Piezo board with 4 sensors?
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@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 Xthe screws (and sensors) are mounted just a tad differently and it makes all the difference and works awesome...
X X XI 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
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@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.
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@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)
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
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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
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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).
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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?
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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.
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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.
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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?
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Yes. What do you have in mind?
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@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.
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@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.
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@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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@arhi Even if this thread is quite old now: thanks for the information you provided! I found this thread since I just bought some of the Andromeda piezo sensors and wanted to know if it is okay to mount them under constant strain - which you obviously did.
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@arhi Maybe as a remark to the setup with the missing fourth screw that did not work for you: if I am not mistaken, these sensors produce a negative signal if they are pulled instead of pushed. That might have been the case in your setup - when you press onto the fourth corner without the screw, you have quite exactly a 1:1 lever arm with its bearing axis running diagonally over the print bed. Thus and assuming the electronics senses both positive and negative signals, in theory the two sensors located on the diagonal axis each see the force +F, while the third one located on the opposite side sees force -F - which means the signals of two of the three sensors cancel out each other. If you can provide that sensor with an additional circuitry that short-circuits the sensor for negative signals, this might well work as well..
(edited to remove stupid logic error..)
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@NeoDue said in Piezo board with 4 sensors?:
in theory the two sensors located on the diagonal axis each see the force +F, while the third one located on the opposite side sees force -F - which means the signals of two of the three sensors cancel out each other
In theory that would be possible. In practice, my 4 channel 1GHz scope say that they are all polarized properly and that signal amplitude in that corner is "pathetic"
I moved to the sensor in the head as the sensor in the table was just not repeatable enough and on the printer that I'm using most these days, I'll be removing piezo completely next time I'm changing the nozzle. Orion in analog mode works decent but it is PITA to setup. Every time I do anything with my hotend it takes me hours to set Orion to work, I had it, next time I'm changing the nozzle I'm removing the Orion from the head and mounting back the bltouch. On other printers, it works nice, but here it's just too pita
...Don't get me wrong, I still love piezo style but something on this printer just don't sit properly, orion either does not trigger at all (probably everything is too stiff) or it triggers ok but print quality is 5#$^@$#%@ because the hotend wobbles
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@arhi Hm. I guess the Orion Sensor is a bit of a pain depending on the geometry of the print head, yes, but I am puzzled about what you say about the Andromeda's... sounds to me like the bed screws maybe got stuck in their guidance due to the off-centered push or something. Force needs to go somewhere
Let's see how the Andromeda sensors will work for my printer and if the "constant spring load/unload if touched" setup I chose really does what it should long-term. The only other chance to fit a decent z sensor onto my Neo without losing precious X-Y motion range would be to mount a BLTouch above the whole printhead unit and then somehow make the touching pin about 12cm longer and guide it through the whole print head... somehow I doubt that would work reliably...
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@NeoDue said in Piezo board with 4 sensors?:
@arhi sounds to me like the bed screws maybe got stuck in their guidance due to the off-centered push or something. Force needs to go somewhere
for the piezo to work you need to have a "hard contact", soft contact won't work. when you remove 4. screw in the region of the 4. screw you have soft contact and piezo does not trigger ( or trigger after moving bed 2-3mm down making it 2-3mm late and useless ) .. the force is there but the way it acts on the 3 piezo sensors is not shaped in the way that it will trigger the andromeda.
Let's see how the Andromeda sensors will work for my printer and if the "constant spring load/unload if touched" setup I chose really does what it should long-term.
I think it should work without a problem. The issues I have with piezo are "instant", once I make them work, they work awesome till next time I remove something, then again they instantly don't work and I need to spend time to make them...
second part of the problem is probing speed with duet where duet is (was, this is changed now in latest beta according to release notes, did not try yet) slowing probing down in analog mode thinking that head is close to the bed and this does not play well with piezo as it creates "soft contact" .. latest beta moves at appropriate speeds so this should be fixed now..
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btw, one additional piece of info, when I replaced the regular wire going from piezo analog output to duet with coax cable (I used some balanced microphone cable) the quality of the signal improved 10000000000x and it was much much much easier to setup and use
