Precision Piezo troubles
I've been bashing my head into the wall for the last week trying to get anything consistent on the Precision Piezo. (4 Piezo bed mount setup)
Its really strange behavior, having my hand near the board triggers it. It seems to have no dead-band sometimes, which makes adjustments impossible as its always triggered.
Then ill think i got it working and a restart or shutdown later with nothing changed. It wont be anywhere near calibrated so i have to start over again.
It has done about 2 successful G29 cycles about 12 points, but fails to detect on random probe points.
Now i've moved it to the print head running 1 drilled piezo. I drilled it to fit between 2 bolted parts. Its not the traditional way, but in testing it worked.
Even after all that, its just not getting better. I don't see what it could be, every wire in the thing minus motor wires is sheilded . That didn't even help with anything.
I really want this thing to work =( its the last thing to get working, the Cherry on top so to speak.
How long are the cables from your piezo to the board?
Make shure that these wires are as short as possible.
You can also replase these small fiddly resistors with a nicer to adjust one like this.
Is your piezo Modul an original one or is it a clone?
Make sure you adjust your VR1 to a value of 0.4MOhm this the recommended, from there you should start to adjust VR2 until it lights then back off to where the LED goes out.
Hope this helps. Yes its a little fiddly but if its dialed in then there is nothing like it.
I found my underbed setup too sensitive with 4 piezos.
I ended up with 2 piezos as sensors and 2 piezos acting as "noise canceling" sensors (2 piezos reversed, bonded to the frame). this works really well:
you can see the 2 "microphone" piezos taped to the frame and the 2 sensing piezos fitted inside the TPU feet.
Each pair of piezos are wired together (+ connected to - and vice versa), this means that they have to be oriented in the same way. Here is a small video so you can see how it works:
As you can see, it won't trigger if I tap the surrounding frame, only tapping the bed triggers the piezo.
Without the pickup piezo's I was getting false triggers from the Z motors causing vibration to the frame.
They are maybe 2 inches now, before they were about 300mm. Changing the length had zero effect.
Its an original module V2, I have long since worn out the old pots and have replaced them with 25 turn pots.
Adding 25 turn pots did nothing as well.
For VR1 it wont go to 0.4Mohm. The only thing im able to measure is 175K to 2K ohm
I did have it bed mounted but figured it was too noisy so its been moved to the print head. I also followed your suggestion on have a second piezo to cancel the noise, I dont see any changed. Tapping anywhere on the printer its picked up
Sorry to hear you're having problems. Can you post a photo of your current piezo setup? I have a couple of things to suggest/check.
Do you have delay before probe enabled? How long?
The kind of random failure you're describing could be caused by a loose wire or poor connection.
Rather than measuring the resistance of VR1 can you measure the resistance between the solder points on the piezo while the piezo is plugged in.