Precision Piezo Z-probe Now available.

I'm going to need some more information to be able to help you properly.

What signal are you probing?
Where is your ground probe connected
How are you measuring the resistance of VR1

VR1 shouldn't need any adjustment, it's mostly there to account for people using different size disks, it's normally the last thing that needs adjusting. VR1 and VR2 have only about 270deg of travel but there are no physical stops, if you go outside this range they go open circuit which with VR1 causes very high sensitivity. Potentiometers this size are delicate, be gentle when adjusting them.

My suggestion is that you set VR1 to the middle of it's travel (blue spot pointing away from the connector), re-tune VR2 and try it with a bare piezo (not stuck to anything).

Be aware that you need to use an insulated tool when testing the piezo, if you touch it with your finger the circuit is sensitive enough to be triggered by the capacitance of your body.

Idris

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

Quote
Moriquendi
I'm going to need some more information to be able to help you properly.

What signal are you probing?
Where is your ground probe connected
How are you measuring the resistance of VR1

VR1 shouldn't need any adjustment, it's mostly there to account for people using different size disks, it's normally the last thing that needs adjusting. VR1 and VR2 have only about 270deg of travel but there are no physical stops, if you go outside this range they go open circuit which with VR1 causes very high sensitivity. Potentiometers this size are delicate, be gentle when adjusting them.

My suggestion is that you set VR1 to the middle of it's travel (blue spot pointing away from the connector), re-tune VR2 and try it with a bare piezo (not stuck to anything).

Be aware that you need to use an insulated tool when testing the piezo, if you touch it with your finger the circuit is sensitive enough to be triggered by the capacitance of your body.

Idris

The signal showing on the oscillioscope is straight from the 27mm drilled pieco disc glued down to my hotend mount (not connected to the board).

Ground probe is on negative terminal on the piezo disc. I didn't do any measurement on the circuit board yet other than with a multimeter to confirm resistance on the pot.

VR1 resistance is measured from center pin to negative on the probe connectors like the attached picture.



And this is how the mount/sensor looks like




As you can see the piezo disc is glued in with epoxy so I can't really take it out to test it again. I was planning on ordering more discs so I could fit one that was not drilled to the mount but now it looks like something is blown I have turned the VR1 pot around so it has had low resitance at one point. Could I have burned something?

I'll leave Idris to chime in on the electronics front, but mechanically I wonder if the disc might be a bit glued to death? I put two drops of super glue on mine one at the "front" of the mount and one at the "back", this encourages the disc to bend. Might be worth a try if no electronic solution works.

A 1v signal will work, a 100mV signal will work, the circuit is a differentiator so its looking for the rising edge. If you want the 10+V you need to strike the piezo with a tool hard.

Edited 1 time(s). Last edit at 08/18/2017 06:56AM by DjDemonD.

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Simon Khoury

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

NEW STOCK AVAILABLE

So we have Piezo kits and Piezo Kit PCB's in stock on the site now.

[www.precisionpiezo.co.uk]

We have PCB's arriving today from our new supplier for the ready made module, so should be able to get some of those on the site early-mid next week.

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Simon Khoury

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

Then it sounds like the sensor is working properly. Thanks for the mounting suggestions tho, will do it like that for my next one. When you said this I'm almost 100% sure I either broke a IC or have the pots wrong adjusted. I set the VR1 to 400kOhm now and VR2 I moved until light came on and slightly back. No chance of getting a trigger this way anymore. It triggered by my fan earlier so something is off.

Realistically you're probably going to have to wait for more piezo disks to find out exactly what's going on. However its very unlikely that you've broken the IC. The most likely problem is with your mount and/or how you've glued the disk into it. As DjDemonD says you don't need much glue.

This circuit doesn't work on voltage directly, rather its how fast the voltage changes that matters. I wouldn't be looking at the voltage coming out of the piezo at all, particularly not when it isn't connected to the board, the reading you will get direct from the piezo is very different to that it will do when it's connected to the board.

One last thing to try would be to connect the piezo to the board and tap directly on the piezo with a hard object, see whether you get a trigger from that.

Idris

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

But I got a blue led when blowing hard at the mount before I started fiddling with the pot meters. Now I can't get it no matter how hard I hit on it. I will order more piezo discs but it would surprise me if it was the disc tbh since the only thing I did between it working and not working was adjusting the pots. Is there any measurement I can do on the circuit board to confirm that the disc is ok? I can measure the disc when it's hooked up also.

First thing to check would be that the centre wire is still connected to the piezo, that solder joint in particularly delicate. If you've bent the disk too far you may have cracked the ceramic or broken it off the brass, that would show up as faint lines on the silver surface. Other than that there's really very little that can go wrong with the disk itself. Check for continuity between the connector and the piezo (brass backing to connector black, silver centre to connector red).

