Sovol SV06/Plus MCU Piggyback for Voron Klipper Expander Board [PRELIMINARY]

KLIPPER EXPANDER

The stock SV06/Plus MCU board doesn't have enough ports for controllable fans.  This mod allows you to mount a Voron Design Klipper Expander board for more.  

The board adds 4 ports for fans or small heaters, a port for an RGB LED strip, 2 thermistor ports, and a single GPIO.  It also adds an I2C port for connecting I2C peripherals such as an 128x64 OLED display or an I2C temperature/humidity sensor.  The board is generally  less than $10 USD shipped from AliExpress.  I bought mine from https://www.aliexpress.com/item/1005002384419036.html 

See https://github.com/VoronDesign/Voron-Hardware/blob/master/Klipper_Expander/Documentation/README.md for documentation.  

The disadvantage compared to my MOSFET mod is that it requires an additional USB connection to the host Klipper computer.  

PRINTABLE FILES

The SV06_Expander_Bracket slips onto 2 existing pegs inside the Sovol MCU enclosure and holds the Expander board in place.  2 optional screw holes can be used to hold the Expander to the bracket.  The self-tapping screws from the Sovol enclosure fan work well here.  A small area has been provided beside the board to isolate/insulate small power conversion modules (for 5V LED strips, etc).   

The SV06_Expander_Front covers the bracket and secures it to the main body of the MCU enclosure.  Access the USB port of the Expander through this.  

The SV06_Expander_Lid is a remix of my MOSFET lid.  It has been modified to cover the other side of the Expander_Bracket.  It also allows porting the bed heater cable out the back of the enclosure instead of down.  

As with my MOSFET lid, print with no top or bottom so that infill becomes a grille mesh.   

STEP FILES

I have included .STEP files for easy remixes.  They have all the make-it-print-nicer fillets removed.  Models are from a slightly updated revision with a spot for a zip-tie to hold the bed cable and slightly larger holes in the Bracket where it slips onto the pegs of the Sovol MCU enclosure.  

MOUNTING HARDWARE

M3 heat inserts can be pressed into the 5mm holes on the Bracket.  Screws through the Expander_Front and Expander_Lid  hold everything together securely.  

WIRING

The fan ports output whatever voltage you supply to the “Power In” screw terminal.  I ran wire from the FAN screw terminal on the main MCU board, giving me 24V, but you could place a 24V to 12V step-down converter in between and all 4 fan ports will be compatible with 12V fans.  

The RGB LED port takes its power separately as well.  I use a small 24V to 5V step-down board to use it with an 8 LED WS2812b strip mounted on my toolhead via the extra 3-pin port there. 

QUIRKS AND PROBLEMS

The silkscreened labels for the MOSFET ports on my board were labeled incorrectly.  The say PA1 PA2 PA3 PA4 when they should say PA0 PA1 PA2 PA3.  

The fan ports are powered from the POWER IN screw terminal, but power for the STM32 MCU chip is supplied solely by the USB port, and therefore by the Klipper host (Pi).  Using the typical 5V-cut USB cable to isolate Pi power from printer power won't work here.  If you have a Raspberry Pi Zero 2W, you will probably need to add a powered USB hub to your setup.  

Extension of the lid and addition of a mounting bracket and door for more space.