## General - Safe / Positron3D to design Nextruder Mount - Safe / Positron3D to design helper board mounts for wiring - TheNexusAvenger / Positron3D to help with Kalico configs for SKR Mini E3 V3.0, Pico(???), other SKR???, and Einsey Rambo (if possible) ## Gareth's Notes from Printables Post [Prusa Nextruder to Voron 2.4 Mount by gareth.ky \| Download free STL model \| Printables.com](https://www.printables.com/model/760274-prusa-nextruder-to-voron-24-mount) - You can but a [MK3.9 upgrade kit](https://www.prusa3d.com/product/original-prusa-i3-mk3-s-to-mk3-9s-upgrade-kit-2/) that has all of the parts needed, but also comes with a bunch of stuff you don't need. - Alternately, Prusa will now sell you _most_ of the individual parts for a Nextruder as [spares](https://www.prusa3d.com/category/nextruder/): - [Load Cell / Heat Break](https://www.prusa3d.com/product/hotend-heatsink-xl-mk4/) - [Love Board](https://www.prusa3d.com/product/loveboard/) - [Nextruder Hot End Assembly](https://www.prusa3d.com/product/nextruder-hotend-brass-0-40-mm/) - [Extruder Motor](https://www.prusa3d.com/product/stepper-motor-e-axis/) - [Nextruder Gears](https://www.prusa3d.com/product/set-pg-assembly-pg-ring/) - 2 x [Nozzle Thumb Screws](https://www.prusa3d.com/product/thumb-screw-m4x8/) - But some important parts are still missing: - Bearings and tube for the tension leaver shown [here](https://help.prusa3d.com/guide/5-nextruder-assembly_529772#540111). - Delrin plastic ring that sits inside the Nextruder PG Cover shown [here](https://help.prusa3d.com/guide/5-nextruder-assembly_529772#540657). - Idler Springs shown [here](https://help.prusa3d.com/guide/5-nextruder-assembly_529772#540867). - The aluminum spacer shown [here](https://help.prusa3d.com/guide/5-nextruder-assembly_529772#540785). - You'll need a wiring harness for the Love Board. It uses these really nice Molex CLIK-Mate connectors, for which no economical crimping tool exists. Parts required: [connector](https://www.digikey.com/en/products/detail/molex/5031492200/5254625), [pins](https://www.digikey.com/en/products/detail/molex/5025790000/2819012), less than ideal [crimping tool](https://www.amazon.com/dp/B078WPT5M1), and some magnifiers. There is a [post here outlining the pin outs](https://klipper.discourse.group/t/load-cell-design/2784/37?u=garethky) for the LoveBoard. Alternately you could buy the offical [Wiring Harness](https://www.prusa3d.com/product/nextruder-main-cable/) and re-wire it to your needs - The HX717 chip on the Love Board communicates back to the main board using SPI. Normally this wouldn't work because the wire run is too long and the signals would get garbled. Prusa used an [ST490ABDR](https://www.digikey.com/en/products/detail/stmicroelectronics/ST490ABDR/599357) to transmit the signals back to the main board. You'll need one of these chips at the other end to decode the signals back into standard SPI. You will also need [a board](https://www.amazon.com/gp/product/B00OKCOKVE) to mount the chip on. - The Fan ports on the love board pulse the positive pin for PWM. Basically all klipper compatible MCU boards pulse the negative pin for PWM. This means you'll have to directly wire the fans.l - You'll have to run a fork of mainline klipper with the load cell probing code in it. Here is the [Community Testing Branch](https://github.com/garethky/klipper/tree/load-cell-probe-community-testing) ## LoveBoard Breakout Some initial info on the LoveBoard: ![[Pasted image 20260128141948.png]] ![[Pasted image 20260122130420.png]] I spent a few hours staring at it under the microscope and prodding it with a multi-meter. So far I’ve found where all but 3 pins of the big connector go: | Connection | Row 2 Pin# | Row 1 Pin# | Connection | | ------------------------------------------------- | ---------- | ---------- | --------------------------- | | EMOTOR (Red / A1) | 2 | 1 | EMOTOR (Green / B1) | | EMOTOR (Blue / A2) | 4 | 3 | EMOTOR (Black / B2) | | ST490AB - Y | 6 | 5 | MULTIWIRE | | ST490AB - Z | 8 | 7 | GROUND | | ST490AB - B | 10 | 9 | H-FAN / P-FAN Shared Ground | | ST490AB - A | 12 | 11 | HT | | 5V Supply + (Loadcell + HX717 supply + regulator) | 14 | 13 | NT | | HEATER 24V - | 16 | 15 | Fans Tachometer | | HEATER 24V - | 18 | 17 | 3.3V in for filament sensor | | HEATER 24V + | 20 | 19 | P-FAN +5V | | HEATER 24V + | 22 | 21 | H-FAN +5V | The HX717 is connected to what I believe is a [ST490AB](https://www.st.com/en/interfaces-and-transceivers/st490ab.html) chip which converts it to [RS-422](https://en.wikipedia.org/wiki/RS-422). (The chip says “S490AB MZ306”) The PD_SCK and DOUT pins are hooked up this, effectively ground isolating the chip from the main board. Pictures of the cable show white/blue twisted pairs in this location which is the expected wiring. I’m pretty sure I can still talk to it via 2 regular I/O pin and an associated ground wire. Fans are reversed from how the Chinese boards normally do PWM. Here the + pins are pulsed but on boards like the Octopus its usually the ground pins that pulse. The ground pin is connected to the relay/transistor network on the board so just swapping the wiring is likely impossible. Also using 12V fans is probably also out. (If I’m wrong about this Id be happy to hear it! Also if you have any ideas for a work around) Luckily I don’t think the board relies on the fan power for anything but the associated indicator LEDs so it could all be bypassed. The unidentified pins (5,15 &17) are probably the Filament Sensor, and 2 signal lines for fan failure. The fan RPM lines go into the relay/transistor network and I think they are reducing the RPM signal to a binary on/off signal so they don’t have to read it with an ADC back on the main board. I cant trace the filament sensor output line at all. I should be able to work out what these do for certain once I get power to the board. But if this is what they are, they are not essential pins. _Update:_ Prusa published the schematics: [https://www.prusa3d.com/downloads/Electronics_drawings/MK4_electronics_schematics.zip](https://www.prusa3d.com/downloads/Electronics_drawings/MK4_electronics_schematics.zip) The Filament sensor is connected to the B channel on the HX717, so they must be switching from A to B periodically while extruding to check for filament. I don’t plan to implement support for this as it would be VERY complicated in klipper to have a sensor that doesn’t report data on a regular interval. The unknown pins on the connecter were the 3.3V supply for the filament sensor, the Fans tachometer and multiwire port. Also it looks like fan power is direct wired and isolated, so if you swap the pins and use the 2 positive pins as negative pins and it should work, but I haven’t tried it. ## Rough Plan - Design simple board to hold the ST490ABDR - Use OEM Nextruder cable assembly with SMD 22-position Click Connector - Female Click for fans??? --> wire harness --> directly to main board