This PPI is designed for operation on systems where the coil common is GROUND.
The microprocessor controls the led brightness and so no resistors are required, simplifying
wiring up.
Power Supply
The controller is designed for use with a DC power supply of between 10V and 25V, or an
AC power supply of between 10V and 16V.
Where there is a choice, the recommended power supply is 12V DC.
Operation
The PPI has 8 channels, each channel with two inputs able to drive two leds on the output.
The inputs cause the associated output to switch when the input voltage rises above around
3V. Also, at this moment the other associated output is switched off.
In this way, only one of the output leds is lit at any one time, that being the one with the most
recent positive input voltage pulse. This means that only one of the route leds for each
channel will be lit at any one time.
Each time an input change occurs, it is stored in memory, so that when the power is switched
off and on again, the led outputs are set automatically to their last recorded condition.
Connecting the Unit
Simply connect one of the PPI input terminals to one end of one of the points motor coils, the
other input to the end of the other coil, and the common of the coils to the COM GND input
to the PPI.
Only one connection from a coil common to the COM GND input of the PPI is required. This
allows the coil voltages to be recognised by the PPI correctly against the ground reference.
Each time the points are operated the yellow led on the pcb will briefly light.
