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16-way Piezo Trigger Inputs Board

 

16-Way Piezo Trigger Inputs

   

The Piezo Trigger Inputs board consists of 16 Sample an Hold (S/H) units each consisting of an adjustable 1M ohm pre-set potentiometer resistor, which adjusts the sensitivity for the drumpad hit. Adjusting the potentiometer in a clockwise manner increases the sensitivity and adjusting the potentiometer in an anti-clockwise manner decreases the sensitivity. 

 

These potentiometers can then decide what represents a soft, medium or hard drum 'hit'. After the potentiometer the signal is fed to a BAT85 Schottky diode, where it is rectified, and then fed to the charge storage capacitor of 100 nF and parallel resistor of 1m ohm. This RC time constant is about:

   

RC = 1x 10^6  x 100 x10^-9  = 100 milliseconds. 

  

After any input 'hit' is detected the software shorts out this charge storage capacitor to prevent multiple triggers and to allow detection of fast drumming.

 

This unit can be wired directly to the MIDI 26-Way drum design, which is a 26-way MIDI drum pad system with a 16-way velocity sensitive circuit, providing a full (0-127) velocity range using piezo sensors. The drums are pre-selected to the MIDI outputs 35-50 for the piezos.

 


 

 

 

*Click to Enlarge*

 

 

 

16-Way Piezo Trigger Inputs

ITEM#: 16PIEZOTRIGGERINPUTS

PRICE:  €32.00


 

 


 

The 16-way Piezo Trigger Inputs unit utilizes:

  • 16 adjustable 1M ohm pre-set potentiometer resistors,
  • 16 BAT85 Schottky diodes,
  • 16 1M ohm resistors,
  • 16 100 nF capacitors.

 

The 16-way Piezo Trigger Inputs unit Circuits:

 

Circuit Schematic:

A circuit schematics above show the Input/Output connections for the 16-Way Piezo Trigger Input unit. The 16 Piezo input connectors are split into four 8-way connectors. Each of these 8-way connectors have 4 piezo signal and 4 piezo ground connections. The 16-way Output connector can be connected to the 16 Analogue Inputs (A0 to A15) of the Arduino Mega board. There are also a pair of Ground (GND) connections to connect the Grounds of both boards together.     

When a Piezoelectric sensor is ‘hit’ it produces a waveform similar to those shown below:

 

 


Looking at the time duration of the waveforms we can see that the peak voltage usually occurs in the first couple of milliseconds. To detect the peak value of the waveform we rectify and filter the piezo waveform to produce the waveforms shown below. Then we write a program to find the peak value. After any input 'hit' is detected the software shorts out this charge storage capacitor to prevent multiple triggers and to allow detection of fast drumming.

 

 

NOTE: Any unused analog inputs should be connected to ground (GND) otherwise they will pick up noise and produce spurious outputs.

 

             

Power Supply:

The unit does not require any power supply voltage but does require a Ground (GND) connection to any connected external board, like the Arduino Drum board.