Auto pressure advance turning by hotend pressure
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@penguinya
a1 mini use pcb coil -
@penguinya what inductance are they measuring to determine pressure for pressure advance calibration?
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@T3P3Tony
It's probably the filament that bends in a certain direction when pressure increases. They could design the filament path in such way, that it bends in a predictable way.
But that would highly depend on the stiffness of the filament and would need a calibration with temp-compensation -
@T3P3Tony Same as the string gauge, it looks like the hotend can move up and down
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RP2040 have two core and fust enough ADC to measure string gauge.
I think it can save pressure data to calculate pressure curve
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@penguinya
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15 minutes, 16 seconds to 17 seconds, the hotend moves up and down.
https://www.youtube.com/watch?v=EZ3BtQ7k9Ak -
I love the idea!
I guess you could write a gcode snippet in daemon.g which continously reads straingauge values and adjusts pressure advance values?
Duet can read sensors via SPI, maybe a dedicated "strain gauge sensor" option would be possible? One could also put together a small PCB that amplifies the strain gauge reading into a voltage that can just be read by a linear analog sensor on the Duet? -
@nikscha macro not fast enough, and this is my idea https://forum.duet3d.com/post/324006
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Automated PA testing is still an early idea. I hope to implement z probe and collect enough PA pressure data for research.
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@penguinya I think it would be fast enough. Just put a "while true" into daemon.g and then a G4 P50 in the body to execute your script every 50ms. (Edit: this wouldn't actually run that frequent, more like 3-6 times a second)
I don't think pressure advance needs to be adjusted that often, right?
Stay in school
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@nikscha Bambu Lab tests pa every print, and 50ms really slow, HX711 can reach 80HZ, Prusa using HX717 320HZ, higher the sampling frequency, the more beneficial for auto PA testing.
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find a better chip for load cell.
CS1237 http://www.asidesigner.com/Files/PartFiles/15315/222/cs1237_datasheet.pdf
spi bus 1.28kHz ADC and PGA -
@nikscha Here is a post about sampling speed
https://forum.duet3d.com/post/251488 -
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@penguinya The introduction of bambulab confirmed my guess.
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Correct me if Im wrong, but I feel like this sensor could also be used for filament runout/jam detection as well. Like if the force expected by feeding the filament is not produced, it could indicate that there is some filament error.
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@Charlie Yes prusa has implemented it
