Nematron Pointe Controller - Manual (Page 88)

Chapter 4: System Design and Installation Pointe Controller User Guide
86
Digital Input Voltage
Any digital input module, AC or DC, is designed to operate within an input
voltage range. The input voltage directly controls the amount of current flowing
through the circuit. The minimum voltage corresponds to a voltage that creates
enough current to produce LED light sufficient to be sensed by the optical sensor.
The maximum voltage corresponds to the maximum current the optocoupler can
handle without being damaged.
I/O “Common” Terminals
For a digital input circuit, one input terminal and one output terminal is necessary
for operation. For practical application, one of these two terminals may be
“common” to several circuits.
In most systems, the power source for all digital inputs is from the same supply. In
such cases, connecting all of the circuit return lines together results in reduced
equipment costs as well as simpler system wiring.
The example above illustrates a digital input board that has eight inputs and two
commons. This can be accomplished with a 10 terminal connector block.