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I/O Unit Wiring Precautions Section 4-8
Inrush Current The following diagram shows two methods that can be used to reduce the
large inrush current caused by certain loads, such as incandescent light
bulbs.
Be careful not to damage the output transistor.
Reducing Noise in I/O
Signals
Whenever possible, place I/O signal lines and power lines in separate ducts or
raceways both inside and outside of the control panel.
If the I/O wiring and power wiring must be routed in the same duct, use
shielded cable and connect the shield to the GR terminal to reduce noise.
Inductive Loads When an inductive load is connected to an I/O Unit, connect a surge suppres-
sor or diode in parallel with the load as shown below.
R
OUT
COM
OUT
COM
R
Example 1 Example 2
Generating a dark current (about 1/3 of the
rated current) through the incandescent bulb.
Inserting a regulating resistance.
Suspended duct
In-floor duct Conduits
1 = I/O cables
2 = Power cables
L
IN
COM
Diode DC input
OUT
COM
Relay output or
triac output
OUT
COM
Relay output or
transistor output
Diode
L
L
+
Surge suppressor
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