Re: Precision Piezo Z-probe Now available.
June 06, 2017 08:19AM
A strain gauge is what you would need for that kind of continuous measurement but they come with their own problems. Strain gauges are highly temperature sensitive and normally have to be used in pairs where only one is exposed to the force and the other, mounted nearby, is used to compensate for temperature changes.

Software integration is a whole 'nother problem.

Idris


{Precision Piezo} Accurate, repeatable, versatile z-probe plus piezo discs, endstop cables, pt100, 50w heaters.
Re: Precision Piezo Z-probe Now available.
June 06, 2017 10:02AM
Update on further stock.

My apologies that we have been out of stock for a while after the early birds. We are going to have PCB's available this week and I will put Piezo20 modules back on sale on the site as soon as I have some made up.

Kits will be available also.

Sorry for those who are waiting. I have logged all enquires I have received and will email/PM those waiting when we have units ready to ship.


Simon.

[www.precisionpiezo.co.uk] Accurate, repeatable, versatile z-probe plus piezo discs, endstop cables, pt100, 50w heaters. PT1000 cartridge sensors plug straight into duet boards and others.
Published:Inventions
Re: Precision Piezo Z-probe Now available.
June 06, 2017 11:04AM
Quote
Moriquendi
A strain gauge is what you would need for that kind of continuous measurement but they come with their own problems. Strain gauges are highly temperature sensitive and normally have to be used in pairs where only one is exposed to the force and the other, mounted nearby, is used to compensate for temperature changes.

Software integration is a whole 'nother problem.

Idris

Hi. I have ESP8266, HX711 module and a load cell on order with the intention of measuring filament pressure. From what I read only large temperature swings would affect results. Speaking of temperature - I think the same issue would apply to piezzo sensors as well.
Re: Precision Piezo Z-probe Now available.
June 06, 2017 11:39AM
Since piezos detect changes in pressure, the piezo controller would need to track the min/median/max pressure change since the last time the printer board checked with it. Then it would work and not matter how slow or bogged down the printer board is with it's duties.

This requires serial communication between the print and piezo controllers. Analog input could still work, but the signal would need to encode multiple pieces of data, such as bitmasking the analog numerical value (seems like serial data would be easier).
Re: Precision Piezo Z-probe Now available.
June 06, 2017 12:51PM
Load cells and most pre-manufactured strain gauges will include a second strain element, mounted at right angles on the same substrate for the purpose of temperature compensation.

You will get a reading but I doubt it will be accurate, any noise in the signal may accumulate and cause a drift in the output signal. I'm not saying it's impossible but it's definitely non-trivial.

Idris


{Precision Piezo} Accurate, repeatable, versatile z-probe plus piezo discs, endstop cables, pt100, 50w heaters.
Trouble with Piezo
June 07, 2017 10:42AM
Hello there,

I just received your sensor and have been trying to configure it for the past few days on a DBOT / DUETWIFI. I am running into a couple problems and wondering if you could help.

The trigger seems to be backwards. When it is lit it is registering as "not triggered" the blue light is on. If I run G30 in the gcode console and the blue light is off, it shows "Error: Z probe already triggered at start of probing move". I have it plugged into the z

I have set up the firmware as such:

Config.g

; Z probe
M558 P1 I1 F500 X0 Y0 Z0                   	; Analog Z probe, also used for homing the Z axis
G31 X0 Y0 Z0 P700                   	; Set the probe height and threshold (put your own values here)


Question: Do I have to change the definition of the switches where my x/y endstops are defined?

Bed.g

; Auto calibration routine for delta printers
; Before running this, you should have set up your zprobe Z offset to suit your build, in the G31 command in config.g.

M561						; clear any bed transform, otherwise homing may be at the wrong height
G31 X0 Y0					; don't want any probe offset for this
G1 X0 Y0
G28						; home the printer

;*** Remove the following line if your Z probe does not need to be deployed
;M98 Pdeployprobe.g			

; The first time the mechanical probe is used after deployment, it gives slightly different results.
; So do an extra dummy probe here. The value stored gets overwritten later. You can remove this if you use an IR probe.
G30 P0 X0 Y0 Z99999

; Probe the bed and do 6- or 7-factor auto calibration
G30 P0 X10 Y10 Z99999 ; top left
G30 P1 X10 Y190 Z99999 ; top right
G30 P2 X190 Y190 Z99999 ; bottom right
G30 P3 X190 Y10 Z99999 ; bottom left
G30 P4 X100 Y100 Z99999 S0 ; centre, and calibrate

;*** Remove the following line if your Z probe does not need to be retracted
;M98 Pretractprobe.g				

G1 X0 Y0 Z150 F15000			; get the head out of the way of the bed

--

I feel like I am close but I also feel like I am not. I did tune the board as per instructions. Right tuning is .4 ohm.

