SNAP PAC Redundancy Option User’s Guide
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1: Welcome
Welcome to the
SNAP PAC Redundancy Option User’s Guide
. Inside you’ll find instructions on how to
set up redundant controllers using two perfectly matched SNAP-PAC-S controllers. This guide
assumes that you understand fully how to use PAC Control
™
and have some familiarity with
Opto 22’s SNAP PAC System
™
.
In This Chapter
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Introduction
While Opto 22 Ethernet-based control systems are extremely reliable, no control system is perfect.
However, with properly configured redundant controllers, in the unlikely event that a controller were
to fail for whatever reason, a second identically configured controller takes over with almost no
down time. The SNAP PAC Redundancy Option provides the tools for developing a control system
with an increased level of reliability that can survive single points of failure, and it can improve your
system’s mean time between failures (MTBF).
A SNAP PAC System configured with the SNAP PAC Redundancy Option includes:
•
Two identically matched S-series PACs
•
A SNAP-PAC-SRA arbiter, a hardware device that controls which controller is active based on
status information returned by each controller in response to the arbiter’s periodic heartbeat
requests. See
“SNAP-PAC-SRA Arbiter” on page
•
A SNAP-RPSW redundant power switch connected to the arbiter and both controllers. This
switch responds to the supply-voltage output from the arbiter, which allows it to reliably restart
a controller. See
“SNAP-RPSW Redundant Power Switch” on page
.
