Mitsubishi Electric NZ2MFB2-16A - Page 109

11 TROUBLESHOOTING
11.4 Examples of Troubles with the I/O Module
107
11
■Calculation example
If the switch with LED indicator with maximum leakage current of 3mA when 24VDC is supplied to the NZ2MFB1-32D is
connected
1. The OFF current of NZ2MFB1-32D is not 1.7mA or lower. Therefore, connect a resistor as shown below.
Z: Input impedance
2. To satisfy the condition that the OFF current of NZ2MFB1-32D is 1.7mA or lower, the current through the connected
resistor should be 1.3mA or higher. From the formula below, the connected resistor (R) is 4.97k or lower.
3. When the resistor (R) is 2.7k, for example, the power capacity (W) of the resistor (R) becomes 0.308W.
V: Input voltage
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 2.7k; and 1 to 2W.
5. OFF voltage when the resistor (R) is connected becomes 4.74V. This satisfies that the OFF voltage of NZ2MFB1-32D is
5V or lower.
Input module
Leakage current 3mA
24VDC
Z = 3.8kΩ
I
R = 1.3mA
3mA
Iz = 1.7mA
24VDC
Resistor
R ≤
I
R
IZ
1.3
1.7
× Z = × 3.8 = 4.97[kΩ]
W = V
2
÷ R = 28.8
2
÷ 2700 = 0.308[W]
× 3[mA] = 4.74[V]
2.7[kΩ]
1
3.8[kΩ]
1
+
1