What am I doing wrong here, any help would be much appreciated....pretty frustrated that I can't get this working (even though it is more than likely user error).

Edited 2 time(s). Last edit at 06/07/2017 10:48AM by onefishtwofish.
Re: Trouble with Piezo
June 07, 2017 10:44AM
Try taking the I1 out of your M558 command. That inverts the sense.
Re: Trouble with Piezo
June 07, 2017 10:57AM
That seems to have done the trick.

The left adjuster:

The unit I bought came prebuilt. Unfortunately for my V3 and Hotend Mount I needed the other mount to connect it to my carriage. I printed the one you supplied on your site and it mounted nicely.

I have a couple questions on tuning.

1. Can you overtighten the top piece to the point where it will will affect the reading? I am not sure if I did that. Triggering seems either really hard or way too sensitive (i have been going in circles here)
2. When tuning, the left tuner, if you turn multiple times does it do anything different? or is it just 180deg that keeps looping? I feel like I may have turned this a few times and am now concerned that it is far off.

Thanks for the quick response Elmo!
Piezo support.
June 07, 2017 11:07AM
Hi,

Yes the I1 means a falling signal (active low) I0 is a rising -active high signal which is what this PCB outputs.

You can use it as an endstop by changing Z0 to Z1 in M558 too. (not applicable to deltas really)

1. The preload needs to be just enough that the unit (and attached hotend) is not wobbly. A lot more will reduce the sensitivity, really tight will mean little or no signal.
2. The adjuster will just go around and around.
If the right one is reading 0.4 m ohm leave it there.
Gently turn the left one until the led comes on and then just beyond the point where it goes out. If this result in too sensitive then turn it a little way further past the point where it goes out.

The adjusters are not designed to be turned indefinitely they can wear out. A drop of wd40 on the adjuster can help to keep the track inside healthy for slightly longer.#

Edited 2 time(s). Last edit at 06/07/2017 12:28PM by DjDemonD.


Simon.

[www.precisionpiezo.co.uk] Accurate, repeatable, versatile z-probe plus piezo discs, endstop cables, pt100, 50w heaters. PT1000 cartridge sensors plug straight into duet boards and others.
Published:Inventions
Re: Piezo support.
June 07, 2017 07:23PM
Thanks for the respons Dj. Ok. So I have made the adjustments.

- It now triggers correctly
- Duet web console is showing pressure on z-probe - Starts at 0 and goes up to 1000
- Probe Set up now looks as follows (which seems to work)
---M558 P1 F500 X0 Y0 Z0
---G31 X0 Y0 Z0 P500

Running the Probe
When I use G32 (which runs bed.g) it starts bringing the bed up for probing
Message: Bed equation fits points [10.0, 10.0, 99999.000] [10.0, 190.0, 99999.000] [190.0, 190.0, 99999.000] [190.0, 10.0, 99999.000] [100.0, 100.0, 99999.000]

Then, I press on the tip of the nozzle, it trips the trigger LED and shows pressure going up to 7-800 in web console. But it doesn't stop the bed? I am certainly missing something or a setting is still incorrect.

Thoughts?
Re: Piezo support.
June 07, 2017 07:25PM
You might want to drop the P value in the G31. The lower the value, the quicker the firmware responds to the touch. Just don't make it too small or you will get a lot of false triggers. I run mine at 10 with very little issue. May bump it up a bit if I start seeing false triggers again.
Re: Piezo support.
June 07, 2017 07:51PM
Odd. I am getting the reading on the Web Portal but even at 10, it is not stopping the bed. No error in the gcode also...i

Here is my bed.g
; Auto calibration routine for delta printers
; Before running this, you should have set up your zprobe Z offset to suit your build, in the G31 command in config.g.

