Piezo board with 4 sensors?



  • I stumbled across the Precision Piezo, and am curious if anyone knows of a kit that can support 4 sensors? This could be a great implementation for bed leveling in my scenario, but with such a large build plate (415mm x 415mm) I fear that 3 would not register if I did a mesh in the corner without a sensor.



  • You will likely find that the build plate is too large to work properly with an under build plate sensor system. A single sensor on the printhead makes more sense if that is physically possible.



  • Further contemplation: As you have found out, the manufacturer only produces a single or 3 sensor kit and I believe there is a reason for that. A 4 point support of the bed is over constrained which generally means that one of the 4 points will not respond properly to the nozzle touching the bed.
    Hopefully somebody else will confirm my thinking.



  • I have build two new printers with underbed sensors from precision piezzo. I use 4 andromeda modules, each in a corner, and connected them in parallel. It works perfect. It is a prusa style printer with 320x320x5mm moving printbed.



  • @Fickert precision piezo has the solution for 4 sensors called "Andromeda"

    my config:

    ; ANDROMEDA ( https://www.precisionpiezo.co.uk/product-page/andromeda )
    M574 Z0 C"nil"                                   ; no Z endstop switch, free up Z endstop input
    M558 P8 C"zstop" H5 F120 T3000 R3                ; P8 unfiltered, P5 filtered, P8 is faster
    G31 P100 X0 Y0 Z0 
    M557 X-114:122 Y-106:114 P5:5                     ; define mesh grid
    M376 H10                                         ; taper compensation during 10mm
    

    Unfortunately I'm not using this, I tried but I was not satisfied with the results on my Ender5 setup. It might work with 4 but I tried to use it with only 3 as I removed one screw on my hot bed 'cause I level only using 3 screws (fourth screw allow you to warp the bed as 3 points define the plane). When using andromeda under 3 screws only the, because they are not evenly spaced the corner of the bed that's close to the 4th removed screw is not sensitive enough so for me was impossible to set the trigger that will not hit false positives on the side with sensors vs not triggering on side without sensor .. but if you use all 4 I think it will work even for 40x40cm table. You might want to contact the guy's from precise piezo and ask them directly, they are super quick to answer emails and very helpful. I do believe orion is much better solution but andromeda exist for a reason 🙂



  • @arhi I am pretty shure you connected them wrong, have a look on the polarity and try again.



  • @CaiJonas said in Piezo board with 4 sensors?:

    @arhi I am pretty shure you connected them wrong, have a look on the polarity and try again.

    Tested few times 😄 I use piezo precision since they first announced it, have a bunch of originals and 2-3 prc clones ... I even use them manually in printers where there's no option to add them (I run the "disk" under the nozzle and move "disk" manually so that nozzle presses disk to bed 😄 ). The problem here is that 225x225 bed without one screw is supported in 3 corners so the fourth corner is rather far from the rest of the bed so if you look at that bed's 5x5 mesh the issue is with 4 points in the corner without screw (and without fourth andromeda) so:

    + + + + +
    + + + + +
    . + + + +
    - - + + +
    - - . + +
    

    point with + is detected great, . sometimes have a problem - is problematic. If I increase sensitivity for - points to detect properly the points on the other side of the bed get triggered randomly, the whole thing gets too sensitive.

    I have simple disks (andromeda was not designed when I installed those) on another printer but instead of sensors being mount like on this ender5

    X       X
    
    
    
            X
    

    the screws (and sensors) are mounted just a tad differently and it makes all the difference and works awesome...

    X       X
    
    
    
        X
    

    I solved the ender with Orion (had weird issue printing their grove holder part, took me few days to print it, looks like this ABS gray spool from dasfilament is behaving differently then rest of my ABS. Dunno why is always the gray stuff that makes problems) so now have 4 andromeda's ready for next printer, maybe I put them on the E3D-MS-TC, we'll see



  • @arhi I has to add the information, that I printed out some special spacers to use under the andromeda modules. It is important to mount them stiff, in my opinion they work reliable if the round piezzo bend over an sharp edge. Have a look to the attached file. Also important is, that the screw which holds the heated bed could move freely through the pcb. Maybe this is an solution for you.

    unterlage_andromeda.stl



  • @CaiJonas that is VERY similar to what I had setup (I actually removed the andromeda sensor's from my E5 this morning 😞 so can't give you the pic of them already mounted but) .. yes the screw could go freely trough the pcb (I actually had to drill the pcb to achieve that)

