Filament monitor using HC-020K encoder

[paboman]

The motor have 200 full steps per revolution (1.8 deg per full step)
The gear ratio is 1:13.76 so the number of full step per revolution is 13.76 x 200=2752 full steps
The hobbed gear diameter is 12mm so the Circumference is 3.14 x 12=37.68mm
with full step than the steps/mm is 2752/37.68=73.03 step/mm
Driver works at 1/16 step so 16x73.03=1168 steps/mm

The extruder motor is connected to E0 but instead of the hobbed gear i mounted the encoder wheel (only for testing)

[dc42]

So instead of a 12mm diameter hobbed gear you have a 26mm extruder wheel. So the amount of extruded filament will be 12/26 of the amount you have assumed in the encoder wheel calculations. (12/26) * 4.1 = 1.89.

[paboman]

That is right! Definitely something I have overlooked.
thanks again

[Monster Delta]

Does the resistor go between A0 and GND OR VCC AND D0?

[dc42]

@monster-delta said in Filament monitor using HC-020K encoder:

Does the resistor go between A0 and GND OR VCC AND D0?

Which resistor are you referring to? If you mean the one to clean up the output of the encoder, it's neither, it's between pins 1 and 3 of the LM393 chip.

[Monster Delta]

@dc42 thank you for clearing that up

[paboman]

@dc42
I am now printing as the printer is ready and sometimes I get error:

Extruder 0 reports too much movement

M591 D0
Pulse-type filament monitor on endstop input 3, enabled, sensitivity 1.89mm/pulse, allowed movement 60% to 300%, check every 10.0mm, current position 0.0, measured sensitivity 1.785mm/pulse, measured minimum 99%, maximum 160% over 4127.0mm

I changed the sensitivity with no luck

M591 D0
Pulse-type filament monitor on endstop input 3, enabled, sensitivity 1.78mm/pulse, allowed movement 60% to 300%, check every 10.0mm, current position 0.0, measured sensitivity 1.799mm/pulse, measured minimum 90%, maximum 218% over 5322.7mm

then when it stops it says maximum was 676%, why ?

M591 D0
Pulse-type filament monitor on endstop input 3, enabled, sensitivity 1.81mm/pulse, allowed movement 60% to 300%, check every 10.0mm, current position 0.0, measured sensitivity 1.820mm/pulse, measured minimum 90%, maximum 676% over 8980.6mm

I increassed the sensitivity to 300% hoping for a workaround solution but still getting the error after many hours.
This is not happening if i print in vase mode

[paboman]

@dc42
David, can you take a look at this please?

[dc42]

Did you add the resistor to your HC-020K board to get rid of the noise on the output?

[paboman]

@dc42
sure, that was the first thing you have figured out.

[dc42]

It could mean that you are still getting noise on the output sometimes. In particular, if the extruder stops with the wheel just on the boundary of blocking/not blocking the light to the opto sensor, there could be noise at that point caused by vibration. You could try reducing the value of the resistor. 10K or lower will stop the sensor working completely, but 15K to 30K might work.

[paboman]

I changed the filament monitor design and before ordering other resistors (with different values) I want to be sure my calculations are right, maybe this time the filament monitor will work just fine with the 45K ohm resistor.

The filament runs on a hobbed gear of 10.55mm in diameter = 33,14 mm in circumference
33,14mm of extruded filament gives 20 pulses
33,14/20 = 1,657 mm/pulse

@dc42 can you confirm this please?

Can the distance from the center of rotation of the sensor affect the reading ?

thanks!

[dc42]

That calculation sounds right.

The distance you refer to will affect how clean the output of the opto switch is. If you use a suitable feedback resistor in the comparator circuit then it shouldn't be too critical, because the comparator will clean up the output.

[create0]

Thank you so much for the indeed, incredible concept to share with. I do admire the effort and will continue to learn from these forums.

[Tony Owens]

Hi @paboman

I'm interested to know how this slotted optoswitch worked out for you as a basic filament sensor? Did you complete your development? Did you encounter any problems you could not solve?

cheers

[paboman]

@Tony-Owens
is working quite well, I would like to reduce the dimension of the assembly in the future.