M561						; clear any bed transform, otherwise homing may be at the wrong height
G31 X0 Y0					; don't want any probe offset for this
G28						; home the printer

;*** Remove the following line if your Z probe does not need to be deployed
;M98 Pdeployprobe.g			

; The first time the mechanical probe is used after deployment, it gives slightly different results.
; So do an extra dummy probe here. The value stored gets overwritten later. You can remove this if you use an IR probe.
G30 P0 X0 Y0 Z99999

; Probe the bed and do 6- or 7-factor auto calibration
G30 P0 X10 Y10 Z99999 ; top left
G30 P1 X10 Y190 Z99999 ; top right
G30 P2 X190 Y190 Z99999 ; bottom right
G30 P3 X190 Y10 Z99999 ; bottom left
G30 P4 X100 Y100 Z99999 S0 ; centre, and calibrate

;*** Remove the following line if your Z probe does not need to be retracted
;M98 Pretractprobe.g				

G1 X0 Y0 Z-150 F15000			; get the head out of the way of the bed

Re: Precision Piezo Z-probe Now available.
June 07, 2017 07:58PM
You sure that Z-150 is correct in the final G1 command? The bed is normally Z=0 with positive values going up. Using a negative value would drive the head into the bed.

I posted all my files here [forums.reprap.org]

I didn't post it in that message, but here are my probe configuration commands
; Z probe and compensation definition
M558 P1 X0 Y0 Z0 F120 T3000 H2 R0.2	; Z probe is a switch and is not used for homing any axes
G31 X0 Y0 Z-0.05 P10			; Set the zprobe height and threshold (put your own values here)
Re: Precision Piezo Z-probe Now available.
June 07, 2017 08:01PM
Looking at my connections to the board, I think I have my z reversed. Which is why all of my settings are backwards. Up = +n Down = -n. I should change it, will make it easier when researching.

It just even isn't probing, Do I need to have these uncommented?
; Z probe
M558 P1 F500 X0 Y0 Z0                   	; Analog Z probe, also used for homing the Z axis
G31 X0 Y0 Z0 P20                   	; Set the probe height and threshold (put your own values here)
; The following M557 commands are not needed if you are using a bed.g file to perform bed compensation
;*** Adjust the XY coordinates in the following M557 commands to suit your build and the position of the Z probe
;M557 P0 X30 Y-25                     ; Four... 
;M557 P1 X30 Y-155                    ; ...probe points...
;M557 P2 X250 Y-125                   ; ...for bed...
;M557 P3 X250 Y-25                    ; ...levelling
;M557 P4 X150 Y-95                    ; 5th probe point for levelling
Re: Precision Piezo Z-probe Now available.
June 07, 2017 08:03PM
When you say it isn't probing, do you mean it is not seeing the nozzle touch the bed or you start the Auto Delta Calibration (G32) and nothing happens?
Re: Precision Piezo Z-probe Now available.
June 07, 2017 08:15PM
So after I enter G32

The bed goes down a bit, then starts its move up to the nozzle.

The z-probe reading definitely went up to 765 reading on the web portal, when I pushed it with my hand. It just doesn't stop the bed.

(FYI, I fixed the z connectors so now the bed goes in the proper direction.)

Edited 1 time(s). Last edit at 06/07/2017 08:18PM by onefishtwofish.
Re: Precision Piezo Z-probe Now available.
June 07, 2017 08:23PM
Are you seeing the blue LED light when you tap the nozzle?
Re: Precision Piezo Z-probe Now available.
June 07, 2017 08:28PM
Yes.

It is very sensitive to the touch.

One thing I do notice is that even though I am getting the blue LED trigger light, I have to press pretty hard to get a reading on the web portal unless I press somewhat hard.

Couple thoughts:

-Could it be how much I tightened the top part of the connector to the v6? My thought is no, if the LED is lighting, it is reading the pressure.

-Why do I have to push somewhat hard on the nozzle to get a low reading. Big "taps" on the nozzle give me a high reading.
Re: Precision Piezo Z-probe Now available.
June 07, 2017 08:34PM
You might need to readjust that left pot again. Turn it clockwise until the blue led comes on and then keep turning until it goes back off, then turn just a little bit more. Not much. You should be able to get it to flash with just a lite tap from a tool handle against the nozzle.

As for the probe reading on the web page, the page is updated at a slow rate compared to what is happening with the printer. It is normal not to see the probe register when running.
Re: Precision Piezo Z-probe Now available.
June 07, 2017 08:41PM
Readjusted the left pot.

- more sensitivity.
- LED is triggering with the slightest touch
- Same slow response from webserver and your explanation makes sense but seeing range from 17-700

Ran G32 again

- Bed goes down a bit
- Bed moves up like it wants to probe
- Touch end of nozzle
- Bed doesn't stop
- Press hard on nozzle and bed doesn't stop

Power down printer to prevent bed from smashing into the nozzle

Most of the time it is a "me" issue. Appreciate you taking the time to triage this with me.... hopefully my settings are just incorrect or something along those lines
Re: Precision Piezo Z-probe Now available.
June 07, 2017 08:44PM
Not sure where to go from here. You might try asking DC42 about it. I believe he is also using one of these probes.
Re: Precision Piezo Z-probe Now available.
June 07, 2017 08:45PM
Understood. Thanks for all the help Elmo... back to the drawing board.
Re: Precision Piezo Z-probe Now available.
June 08, 2017 03:22AM
You won't see a response on the web interface for a normal touch. The trigger pulse is very brief, only a few milliseconds, and it doesn't normally have time to register with the web interface. If the LED is flashing then the board is triggering and the controller will recognise it even though it doesn't show on the web interface.

