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Caution
Supply Voltage
Condition
Do not power the MMI and inductive DC loads, or input
circuitry to the PLC, with the same power supply.
The 24 VDC output from some PLC's may not have enough
current to power the DC powered MMI.
Terminal Block
Connections
To make a connection, strip about 1/4" of insulation off the
end of the wire, turn the connector screw counterclockwise
until the gap is wide open, insert the wire all the way in, and
turn the screw clockwise until it is tight.
For DC powered units, connect the positive DC line to terminal
3 and the DC ground to terminal 4. For AC
powered units, connect the AC lines to terminals 3 and 4.
Caution
Power Cycling
Power supplies with large capacitive outputs may cause
problems if power is cycled within a short time period. The
power supply’s capacitor will supply enough current to keep
the microprocessor running for a few minutes but not enough
to keep the display active. If full power is restored during that
time, the microprocessor may not initialize the display
module. The result is that the display will remain blank or
show just the cursor in the upper left-hand corner and the rest
of the unit will be fully functional.
To remedy this problem, run power to the unit through a
“seal in” circuit or remove the capacitor (the MMI is not
affected if power is unregulated) or wait sufficient time between
power cycles.
Caution
Wire Routing
Wire lengths should be minimized (Maximum 1600' (500 m)
shielded, 1000' (300 m) unshielded).
Wires should be run in pairs with a neutral or common paired
with a hot or signal line.
If wiring is to be exposed to lightning or surges, use appropri-
ate surge suppression devices.
Keep AC, high energy, and rapidly switching DC wiring
separate from signal wires.
Equip ungrounded DC supplies with a resistor and capacitor in
parallel to earth ground. This provides a path for static and
high frequency dissipation. Typical values to use are 1MOhm
and 4700pF.
