Using Digital I/O Modules; Using Digital Input Modules; Using Lwo400, Lwo450, And Lwo460 Contact Output Modules; Figure 5-1 Connecting A Special Resistor To An - Hitachi HSC-2100 Hardware Manual

5 MAKING USE OF MODULES

5.1 Using Digital I/O Modules

5.1.1 Using digital input modules

Digital input modules may encounter an input error due to leakage current when they are used for
direct-current input through a switch with LED indicator. In these cases, add a special resistor
between the input terminal and common, as shown below. The resistor has a resistance that
produces a voltage lower than or equal to the OFF voltage.
Figure 5-1 Connecting a Special Resistor to an LWI400/LWI450/LWI460/LWI470 Module

5.1.2 Using LWO400, LWO450, and LWO460 contact output modules

(1) Surge absorber circuit
Contact output modules may be used to drive an inductive (L) load. To drive an L-load
successfully, it is recommended that a surge absorber circuit be attached to the contact output
module, as shown below. The purpose of the surge absorber is to absorb flyback voltages
that will be generated when current flow to the load is cut off. These flyback voltages may
be a source of noise.
Note: When driving an L-load with DC power, be sure to attach a surge absorber circuit to
the driver module.
(a) Driving an L-load with AC or
DC power -- Case 1
Output module
(c) Driving an L-load only with DC power
Output module
Leakage
current Resistor
r c
L
Load
～
r = impedance of load
c = 0.1 μF
L
Load

Figure 5-2 Surge Absorber Circuits

Input
LWI400/LWI450/
LWI460/LWI470
Common
(b) Driving an L-load with AC or
DC power -- Case 2
Output module
5-2
Varistor
L
Load
～