IDeATe

Outcome

Working with Inputs and Sensors

In this second Skills Dev, we explored input devices and sensors and worked to combine them with if statements to produce a desired action. After working through the Lab tutorials to understand basic inputs and sensors, I created a simple 2-in 1-out device, presented with a simple use case.

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Getting Inputs: Using a Pushbutton

To introduce inputs, we explore pushbuttons, and how to use one to turn on/off an LED.

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// We will be using D2 to control our LED
int ledPin = D2;

// Our button wired to D0
int buttonPin = D3;

void setup()
{

  // For input, we define the
  // pushbutton as an input-pullup
  // this uses an internal pullup resistor
  // to manage consistent reads from the device

  pinMode( buttonPin , INPUT_PULLUP); // sets pin as input

  // We also want to use the LED

  pinMode( ledPin , OUTPUT ); // sets pin as output

}

void loop()
{
   // find out if the button is pushed
   // or not by reading from it.
   int buttonState = digitalRead( buttonPin );

  // remember that we have wired the pushbutton to
  // ground and are using a pulldown resistor
  // that means, when the button is pushed,
  // we will get a LOW signal
  // when the button is not pushed we'll get a HIGH

  // let's use that to set our LED on or off

  if( buttonState == LOW )
  {
    // turn the LED On
    digitalWrite( ledPin, HIGH);
  }else{
    // otherwise
    // turn the LED Off
    digitalWrite( ledPin, LOW);
  }
}

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Getting Inputs: Using a Switch

Next, we consider switches to turn on/off an LED. The code is the exact same as the pushbutton code.

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// We will be using D1 to control our LED
int ledPin = D2;

// Our button wired to D3
// We wire D0 to the middle terminal on the switch
// And any of the two other terminals to ground
int switchPin = D3;

void setup()
{

  // For input, we define the
  // switch as an input-pullup
  // this uses an internal pullup resistor
  // to manage consistent reads from the device

  pinMode( switchPin , INPUT_PULLUP); // sets pin as input

  // We also want to use the LED

  pinMode( ledPin , OUTPUT ); // sets pin as output

}

void loop()
{
   // find out if the button is pushed
   // or not by reading from it.
   int buttonState = digitalRead( switchPin );

  // Using a pulldown resistor we get a LOW
  // Signal when its on
  
  if( buttonState == LOW )
  {
    // turn the LED On
    digitalWrite( ledPin, HIGH);
  }else{
    // otherwise
    // turn the LED Off
    digitalWrite( ledPin, LOW);

  }


}

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Getting Inputs: Using a Potentiometer

Then, we look at potentiometers, which use analog input to control LED brightness across a range of values, rather than just on/off.

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// Define a pin that we'll place the pot on
int potPin = A5;

// Create a variable to hold the pot reading
int potReading = 0;

// Define a pin we'll place an LED on
int ledPin = D2;

// Create a variable to store the LED brightness.
int ledBrightness = 0;

//
void setup(){

  // Set up the LED for output
  pinMode(ledPin, OUTPUT);

  // Create a cloud variable of type integer
  // called 'light' mapped to photoCellReading
  Spark.variable("pot", potReading );
}

void loop() {

  // Use analogRead to read the potentiometer reading
  // This gives us a value from 0 to 4095
  potReading = analogRead(potPin);

  // Map this value into the PWM range (0-255)
  // and store as the led brightness
  ledBrightness = map(potReading, 0, 4095, 0, 255);

  // fade the LED to the desired brightness
  analogWrite(ledPin, ledBrightness);

  // wait 1/10th of a second and then loop
  delay(100);
}

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Working with Sensors: Using a Photoresistor

To understand sensors, we explore using a photoresistor (light sensor) to obtain ambient light readings and output these readings as brightness of an LED.

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// Define a pin that we'll place the photo cell on
// Remember to add a 10K Ohm pull-down resistor too.
int photoCellPin = A0;

// Create a variable to hold the light reading
int photoCellReading = 0;

// Define a pin we'll place an LED on
int ledPin = D2;

// Create a variable to store the LED brightness.
int ledBrightness = 0;

void setup()
{
  // Set up the LED for output
  pinMode(ledPin, OUTPUT);

  // Create a cloud variable of type integer
  // called 'light' mapped to photoCellReading
  Particle.variable("light", &photoCellReading, INT);

}

void loop()
{
  // Use analogRead to read the photo cell reading
  // This gives us a value from 0 to 4095
  photoCellReading = analogRead(photoCellPin);

  // Map this value into the PWM range (0-255)
  // and store as the led brightness
  ledBrightness = map(photoCellReading, 0, 4095, 0, 255);

  // fade the LED to the desired brightness
  analogWrite(ledPin, ledBrightness);

  // wait 1/10th of a second and then loop
  delay(100);
}

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Practice Exercise: Combining Sensors and Inputs

Prepare a simple 2-in (sensors or inputs) 1-out (LED) device (i.e. your project will use three components (resistors and wire don't count!) and at least one must be a sensor). Present a really simple use case for a connected sensor device (perhaps solve a simple problem in your home).

For this final exercise, I combined a Force-Sensing Resistor and a pushbutton with an LED. If the button is pressed, then the LED will light up with a brightness proportional to the force detected on the FSR. A simple (maybe not simple) use case might be if a family member wants to communicate with you through your bedroom door, they will push the button and press the FSR according to how urgently they need you for something. This urgency will translate as LED brightness, which you are able to glance at from your desk.

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// Our button wired to D4
int buttonPin = D4;

// Define a pin that we'll place the fsr on
int fsrPin = A5;

// Create a variable to hold the pot reading
int forceReading = 0;

// Define a pin we'll place an LED on
int ledPin = D2;

// Create a variable to store the LED brightness.
int ledBrightness = 0;

//
void setup(){

  pinMode( buttonPin , INPUT_PULLUP); // sets pin as input
  
  // Set up the LED for output
  pinMode(ledPin, OUTPUT);

  // Create a cloud variable of type integer
  // called 'light' mapped to photoCellReading
  Spark.variable("force", forceReading );
}

void loop() {

  // find out if the button is pushed
   // or not by reading from it.
   int buttonState = digitalRead( buttonPin );
  
  // Use analogRead to read the FSR reading
  // This gives us a value from 0 to 4095
  forceReading = analogRead(fsrPin);

  // Map this value into the PWM range (0-255)
  // and store as the led brightness
  ledBrightness = map(forceReading, 0, 4095, 0, 255);

  if( buttonState == LOW )
  {
    // fade the LED to the desired brightness
    analogWrite(ledPin, ledBrightness);
    delay(500);
  }else{
    // otherwise
    // turn the LED Off
    digitalWrite( ledPin, LOW);
  }
 
  // wait 1/10th of a second and then loop
  delay(100);
}

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Reflection & Next Steps

After going through this activity, I felt like the beginning tutorials on inputs and sensors were actually very helpful to run through and provided helpful base code to add to for future projects. I particularly enjoyed the practice exercise and the freedom/creativity it provided, since it helped me think more practically about our final project in this class.

After this activity, I will move onto Skills Dev 3. I will also use some of the things we covered (like the practice exercise) for our final project.

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Outcome

Working with Inputs and Sensors

Getting Inputs: Using a Pushbutton

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Getting Inputs: Using a Switch

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Getting Inputs: Using a Potentiometer

Then, we look at potentiometers, which use analog input to control LED brightness across a range of values, rather than just on/off.

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Working with Sensors: Using a Photoresistor

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Practice Exercise: Combining Sensors and Inputs

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Reflection & Next Steps