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The I/O Network The RS485 Network and Hardware Setup • 6-5
Emerson Retail Solutions supplies a wide variety of
24VAC transformers with varying sizes and either with or
without center taps.
Table 6-2 shows the transformer sizes
and whether they are center-tapp
ed or non-center-tapped.
Table 6-3 lists each board, the board’
s rating, and whether
or not the board must use center-tapped power.
Table 6-2
- Transformers Compatible with I/O Network Boards
Xformer P/N VA Rating Input Voltage Center Tap?
640-0041 50 VA 110 VAC No
640-0042 50 VA 220 VAC No
640-0056 56 VA Multi-tap (120/208/240 VAC) Yes
640-0050 75 VA 110 VAC No
640-0045 75 VA 220 VAC No
640-0080 80 VA Multi-tap (120/208/240 VAC) Yes
Table 6-3
- Device Power Requirements
Unit Amps VA VA C Center-
tapped?
16AI 0.25 5.0 24 Yes
8RO/SMT 0.75 15.0 24 Yes
4AO 0.5 10.0 24 Yes
8DO 1.5 18 24 Yes
8IO/ARTC 0.75 18 24 No
IRLDS N/A N/A 120/240 N/A
RLDS N/A N/A 120/240 N/A
MultiFlex
ESR
3.3 80 24 Yes
MultiFlex
16
0.25 6 24 Yes
MultiFlex
8
8, 88AO,
168, and
168AO
0.75 15 24 No
MultiFlex
1616
L,
1616LAO,
1616LDO
1.0 20 24 No
To select a power transformer for
a board or a series of
boards:
1. Determine what the total VA is for the boards
that
will be powered by the transformer
(see Table 6-3).
Example: Two MultiFlex 168AOs (15 VA
each), a
nd one 8DO (18 VA) boards are to
be powered by one transformer. The total
VA is:
2 15VA 1 18VA+ 48VA=
2. Use a transformer that has a power rating
higher than the total calculated VA
(see Table 6-2).
Example: For boards totalling 48VA, a 56VA trans-
former is sufficient, since 56VA is greater than
48VA.
I/O Board Transformers should be located within 10
feet
of the board it is powering, preferably within the
board enclosure.
6.1.9.1 Wiring Types
For powering I/O boards, use only the listed wire types
from Table 6-4. Three-conductor non-shielded cables are
the recommended wire for connecting between
the center
tapped transformer and the I/O boards. The third conduc-
tor should be connected to earth ground. If boards use a
center
-tapped transformer, also connect the center tap to
the earth grounded third conductor.
Table 6-4
- Power Wiring Types
Power Wiring Types
14 AWG Belden 9495
18 AWG Belden 9493
The wire length from the transformer and the number
of boards connected to the same wire determines the type
wire gauge used. In most cases, the distance between the I/
O boards and the transformer that supplies power to them
is not enough to be concerned with. But it is very import-
ant not exceed this maximum wire
length or the boards
will malfunction.