BusWorks® Model 989EN U
ser’s Manual Modbus TCP/IP Digital I/O & Counters
_________________________________________________________________________________
_______________________________________________________________________________________
Acromag, Inc. Tel:248-295-0880 Fax:248-624-9234 Email:
7
+
TB3
I/
O
EXC
P
W
R
36
RTN
EXC+
34
GND
33
31
DC+
35
TB3
CH15
32
DC-
✓
Connect 8-28V DC to the excitation terminals labeled EXC+ and RTN.
Optionally you can jump DC input power to Exc+ as long as it does not
exceed 28VDC. Observe proper polarity. For supply connections, use
No. 14 AWG wires rated for at least 75
C.
CAUTION:
Do not exceed
35VDC peak.
IMPORTANT:
You MUST connect an excitation supply to the excitation
(EXC) and Return (RTN) terminals in order to operate I/O.
CAUTION: Risk of Electric Shock
– More than one disconnect switch may
be required to de-energize equipment before servicing.
✓
Connect Earth Ground as shown in the connection drawings on previous
page. Additionally, connect the GND terminal (TB3-33) to earth ground.
The ground connections noted are recommended for best results. If
sensors are already grounded, use caution and avoid making additional
ground connections which could create ground loops.
The module housing is plastic and does not require its own earth
ground.
✓
Connect digital input signals to the input terminals as shown on the
following page. The tandem outputs must remain OFF in order to drive
inputs externally.
To drive the inputs from an external source, you must turn the
corresponding outputs OFF, or the output channel will be in contention
with your external input signal.
IMPORTANT:
You MUST connect an excitation supply to the excitation
(EXC) and Return (RTN) terminals in order to operate I/O. External
excitation should be from 8 to 28V and must provide 36mA (288mA
peak), plus any output load current.
Inputs source wetting current to sense switch closure. By default, this
current is set to switch to 16mA for 20ms after crossing the 4V input
threshold, then return to 2mA continuous. The higher level of initial
current will help to prevent oxide buildup on external switch contacts.
The current can also be set to only source 2mA continuous. This
current can also be turned OFF by tri-stating the port inputs.
CONNECTIONS
Excitation
Note: Excitation can be
optionally be sourced from the
input power supply.
CAUTION: Excitation
voltages greater than 28V do
not guarantee I/O operation.
Make sure that if you jump
input power to excitation, that
it is less than or equal to
28VDC.
Earth Ground
Warning: To comply with
safety and performance
standards, use shielded cable
and connect earth ground as
noted. Failure to use good
wiring and grounding practices
may be unsafe and negatively
affect performance.
Digital Inputs
Inputs are active-low, with 4V
thresholds (3.7-4.3V range).
Input connections require an
external excitation source.
Limit input voltages to less
than 31VDC maximum.
Inputs include wetting current
pull-ups to sense switch
closure, which also allows the
open-drain output to operate
without adding a pull-up.
