Precision Piezo Z-probe Now available.

SupraGuy - once its setup you'll enjoy it immensely. It's very sensitive.

Alan - yes we've been working with pyr0ball on thingiverse to bring his system along. I'll wait for Idris to chime in here. It's very similar it incorporates a monostable output which is tied to the red LED.

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Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Published:Inventions

I'm hoping so.

My MBot printer has bed leveling using a 3 point method that uses a normal endstop switch that triggers about 1.6mm above the nozzle. There are cutouts in the bed in the 3 defined locations. This should be fine, but the bed leveling doesn't work quite right, since the build surface isn't as flat as it should be, particularly near the front cutout. This is better since I replaced the acrylic with sealed MDF and bolted a 3mm aluminum HBP to it, but the cutouts bug me, and make it a pain to make the platforms, which I'd like to be able to easily replace. (Actually, I use shims on the MDF, to the height of the HBP + glass) I really want to get rid of that junk and be able to use mesh levelling to the actual build surface.

My I3 rebuild didn't have bed levelling before, and I'm not spending money on improvements until I get it working first. Even if the electronics aren't great, and it lacks features, I need to at least prove to myself that it works reasonably well before I spend money on things to make it better. I've left some room for things to be better if it's worth buying the parts. Not sure what I'm going to do about the 4 post bed mounting though.

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MBot3D Printer
MakerBot clone Kit from Amazon
Added heated bed.

Leadscrew self-built printer (in progress)
Duet Wifi, Precision Piezo parts

So I've been doing some reading.

The documentation seems to indicate that I want the disc to either flex of be squeezed. Can I set it up so that contact relieves pressure instead? As I understand, the piezo element reacts to a change in pressure, can I set it up so that contact relieves pressure instead? I'm trying to evaluate different setup methods, and this seems to be a potential solution. It wouldn't be too difficult to reverse the leverage if this is not adequate.

I'd have to guess that sensitivity is going to be affected by the mounting setup as well. If I use a class 2 lever to activate the sensor, I imagine that sensitivity would be reduced.

My current thought would be to ditch the springs in the mounting screws, and set up a spring replacement using the piezo sensors as a base, and applying tension to the mounting screws holding the heat bed down. Inside of the triangle these form, pressure would increase. Outside of the triangle, pressure would decrease on the opposing sensor.

Feasable? Reasonable?

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MBot3D Printer
MakerBot clone Kit from Amazon
Added heated bed.

Leadscrew self-built printer (in progress)
Duet Wifi, Precision Piezo parts

You can certainly use them in pressure release mode just reverse polarity of the piezo.

See my bed mount design on thingiverse. [www.thingiverse.com] it's simple but it works on delta and i3 style, I haven't got it to work well on corexy it's too sensitive to inertia from the bed as it moves up to probe.

The teeter-totter type problem doesn't seem to manifest with this tech like it does with fsrs, Piezos are too sensitive even if you lift on one and press on the other two you still get a usable trigger.

Some people are just using one in the middle of the bed like a microphone.

Edited 1 time(s). Last edit at 02/23/2018 04:53PM by DjDemonD.

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Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Published:Inventions

Quote
Moriquendi
Hi Phil,

It would appear that you've found an issue with the PP20 and the MKSbase, 3.1v should register as a logic high but perhaps there's more hysteresis on that pin or some form of protection that's interfering. I haven't used an MKSbase but I have been using a Smoothieboard for a couple of years and it doesn't have this issue.

Idris

Hi Idris,

It seems like my PP20 board is functioning as intended then, which is good to know. I've just put in an order for a Duetwifi to replace the MKS board, so that should sort out the Zmin problem, as well as a few other problems as well.

Thank you for your help,
Phil

Hello,

I've installed my Piezo20 module with a custom mount on my Robo3D R1 and E3D V6 hotend; wired into the Z min (replacing the Robo's stock NC Z limit switches). When sitting idle, I can trigger the piezo. When VR2 is tuned to just below activation, it will trigger immediately on negative z movement. When tuning a little lower sensitivity, it pushed into the bed and does not trigger anywhere sufficiently.

The E3D fan is right below the PCB. Is this a problem?

I think it might have the piezo squeezed, which I gather restricts the range of sensitivity. If that's the case, then I will remove it and adjust.

I appreciate any thoughts and recommendations!

Jim



Edited 1 time(s). Last edit at 02/23/2018 11:51PM by SpectreGadget.

Thanks for doing the video. Can you try one thing out, can you video pushing (not tapping) upwards, then holding a little pressure on then releasing it?

