Pwm_cycle_time causes random heater_bed error

Basic Information:

Printer Model: Voron 2.4r2
MCU / Printerboard: Octopus / ebb36
klippy.log (916.3 KB)

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Describe your issue:

I have a strange issue, as soon as I uncomment the pwm_cycle_time: 0.02 line I added to avoid my house’s lights to flicker, i have a random error, sometimes I have a heater_bed not heating at expected rate. As you would see here in the screenshot.

It’s random, sometimes bed heats normally, and when this error occurs, it’s after staying at around 96°C approximately.

When I comment pwm_cycle_time I don’t have this error anymore, my lights flickers, but clearly no error anymore :slight_smile:

I was thinking something about the hz frequency of the ssr or something like that but I’m not enough expert on this side.

Does someone here have the same exact error and found a fix?

Have you done a PID calibrate then?

Yes, with and without the pwm_cycle active.
Same error.

Try a cylce time of 0.04 or 0.2
SSR typically switch on zero crossing of the sine wave and thus minimum swtich time is at half cycle

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That’s it, why I thought it was something about the frequency, when there’s this error, before that the temp stay around the same value, like if there was not enough power to make it heat more