SA- SLOW ACCELERATE
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SA-SLOW ACCELERATE
Slow Accelerate units can automate all or part of a model railway.  The units give a gradual and adjustable acceleration, braking, and speed and operate signals and points automatically.
Overload current protection is provided to protect the units and locomotives from being damaged by short circuits resulting from derailments etc.
Points and signals are controlled with relay contacts from relays built into the boards.  LED or bulb signals can be operated.
The point control works in the same way as the IRDOT-P. 10 amp rated relay contacts close for approximately 1 second to power solenoid point motors.
The units need to know where trains are so that they can start slowing or stopping the trains.  Either IRDOT-1s or reed switches can be used for this.  The advantage of using IRDOT-1s is that the front of the train is always stopped at the correct place.  With reed switches the train is stopped when the magnet arrives over the reed switch.
ADJUSTMENTS
All the SA units have gradual acceleration and braking built in. Each board has the following screwdriver adjustments:

DELAY TIME: This adjusts the length of time between trains arriving and  departing.

MAXIMUM SPEED: This adjusts the fastest speed the train reaches.

MINIMUM SPEED: The minimum speed setting is provided so that the train will stop at exactly the right place.  When the train slows, it slows to the minimum speed setting, not to a stop.  This allows it to continue moving slowly until it is detected at the stopping position.  Power is then switched off the track by the SA board.

ACCELERATION/BRAKING: This adjusts the rate at which speed increases or decreases.  The length of track over which this happens can be from a few inches to approx.10 foot.
LED INDICATIONS
The SA boards have a red and a green LED.  These show what the SA board is doing. 
RED LED lit: train is braking or travelling at minimum speed.

GREEN LED lit: train is accelerating or travelling at maximum speed.

RED and GREEN LED's FLASHING ALTERNATIVELY: the SA board is timing the adjustable delay between one train arriving and another departing or a train waiting at the station.  The longer the flashes the longer the delay.

RED AND GREEN LED's BOTH LIT: There is an overload on the track caused by a derailment or short circuit.  Current is automatically cut off from the track until the short circuit is removed.  This safety feature protects both the SA board and the locomotive from damage.
SWITCHING BETWEEN AUTOMATIC AND MANUAL CONTROL
To switch between automatic and manual control a DPDT ( Double Pole Double Throw)  switch is used. Throwing the switch connects either the SA boards' output or the controller track output to the track. If a DPDT centre-off switch is used the central position of the switch will isolate the track.
If the SA board also controls points then manual switches may be wired to the point motors .An on/off switch may also be required to disconnect the point motors' power supply from the SA board. This prevents the SA board switching the points as trains are manually driven over detectors.