If it triggers as you push up its okay, if it triggers as you release then the piezo disc is reverse polarity. Flip the plug over on the piezo disc. Sometimes you have to retune vr2 then try again.

If it's correct polarity then it's a case of getting the sensitivity right, and ensuring you are using pause before probing of at least 400ms but you can use more delay.

It looks like a corexy so upwards movement of the z axis should NOT usually cause too much mechanical noise and false triggers.

Edited 1 time(s). Last edit at 02/24/2018 05:48AM by DjDemonD.

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Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Published:Inventions

Hello DjDemon,

so your test actually works (as the board), by just unplugging the green connection i get the proper behavior.
I found out it was bad wiring, one diagram i had of the board indicated the wrong orientation of the pins, so i was inverting +5v and TRG. Using the multimeter i was able to figure out the right polarity.

Now i will try to configure Marlin and see what happens

Schematic for the v2 boards is here, I could have sworn I posted it on our website somewhere but obviously not.

Edited 1 time(s). Last edit at 02/24/2018 04:44AM by Moriquendi.

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{Precision Piezo} Accurate, repeatable, versatile z-probe plus piezo discs, endstop cables, pt100, 50w heaters.

Quote
diego.trinciarelli
Hello DjDemon,

so your test actually works (as the board), by just unplugging the green connection i get the proper behavior.
I found out it was bad wiring, one diagram i had of the board indicated the wrong orientation of the pins, so i was inverting +5v and TRG. Using the multimeter i was able to figure out the right polarity.

Now i will try to configure Marlin and see what happens

It is important to check wiring. On piezo boards up to universal kit v2 and Piezo20 v0.x it's VCC, Sig/TRG, GND (red, green, black).

Once we get to v1.1 Piezo20 it goes VCC, GND, Sig/TRG which is the default for endstop cables.

There is not yet a universal kit pcb with this new wiring scheme but I'm sure there will be soon.

The wiring at your controller is up to you.

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Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Published:Inventions

If in doubt, check the labels on the board.

Idris

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{Precision Piezo} Accurate, repeatable, versatile z-probe plus piezo discs, endstop cables, pt100, 50w heaters.

Quote
DjDemonD
Thanks for doing the video. Can you try one thing out, can you video pushing (not tapping) upwards, then holding a little pressure on then releasing it?

If it triggers as you push up its okay, if it triggers as you release then the piezo disc is reverse polarity. Flip the plug over on the piezo disc. Sometimes you have to retune vr2 then try again.

If it's correct polarity then it's a case of getting the sensitivity right, and ensuring you are using pause before probing of at least 400ms but you can use more delay.

It looks like a corexy so upwards movement of the z axis should NOT usually cause too much mechanical noise and false triggers.

That was it, exactly! For some reason, I didn't think that was it, but it sure was. I can't post a video, but know that I am a happy camper. Thanks!

Next step, UBL probing!

Jim

Labels on the MKS are non-present.
Using a multimeter actually saved me from hours of blind tests

So, for anyone interested in how to configure on the FLSun Kossel Delta and Marlin with the PrecisionPiezo V2 universal board, here you go:

I used an underbed mount, i like to not have more wires going to the effector

#Printed Parts:
[www.thingiverse.com]
i added a small rubber adhesive layer to insulate from heat and keep the bed from moving. This rubber is pretty hard and does not flez.

#Wiring:
Just wire the Z Endstop connector, like this:
Red with +5v
Black with GND
Green with Sig

Beware that if using the switches, the red wire from the switch is wired to SIG (so with PrecisionPiezo it must connect to the green cable)

# Calibration (you need a decent multimeter):
Follow the manual for calibrating the PP board.
Use a decent multimeter to assess V1 resistance

#Firmware (Marlin):

Z_MIN_ENDSTOP_INVERTING true
Z_MIN_PROBE_ENDSTOP_INVERTING true

activate (by removing the leading // )
PROBING_HEATERS_OFF
PROBING_FANS_OFF

Z_PROBE_SPEED_FAST 4000
Z_PROBE_SPEED_SLOW 600

disable (by commenting with //)
ENDSTOPPULLUPS

Spectre gadget - glad it's working 9/10 problem cases are piezo polarity I wonder if we can design a polarity independent circuit.

diego.trinciarelli - thanks for writing this guide.

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Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Published:Inventions

This is a preliminary result of my testing various size piezos with my underbed mount. The photos I have posted previously. The file is written using Notepad++. According to the data collected there seem like not much difference between the various piezos as far as Standard deviation goes. Thoughts?

