Precautions For Dc Input Modules - Toshiba V Series User Manual

Chapter 3 Precautions

3.1 Precautions for DC Input Modules

(1) Read conditions for the ON/OFF changes of the input signals are :
Input ON time ≥ ON delay time (OFF → ON)+Input reading cycle
Input OFF time ≥ OFF delay time (ON → OFF)+Input reading time
The "input reading cycle" means the CPU module scan cycle for the refresh input, or
the execution interval of a direct input instruction when the instruction is used.
(2) For some external contacts, the input current of modules may not be able to
maintain contact reliability. In the case, install a bleeder resistor between the input
and common terminals to increase the contact current.
V
(An example of selecting a bleeder resistor R)
Input Voltage V= 24Vdc
Input module DI633(8mA/24Vdc)
When the contact requires 50mA current ;
Resistance value R of a bleeder resistor
Wattage P of the bleeder resistor
6F8C0836
for I/O Modules
Contact Input module
I I
1
I
2
V
R=
I - I
1
2
V
× (2.5-3)
Wattage P>
R
24[V]
R=
50[mA] – 8[mA]
2
(24[V])
P=
(570[ Ω ]) X(2.5 – 3) 3[W]
=570[ Ω ]
119