α
2 Simple Application Controllers
Function Blocks 6
6 - 51
6.21
Pulse Width Modulation
The function block emits a continuous pulse train output when an input is given at a preset duty
cycle.
Table 6.22: Pulse Width Modulation
Note:
The ON/OFF time cannot be less than one scan time for the controller; otherwise, the PWM
Function Block will not perform its assigned task for the time specified. Users can monitor the
scan time from the
α
2
Series Controller. Scan time is dependent on the user-program;
therefore, caution is needed as and when time units are selected.
1 ) PWM operation time chart.
Note:
10ms step for minimum resolution.
Function
Set Item
Description
I
Input pin for the pulse width modulation function block
FB
1) The PWM function operates concurrently with the input pin status
set ON.
2) The width of the pulse is dominated by the duty and value of the
period.
3) Duty (setting range:0-100%)
a) Constant Value
b) Analog In
c) FB Value
4) The period is restricted to a setting range: 1 to 32767 x 100ms
(*Note)
Output
The function block is used to control the width of the output pulse
based on a specified period of time and duty.
1) The bit output pin is set on for the length of the duty specified.
2) The following items are available for other function blocks:
a) Set Period
b) Current Period
0
0
0
W
P
O
I
M
P
Input pin
OFF
ON
Output pin
OFF
ON
OFF
Duty: 70%
(ON Time: 70%)
Set cycle
Current value
in cycle
