Instructions for the Sa-7
INSTRUCTIONS FOR THE SA8-SB
OPERATION
The SA8-SB controls a station stop with a two aspect starter signal and forms a signalling block section.
When the train crosses the TES detector it will slow then stop at the station for an adjustable time. If there is no train in the next block section the signal will change to green and the train will accelerate away. If a train is in the next block section the signal will remain at danger and the train will remain in the station until the next block section is empty.
Once the next block section becomes empty the signal changes to clear and a few seconds later the train gradually accelerates away. On being detected by IRDOT-1 at C the SA8-SB knows the train is leaving the block section and the signal will return to danger.
Two train detectors are required per block section. These can be either IRDOT-1 or reed switches. One is used to detect a train entering the block section (TES) the second to determine when the train has reached the position it is required to stop at (STOP). A third connection is made to the TLS (train leaving section) terminal to tell the SA8-SB the train has left the block section. This shares the IRDOT-1. ( C ) used for TES of the next block section.
POWER SUPPLY
There are two methods of powering the unit. If entirely automatic operation is required the unit can be powered from a single 12 to 16 volts AC or DC supply. Alternatively the train speed can be adjusted by wiring a controller into the SA8-SB. The controller will then determine the speed until the SA8-SB decides the train must brake and stop. The SA8-SB will then override the controller. Either a 12 volt DC supply or a 16 volt AC supply is needed in addition to the controller. The controller can also operate sections of the line not controlled by the SA8-SB and will give a smooth passage from a controller operated section to the SA8-SB operated section. Feedback controllers will not work with the SA8-SB.
Note: The positive output of the power supply is referred to as "12 volts" and the negative output as "0 volts"
The diagrams show the wiring required for each arrangement. The link wire is left in place for 12 volt DC operation. For AC operation the link wire is replaced with a diode and a capacitor fitted as shown on the next page.
If an AC supply is used a diode and capacitor are needed. Silver band of diode and minus signs on capacitor show which way around the components legs go.
One power supply can be used to power a number of SA8-SBs. The number will depend on the current rating of the power supply. Typically for 00 gauge a 1 Amp power supply will power four SA8-SBs. When extra power supplies are used all the 0 volt terminals should be connected together.
The IRDOT-1 and SA8-SB must use the same power supply. They are wired as shown below.
The diagram shows terminal "6" of the IRDOT-1 and terminal "0" of the SA8-SB connected to the negative or 0 Volts connection of the power supply. Terminal "1" of the IRDOT-1 and terminal "+" of the SA8-SB connect to the positive (or 12 volts) connection of the power supply.
ELECTRICAL SECTION
A separate electrical section is required for each block section. One rail (right hand rail looking in direction trains are travelling) needs two isolation gaps the other rail providing a common return. The electrical section must extend beyond the signal to provide enough track for a train stopped at the signal to accelerate to maximum speed. This needs to be the same distance as the braking distance between TES and STOP.
TRAIN DETECTOR CONNECTIONS
Terminal 2 of the first IRDOT is connected to the TES terminal and terminal 2 of the IRDOT at the signal to the STOP terminal. This wiring causes the train detectors to apply 0 volts to the terminal upon detecting a train. The effect of operating these two terminals together with the "TLS" "RR" and "OI" terminals can be experimented with by temporarily connecting a wire between one of these terminals and the "o" terminal, which is at 0 volts. Remember that they must be operated in the correct sequence. "STOP" does not work until after "TES" has been operated. "TLS" must be operated before "TES" will operate a second time. "OI" only slows the train when the train is between "TES" and "STOP"
Reed switches are wired between 0 volts and the appropriate terminal.
WIRING TO THE SIGNAL
The signal is controlled from the contacts of a single pole change over relay on the SA8-SB. These contacts are accessible at the three terminals as shown. The contacts are electrically isolated and are wired in just the same way as if a single pole change over switch was used to operate the signal.
Either bulb, LED or (by using the relay to operate a slow motion point motor, permanently energised solenoid or second modified relay) semaphore signals can be operated.
OVERRIDE/INTERLOCK (OI) CONNECTION
This operates when 0 volts is applied to the terminal. Its effect is that whilst 0 volts is applied a train entering the block section will slow and upon reaching TLS stop. When the 0 volts is removed the signal will change to clear and the train accelerate away. A switch or point operated contact can be wired to apply 0 volts from the "o" terminal. This will cause the train to slow and stop when a point is wrongly set or give manual stopping from a switch.
