Keep vacuum chuck powered through system restarts?

General Discussion
1

Hi folks, I have an AON3D M2+ running Klipper, and it uses a vacuum chuck to hold build sheets on the bed, in a heated chamber so messing with stuff in there is pretty annoying.

I’m trying to use initial_pins in menuconfig and the value / shutdown_value parameters on the [output_pin] config block to keep the pump on throughout restarts so I don’t have to fiddle with it again every time I eg save my config. I’ve got it so it comes back on after a restart, but there’s a brief blip of low state on the pin which is enough to kill my vacuum.

Is this just a limitation of the processor, or am I missing a config setting someplace? It’s an atmega2560 board, specifically a Controllino Mega which is a glorified Arduino with some relays on it.

The config block is

[output_pin vacuum_bed]
pin: PL0
pwm: false
value: 1
shutdown_value: 1

And the initial_pins field in menuconfig is just PL0

Thanks!
-Nick

2

You will never get rid of that blip. The blip is when it is restarting.

I fixed this issue on a machine a few years back by adding a timer relay. You use an output from your board to trigger the timer relay and then set the timer relay to have an off delay of however long you want.

3

Alright that’s more or less what I was expecting. I’ll see about adding a delay term in hardware like you suggest, thanks!

4

Agreed - what you have configured I think is the best possible that can be done from software.

That said, I think the atmega2560 GPIOs go into high-impedance mode on a reset, so a hardware pullup resistor on PL0 may be an alternate fix.

-Kevin