Mix between IR sensor and Piezo probe

fma

Hi!

My idea to use a piezo on my future water-cooled hotend does not look so good. And putting piezo under bed, in my case, is not easy either.

So, I plan to use DC42 IR sensor. But I would like to auto-calibrate it (Z offset). For that, I'm think to use a piezo in a fixed position, outside the print surface. Then, I can probe on this position with both IR and piezo, and compute Z offset.

I have a few questions:

would it be possible to use the IR sensor PCB for both IR and piezo probe? I read that it is able to read piezo, but I don't know if both could work together (switching from one to another with an externa signal, from expansion port, for example);
from a firmware point of view, is the auto-computation of this Z offset possible?
About IR sensor, is it possible to mount the leds and sensor on another smaller PCB, wired from the main PCB? And is it possible to have a longer range to avoid mounting the leds/IR so close to the nozzle? 20-25mm would be nice.

Thanks for your help.

DjDemonD

We did chat briefly about whether the ir board could use the piezo sensor. Whatever threshold it is programmed with would probably need to be changed. However I'd suggest connecting one sensor to the z probe connector and the other to the z min endstop. Although using both as you intend to is probably unnecessary (although an interesting experiment) as once you know the H value for the ir sensor for any given frequent utilised probe point it is a constant and measuring it only needs to be done once.

fma

The Z offset needs to be done each time you change the nozzle, or remove the hotend…

Didn't think to use both z min and probe input! Thanks for the idea.

DjDemonD

Let us know how it works I am interested to see how it goes.

fma

I have a question: how does the output probe signal works, on Duet? It could be used to switch between sensors (using an analog switch, driven by the probe output signal)…

And how the probe input works, in analog mode? What voltage does the Duet expect to trigger? I read that a simple FSR could be used that way; I have one in my stock...