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Chapter 4. Basic instructions
4-35
A chattering prevention circuit (example of TMON instruction)
1. Operation
A input signal from limit switch has chattering noise. By using TMON instruction, a stabilized
signal can be obtained from a noisy input signal.
2. System diagram
I/O
Description
P020
Limit switch output
M0020
Stabilized signal of P020
T000
Chattering prevention timer
3. Program
0
1
2
.
.
.
.
.
.
F
Stabilized signal
(a fixed period)
T
Cart
Moving direction
L.S
The limit switch output
with low speed of cart
The limit switch output
with high speed of cart
Input module
P02
(
M0020
)
P020
T000
[
TMON T000 0002
]
Even if P020 trembles after P020
turns on in a moment, M0020
keeps its on state for 0.2 second.