CHAPTER
1.
INTRODUCTION
1.1. General Description
The most common method of interfacing a microcomputer system, such as the
PC, is through the use of programmable digital input and output registers.
With digital output registers, the computer can write data into the registers,
treating the register as an I/O port. The output of these registers can then be
wired to an interface device, such as a relay. Thus, by writing data to an output
register, it would be possible to activate and deactivate a relay. The relay could,
in turn, control, for example, the power to a motor.
Digital input registers are similar but are used to sample the status of signals
attached to their inputs. For example, if a program wants to determine if a
switch is open or closed, the switch can be tied to the input of a digital input
register. A digital input register can be thought of as an I/O port that has wires
attached to individual bit locations. When read, the data results reflect the state
of the signals on the wires.
Designed with this idea in mind, the PCL-725 Relay Actuator & Isolated D/I
card is an IBM PC add-on card that offers you 8 relay actuators and 8 opto-
isolated digital inputs on a single board.
Typically, the 8 on-board relays can serve as ON/OFF control devices or small
power switches. The 8 opto-isolated D/I channels are ideal devices for
collecting digital inputs under noisy environment or floating potential. Also, the
8 isolated inputs provide the best method to prevent the ground loop problem.
For easy monitoring, each relay is equipped with one red LED to reflect its
ON/OFF status. Each input channel is jumper selectable to either isolated or
non-isolated input. Access to input and output channels is made possible
through a on-board 37-pin D type connector.
