ESP32 flash Hz bar artefacts

[Simon7381]

There seems to be a Hz interference with the LED used for the flash. Please note, I have rotated the image 270d, so these are horizontal banding lines with the print bed to the right and extruder at the bottom.

• With the LED off and illuminated by room LED lights:
• • 
• With the LED on constantly and illuminated by room LED lights:
• • 
• With the LED on flash and illuminated by room LED lights:
• • 
• With the LED on flash:
• • 
• With the LED on flash, battery USB:
• • 
• Original Prusa Enclosure LED strip:
• • 

I'm in the UK with 50Hz electricity, with ESP32 from https://amzn.eu/d/54PickP I've tried different USB power supplies, including a battery to eliminate the 50Hz mains frequency.

I guess this is the LED on the board, but is it I've got a bad board or is this some LED driver pulsing the flash, is there any setting that can be done to eliminate or tune out this interference banding?

[johnyHV]

Hello @Simon7381. I am in the EU and also have 50Hz electricity. I haven't seen this problem yet. Currently, you need to manually change the setting in the code, in the mcu_cfg.h file, and variable

`

define FLASH_ON_STATUS 205 ///< PWM intensity LED for ON. limitation to 80%. 2^FLASH_PWM_RESOLUTION * 0.8% = 204

define FLASH_PWM_FREQ 2000 ///< frequency of pwm [240MHz / (100 prescale * pwm cycles)] = frequency

`

In the future I can added new parameter on the WEB page, for settings PWM intensity. Can you test change at first step FLASH_ON_STATUS ?

[Simon7381]

Hello @Simon7381. I am in the EU and also have 50Hz electricity. I haven't seen this problem yet. Currently, you need to manually change the setting in the code, in the mcu_cfg.h file, and variable

`

define FLASH_ON_STATUS 205 ///< PWM intensity LED for ON. limitation to 80%. 2^FLASH_PWM_RESOLUTION * 0.8% = 204

define FLASH_PWM_FREQ 2000 ///< frequency of pwm [240MHz / (100 prescale * pwm cycles)] = frequency

`

In the future I can added new parameter on the WEB page, for settings PWM intensity. Can you test change at first step FLASH_ON_STATUS ?

I had been lazzy and used the binnary to upload, so will give me an excuse to get the arduino setup on Monday 😀 Will let you know, thanks

[Simon7381]

@johnyHV Hi, so dropping the FLASH_PWM_FREQ to 500 has shown a great improvement:

So would be a case of finding the right setting to eliminate the PWM interference, btw is there any reason why FLASH_ON_STATUS has a 80% limitation, didn't want to try 100% and break something as I would assume this will eliminate any Freq scan lines.

[johnyHV]

Hi @Simon7381 . LED diode on the PCB don't have resistor for the current limitation. So currently is for testing changed PWM to 80%. Maybe this "solution" should be help extend LED diode life time. Can you try use original PWM frequency, and 100% PWM ?