Arduino Code:

int analogPin = 0;
int analogValue = 0;

void serialEvent(Serial myPort) {
// Get the byte
int inByte = myPort.read();
// Print it
//println(inByte);
// Set the drawing color
stroke(123,128,158);
// Draw the line
line(graphXPos,height,graphXPos,height-inByte);
// At the edge of the screen, go back to the beginning
if(graphXPos >= width) {
graphXPos = 0;
// Clear the screen
background(48,31,65);
}
else {
// Increment the horizontal position for the next reading
graphXPos++;
}
}


Arduino Code:

/*
Theremin

void loop() {
// get a sensor reading:
int sensorReading = analogRead(0);
// map the results from the sensor reading's range
// to the desired pitch range:
int pitch = map(sensorReading, 50, 800, 100, 1000);
// change the pitch:
noiseMaker.play(pitch);
}


In this lab, the diagram shows the analog input as two photocells wired in series. I’m not sure I understand the analog readings produced as a result of this. For example, when both photocells were fully exposed to light the reading was about 200. When the right photocell was covered, the value jumped to 600-800. If only the left photocell was covered, it lowered the reading to about 50. If both were covered, the value leveled out around the same 200 as when they were both fully exposed. I’m not sure I understand the circuit and why these variable resisters were producing these values.

Homemade Soil Humidity Sensor

Sensor reading when dry

Sensor reading when wet

The alert system functions by illuminating the green LED while the plant is properly watered and switches the red LED on when the plant is in need of watering (or dry). Also, when the soil is dry and the plant is watered, the system will turn the red LED off and the green LED on.

A small improvement to this system would be to have the green LED dim proportionally as the soil becomes more and more dry, then the red LED would ultimately turn on when the soil is completely dry.

A couple long-term improvements would be to (1) devise an automated watering system or (2) have the plant twitter or sms the owner’s phone to remind him/her that it needs to be watered.

void loop() {
potValue = analogRead(potPin); // read teh pot value
analogWrite(led, potValue/4); // PWM the LED with the pot value (divided by 4 to fit in a byte
Serial.println(potValue); // Print the pot value back to the debugger pane
delay(10);
}


PComp-Wk2-Lab from Steve Aquillano on Vimeo.

To begin I translated the circuit to the breadboard. Afterward I compiled and uploaded the program to the arduino microcontroller.

End result: When the switch is off, the red led is on. When the circuit is switched on, the red led turns off and the yellow led turns on.

Switch Off

Switch On

// declare variables:
int switchPin = 2; // digital input pin for a switch
int yellowLedPin = 3; // digital output pin for an LED
int redLedPin = 4; // digital output pin for an LED
int switchState = 0; // the state of the switch

void setup() {
pinMode(switchPin, INPUT); // set the switch pin to be an input
pinMode(yellowLedPin, OUTPUT); // set the yellow LED pin to be an output
pinMode(redLedPin, OUTPUT); // set the red LED pin to be an output
}

void loop() {
// read the switch input:
switchState = digitalRead(switchPin);

if (switchState == 1) {
// if the switch is closed:
digitalWrite(yellowLedPin, HIGH); // turn on the yellow LED
digitalWrite(redLedPin, LOW); // turn off the red LED
}
else {
// if the switch is open:
digitalWrite(yellowLedPin, LOW); // turn off the yellow LED
digitalWrite(redLedPin, HIGH); // turn on the red LED
}
}

PComp-Wk1-Video from Steve Aquillano on Vimeo.