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bigtreetech / BIGTREETECH-SKR-mini-E3

BIGTREETECH SKR-mini-E3 motherboard is a ultra-quiet, low-power, high-quality 3D printing machine control board. It is launched by the 3D printing team of Shenzhen BIGTREE technology co., LTD. This board is specially tailored for Ender 3 printer, perfectly replacing the original Ender3 printer motherboard.
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[BUG] FAN0 no control with BUCK Converter #284

Open cgeorgeot opened 4 years ago

cgeorgeot commented 4 years ago

Description

I have upgraded fans on SKR MINI E3 V2 (Ender 3 Pro) with Noctua NF-Axxxx FLX 12V for the Hotend fan and also filament fan. I've installed Buck converter LM2596S to convert 24 to 12V.

I know that FAN0 is controllable and FAN1 is uncontrollable, reverted from stock motherboard. First one is for the filament fan and the second for the motherboard.

The firmware is from stock.

Expected behavior Want to control FAN0 regulation

Actual behavior FAN0 is always on !

Ideas and suggestions 1- Buck converter doesn't work properly ? 2- Have to modify firmware //#define FAN_MIN_PWM 50 //#define FAN_MAX_PWM 128 3- Why I can't control FAN0 ? Is this due to the buck converter ? 4- If I install buck converter between PSU and motherboard, normally I'll have 12V for all ports and the motherboard, right ? But what about the BED and Extruder ? Does they support 12V instead of 24V ?

Regards

CRTified commented 4 years ago

It is pretty likely that you can't control FAN0 because of the buck converter. The LM2596S can output 12V when it is supplied with (according to the datasheet) 15V or more, and the input of it is probably smoothed (Thus, the PWM signal is more or less removed).

You could power the LM2596S directly from the power supply to have a 12V rail, and use a MOSFET (with gate on the FAN0 output) to control the output for the 12V fan, but that would make the whole construction pretty ugly. I'd suggest you get a quieter 24V fan.