminal arrangements for the IRDASCs:
Wiring the IRDASC-1 to the signal
The IRDASC-1 is supplied with built in current limiting resistors required for the signals LEDs. If a resistor is supplied with the signal it is not needed. The left hand diagram shows the usual connection to an LED signal with the LEDs commoned to negative. The right hand diagram shows how to wire an LED signal using only two wires.
Wiring IRDASC-2 to the Signal
The IRDASC-2 uses built in relay contacts to switch the signals. These are shown by blue lines in the diagram. Wiring the signal is therefore identical to using a changeover switch. The signal may be powered by either the same supply used for the IRDASC or a separate power supply. The relay contacts are rated for 2 amps.
The diagram shows the signal wired to use the same supply as the IRDASC. Wiring to the relay contacts is shown. It is identical to wiring to a changeover switch.
Wiring IRDASC-3 to the Signal
The IRDASC-3 uses a double pole relay for connections to the track and signals. This allows electrical isolation between track, signals and the IRDASCs power supply. The relays will switch up to three amps.
The diagram shows the arrangement for using a separate supply for the signal. The signal could also be powered from the same supply as previously shown for the IRDASC-2. Note how the internal relay connects both 2 and 4 or 2 and 5 to light the correct bulb. If a resistor is wired into the supply LED signals can be used.
Train entering Section Terminal
Activating this terminal "tells" the IRDASC that a train is approaching. It causes the signal to change to green. The "train entering section" terminal is usually wired from the "train detected" terminal of the previous IRDASC. It can also be operated by terminal 2 of an IRDOT-1, a reed switch or a normally open push button switch. The push button switch is useful for a starter signal. It is pressed when the train is due to depart.
After passing the signal, the train will reach the IRDASC. The IRDASC returns the signal to red when it detects the train. Whilst the train is detected the IRDASC operates the "train detected" terminal. This terminal can be wired to the "train entering section" terminal of the next IRDASC. This sets the next signal to green.
Wiring Summary
To make the signal change to green as a train approaches and return to red as it passes the following connections are made. Two wires to power the IRDASC. Three wires to the signal. One wire to the "train entering section terminal from the previous IRDASC, (or from an IRDOT-1, a reed switch or a push button switch). Using the remainder of the terminals to provide more advanced operation is optional.
Extra features of the IRDASC
"OVERRIDE/INTERLOCK" (OI) TERMINAL
As well as its use for block sections this terminal provides:
INTERLOCKING TO POINTS:
This causes the signal to stay at red when trains approach if a point is wrongly set. It is useful at junctions.
MANUAL OVERRIDE:
A switch can be operated to cause the signal to stay at red for trains stopping at a station. Similarly the relay of the Dual Timer can operate the "OI" terminal.
The override/interlock terminal operates when connected to 0 volts. To experiment fasten a piece of wire on to terminal 6 then touch the override/interlock terminal with the wire. If the signal was at green it will change to red. Removing the wire returns the signal to green.
Points and signals are interlocked by wiring the override/interlock terminal to a contact operated by the points movement. The contact is wired to connect terminal 6 to the over ride/interlock terminal when the points are wrongly set. When the point is correctly set, no connection is made. A toggle switch can also be used to connect terminal 6 and the override/interlock terminal to give manual control of a signal at a station. The switch is operated for stopping trains causing the signal to change to red until the switch is released. For through trains the switch isn't changed and so the signal changes to green for approaching trains. A double pole switch can be used; the second pole isolates the track in front of the signal. To make the signal remain at red when the next block section up the line is occupied; connect from the "train in section " terminal of the next IRDASC to the override/interlock terminal.
Many wires can be connected to an override/interlock terminal. When any one of these connections operates the override/interlock terminal it causes the signal to remain at danger for approaching trains. The signal will only change to green when none of these wires is at 0 volts.
