^^ this is why I put in that NO GPIO relay in the schematic. I’m waiting for the relays to get here this weekend. I’ll know next week.
Can you share your wire diagram for the cheap way with a single pole relay? I’m not visualizing how to do it with only one switch per motor. let alone one switch per coil to completely isolate the coils from the board as @MakerJim encouraged.
klipper restarts the firmware any time you make a setting change, like add a new macro, change an offset, add filament sensor, change default acceleration, pressure advance, extrusion calibration, etc… but it doesn’t do it on its own, it does it when you tell it to, so it is totally within the user’s control. if you emergency stop then of course it crashes. If the print fails and idle motor current isn’t set and your END_PRINT macro has G84 in it, then every time your print ends or fails, it will crash. These are preventable, so I don’t think springs are necessary, but I’ve just gotten used to crashing the bed and I’m putting this electrical fix on the z motors so the bed won’t crash anymore and it won’t break anymore weakly printed mounts.
I agree, 1000%, but boards have still died because of it. The one that I did not see before was what makerjim linked above, did you see that? X endstop issue caused a reset? That threw me for a loop, seems it should just stop and sit in an error state.
Either way to help offset the inevitable mistake, wiring it to power and some sort of GPIO pin should catch everything, I ideally it would just be motor enable pin but I was told that is not an always on pin that is just a signal so it will not work (needs to be verified).
hahahaha
all I did was grab one coil and added it into the relay. When there is no power they get shorted together. When there is power or a signal they act as normal.
The bed crash because of the endstop was me. And it was an odd case. That endstop was plugged into the tool head board. When it went looking for it the plug was barely on and I believe it gave it a random signal which caused the EBB to shut down. Any MCU disconnect will cause klipper to reset. On another printer I used to get that all the time because I was running the BTT usb cable that came with the board. Now that I am running a better usb cable it rarely happens.
But any kind of temperature error will cause a reset. That’s a safety feature so that the control board resets and doesn’t hang with a heater on 100% and burn your house down
I’ve been reading data sheets for the BQ processors. The IO pins go to high resistance on reboot. Would it make sense to have one set up with a pullup connected to ground (low current) so when it goes to high resistance, the voltage goes to 0 because no voltage would be applied and then the relay would trigger. Looking into how to do that, but I’m sure it can be done. Not sure if that is a valid approach though. It could be one of the endstop pins or one of the pwm pins that are available on the octopus I’m using.
I really really don’t think you need both coils on all the steppers. One holds like 5lbs of direct pull. but I bet adding two is only a few pennies more.
On the relays I have they have a selectable trigger (high or low) that is what I would use for whatever pin you found, thinking a “board cooling fan”, that would be always on when power is on.
Then of course the main power, if that cuts the relay resets (Normally Closed). Amazon.com
when the board resets because of USB disconnection, the motors drop. A warm boot. That is the one I’m trying to capture. Have not found the right pin yet.
