31.5.8 PWM Output

PWM output is a feature that outputs a pulse with a set output frequency when the set duty turns ON. A maximum of four channels can be set for PWM output in the LT3000 Series or STC6000 Series, and 2 channels in the LT4000 Series, which can be individually set. By connecting SSR to PWM output terminal, analog control for heaters becomes possible. The main features of PWM output are shown in the following table.

Summary of functions	Data Storage
Sets the output frequency	31.5.8.1 Output Frequency - PWM Output
Sets the ON Duty	31.5.8.2 ON Duty Value - PWM Output
Parameter change	31.5.8.3 Parameter change request and change completion acknowledgment - PWM Output
Checks abnormal status of the output frequency and ON Duty	31.5.8.4 Abnormal Status of PWM Output - PWM Output
Starts and stops the PWM output	31.5.8.5 PWM Output Control - PWM Output
Checks the status of start and stop PWM output	31.5.8.6 PWM Output Status - PWM Output
Checks the status of the output terminal	31.5.8.7 PWM Output Terminal Status - PWM Output

Summary

In GP-Pro EX, you can set up the initial value for each parameter. After the system is running, you can change parameters with system variables.

The procedure for setting the PWM output is summarized below.

Part of the settings can also be set up with logic program I/O driver instructions.
32.23 I/O Driver Instructions

Setting Up Initial Values

Refer to the setup procedures for GP-Pro EX

Changing After System is Running

Set the output frequency and the ON duty value.
Set the parameter under [Request Special I/O Parameter change].
Under [Special I/O Parameter Change Completed], acknowledge that the parameter has been changed.
Output the data with [Control Special I/O].
See "Special I/O state" for acknowledgment.

The [Request Special I/O Parameter Change] and [Special I/O Parameter Change Completed] operations reflect all the CH parameters you change.
Right after transferring, operations use parameter values set up in GP-Pro EX. Any restarts, which include going off-line, reset, and turning power OFF, use stored system variables as parameters.

Precautions when changing the Frequency/ON duty value

When you change the frequency value or ON duty value during PWM output, PWM output is reset. As a result, pulse output frequency and duty ratio may differ from the defined settings directly before and directly after the change.

#L_PWM*_WHZ: Frequency

#L_PWM*_STY: ON Duty Value

y0: PWM Output

1) When you change the ON duty value (#L_PWM*DTY), PWM output (y0) is reset. Then pulse output uses the defined frequency (50Hz) and ON duty value (50%).
2) Changing the output frequency (#L_PWM*WHZ) resets PWM output (y0). Then pulse output uses the defined frequency (100 Hz) and ON duty value (50%).