Mitsubishi Electric FX5U User Manual page 88

■ In the case of 2-wire proximity switch
Use a two-wire proximity switch whose leakage current, I is 1.5 mA or less when the switch is off.
If the resistance is larger than leakage current, I of 1.5 mA, connect a bleeder resistance Rb (k), obtained by the following
formula as shown in the following figure.
Item
Bleeder resistance Rb (k)
24V
S/S
PLC
X
(sink input)
0V
■When the input signal cannot be received because the current is insufficient
The current rating for the CPU module in X020 or more and the I/O module is 4 mA.
In some cases, depending on extension devices used, it may not be possible to receive the input signal, due to the insufficient
current. Take the following action in such case.
PLC
5.6 k
X
S/S
External resistor
(for input current adjustment)
In the case of capturing high-speed pulses
When capturing pulses of a response frequency of 50 to 200 kHz on using the input X000 to X007 (FX5U-32M is X000 to
X005.), wire the terminals as stated below.
• The wiring length should be 5 m (16'4") or less.
• Use shielded twisted-pair cables for connecting cables. Ground the shield of each shielded cable only on the CPU module
side.
• Connect a 1.5 k (1 W or more) bleeder resistance to the input terminal, so that the sum of the load current of the open
collector transistor output on the mating device and the input current of the CPU module is 20 mA or more.
The above-mentioned restrictions are due to specifications of connecting device (encoder etc.).
Please adjust the cable length and load, for connecting device.
6 WIRING
86
6.5 Input Wiring
FX5U-32M X000 to X005
FX5U-64M, X000 to X007
FX5U-80M
FX5U-32M X006 to X017
FX5U-64M, X010 to X017
FX5U-80M
FX5U-64M, X020 and
FX5U-80M subsequent
I/O module
Bleeder
resistance
2-wire
Rb proximity
I
sensor
Input current
Adjusted in accordance
with the connected device
Proximity sensor
Specifications
7 / (I-1.5) or less
7 / (I-1.5) or less
9 / (I-1.5) or less
0V
S/S
I
PLC
X
(source input)
24V
Bleeder
resistance
2-wire
proximity
Rb
sensor