IRDASC TERMINALS
- To Power supply (AC or positive DC)
- Train In Section "TIS"
- To signal Red LED
- To signal Green LED
- To Train detected LED
- To Power supply AC or DC negative
- To train in section LED
- Train entering Section "TES"
- Override/Interlock "OI"
- Reverse Running "RR"
- Train detected
- To Power supply (AC or positive DC)
- Not used
- Relay contact to green bulb
- Relay contact to red bulb
- Relay contact to signal power
- To Power supply AC or DC negative
- Not used
- Reverse Running "RR"
- Train Entering Section "TES"
- Override/Interlock "OI"
- Train detected
- Train In Section "TIS"
- To Train in section LED
- To Power supply (AC or positive DC)
- Relay contact to signal power supply
- Relay contact to track isolation
- Relay contact to red bulb
- Relay contact to green bulb
- To Power supply AC or DC negative
- Relay contact to track isolation
- Reverse Running "RR"
- Train Entering Section "TES"
- Override/Interlock "OI"
- Train detected
- Train In Section "TIS"
- To Train in section LED
"TRAIN IN SECTION" TERMINAL:
When the IRDASCs block section is occupied this terminal switches to 0 volts. See " block section" above for an explanation.
"REVERSE RUNNING" (RR) TERMINAL:
This terminal is used to allow correct signal operation when there is bi-directional running along a line. When a train is to run against the signals the reverse running terminal sets the signal to red. Unlike using the override/interlock terminal the "reverse running" terminal clears the IRDASCs memory of a train in its block section. If this input is not used then a reverse running train will cause each IRDASC to detect a train leaving the block section before the train entering section message; the result of which is to wrongly leave each signal at green after the train has left the block section. The "REVERSE RUNNING" terminal can be activated with a changeover switch. It can also be operated automatically with the Train Direction Detector. A single Direction Detector or changeover switch will operate all the "reverse running" terminals of a chain of IRDASCs.
The "RR" terminal has a second use as a reset to set all the signals to red. In this case all the reverse running terminals are connected to a single push button switch.
"TRAIN IN SECTION LED"
This terminal is used if you wish to have a signal box style illuminated track diagram. The terminal lights an LED whilst a train is in the block section. As trains travel around the layout you will see each LED lighting in turn as the train travels from one block section to the next.
ISOLATING THE TRACK WITH THE IRDASC-3:
The IRDASC-3 can isolate the track in front of a red signal. Power is switched onto the track when the signal is green. Hence trains will be automatically stopped by the signal if the points are incorrectly set; the next block section is occupied etc. Relay contacts (rated at 3 amps) isolate the track so keeping the track, signalling and IRDASC electrically separate. The isolated section should be just in front of the signal where the engine is to stop and slightly longer than the longest engine. For bi-directional running a diode will feed current into the isolated section for trains running against the signals.
Several trains can be run on the same line by using a number of IRDASC-3 controlled block sections. When one train begins to catch up with another it will automatically stop at the next signal until the next block section is empty.
AUTOMATIC CONTROL OF A QUEUE OF TRAINS IN HIDDEN SIDINGS:
Where two or more trains are stored on a long hidden siding IRDASC-3s can be used to make the trains move up one position when the leading train leaves. A switch connecting 0 volts to the "override/interlock" terminal will control exit from the storage sidings. The IRDASC 3 will isolate the track when the switch operates.
ELECTRICAL OPERATION OF SEMAPHORE SIGNALS:
the IRDASC-2 or IRDASC-3 can operate Semaphore signals. Instead of bulbs these boards will switch low current solenoids, memory wire or a relay with a moving arm (our relays are not suitable) to move the semaphore signal.
JUNCTIONS:
Both facing and trailing junctions can be correctly signalled. Signals, points (and even isolating sections if the IRDASC-3 is used) can be interlocked. This is explained in detail in the instructions.
Specifications
| Voltage | 12 to 16 volts, AC or DC | |
| SIZE | ||
| Inches | Millimetres | |
| Length x Width | 4.8 x 1.2 | 123 x 31 |
| Height of infrared components | 0.9 | 22 |