TIP for S7-1200 und PWM

Hi,

Here there is some tips about the use of PWM in S7-1200.

To configure a PWM do you need:
1 – Configure the properties of the PWM in the CPU properties (Device Configuration). Important properties:

1 a – Time Base: that is the unit scale used in the property 1c.

1 b – Pulse width format: define the pulse width scale in the user program. For example: if you choice 100, the user set point should stay between 0-100. if you choice 1000, the user set point should stay between 0-1000. And so on. (if you use S7-analogic format, the set point should stay between 0-27648).

1c – Cycle time: corresponds to the ON time + OFF time of each cycle.

1d – Initial Pulse width: initial value of the setpoint to the PWM (when there is a start of the CPU).

2 – You need to call a block (CTRL_PWM) in OB1, give the PWM name and an enable signal.


Behavior:

While the PWM is not enabled by the CTRL_PWM, the digital output works like a normal digital output.

Once the PWM is enabled, the output is dived by the PWM. Note however that the monitoring of the digital output, follow the digital logic.