How to make a pulsing/breathing pwm output on a PLC?

ndzied1 said:

Here is an example of a PWM type simulator in free software. CoDeSys.

The PWM in this example is 10hz and is outputting the PWM equivalent of a Sine wave with a 5 second period.

I used a function generator to create a sine wave with the period I would want the lights to pulse at and scale that sine wave to 0 to 1.0.

Then I run a timer that resets itself every cycle (10Hz -> 100ms timer). I then create a number from 0 to 1.0 by dividing the elapsed time of the timer by the total time of the timer. So this number represents a fraction of the elapsed time. i.e., when the number is 0.3, 30% of the period has passed. When the number is 0.75, 75% of the period has passed etc.

Lastly, compare the current percentage of the PWM period to the sine wave percentage. If the PWM period percentage is <= the Sine wave percentage then turn the output on, otherwise, turn it off.

Here's a little video...

https://youtu.be/rDETvu1tuDE

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rjk_cmh said:

Wow, you're awesome. Thanks for providing me with a starting point. I will have to copy it and tinker with the variables before I will have any idea of how the heck it works, but I think the video will be a lot of help.

I'm guessing that the next thing I will need to discover is how to linearize it properly for an LED. My understanding is that human eyesight resolves light in a nonlinear fashion, so I will have to adjust the ramping to accommodate that.

Thanks again.

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