Idris

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

Quote
Moriquendi
First thing to check would be that the centre wire is still connected to the piezo, that solder joint in particularly delicate. If you've bent the disk too far you may have cracked the ceramic or broken it off the brass, that would show up as faint lines on the silver surface. Other than that there's really very little that can go wrong with the disk itself. Check for continuity between the connector and the piezo (brass backing to connector black, silver centre to connector red).

Idris

This sounds like something I can measure? What values should i expect on the input? The wire must be connected because I measured 2volts when moving it. I also added epoxy to the wires to secure them.

I've looked at the images on a PC not a phone, and I really think it's too much glue, test the piezo pcb board with another piezo disc loose, if a gentle tap triggers it then the pcb is working. Print another bracket and bond in another piezo disc with minimal adhesive on the underside only, that way the disc can bend when the bracket moves, we're only talking 0.1mm so thick adhesive will prevent that movement and make it have poor sensitivity.

Ill update thingiverse regarding the bonding.

Come to think of it I have a piezo film sensor to play with might work great in this application.

Edited 1 time(s). Last edit at 08/18/2017 11:36AM by DjDemonD.

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Simon Khoury

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

Yes I will def put less glue on it next time after you told me, but why do it work, I adjust the pots and boom not working anymore and not possible to adjust back?

I actually sent my m8 a video of the sensor triggering when I blew on it like it was a candle that's how sensitive it was. Next minute it won't trigger when I'm banging it with a sledgehammer (figure of speech..) Could be I bent/broke the sensor during a crash in the buildplate ofc but all this sounds like things that should be possible to quantify on a oscilloscope?

Can I use a speaker/buzzer from a toy to test it or else I have to wait a week for parts. I would just like to know if the pcb is blown in case I have to order that as well or if it's just the piezo. If I just order piezo now and get them in a week and realize it's the card then it's one week+ before I get the card so that's why it would be nice to find out what's broken by measuring.

Edited 1 time(s). Last edit at 08/18/2017 12:38PM by minim.

If you want I will send you a spare board to see if its the board, if it is send the old one back, if it isn't then either keep it and I'll invoice you or send it back.

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Simon Khoury

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

I'm trying to eliminate possibilities here, please can you measure and tell me:

The resistance between the silver top of the piezo and the PZ+ pin on the board with the piezo plugged in.

The resistance between the brass bottom of the piezo and the PZ- pin on the board with the piezo plugged in.

The resistance between the PZ+ and PZ- pin with the piezo plugged in. This value will continue to drop as you measure it, read the first value.

The resistance between the PZ- pin and the top of VR1.

The voltage between the GND pin and the top of VR2 with the board plugged in.

If you can give me these readings I may be able to work out what's going on.

Idris

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

Thanks for the help I'll try my best to provide the info you ask for.

- two first is 0.0 to 0.01ohm.
- between pz+/- is 0.62Mohm sinking like you said if I keep it on for a while.
- Pz- and top of VR1 is 0.6Mohm (tried 0.4 aswell). If I read off my instrument correctly.. I'm used to my fluke at work and this is just some old stuff I had in school years ago ^^ Se attached photo
- 0.0V. I do get 3.29V on another connection on the pot tho. Look at attached photo.

VR1 res:


VR2 measurement:


I've also added a video of the piezo element testing just the element on the oscillioscope. It's generating 2volts on a fingertap but it's not enough to illuminate the led lamp on the pcb if i connect it.

Youtube - piezo testing

Quote
DjDemonD
If you want I will send you a spare board to see if its the board, if it is send the old one back, if it isn't then either keep it and I'll invoice you or send it back.

Don't worry about it. I will order a new one if we find out that it's broken. It's me fiddling with the pots that most likely broke it if anything so I wouldn't want you to pay for my mistakes I think the shipping is more pricey then the board itself so not worth it to send back/forth If this piezo measurement works good I will mount it to my other printer also so then I need two boards. Will see what we can figure out troubleshooting and then I'll order a new one if we come to the conclusion that it's broken. Or maybe just new parts from rs components when I order new piezos.

No problem, here to help.

Your VR2 measurement is the issue. Either the pot is broken or it's set incorrectly. You should be reading roughly half of the supply voltage between GND and the top of VR2. The other voltage you mention (3.29v) is your supply voltage and doesn't really have anything to do with VR2.

Here's what I'd like you to do if you can.

Connect the black multimeter lead to GND. Connect the red multimeter lead to the metal shaft of a screwdriver. With the board powered on slowly turn VR2 all the way round using the screwdriver while you watch the voltage on the multimeter. As you turn you should see a voltage on the meter. If you don't (and you're sure the meter is connected properly) then VR2 is broken. If you do then carefully turn VR2 until the voltage reads 1.5v. Try to trigger the board again.

