Add a section with supporting information for each project

Theremin using ultrasonic sensor and passive buzzer. First create a function to play a specific frequency. The frequency determine the pitch of a note, which is measured in Hz. The inverse of Hz is period (Hz=1/T). The period is the number of cycles or oscillations per second. To get the buzzer to play a specific note, the buzzer must oscillate at the given frequency for a note. Since you can't directly control the frequency of the buzzer, you have to simply alternate between HIGH and LOW states every “period length” of time, which will cause a vibration of the correct frequency. However, we instead use the “half period.” This is because the period in real life refers to the time it takes to complete one complete cycle, whereas the “HIGH and LOW” states for the buzzer only last for half of each period.

Foe the ultrasonic sensor, the TRIG pin receives an input form the gpio pin, which triggers an ultrasonic pulse to be sent, which is then bounced back and detected by the echo pin. The trick is to use the speed of sound in air (in cm/microsecond) to determine the time that the sound signal is sent and the time that the signal is received back to determine the distance of an object from the sensor.

The final part is bringing everything together, which includes mapping specific frequencies to distances form the sensor. Since we already have the functions for the distance and frequency, the mapping is very straightforward. It just involves using basic algebra using the variable “distance” to map the lowest frequency to the minimum distance, and the highest frequency to the maximum distance.

Ultrasonic Sensor: An ultrasonic sensor measures distance by emitting ultrasonic waves from the sensor head, which are then reflected back toward the sensor to be detected. The sensor determines the distance by measuring the time it takes for an emitted ultrasonic wave to be returned to the sensor. The sensor has 4 legs which are labeled GND, TRIG, ECHO, and VCC. The VCC pin receives the power from the 5V pin. The TRIG pin is responsible for controlling the generation of ultrasonic waves. The ECHO pin is responsible detecting the ultrasonic waves being sent back.

Passive Buzzer: Uses the frequency of an AC input to create an oscillating electric field. The oscillating electric field then causes a thin, inner diaphragm to vibrate, which creates sound waves. Higher frequencies cause a faster vibration and a higher pitch. A lower frequency corresponds to a lower pitch.

Joystick: The joystick is a component that computes the position of its handle relative to its base as values of x, y and z on a 3-dimensional plane. Like on a 3-dimensional graph, the y-axis correlates to forward and backwards and the x-axis correlates to right and left, while pressing the handle down like a button adjusts the calculations along the z-axis. The five pins positioned to the left of the joystick are, from top to bottom: ground, (+)5 voltage power, x-variable, y-variable, and GPIO Pin input. The x and y-variable pins are connected to an analog-to-digital converter (ADC) device used to help process the information regarding the position of the joystick controller to the computer.

Passive Buzzer: Using the diagram and code from GitHub's Tutorial C, wire up the passive buzzer along with a transistor, and a button (as seen in the diagram). Copy and paste the code into a your wus1.c file (don't forget to remove the old code before pasting). Change the “void main” to “int main”, otherwise you will get a warning (Note: you can still run the program with the “void main”, however, you will get a warning when you run the “make” command). Double check the code to make sure everything copied properly and everything makes sense logically. If not, ask Matt to help explain. Once you're sure everything is correct, run your “make” command, then “./wus1”