    IMG_4088_r.jpg

    this is the mockup how they were mounted, it's upside down, the black thing with 3 hole (bottom of the pic) simulates bed, then it comes the spring, then it goes trough the bed holder (hole ~1mm larger then the screw), then sits on printed part similar to your that rises the andromeda up, screw goes trough plastic, trough andromeda, there is a small shell to make contact between wheel and the andromeda even more focused and finally wheel screwed on to the screw so that andromeda is on the verge of bending ... and as you can see the bed map except for the removed 4th screw (this one on the picture 😄 ) all three points worked flawlesly (even better than orion) but that corner where the fourth screw is removed it was just not getting it... spent 2 weeks trying to tweak decided to give up and ordered orion, mounted orion and I'm happy with it 🙂

    but again, if one is a normal person and uses all four screws as designer intended everything will work flawlesly, I just don't want to return 4th screw back 🙂



  • I have to say I experimented a bit with this duet2eth board while I was waiting for some other parts and I never made bed leveling sensors work so easy before, I tried capacitive, inductive, bltouch v2, bltouch v3, bltouch PRC clone, optical, andromeda, orion... everything works immediately ... the andromeda thing is awesome and works like a charm if you use it as intended



  • The Precision Piezo Universal boards have all the inputs connected in parallel. So long as you get the polarity correct you can connect any number in parallel (within reason).



  • Wow, been busy at work and getting home late, forgot about my question. Glad to see everyone chiming in so quickly!

    While I was away though, I think I determined a single piezo sensor between my gantry and mgn block would make the most sense, and more simple right?

    I did not know that was what the andromeda was for! Awesome, I skipped right past it. Now I have two options to try. 🙂 Still, for meshing my bed, the piezo in the gantry would probably be the most accurate? My heat bed is a large 415mm x 415mm x 6.35mm thick aluminum plate. Would the weight begin to lessen the accuracy of the piezo's when probing the bed for a mesh?



  • Okay anyone with the universal board, do you know if it is possible to tune a piezo such that it is in a compressed state normally (Voltage is high) and then when I probe the bed the piezo is uncompressed (voltage is low) to trigger the endstop? or is it purely voltage spike that the universal board can register?



  • First you have to understand what a piezzo does. Let me try to explain. It produced "voltage" when you bend it. It doesn't matter in which direction, this only affect the polarity. Next thing is, it doesn't store the voltage when bended. In common the universal board mesured the voltage which emerge when you bend it, bend it more or in the other direction.



  • The voltage generated is proportional to how much & how fast you bend it. The Universal board processes that voltage and produces a cleaned-up active low digital o/p.



  • Noted, so it generates voltage just on the motion of compression or bending. I suppose I just need to get a few to play with. So technically having a piezo in compression, then relaxing it will still generate a voltage correct?



  • Yes. What do you have in mind?



  • @Fickert said in Piezo board with 4 sensors?:

    So technically having a piezo in compression, then relaxing it will still generate a voltage correct?

    Exactly, it reacts to a change not to pressure. For e.g. my andromeda's were tensioned when bed is normally sitting on them and when you press on the bed it actually releases the tension on the andromeda, that works exactly the same as the andromeda's were relaxed and I added tension... the disk itself produce voltage on change. You can try it yourself, get a piezo speaker from a toy, postcard, old watch/calculator, hook a simple voltmeter to the leads and play with it, press it then release it, you will see a voltage spike when you press, then while you keep the pressure voltage is gone, then you release and voltage spike is back there :). It is important if you use multiple sensors in parallel you match polarity 'cause they will cancel each other out if you reverse it.



  • @arhi This is awesome news, that means with my scenario it should work great. I thought I had a piezo buzzer from my days of ardupilot / pi building of drones but doesn't look like it. Will order some they're cheap enough.



  • @Fickert when I first saw the post by precise piezo about their system on reprap.org I was astonished how no one thought of this before 😄 and had to try immediately. I could not find a piezo disk around me so I ordered myself immediately one "music telegram" via phone. It arrived in few hours 😄 so for ~1eur I got piece of paper with some image and text + some noise generator (they call that a song) and a piezo speaker 😄 ... 10 or 100x more expensive than the price of the disk alone in a proper shop but got delivered in few hours, on my doorstep 😄

    I have a plan for one new machine (design ready in my head, should start building in summer) and I plan to use switches + piezo sensors for homing to have repeatability on power failure and "complicated tool changes", but that's some other story for some other time.

    Try the piezo sensors, you will love them. When they are properly set they work awesome. The simple disks in holders like the old version work great, the new thing precise pieze guy's made (andromeda and orion) are AWESOME


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