Nematron OptiLogic Series - Manual (Page 8)

Optimation, Inc. (256)883-3050 8
www.optimate.com
OptiLogic Series
AC Inputs
AC digital inputs are typically supplied
either directly from line voltage or transformed
down from line voltage. The most common AC
inputs are 120VAC and 24VAC, although any
voltage range is possible.
A typical AC input circuit is shown
below. As shown, the physical optical emitter
on the input module consists of two LEDs of
opposite polarity. An AC (alternating current)
connection flows current one way, then the
other. Light is emitted in both cases.
There is a short period when voltage, and
therefore current flow, switches from one
direction to the other when no current flows.
This is called zero crossover. During zero
crossover, the digital input circuit must
“debounce” the signal to ensure that the system
does not provide a false indication that the input
contact is not closed when it is, in fact, closed.
OptiLogic AC digital inputs handle such zero
crossover conditions.
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 below illustrates a digital
input board that has eight inputs and two
commons. This can be accomplished with a 10
terminal connector block.
10
10
9
9
8
8
7
7
6
6
5
5
4
4
3
3
2
2
1
1
10-30VDC
Sourcing
Sinking
10-30VDC
IN7
IN7
IN6
IN6
IN5
IN5
IN4
IN4
IN3
IN3
IN2
IN2
IN1
IN1
IN0
IN0
Input module
optical
isolation
To
OptiLogic
processor
sensor