Does it really matter (in terms of sensitivity) which side of the piezo disc gets pushed in? Shouldn't a flex in any direction cause a trigger? I'm finding I need to relocate wires due to their bad placement on some discs. I have room to flip them and then the push would be on the all-metal side instead.

Chowa - interesting results. The anti-noise piezo setup does seem to improve the range and std deviation. I think the lack of difference between sizes of piezo can be explained by either the fact that they are being used as vibration sensors in some applications in which case it probably matters little what size they are, or in the case where they are being used in compression or flexing there is less difference as the larger piezos have stiffer brass discs.

firefly555 - no you can push from either side. Just flip the polarity depending on how it functions.

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Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Published:Inventions

If you reverse the mechanical direction you also need to reverse the electrical polarity, other than that it'll work fine.

Idris

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{Precision Piezo} Accurate, repeatable, versatile z-probe plus piezo discs, endstop cables, pt100, 50w heaters.

Quote
DJ
I wonder if we can design a polarity independent circuit.

I think, that's called "precision rectifier", an op-amp circuit that rectifies the signal without diode voltage losses.

Wikipedia

Why not use a microcontroller? It's simpler than using op amps and comparators, and you can program it to be polarity-independent.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

We are working on it. Hoping to have an autocalibration routine enabling any piezo to be used.

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Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Published:Inventions

I just made an underbed bracket that mounts on my single slot 2010 extrusions. It's a Remix of another underbed Piezo bracket, although it's "remix" button wasn't enabled. The top can rotate, because my bed is square. But it'll work with round beds too, I guess.

Sidemounted Piezo bracket

Looks good. If it's a remix of mine don't worry about it, at least it's not on sale in China

Edited 2 time(s). Last edit at 02/25/2018 07:52AM by DjDemonD.

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Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Published:Inventions

The Schotsky diodes are already used in the input to the open amp to clamp the signal from the piezo. Perhaps a Schotsky bridge rectifier could be used? In my testing of the piezo from 12 to 41 mms diameter there is more than enough signal available to operate the circuit. In tuning the electronics, I found that the sensitivity had to be increased for the 12mm disk and decreased for the 41mm disk. My test rig photos have been published here previously on this thread as well as most recently the data for all four disk sizes. Since I do not have a delta, I can't comment on those implementations. Perhaps the resonant frequency of each disk size may have to be taken into consideration? The Murata specs are 9kHz, 6.3 kHz, 4.6kHz and 2.2kHz for the 12, 20, 27, and 41 mm disks. My tests were conducted on a bed 400mm wide x250mm deep. And my preference is the 27mm disk. The other specs are resonant impedance and capacitance. Might need to get delta to see what problems those exhibit.

Stef

Quote
Moriquendi
[attachment 102878 V2.11schem.jpg]Schematic for the v2 boards is here, I could have sworn I posted it on our website somewhere but obviously not.

Your first stage is more of an Integrator than a differentiator !
A low pass filter. (with the R in // with the cap)

Edited 2 time(s). Last edit at 02/25/2018 11:59AM by MKSA.

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"A comical prototype doesn't mean a dumb idea is possible" (Thunderf00t)

Quote
o_lampe

Quote
DJ
I wonder if we can design a polarity independent circuit.

I think, that's called "precision rectifier", an op-amp circuit that rectifies the signal without diode voltage losses.

Wikipedia

A simple bridge rectifier would be enough considering the high voltage output by piezo. In fact it would even clip the low level noise.

Edited 1 time(s). Last edit at 02/25/2018 11:54AM by MKSA.

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"A comical prototype doesn't mean a dumb idea is possible" (Thunderf00t)

Good idea definitely worth considering. Depends if we go to a microprocessor or stick with analogue. It's worth thinking about as most issues are reverse polarity rather than anything more complicated.

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Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Published:Inventions

Quote
DjDemonD
Good idea definitely worth considering. Depends if we go to a microprocessor or stick with analogue. It's worth thinking about as most issues are reverse polarity rather than anything more complicated.

The other advantage of a software solution is that you can better protect the design from the thieves from over there.

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"A comical prototype doesn't mean a dumb idea is possible" (Thunderf00t)

Not if you make it open source you can't, that's kinda the point.

I'll do some investigation into the rectifier, however, there are developments coming that might make it unnecessary anyway.

Idris

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{Precision Piezo} Accurate, repeatable, versatile z-probe plus piezo discs, endstop cables, pt100, 50w heaters.