Detect Extruder/Hotend during powerup or Print

ZipZap

Hello fellow printers,

coming from a RAMPS 1.4 i want to go to a Duet2Wifi for my next Printer.
I have just one question regarding changing toolheads (via magnets):

Is there a way to detect which extruder/hotend is currently in use - or said better: Which one (or none at all) is positioned on the magnetic holder.
During or after a print its easy, you just tell the Duet to park all hotends after finishing so on the next print (or machine startup) you know exactly which hotend is in use - its none.

But what is in the case of a poweroutage or an emergency cutoff of power?
When the Printer starts, it is "unknown" which hotend is placed on the holder.
Sure, you could just position it by hand on startup. But is there a possibility to detect which one is in use via a microswitch or similar?

For example:
There are multiple toolheads, on the parking station of each one is a microswitch. when the hotend is in the parking station, the switch is pressed, when it is in use, the switch is released (NC or NO, whichever is preferred). So the printer would know (and could check on startup) exactly which hotend is in use and which one is parked.

Question from a non-programmer (who is very willing to learn):
Is this a feature in the current FW or could this be implanted by myself? If im correct, the Duet2Wifi has free IO-pins for general use, could these be rewired?

I want to create a more industrial printer for my company, which should be nearly "idiot proof". It would be bad, if you start the machine and tell it to pick up a hotend while already having one on the holder. This would mean an instand crash and possible damage to the machine.

Many thanks in advance and greetings from Germany,
Julien

dc42

@ZipZap said in Detect Extruder/Hotend during powerup or Print:

For example:
There are multiple toolheads, on the parking station of each one is a microswitch. when the hotend is in the parking station, the switch is pressed, when it is in use, the switch is released (NC or NO, whichever is preferred). So the printer would know (and could check on startup) exactly which hotend is in use and which one is parked.

That's already supported, and I am using it on my tool changer; except that as the tools concerned use Duet 3 tool boards, the switch is actually on the tool (to save wiring) instead of on the dock. But either way will work, just make sure that if you are not using tool boards, you have enough spare inputs on the Duet for all of the dock switches.

ZipZap

Thank you for the really fast reply.

So it is basically possibe to reconfigure unused IO-pins (like endstops or the 2x25 expansion pins) on the Duet2Wifi to my liking? It would be two real hotends and two dummys (just a PWM).
Just now i am working myself through a dummy-firmware to learn the basics, coming from marlin this is a little bit "different".

I was thinking about the Duet3-6HC, but i have a certain budget for this project and such a luxury board including a fair amount of useful addons is just too much (at the moment). So i am "stuck" with a Duet2Wifi for the moment until i could do major upgrades.

/Julien

With conditional logic you might be able to use a single pin, and have different values resistors on different tools, and make descisions based on the analouge value read from the tool holder. you'll be limited to the resolution and noise floor of the adc, but i suspect you should be able to identify a whole bunch of tools with that method.

ZipZap

@bearer thats why i thought of reusing pins that would be connected to a Duex2/5, because these are free at the moment.
I would prefer digital Pins, so there is no fiddeling with noise regarding the ADC.

@ZipZap Tbh I don't think noise will be an issue even with tens of tool, but if you have enough digital pins then go for it.

ZipZap

@dc42 said in Detect Extruder/Hotend during powerup or Print:

That's already supported, and I am using it on my tool changer; except that as the tools concerned use Duet 3 tool boards, the switch is actually on the tool (to save wiring) instead of on the dock. But either way will work, just make sure that if you are not using tool boards, you have enough spare inputs on the Duet for all of the dock switches.

Sounds great. Would you mind giving me a hint on where to start looking (ist there a certain M-code for this)?
My research in the WWW only gave me results for filament-detection or Sensorlese homing.

/Julien