Piezo polarity - What is right?

[mprinz]

Hi,

I got trapped by this article:

https://www.r-drums.com/english/manuals ... m-trigger/

Remember: red = positive and black = negative is not always correct!

Therefore, R-drums measures the polarity of all their 27mm piezos (this only works with an oscilloscope) and the connection to the negative polarity is provided with a white mark (valid for conventional use > piezoceramic layer above, mechanical shock pulse from the top toward the piezoceramic).

Together with this wiring diagram

https://www.r-drums.com/english/manuals ... igger-set/

image.jpg (137.6 KiB) Viewed 1600 times

I measured the piezo without cone tapping on the top with the ceramic on top and I got a negative puls on the oscilloscopes probe.
Ok, "valid for conventional use > piezoceramic layer above, mechanical shock pulse from the top toward the piezoceramic" ...
I soldered this cable to the tip. And somehow I just got velocities far below 127. Only 72... on every strong hit, and the transients looked like
cutted off at the top end.

Then I switched the polarity and I was fine.
So, I guess, the R-Drum guys meant the negative puls of the piezo to tip when the cone is installed.
Because - you get a peak to the opposite pole with trigger cone on top than with tapping the naked piezo at the top.

I find this worth to share here.
I take a look to the eDrumIn manual once again ... hmmm ... It would have worked, if I had tried the Yamaha button?
But when I now toggle the Yamaha button the transients doesn't change.

[Rob]

On the first generation ED4, it's important to use Roland style wiring. On ED4R2 and ED10, it makes no difference. The Yamaha button doesn't affect how the signal is read from the pad, it only affects a few aspects of how the data is processed.

[Sly]

On the first generation ED4, it's important to use Roland style wiring. On ED4R2 and ED10, it makes no difference. The Yamaha button doesn't affect how the signal is read from the pad, it only affects a few aspects of how the data is processed.

From eDRUMin manual, the Roland wiring is reverse from what I know. It's known that Roland use brass on tip and ceramic on sleeve on their PS compatible pad for the head piezo.

[mprinz]

That's the point:

The only thing that matters is the polarity of the puls.
Or it did, since the new edrumin4 R2 don't care about that.
Wire colors, brass or ceramic are not relevant on piezos.

During my tests with the Jobeky snare I fooled myself ...
and it didn't work with the negative puls on the sleeve.
I got only quite limited dynamics.

[Sly]

That's the point:

The only thing that matters is the polarity of the puls.
Or it did, since the new edrumin4 R2 don't care about that.
Wire colors, brass or ceramic are not relevant on piezos.

During my tests with the Jobeky snare I fooled myself ...
and it didn't work with the negative puls on the sleeve.
I got only quite limited dynamics.

There's a fact that Roland has all their PS compatible pad with head piezo wired with brass on tip and ceramic on sleeve. Reversing the polarity make the PS to stop working on a Roland module. Roland PS is knonw to required a first negative wave to get PS to work.
Jman when he was still there had test some full batch of piezos and indeed reported that maybe 1% of the batch had a reversed polarity (meaning first positive wave when wired with brass on tip). I don't know how or if Roland test their piezo before to implement them...

[Rob]

I'm updated the wiring diagrams in the eDRUMin manual.

[Sly]

Alright Rob, and I think the yamaha is reversed too, I'm less sure but Yamaha should have brass on sleeve and ceramic on tip.

[Rob]

Ya Sly, I had the Roland and Yamaha diagrams backwards. Should be fixed now.

[mprinz]

[mprinz]

Hi Sly, hi Rob,

ok thank you, that's what I want the DIY guys to take care of.
I am a bit surprised about the 1% of reversed polarity, but in this case I would guess, the piezo companies check their discs before mounting them to the brass. Or at least... when their deliver to certain companies for certain purposes.

But ... I noticed that the polarity of the waves is different with and without mounted cone. And that was the trap that got me...