www.megadrum.info

Completing my DIY mesh pads seems to be more challenging than I thought...
Currently, I'm facing a very strange phenomenon. I have a 56-input Megadrum built by Dmitri with a PS board. As a test, I soldered a 35mm piezo to a wire with a TRS jack. The piezo ceramic is soldered to the sleeve, and the brass to the tip. A third core of the wire is soldered to the ring, but it is not connected to anything at the other end. I loaded the "Basic" factory settings using Load ROM Kit and Load ROM Map in the Megadrum menu. I connected the jack to the Snare input. All other inputs of my Megadrum are disconnected.
My problem is that when I hit the piezo with my finger, I occasionally get rim hits in the MIDI Log of MDM. How can that be? Nothing is connected to the ring of the TRS jack.
You can see my settings below, and the green rim hit in the Log.

halifax30 wrote:A third core of the wire is soldered to the ring, but it is not connected to anything at the other end

This serves as an antenna picking up noise. Either connect it to ground or disable the input by setting it's Note to 0. This has been asked too many times, I'd better add it to FAQ.

Thanks, Dmitri. Setting the notes to 0 on the rim solved the problem.
One question, though. Why was the rimhit note produced when the pad Type was set to 'Single Piezo'? I thought in this case Megadrum thinks that the pad only has 1 piezo and ignores the signal coming in on the ring contact (be it a 'real' signal or just noise) and rimhit notes will never be produced.

It means that both inputs are handled as individual inputs.

Sorry, now I found it in the on-line documentation.
What confused me was the different terminology in the Megadrum menu (DualHead = No,Yes,3Way) and the Megadrum Manager (Type = Single Piezo, etc.). Perhaps it might worth to change the terminology in Megadrum Manager. So less rookie will ask the same question in the future.

I went one step further. I soldered a stick-piezo between the sleeve and the ring of the TRS jack. I plan to use this as my rim piezo.
I restored my settings to the ones in my first post.
The sensors are not built into any pad. The head piezo is on my desk and I'm holding the stick-piezo in my hand and I'm hitting them with my finger or fingernails.
I get only two kinds of hits in the MDM Midi log: head and 3rd zone. How can that be? Since the Type is set to Single Piezo, shouldn't I only get head and rim hits?

Show the config and the MIDI Log screenshots.

Here you are.
Just for info, the stick-piezo is this type: http://www.ebay.com/itm/221251338893.

MDM recognizes zones by note numbers. If some zones have the same Note then MDM may misidentify the zone. Besides input 5, you have set Note 37 on one of the 3rd zones, possibly on the 3rd Snare zone. Set Type to 'Dual or 3way Yamaha', check what Note is set to there and change it to 0 if you don't use 3rd zone.

This is confusing, but I guess MDM determines the zones based on the incoming MIDI data and the MIDI doesn't contain information about exactly which input and which zone was activated on Megadrum, so it cannot do any better than searching for the note number in the settings. Is that correct? Anyway, very useful info to clear up confusion.