Here's my printable optical encoder wheel filament sensor!

arhi

@fractalengineer said in Here's my printable optical encoder wheel filament sensor!:

@arhi @T3P3Tony That just made me think; how about a mechanical freewheel physically stopping the encoder from spinning backwards; could be a ratchet or one-way bearing -although I don't know of any smaller than 608 size) or something else

can be done for new desings, will not work for existing ones + IMO that's a wrong approach to solving software issue

fractalengineer

Just published the updated model using a $3 Schmitt trigger equipped arduino sensor;

Getting much more consistent reading

Check it out there

https://www.thingiverse.com/thing:4445504

o_lampe

@arhi said in Here's my printable optical encoder wheel filament sensor!:

There is no way a filament will move in contra direction of the motor

@fractalengineer thanks for warming up this thread.
I read it and the above quote made me think of murphy's law.
YES there is a way filament pressure builds up so hard ( eg. Bowden setups) that the stepper looses control and gets pushed backwards a few degree (visible and audible). That happens regardless of the DIR pin value.
I've seen that happen regularly with a Diamond mixing hotend and three 0.9° steppers.

arhi

@o_lampe possible, dunno, I assume the motor can skip steps, it can even chew the filament so motor is spinning but filament is not moving, but never seen filament going backwards trough motor .. .but yes, with bowden everything is possible, I don't use bowden, ever, I always believed it is a terrible way to do things especially as I almost never use PLA and the "springy" filaments I use really hate bowden setups

o_lampe

@fractalengineer said in Here's my printable optical encoder wheel filament sensor!:

Schmitt trigger equipped arduino sensor

The endstop definition already has a threshold parameter. I was wondering, why that was not enough? Does the Schmitt-Trigger offer a bigger hysteresis or what's the difference?

fractalengineer

@o_lampe Excellent question; it worked about fine for me with pretty high tolerance (ended up running 25-200%) but would still get occasional spikes at 400% triggering false positives

Then @JohnOCFII made this awesome in-depth investigation using a logic analyzer and found out that the signal was indeed noisy and implementing a schmitt trigger solved the issue; https://forum.duet3d.com/topic/19284/inconsistent-results-with-optical-encoder-wheel-filament-sensor

So I found an IR sensor that has a shmitt trigger integrated and modified the housing for it

alankilian

This post is deleted!

rkaronde

I remixed the design by Fractalengineer to use the Duet3D Laser Filament Monitor, and it seems to be working well.
https://www.thingiverse.com/thing:4796741

o_lampe

@rkaronde
Hi, nice design.
You should give @fractalengineer more credit in your thingiverse-description by editing the the two typos in his name:

Fractalenginner 
Frantalengineer

How difficult is the shaft to print? Just wondering if it wouldn't be easier to glue the disks to a steel or carbon rod?

rkaronde

Oops, fixed the typos. Thanks for catching them.

The shaft is really easy and quick to print. It has a few different sections of varying diameters and a hexagon shape on it. These are really important parts of the overall design.

Getting those craved on a steel/carbon rod would be hard

blt3dp

I’ve been looking to add something like this to my printers for a while. I was wondering if maybe a non-printed wheel might improve things. Thinking it’d take out any potential inconsistencies that may exist using a printed part.

Maybe something like this?
https://www.adafruit.com/product/3782?gclid=EAIaIQobChMIoajljtm37wIVaR-tBh3jyAO0EAQYAiABEgIQAvD_BwE

fractalengineer

@blt3dp Yep depending on your printing accuracy you may have reading inconsistencies due to variation in the slots sizes.

Hence why I'm setting readng over 50mm; that's the distance it takes it to make one revolution, averaging out this variation.

There are plenty of plastic molded wheels you could use to get more consistent slots, if you redesigned the shaft and possibly the housing to fit

I was also thinking of laser cutting the wheel in acrylic for instance