I/O Unit Wiring - Omron SYSMAC CQM1-ID212 Operation Manual

Wiring and Connections

2-5-4 I/O Unit Wiring

! Caution
WARNING
!
Leakage Current (24 VDC)
Inrush Current
28
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Note To satisfy the EC directives (low-voltage directives), provide reinforced insula-
tion or double insulation for the DC power supply used with the I/O Unit.
The following information must be considered when connecting electrical
devices to I/O Units.
Tighten the terminal screws to a torque of 0.5 to 0.6 N S m.
Do not apply voltages exceeding the input voltages to Input Units nor voltages
exceeding the switching capacity to Output Units. Doing so may result in
damage or destruction of the I/O Unit or result in fire.
A leakage current can cause false inputs when using 2-wire sensors (proximity
switches or photoelectric switches) or limit switches with LEDs on 24 VDC.
If the leakage current exceeds 1.3 mA, insert a bleeder resistor in the circuit to
reduce the input impedance, as shown in the following diagram.
2-wire method
sensor, etc.
R = 7.2/(2.4I–3) kΩ max.
W = 2.3/R W min.
The equations above were derived from the following equation:
Input voltage (24)
R 
Input current (10)
I 
Input voltage (24)
R +
Input current (10)
W ≥ Input voltage (24)/R  Input voltage (24)  tolerance (4)
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.
Example 1
OUT
R
COM
Generating a dark current (about 1/3 of the
rated current) through the incandescent bulb.
Be careful not to damage the output transistor.
Input power
supply
R
Bleeder resistor
I: Device's leakage current (mA)
R: Bleeder resistance (kΩ)
W: Bleeder resistor's power rating (W)
≤ OFF voltage (3)
Example 2
OUT
R
COM
Inserting a regulating resistance.
Section 2-5
SYSMAC