Duet3 with PINDA 2 probe setup

kb58

@phaedrux Though this is an old thread, it still seems relevant since presumably more people are now running Duet3 boards:

I understand that the thermistor is intended to compensate for the trigger height that varies over temperature. Has anyone calculated the height compensation coefficients? Even with that done, how is the result applied to the sensed height? AFAIK, the sensor output is open collector, so it's something of an "all or nothing" output. If so, how can this 0/1 output be adjusted in any way? Hoping to hear otherwise!

kb58

@kb58 Some work has happened in this thread, https://forum.duet3d.com/topic/16972/pinda-2-probe-with-temperature-compensation/5?_=1593546022132

But it ends with it being unclear whether it works when it's all said and done.

I wonder if a roundabout way to accomplish the same thing is to use bed temperature, coupled with plotting how the reported height varies over temperature. Like I said though, I'm not sure how to apply the value to the sensed height... unless the open collector output is actually analog.

Of course, the question has to asked: is the temperature-dependent height trigger variations enough to make it worth doing? Does anyone know what the variation is?

oliof

@kb58 considering there are now higher-frequency sensing probes (that's what superPINDA and all the unbranded variants are) that do away with temperature compensation because it's not required anymore, I would say it's not worth it.

martin7404

I went from pinda2 to superpinda on my CoreXY machine , printing 24/7 almost 4 weeks now with long 24 h+ prints, enclosed about 55 deg C inside , not a single hiccup

kb58

@martin7404 Where are you guys finding the superPinda sensors? Searching on the term only turned up one UK vendor, and Pinda themselves, who only sell to registered owners.

Guess I'll check around for off brand alternatives, looking for ones without the white thermistor wire.

martin7404

@kb58 i have mk3
You can ask somebody in UK with mk3 to order it for you. Or just ask prusa

aniron

@kb58 Prusa sells the SuperPINDA as an upgrade kit for the Prusa Mini. You don't need have a Prusa mini purchase on your account in order to purchase the upgrade kit.

https://shop.prusa3d.com/en/original-prusa-mini/1399-original-prusa-mini-to-mini-upgrade-kit.html

kb58

@aniron Okay, good to hear, this should help out others. For me however, I discovered that inductive-type probes are affected by beds with magnets in them, which seems to confuse the sensor slightly and produces errors. I changed over a BLTouch and suddenly the "lumpy" bed became very flat!

aniron

@kb58 hmm, just how lumpy did your bed get due to magnets?

I've seen some extreme cases online like the one below, but have never experience anything akin to that on my own printer using the prusa 12V bed. Perhaps I have been proving sparsely enough that by luck I have missed the hotspots.

1552583022865-screenshot_2019-03-13-gcore-1.png

kb58

@aniron Right, it depends where the probe ends up relative to the magnet. In the worst places, it was reporting "lumps" of up to about one millimeter. I finally figured out what was going on when the magnetic sheet was pulled off to see where the probe was, and it was right over one magnet when reporting the worst problem. After being replaced with a BLTouch, the "uneven" bed became really flat.

Like you said though, as long as the probe is kept away from magnets, it'll avoid the worst of the problems, so it's probably fine then.