temperatureswitch at reboot time

Controllers Smoothie
1

I have been able to use the temperatureswitch configuration to get my hotend heatsink fan to turn off and on, but only after the hotend has gone above the threshold for the first time.

When the hotend is room temperature and I boot the printer, the fan immediately turns on even though the hotend temperature is below the temperatureswitch threshold. Here are the steps:

  1. boot with hotend temp below threshold - fan on (can I change this?)
  2. temp goes from below threshold to above - fan on (ok)
  3. temp goes from above threshold to below - fan off (ok)
  4. temp goes from below threshold to above - fan on (ok)
    …continues to do the right thing as it crosses the threshold in either direction

Is there a way to have the fan off when I first boot the printer and the hotend is below the threshold?

David

Imported from wikidot

2

If you add a on_boot.gcode file to the SD card, whatever you put in there will be executed at boot time. If you put a gcode that turns the fan off in there, it should solve your problem … *I think*

3

Arthur,

Thanks for introducing me to on_boot.gcode. Your tip works for the scenario I described (booting with a cold hotend), but after doing more testing I found another scenario that could be disastrous. If for some reason I boot with the hotend already above the temperatureswitch threshold, I would turn off the fan in on_boot.gcode and if I then heated the hotend to printing temperature, the fan would stay off and damage my printer.

My testing shows that temperatureswitch only triggers when it detects the temperature has crossed the threshold in one direction or the other. So if the hotend is below the threshold, like in my original observation, temperatureswitch doesn’t force the fan to turn off if it is on, and if the hotend is above the threshold, it doesn’t force the fan to turn on if it is off.

So I won’t force the fan to turn off in on_boot.gcode because I don’t want to risk a bigger problem than my current problem of a noisy fan cooling an already cold hotend heat sink (maybe I’ll just find a quieter fan!).

Thanks for your quick reply,
David