Connecting and reading a pulse generating encoder

oc_geek

I try to ask even if i fear to know the answer already..

For an Multi-Material-Unit project (in the Voron 3D printer context) we would need the ability to :

reset the counts
fetch the actual counts

out of a pulse generating encoder (200 to 500 Hz is the rate)

Is there any way to do so with Duet fw at present ?
If so how...

(looked at the 1HCL too but it's targeting quadrature encoders..so..no go)

thanks

pfn

@oc_geek I thought about doing g this with a smart filament sensor.

For the purpose of loading and changing filaments, I would set the sensor pin to gpio input and reset a global count variable 0. As a load operation runs, the gpio input should run a triggerN.g file, that would increment the global variable by one for each pulse.

Once the operation is done (checking if the bowden got loaded, or if the extruder was able to feed filament) read the global variable and reset it to 0.

This should work well for the carrot feeder and avoids having to setup a print head filament sensor (that is setup after the extruder gears, a real pain for non voron printers)

oc_geek

@pfn yeah that is indeed for the new CF 1.1 which uses a pulse counter on the unit. In clipper they dev a piton module so macros are gone and the porting to RRF is no more an option

I like your idea. And yeah i'm in on the global variables (that was my target too) but i miss the way to count the pulses event (at that speed too)

Could you please elaborate more on the wiring and how would you read (or detect the trigger in that logic) the pulse.
On the printhead (extruder) there is a (hall sensor) filament sensor which detects the filament reached past the gears but that is something manageable which (i thinnk) is doable
thanks

(p.s. Mini 5+ it is in my case)

T3P3Tony

@oc_geek how is it interfaced? What protocol?

pfn

@oc_geek the output signal pin from the TCRT5000 would go into any of the ioN.in pins

Configure the pin as appropriate with
M950 J0 C"ioN.in"
M581 P0 T0 ...

Create /sys/trigger0.g and add code in there to do whatever is needed.

I haven't tried putting together an ercf yet, but it's on my list of things to investigate.

oc_geek

@t3p3tony Hi Tony, thanks for coming by

I have to confess i'm totally ignorant. I'm just trying to figure out if there is a way for RRF to use the Enraged Rabbit MMU 1.1 (Voron)

The pulse sensor is a TCRT5000 (IR Infrared)

TCRT5000 infrared reflective sensor
Detects the reflected distance: 1mm ~ 25mm Applicable
The working voltage: 5V
The output format: digital signal (0 and 1)

I suppose it just sends digital 0 or 1 (without a specific protocol)

Any advice help is very much appreciated in advance

oc_geek

@pfn
Thanks for the explanation.

I realize just now that this is the same "trick" i use for the filament sensor which is on my Mini5+ while i use the 1LC as tool board. Makes sence

That way you basically invoke the trigger and add 1 to the counter. Good idea. I hope it can stand the 500 Hz rate though... @T3P3Tony (do you know ?)

So couple of macros (count and reset) and we shall be in the game

I'm at the same stage of yours atm.
I have bought some of the key parts but have not yet printed it.
I hope we RRF folks are in the game too

T3P3Tony

@oc_geek so this is generating pulses at 500hz? There must be more too it if there is a pulse counter on the unit itself.

pfn

@oc_geek 500Hz rate? why is it so high? It should only trigger once per unit distance (which shouldn't be much lower than about 1mm per pulse...)

T3P3Tony

@oc_geek yeah the TCRT5000 is a reflective optical switch or potentially a distance sensor depending on how it was used. is there a rotating element with slots in?

o_lampe

@oc_geek you could use a frequency divider to reduce pulse count/second . They will reduce by 2,4,8 a.s.f. depending on their setting.
A small ATtiny or PIC processor can do the trick, too.
Then, when Duet gets triggered , add 2,4,8 pulses to the equation instead of 1.

In any case make sure, the pulse counting macro is as short as possible. Otherwise you might miss incoming pulses.
Write another macro to read the global pulsecounter and go on from there.

oc_geek

@t3p3tony as far as i could see from the Discord ERCF 1.1 discussion it reads a Bondtech gear which rotates with filament
Filament running at 20 mm / sec so that's where the 200 - 500 Hz comes from (i'm just reporting what i was told)

T3P3Tony

@oc_geek so whats the pulses/mm of this sensing arrangement. There is existing code for using a pulse based filament monitor
https://duet3d.dozuki.com/Wiki/M591#Section_M591_RepRapFirmware_Num_3

Type 7

dc42

@oc_geek what's the purpose of measuring the counts? Is it to detect if the mechanism is jammed?

With a simple pulse generating encoder, you will not be able to determine in which direction the mechanism is moving. Might that be a problem?

oc_geek

@dc42 i understood they use it to determine the filament position (real travel distance) when loading a specific filament in the MMU down to the tool head
With the encoder they say it is possible to meisure with a precision of 1 mm
Direction is derived by other means and hold by other variables

All that said would it be possible to use triggers to follow it up @ e.g. 250 Hz ?

oc_geek

@t3p3tony i saw that but it wont be possible to inquire the position nor to reset it (unless i'm reading it wrong)

Dan1990

The Klipper firmware seems to work fine with the ERCF, so perhaps will be valuable to check their code? It wIll gives more understanding towards what oc'geek and many others trying to get. (The voron - duet community is big )

That is the link to the PCB for ERCF:

https://github.com/Tircown/ERCF-easy-brd

Link to the project:

https://github.com/EtteGit/EnragedRabbitProject

oc_geek

@dan1990 rightly said

in particular the part responsible for the Pulse Generating encoder is a Klipper module written in python

pfn

@oc_geek why would you need 250hz? 1 pulse per mm, feed rates are usually like 10mm/s at most... (browsing that code, it looks like it's set at 1.5mm/pulse and something like 100mm/s feed rate, it's probably reasonable enough?)

oc_geek

@pfn as i wrote this came from the Author of the unit itself... it's not that i need something..

The sensor is used ONLY when loading / unloading the chosen (between nine) filament to the tool to make sure it arrives where intended and does not jam the unit and so on...
I think they do that faster than a print feed rate to reduce the overall print time...(e.g. 1000 filament changes in a print would matter..)

that said i did not got any data point from the Duet team on which rates (Hz) are reachable using a trigger... or any other offered solution...