Oddbean

@e5030cd9 @5756e48c This may be a very naive question, so my apologies upfront, but can't you control all of this directly from the Pi, no external MCU required? My Klipper knowledge is very limited but I swear I remember seeing a method to control the GPIO pins with it before.

@c75e3dac Good question and correct initial assumption! No, I can't. The dimmer I use for my limmers are called TRIAC dimmers. AC signals have alternatinf current and voltage. The current is a sine wave and voltage a cosine wave. Thus, they are always out by 90°. The TRIAC detects when the current signal crosses the zero line and then only changes the PWM voltage. This removes flickering and is more energy efficient. Detectong this switch must be done at 2x 60Hz due to the Nyquist-Shannon sampling theorem. This detection is done with a hardware interrupt pin to allow the software to run faster. The #RaspberryPi and #Klipper do not support this. So I use a separate peocessor, which does allow this and communicate it back to Klipper and basically only gets the PWM signal and then does the rest. @5756e48c #3dprinting

@c75e3dac This is called phase voltage control, and the signal output will look something like this. @5756e48c #3dprinting https://files.techhub.social/media_attachments/files/111/021/042/849/627/298/original/3d27f4f4670ef229.jpg https://files.techhub.social/media_attachments/files/111/021/056/504/851/491/original/009f9e88aba2f3c4.png https://files.techhub.social/media_attachments/files/111/021/062/671/936/881/original/0e100affbf853bc2.jpg

@c75e3dac Also, we can cheat the Nyquist-Shannon sampling theorem by rather than detecting and interrupting them, by triggering the crossing. Thus, we need hardware detection and not software detection. For the same reason the #Klipper docs mentiones its PWM isn't the best. @5756e48c #3dprinting