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Wiring Examples
Precautions when Connecting Two-wire DC Sensors
1,2,3...
Note Do not use the following wiring with voltage-output devices.
+
Output
0 V
Note The CJ1M CPU Unit's inputs have a set polarity, so the inputs will not go ON if
the wiring is reversed. Always double-check the wiring before turning ON the
power.
Check that the following conditions are met when using a two-wire sensor as
a 24-V DC input device. The sensor may malfunction if the conditions are not
met.
1. Check the relationship between the PLC's ON voltage and the sensor's re-
sidual voltage.
≤ V
− V
V
ON
CC
2. Check the relationship between the PLC's ON current and the sensor's
control output (load current.)
(min.) ≤ I
I
OUT
− V
I
= (V
ON
CC
Connect a bleeder resistor (R) if I
ing equation to determine the proper bleeder resistance.
R ≤ (V
− V
CC
Power W ≥ (V
3. Check the relationship between the PLC's OFF current and the sensor's
leakage current.
≥ I
I
OFF
leak
Connect a bleeder resistor (R) if I
equation to determine the proper bleeder resistance.
R ≤ R
× V
IN
OFF
Power W ≥ (V
Two-wire sensor
V
: Power supply voltage
CC
V
: PLC's ON voltage
ON
V
: PLC's OFF voltage
OFF
I
: PLC's ON current
ON
I
: PLC's OFF current
OFF
R
: PLC's input impedance
IN
4. Precautions Regarding the Sensor Inrush Current
If the sensor power supply is turned ON when the PLC is already ON and
capable of receiving inputs, the sensor's inrush current may cause a false
Sensor
power
supply
IN (24 V DC)
IN (0 V)
R
≤ I
(max.)
ON
OUT
− 1.5 [PLC's internal residual voltage]*)/R
R
is less than I
ON
(min.) − I
)/(I
)
R
OUT
ON
2
− V
/R × 4 [Tolerance]
)
CC
R
leak
× R
− V
/(I
)
leak
IN
OFF
− V
2
/R × 4 [Tolerance]
)
CC
R
V
R
R
V
CC
V
:
Sensor's residual output voltage
R
I
: Sensor's control output (load current)
OUT
I
: Sensor's leakage current
leak
R:
Bleeder resistance
Section 3-3
CJ1M CPU Unit's
built-in I/O
IN
(min). Use the follow-
OUT
is greater than I
. Use the following
OFF
CJ1M CPU Unit's
R
IN
built-in I/O
33
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