Here it is.... the circus diagram to end all circus diagrams.... even a "how this all works" dialougue.... OK so all you electronics whiz kids can you tell me if it is worth making up a Vero Board prototype?
Model Tramway Signalling System
Simple Block Module
Inputs
Reed switches connected to the inputs must be capable of carrying 600 microAmps. They are held HI by resistors and connect to the 0 volt rail. The switches are operated by magnets on the vehicles.
Inputs may also be driven by CMOS gates.
Outputs
LED outputs are intended to drive two Red/Green common cathode LEDs. Output current is 20 milliAmps to each LED.
Relay contacts are normally open. The contacts are closed when the circuit is reset.
Operation
All inputs are pulled high by resistors and are activated by normally open reed switches connected to the 0 volts rail. The reed switches are operated by magnets on the vehicles.
The RST (reset) input is also held high and is connected to the 0 volt rail to reset the module. When the module is reset, the relay is operated, the relay contacts are closed and LED1 and LED2 outputs are HI (LEDs light).
When a magnet is brought into proximity of the reed switch connected to a1, the a1 input goes LO, the output relay is released thus opening the output contacts. LED1 and LED2 outputs go LO extinguishing these LEDs, LED3 and LED4 go HI.
The output remains in this condition when the a1 reed switch is released and the a1 input returns to HI.
When a magnet is brought into proximity of the reed switch connected to a2, the a2 input goes LO, the output relay is operated thus closing the output contacts restoring the circuit to reset condition.
The output remains in this condition when the a2 reed switch is released and the a2 input returns to HI.
Dual Bidirectional Addon
The Dual Bidirectional Addon combines with two Simple Block Modules to control traffic in a bidirectional section of track.
Inputs
Reed switches connect to the inputs a11, a12, a13, b11, b12, b13 and RST
Outputs
The outputs from the module connect to two simple block modules a and b controlling traffic in the A and B directions respectively. The output RST connects to both Simple Block Modules.
Operation
RST performs the normal reset function on both Simple Block Modules as described above.
When the input reed switch a11 or b11 is operated, outputs a11 and b11 go LO, releasing the relays in both Simple Block Modules, removing power from track sections in both directions thus preventing a rear end collision from following traffic and head on collision with traffic in the other direction.
Reed switches a13 and b13 are placed to detect traffic that enters the unpowered sections of track while traffic traverses the bidirectional section. When the reed switch is closed, the presence of a vehicle is recorded and stored in a latch. The latch remains operated when the reed switch opens again.
A vehicle travelling in the A direction will operate reed switch a11 on entry to the bidirectional section and a12 on exit. A vehicle travelling in the B direction will operate switches b11 and b12.
When a vehicle exits the bidirectional section, the Module checks to see if any vehicles are waiting and reacts as follows:
Vehicle travelling in A direction
No vehicles waiting
Modules A and B reset
Vehicle waiting in A direction
Modules A and B reset
Vehicle waiting in B direction
Module B reset
Vehicles waiting in A & B direction
Module B reset
Vehicle travelling in B direction
No vehicles waiting
Modules A and B reset
Vehicle waiting in A direction
Module A reset
Vehicle waiting in B direction
Modules A and B reset
Vehicles waiting in A & B direction
Module A reset
Thus in heavy traffic conditions, traffic will traverse the bidirectional section alternately in each direction.
The traffic waiting latches a13 and b13 are reset by switches a11 and b11 respectively when the waiting vehicles move off.