WIRING BETWEEN BLOCK SECTIONS
The OI (override interlock) terminal is wired to the TIS (train in section) terminal of the next block section. The TIS terminal switches to 0 volts when there is a train in the block section so operating the OI terminal. This connection is to prevent trains moving into the next block section when it is occupied.
TIS operates from the train being detected at the TES until 4 seconds after the train has cleared the TLS detector. As well as the TIS connection as many switches as required can be wired into the OI terminal. The train will slow and stop if any one of these connections are at 0 volts.
The connection shown causes the operation of the OI input so braking and stopping a train in the previous block section.
REVERSE RUNNING CONNECTION
The use of this is optional and it is only required where trains run in both directions. Running in the reverse direction is only possible when a controller is wired into the SA8-SB.
If a train is running in the reverse direction to the signals the train will cross STOP before TES. This will result in the signal being left at clear and the train in section outputs operating. The reverse running input is provided to overcome this. The effect of this input is to prevent the SA8-SB from registering that a train is in the block section. It therefore leaves the signals at danger.
The "RR" input operates by connecting it to 0 volts. This connection can either be made with a switch which is operated for reverse running trains or with the "Direction Detector" which automatically senses which direction the train is running. In either case where there are several SA8-SBs along a line all the RR inputs can be wired together so that they are all operated by a single switch or a single Direction Detector. D4 is the reverse running terminal.
SECTION OCCUPIED LED (Terminal A)
This terminal can be wired to an LED on a mimic panel. The LED will be lit whilst a train is in the block section. ie from the train reaching TES until TLS is cleared. Wire from terminal "A" to the long leg of the LED, wire the shorter leg of the LED to the "o" (0 volts) terminal
TESTING AND SET UP ADJUSTMENTS
There are three screwdriver adjustments on the SA8-SB board:
ACC/BR: This governs how fast the train accelerates and brakes. Clockwise is very abrupt. Turn anti-clockwise to make the braking and acceleration more gradual.
MAX SPEED: This controls the maximum speed of the train. Anti-clockwise for faster.
MIN SPEED: When the train brakes it slows down until it reaches the minimum speed then continues at this speed until stopping when detected by the STOP train detector. The minimum speed should be set as slow as possible. Turn the adjustment clockwise for slow.
Initially set up the adjustments as follows:
MIN SPEED = slow (clockwise)
ACC/BR = abrupt (clockwise)
MAX SPEED = fast (anti-clockwise)
On first powering the unit the signal should be at danger. The signal changes to clear as a train crosses the TES detector provided the OI (override interrupt) input is not at 0 volts. Shortly after the train crosses the TLS detector the signal will return to danger. The operation of the signal switching relay will be heard as a faint clicking sound every time the signal changes.
If the unit is entirely powered from a power supply adjust the MAX SPEED setting to the required speed. If the maximum speed is to be determined by the controller setting leave it turned to maximum.
To set up the adjustment for MIN SPEED and ACC/BR (rate of acceleration and braking) arrange for the OI terminal to be operating. Temporarily wiring OI and terminal "o" will accomplish this. When the train is first detected at TES it will rapidly reduce speed and halt. Adjust the MIN SPEED setting until the train just moves . Now repeatedly run the train into the signalling section adjusting the ACC/BR adjustment until the train continuously brakes between TES and STOP reaching its minimum speed at STOP. Note that whilst the overload/ interlock connection is in place the train will stop on reaching "STOP".
SA8-SB LEDs
The two LEDs on the SA8-SB give the following indications:
Red LED lit = Braking
Green LED lit = Acceleration
Red and Green LEDs lit = Overload
Overload protection is built into the SA8-SB. If an excessive current is drawn from the unit then the overload circuit will prevent the unit from being damaged by switching off power to the track. This fault condition is shown by the red and green LED's both lighting. As soon as the fault is rectified the unit will resume normal working.
Heathcote Electronics, 1 Haydock Close, Cheadle, Staffs, ST10 1UE, Tel/Fax 01538 756800
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Below is a diagram to show how 2 trains may be operated on an oval with a SA7-SB and SA8-SB board
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