BusWorks
Model 903MB/902MB/901MB Network I/O Module User’s Manual Digital I/O
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Pullup Installation & Removal (See Drawing 4501-811)
Sockets are installed on the board to accept SIP resistor
networks for optional I/O pullup installation. One 8-pin SIP
socket is provided for every four I/O channels (port). These 8-pin
sockets accept SIP’s of four isolated resistors with the even-
numbered socket pins in common with the EXC+ terminal. Three
5.6K
Ω
resistor SIP’s are installed from the factory, but may be
changed or removed as required by your application. The cover
must be removed to access these sockets (see Drawing
4501-811). For the 5.6K resistor SIP provided, power must be
limited to less than 0.4W per resistor element. Limit excitation
voltages to 35V or less, and drain currents to less than 0.5A.
Your choice of SIP resistor may further limit current and voltage
according to its power rating (ratings of 0.2W, 0.3W, or 0.4W per
resistor element are typical). Refer to the I/O Specifications
section for recommended resistor types and suppliers.
IMPORTANT:
You must provide I/O excitation to operate the
outputs and prevent inputs from floating. You may utilize the
internal 5.6K pullup resistors installed in sockets on the board by
connecting a 5-35V excitation supply to the port EXC & RTN
terminals to complete the circuit. Optionally, the internal pullups
may be removed and the I/O terminals can be wired to an
external pullup or load/excitation circuit in similar fashion.
If your application delivers power to the I/O terminal rather than
the port excitation terminal, then the port pullups should be
removed to avoid coupling currents to adjacent port channels via
the pullup resistors.
Outputs are the open drains of n-channel mosfets in series with
output pullup resistors tied in common to the port EXC terminal.
Input circuits utilize these same pullups to the port EXC terminal.
Failure to complete this circuit by providing an excitation supply
and/or pullups will leave the inputs and outputs floating and/or
inoperable (Refer to Simplified Schematic 4501-809).
Mounting
Refer to Enclosure Dimensions Drawing 4501-815 for
mounting and clearance dimensions.
DIN Rail Mounting:
This module can be mounted on "T" type
DIN rails. Use suitable fastening hardware to secure the DIN rail
to the mounting surface. Units may be mounted side-by-side on
1-inch centers for limited space applications.
"T" Rail (35mm), Type EN50022:
To attach a module to this
style of DIN rail, angle the top of the unit towards the rail and
locate the top groove of the adapter over the upper lip of the rail.
Firmly push the unit towards the rail until it snaps solidly into
place. To remove a module, first separate the input terminal
block(s) from the bottom side of the module to create a clearance
to the DIN mounting area. Next, insert a screwdriver into the
lower arm of the DIN rail connector and use it as a lever to force
the connector down until the unit disengages from the rail.
Electrical Connections
Digital I/O, network, and power terminals can accommodate
wire from 12-24 AWG, stranded or solid copper. Strip back wire
insulation 1/4-inch on each lead before installing into the terminal
block. Since common mode voltages can exist on signal wiring,
adequate wire insulation should be used and proper wiring
practices followed.
It is recommended that I/O, network, and power wiring be
separated for safety, as well as for low noise pickup. Note that
I/O, network, and power terminal blocks are an industry-standard
plug-in type that can be easily removed to facilitate module
removal or replacement, without removing individual wires. Be
sure to remove power before unplugging the terminals to uninstall
the module, or before attempting service. All connections must
be made with power removed.
CAUTION:
Risk of Electric Shock - More than one
disconnect switch may be required to de-energize the
equipment before servicing.
1.
Power:
Refer to Electrical Connections Drawing 4501-813.
Variations in power supply voltage within rated limits has
negligible effect on module accuracy. For supply
connections, use No. 14 AWG wires rated for at least 75
°
C.
The power terminals are diode bridge-coupled and not
polarized. Unit is powered from 10-36VDC, or 24VAC only.
2.
Digital I/O:
Connect I/O per Electrical Connections Drawing
4501-813. Observe proper polarity when making I/O
connections (see label for input type). All outputs are the
open-drains of n-channel mosfets whose source terminals
share return (RTN). I/O pullup resistor SIP’s are installed in
sockets on the board and connected to the port EXC+
terminal. All terminals include transient voltage suppression
and integrated snubbers, but may require additional
protection when switching inductive loads (see below). Refer
to the SPECIFICATIONS section for output specifications
and see the module side label for terminal designations.
Note that outputs are for current-sinking (low-side switching)
applications only. Inputs are active-low. The I/O circuitry is
electrically isolated from the power and network circuits. If
necessary, an interposing relay can be used to switch higher
currents as illustrated in the Interposing Relay Connection
Drawing 4501-814.
Note
: Outputs go to their OFF state following a software or
power-on reset of the module. Outputs may be optionally
sent to user-defined states following a watchdog timeout.
IMPORTANT - Protection With Inductive Loads:
The
output DMOS type mosfets have integrated shunt diode
clamps connected from drain to source to help protect the
output switch from damaging reverse emf voltages that are
generated when switching inductive loads. You are
encouraged to add external protection local to the inductive
load for added protection and to prevent this emf from being
distributed across the connection media. For DC inductive
loads, place a diode across the load (1N4006 or equivalent)
with cathode to (+) and anode to (-).
3.
Network Connections:
Wire network as shown in Network
Connections Drawing 4501-805. Network common (COM)
should connect to earth ground at one point.
4.
Grounding:
See Electrical Connections Drawing 4501-813.
The module housing is plastic and does not require an earth
ground connection.
WARNING:
For compliance to applicable safety and
performance standards, the use of shielded cable is
recommended as shown in Drawing 4501-813. Further, the
application of earth ground must be in place as shown in
Drawing 4501-813. Failure to adhere to sound wiring and
grounding practices may compromise safety & performance.
