When Z approaches 0, the result is free fall. The gravitational acceleration normally decreases, but moves reverses acceleration when the gadget is not in use, so if the paper cup is faced upward, the sensor shows X and Y as 0, with Z as a positive value. The accelerometer is attached horizontally on the base of the paper cup, with the Z axis facing upward. The addition of an accelerometer helps clue users as to the correct angle to hold the gadget when speaking or listening. If another form of transmission is used other than XBee, you may need to make appropriate adjustments. Using a piezo electric effect element means voice quality is not great, but in this case, simply understanding what was being said was good enough. Incidentally, normal telephone transmission uses 8-bit quantization with an approximate sampling frequency of 8kHz. To leave plenty of time, I set it to 4,000 cycles per second-a sampling frequency of 4kHz. I set the voltage split (quantization) to 8 bits in 256 steps allowing a maximum of 14,400 cycles per second.
I used XBee Series 1 for communication in the project, so I set the maximum serial speed to 115,200bps. The last thing that needs to be done is to decide the frequency for the voice and how many steps it will be divided into. Neither a special protocol nor data format are required rather, a simple format is used. The sender writes the value read in analogRead in a serial transmission, while the receiver uses analogWrite to read the value also in serial. If you have used Arduino or other GR boards, you may already have some idea of how the sketch should be made based on the above description. So, the paper cup vibration due to the piezoelectric effect generates the sound of the voice. In other word, the piezo device is deformed by voltage change. Earlier, the piezoelectric vibration was converted into voltage vibration, but you can do this the other way around as well. (4) Data received by the receiver is output as analog and converted back to voltage vibration. (3) Next, we use XBee to send data to the receiver’s GR-KURUMI. In this case, the voltage from 0V to 3.3V is divided into 256 steps and expressed as 8-bit data. (2) This voltage transformation is read by the GR-KURUMI analog port and changed into digital data. In other words, the pneumatic oscillation (the voice) is converted to an electric signal. Therefore, if you speak facing the paper cup, the vibration from your voice will be carried from the cup to the piezoelectric device, producing a wave of voltage. The additional pressure from the device will result in conversion to voltage. (1) First, just attach a piezoelectric device to the bottom of the paper cup. The basic mechanism is incredibly simple.