I'm curious, your bed.g refers to bed levelling for a Delta but you talk about your bed moving. Are you using a delta with a moving bed?

Idris


{Precision Piezo} Accurate, repeatable, versatile z-probe plus piezo discs, endstop cables, pt100, 50w heaters.
Re: Precision Piezo Z-probe Now available.
June 08, 2017 03:35AM
If you want to see triggers on the web interface tap repeatedly. You might see the value rise and the z-probe box change to red. This is a trigger.

Turn your motor currents down to 500ma and have a probe, any head crash will be very low drama.


Simon.

[www.precisionpiezo.co.uk] Accurate, repeatable, versatile z-probe plus piezo discs, endstop cables, pt100, 50w heaters. PT1000 cartridge sensors plug straight into duet boards and others.
Published:Inventions
Re: Piezo support.
June 08, 2017 08:27AM
Another question about RRF/Duet here on duet forum (might be the same question?)

[www.duet3d.com]

If it's useful to anyone, but please keep official support here on this thread.

Edited 1 time(s). Last edit at 06/08/2017 08:29AM by DjDemonD.


Simon.

[www.precisionpiezo.co.uk] Accurate, repeatable, versatile z-probe plus piezo discs, endstop cables, pt100, 50w heaters. PT1000 cartridge sensors plug straight into duet boards and others.
Published:Inventions
Re: Piezo support.
June 08, 2017 11:42AM
I installed on my Smoothie delta. Wow it's a huge upgrade from my old FSR print bed. Way higher repeatability, and a solid print bed that cannot move around.

My $15 E3D clone didn't work with it's screw in Bowden coupler, so I ordered another knock off that has a proper pressed in coupler.


Could small stiff springs be used to hold pretension on the piezo? Use one on each of the four corner screws, and tighten until springs are fully compressed (but don't overtighten the screws). Then each corner has exactly the same pressure, and it should reduce any potential backlash.
Re: Piezo support.
June 08, 2017 12:05PM
Glad it's working, I've been toying with making an assembly jig which would just be a spacer at approximately the gap present with a piezo disc is installed. You'd tighten all four screws down onto the disc, if it was still loose you could turn the screws one by one but by a measured amount . right now I tighten them all and eyeball which ones to tension to get nice preload but a level and firm hotend.

Springs and guide rods (used on previous models) are unnecessary complexity, the spring element is the disc itself.

Edited 1 time(s). Last edit at 06/08/2017 12:06PM by DjDemonD.


Simon.

[www.precisionpiezo.co.uk] Accurate, repeatable, versatile z-probe plus piezo discs, endstop cables, pt100, 50w heaters. PT1000 cartridge sensors plug straight into duet boards and others.
Published:Inventions
Re: Precision Piezo Z-probe Now available.
June 08, 2017 08:00PM
Quote
onefishtwofish
Ran G32 again

- Bed goes down a bit
- Bed moves up like it wants to probe
- Touch end of nozzle
- Bed doesn't stop
- Press hard on nozzle and bed doesn't stop

When you "Touch end of nozzle" and/or "Press hard on nozzle", are you seeing the blue LED triggering? From what I understand, the piezo triggers to (rapid) changes in pressure... if the pressure change is slow, it won't trigger.
Re: Precision Piezo Z-probe Now available.
June 10, 2017 10:57AM
Apologies things have been a bit slow my kids been sick so it's had to take a backseat. But I've got pcbs and Piezos in decent numbers so will be getting some stock onto the website soon.


Simon.

[www.precisionpiezo.co.uk] Accurate, repeatable, versatile z-probe plus piezo discs, endstop cables, pt100, 50w heaters. PT1000 cartridge sensors plug straight into duet boards and others.
Published:Inventions
Re: Precision Piezo Z-probe Now available.
June 18, 2017 01:39PM
Hi,

since it seems that few people use the piezo on duet, did you directly connect the 5v pin of the piezo to the 3,3 VCC pin on the duet ? or is it related to the INT 5V_EN jumper ?
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