Idris

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

Spot on Idris! Did as you said and it was showing 0V at the beginning and adjust to 1.5V. Then it was triggering like before. I then adjusted the VR1 to 0.8Mohm and redid the VR2 with adjust until trigger and then slightly back. Seem to be working now. Will test some probing but if anything is wrong now it's my overgluing of the sensor or the mount i guess.

Thank you very much for good support guys! I had a hunch it wasn't the sensor since it came after I was fiddling with the pots I did adjust VR2 like the manual describes (adjust until led comes on and then the other way so it goes off again) but I must have been doing it the oposite end of the light trigger or smt ^^

Well I'm glad we got it fixed.

It's unfortunate that the pots don't have mechanical stops, it can be easy to lose your place. I normally put a spot of blue paint to make a pointer but it seems I missed yours, sorry.

When you come to rework your mount, here are some things to keep in mind.

Bending the piezo rather than squeezing it produces a larger signal.

Maximise rigidity between the piezo and nozzle (Cyanoacrylate, superglue, is much more rigid than epoxy)

Plan where you want the mount to flex and make it rigid everywhere else.

Always keep your finger by the power switch in case something goes wrong.

Best of luck, Idris

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

Glad it's all sorted.

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Simon Khoury

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

Thank you for the ideas and thoughts about the mount. I think you are right about the epoxy to bad I didn't think about that yesterday when I glued it in. Regarding that, when I have mounted it as I have it is made to flex the most in the middle of the piezo element. Wouldn't it then be best to glue down the whole element with CA/superglue so it's secured in the centre also and flexes along with the plastic in the mount?

I got it working very nice now with only a gentle fintertap to make it trigger but if I test it on the bed it plant the nozzle and pushes it 2-3mm upwards like in the video. Almost like the trigger signal is delayed but I think it's related to the flex in my mount. I will redesign it and order more sensors and see if I can make it work better. Sensitivity I tried adjusting as low as 300 but now it also triggers from only Z axis movement occasionally so I can't increase the sensitivity more.

[www.youtube.com]

Sounds ridiculously stupid but make sure the piezo polarity is correct, or just try flipping it and a quick retune and try again. This is my go to solution if I get sloppy "delayed" triggering.

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Simon Khoury

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

Quote
DjDemonD
Sounds ridiculously stupid but make sure the piezo polarity is correct, or just try flipping it and a quick retune and try again. This is my go to solution if I get sloppy "delayed" triggering.

You guys rock! I connected black lead to PZ+ and red to PZ- now and boom it triggers perfectly on all spots on bed and I can't even see the bed/mount moving anymore. Will do a testprint but from these tests it looks solid.

A couple of points about the polarity. As far as I have been able to discover, all genuine Murata piezos have the same polarity while no-name piezos may be completely random or a whole batch may be very closely matched and all the same polarity - but the opposite to Murata ones. Also beware that it is possible for non Murata ones to have got into the supply chains of even the most scrupulous re-sellers.

Mike

DjDemonD let me know if you want the STL or if I can upload it to thingiverse. This is for the 27mm but it's basically a "rippoff" of your design for the 20mm so I won't publish it if it's not okay with you or if you want to publish it yourself Just think that since it work it should be published for others to enjoy if they want to try out piezo sensor.

The probing looks a bit better now. Consistant result within -0.098 and -0.101 so it's just as good as the IR sensor I came from but this also works perfect on PEI sheet
[www.youtube.com]

Edited 1 time(s). Last edit at 08/18/2017 04:08PM by minim.

Hi dude, yeah publish it, its Idris's design but its out there, yours is just a variant. Chuck the link on here and I will link to it from the 20mm one. Thats one of the beauties of this system, no offsets, and its broadly tolerant of almost every material you might want to print on.

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Simon Khoury

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

I published it as a remix of the original one so the link should be in there. [www.thingiverse.com]

I was making it hard for myself adjusting those pots so wrong and not testing with polarity both ways but in the end it was all good

His All
One question regarding the V1.22 board is the qrd pin electrically the same as the led - ? I need a spare pin for the shielding. Have been following the discussion with interest. BTW, that drilled 20mm piezo that you sent Dj, I was able to sand the rough edge with P400 paper. Have not tested as yet want to see if the hole makes it less sensitive. My initial test with one piezo and shielded cable was encouraging. Will try and post the video again.
Steve

Not sure what you mean by the qrd pin?

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Simon Khoury

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

Ground grd not qrd, my bad.

I'll leave that one to Idris for a definitive answer, my multimeter reads quite high resistance between those two pins so I presume they are not the directly connected.

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Simon Khoury

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