Examples Of Troubles With The I/O Module; Troubleshooting For Input Circuit - Mitsubishi Electric NZ2GF2B1-16D User Manual

12.6

Examples of Troubles with the I/O Module

12.6.1

Troubleshooting for input circuit

This section describes the troubleshooting for input circuit.
(1) An input signal does not turn off No.1
Drive by a switch with LED indicator
Leakage current
(a) Calculation example
When 24VDC is supplied to the input module on the condition a switch with LED indicator with maximum
leakage current of 3mA is connected
1.
The OFF current through the input module is not 1.7mA or less. Therefore, connect a resistor as
shown below.
2.
To satisfy the condition, the current through the connected resistor should be 1.3mA or more.
From the formula below, the connected resistor is lower than 4.97k&Greek_L_Omega;.
3.
When the resistor (R) is 3.9k&Greek_L_Omega;, for example, the power capacity (W) of the
resistor (R) becomes 0.179W.
4.
Because the resistor requires the power capacity of 3 to 5 times as large as the actual current
consumption, the resistor connected to the terminal should be 3.9k&Greek_L_Omega; and 1 to
2W.
250
Cause
DC input (sink)
Input
module
Leakage current 3mA
3mA
I =1.3mA
R
24VDC
I : I = Z (Input impedance): R
R Z
I
Z
R Z (Input impedance) =
I
R
W = (Input voltage)
Connect an appropriate resistor as shown below so that a current through the
input module may become lower than the OFF current.
For the calculation example of a resistor to be connected, refer to (a).
Input module
24VDC
Iz=1.7mA
Input impedance
R
3.8k
1.7
3.8 = 4.97[k ]
1.3
2 2
R = 26.4 3900 = 0.179 [W]
Action
DC input (sink)
Input
Resistor
module