SNAP POWER SUPPLIES
SNAP PAC R-Series Controller User’s Guide
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installed, but no modules. All wiring connections are made to the field connectors on the top of
each module.
SNAP Power Supplies
Primary Power Supply
NOTE: For a more general discussion of using power supplies with Opto 22 systems, see Opto 22 form
#1271, a technical note available on our website at www.opto22.com.
SNAP PAC racks use a 5 VDC power source (5 VDC [-0.0, +0.1] at minimum 4.0 amps recommended).
For systems using AC source voltage, the SNAP-PS5 or SNAP-PS5U power supply is recommended.
For DC systems, such as those using DC backup power, the SNAP-PS5-24DC offers DC-to-DC power.
In general, we recommend you
use an independent, isolated, regulated power supply locally
with each rack
. Local isolated supplies offer these advantages:
•
Short supply conductors, which minimize losses
•
Power redundancy, so the failure of a single supply causes only a single rack failure, not a total
system failure
•
Fewer voltage drops and ground loops. (Voltage drops and subsequent ground loops may
occur when power is distributed over a large system.)
Always
use a separate power supply for the field side of the I/O
. Using the rack supply for field
actuation and monitoring defeats the isolation the I/O module offers and therefore increases the
chance of a ground loop within the control system. Additionally, a sudden change of current on the
field side can cause undesirable voltage fluctuations that may interfere with the computer’s
operation.
Determining Power Requirements
Both the SNAP-PS5 and the SNAP-PS5-24DC power supplies provide 5 VDC power for loads up to
4 amps. The SNAP-PS5U provides 5 VDC for loads up to 5 amps. In most cases this power is sufficient
for a SNAP processor, a rack, and the associated I/O modules. However, some combinations of
