Hi. I’ve been thinking about this for a while. Recent events have made being less dependent on global supply have sparked interest again.
Several control parts are out of stock for FarmBot so I’m going homebrew. I’m an engineer and work in automation, motion control, modbus, mqtt etc. I have over 70 pi CM4 based systems running node-red without issue - can’t say the same for pi4B. Edatec make the boards and HMI. Very good.
My plan.
Cm4 - 2gb ram 8gb Emmc.
Waveshare nano for usb and 40pin header
https://www.waveshare.com/cm4-nano-a.htm
Nodered - not much it can’t do and I can write custom code where necessary. It will handle coms to farm server and send gcode to controller. RealVNC to access.
Duet 3d RepRap controller (clone initially)
RepRap already has node-red modules. In my experience cheap motor and good controller is better than the other way round. This will probably be enclosed because of critters in the city so the fan control and thermocouple inputs will be useful. It has IO and if I need more I’ll add a rs232 IO board and use 12 or 24v sensors. Using Modbus from node red for coms
Ip 67 open loop NEMA17. Duet 3d has stall and overload detection. I don’t think I need the accuracy of micro step. And running at “low” rpm with a good driver shouldn’t miss steps. If the encoder is critical I’d rather use a dc servo with built in controller. But then ip 65 ip67 get pricey
Gt3 belt, a bit more expensive than gt2 but much higher torque to enable stall detection. Even my 3d printer jumps teeth that’s gt2. Not a fan even a 50oz motor with the right gearing can easily over power it.
8020 framing other parts from Misumi. My go to engineering supplier. Or custom from Rapiddirect, a very good affordable prototyping manufacturer.
I’m toying with the idea of using igus dryspin lead screw and nut for the z axis. Lower holding torque. Improved accuracy. Weight might be a little more but no pulleys and plastic bearings probably offsets it.
FarmBot tooling and server.
Any roadblocks that jump to mind? Or similar projects? Before I pull the trigger.
Plus side I already have raised beds,
Thanks for making this all open source.