Ultrasonic sensor

The following code outputs the distance:

  1. #define echoPin 11 // Echo Pin
  2. #define trigPin 12 // Trigger Pin
  3.  
  4. long duration, distance; // Duration used to calculate distance
  5.  
  6. void setup() {
  7.  Serial.begin (9600);
  8.  pinMode(trigPin, OUTPUT);
  9.  pinMode(echoPin, INPUT);
  10. }
  11.  
  12. void loop() {
  13.  digitalWrite(trigPin, LOW);
  14.  delayMicroseconds(2);
  15.  
  16.  digitalWrite(trigPin, HIGH);
  17.  delayMicroseconds(10);
  18.  
  19.  digitalWrite(trigPin, LOW);
  20.  duration = pulseIn(echoPin, HIGH);
  21.  
  22.  //Calculate the distance (in cm) based on the speed of sound.
  23.  distance = duration/58.2;
  24.  
  25.  Serial.println(distance);
  26.  
  27.  delay(50);
  28. }

Photoresistor controlling LED

With a photo resistor you can control something from your Arduino board depending on light intake. The following circuit shows how to connect your photo resistor to the Arduino board and read the values.

  1. int ledPin = 3;
  2. int photocellInput = 0;
  3.  
  4. void setup()  {
  5.   pinMode(ledPin, OUTPUT);
  6. }
  7.  
  8.  
  9. void loop()  {
  10.  
  11.   photocellInput = (analogRead(0)/4); // Divides input 0-1023 to resemble to 0-255
  12.  
  13.   analogWrite(ledPin, photocellInput);  
  14.   // The delay can be change to get the desired dimming effect
  15.   delay(20);                            
  16. }

Decision maker with LEDs

The following circuit and code shows an example of a decision maker made with LEDs. Pushing the button will make the LEDs flash in a random order for 1 second. Then displaying the random decision where one LED lights up for 3 seconds and then reseting.

  1. int timeShowRandom = 1000;
  2. int timeShowDecision = 3000;
  3. int timeBlink = 50;
  4. int buttonPin = 3;
  5.  
  6. int buttonPress = false;
  7. int randomNumber;
  8. int previousNo = 0;
  9. int timePassed = 0;
  10.  
  11. void setup() {    
  12.   // Set button pin
  13.   pinMode(buttonPin, INPUT);
  14.   // Set output pins  
  15.   pinMode(12, OUTPUT);
  16.   pinMode(11, OUTPUT);
  17.   pinMode(10, OUTPUT);
  18.  
  19. }
  20.  
  21. void getRandomNo() {
  22.   int rand = random(10,13);
  23.   if(rand == previousNo) {
  24.     getRandomNo();
  25.   } else {
  26.     randomNumber = rand;
  27.     previousNo = randomNumber;
  28.   }
  29. }
  30.  
  31. void loop() {
  32.   // Check if button is pressed
  33.   if(digitalRead(buttonPin) == HIGH && buttonPress == false) {
  34.      buttonPress = true;
  35.   } if(buttonPress == true && timePassed <= timeShowRandom) {
  36.     getRandomNo(); // Get random pin number
  37.     digitalWrite(randomNumber, HIGH);
  38.     delay(timeBlink);  
  39.     digitalWrite(randomNumber, LOW);
  40.     delay(timeBlink);  
  41.     timePassed = timePassed + (timeBlink * 2);
  42.   } else if(buttonPress == true) {
  43.     digitalWrite(random(10,13), HIGH); // Set random pin on
  44.     delay(timeShowDecision); // For x seconds
  45.     buttonPress = false; // Set button to be enabled again
  46.     timePassed = 0;
  47.   } else {
  48.     // Reset all output pins
  49.     digitalWrite(10, LOW);
  50.     digitalWrite(11, LOW);
  51.     digitalWrite(12, LOW);
  52.   }    
  53. }

Detect switch on digitalread

  1. const int buttonPin = 3;
  2. int buttonState = 0;    
  3.  
  4. void setup() {
  5.   Serial.begin(9600);  
  6.   pinMode(buttonPin, INPUT);    
  7. }
  8.  
  9. void loop(){
  10.   buttonState = digitalRead(buttonPin);
  11.   Serial.println(buttonState);
  12. }

Flexi force sensor

How to hook up a Flexi Force sensor with Arduino and read out the values.

  1. int fsrReading;
  2.  
  3. void setup(void) {
  4.   Serial.begin(9600);  
  5. }
  6.  
  7. void loop(void) {
  8.   fsrReading = analogRead(A0);
  9.   Serial.print("Analog reading = ");
  10.   Serial.println(fsrReading);
  11.  
  12.   delay(100);
  13. }

See example of how to use a Flexi Force sensor with Arduino.

Arduino Ethernet Shield hooked up to LED message display

This hack allows you to display messages to a standard Amplus LED Message Display from Clas Ohlsson. The display is controlled by a remote control and via a RJ14 cable plugged into the screen. Serial data is transmitted from cable to the screen. The LED Message display expects the message you pass to it to be encrypted with a check sum. With the help of Rasmus blog post I could generate this checksum in Arduino. I turned his Perl code into Arduino code that you can see below.

  1. int stringToInt(String thisString) {
  2.   String letters = " !’#$%&’()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[/]^_`abcdefghijklmnopqrstuvwxyz{|}~";
  3.  
  4.   int newstr = 32 + letters.indexOf(thisString);
  5.  
  6.   return newstr;
  7. }
  8.  
  9. String generateMessage(String inputString) {
  10.  
  11.   byte checksum = 0×74;
  12.   int i;
  13.  
  14.   for(i = 0;i < inputString.length();i++) {
  15.       String currentChar    = inputString.substring(i,i+1);
  16.       int asciiChar         = stringToInt(currentChar);
  17.       checksum = checksum ^ asciiChar;
  18.   }
  19.  
  20.    String hexStr =  String(checksum, HEX);
  21.    hexStr.toUpperCase();
  22.    
  23.    String message = "<ID00><L1><PA><FE><MA><WC><FE>" + inputString + hexStr + "<E>";
  24.    return message;
  25.    
  26. }
  27.  
  28. String myString = "My led display message here";
  29.  String mess = generateMessage(myString);
  30.   Serial.print(mess);

Download my Arduino library on Github to try this out.

Control servo motor

The servo motor can be controlled by using the servo library(Servo.h) in Arduino IDE. Plug in the control wire of the servo motor into one of the PWM pins. Attach the servo object to that pin.

  1. Servo servoMotor;
  2. servoMotor.attach(9);

To rotate the servo motor pass in a number between 0 and 180. The servo motor can only move up to 180 degrees.

  1. myservo.write(90);
  2. delay(2000);
  3. myservo.write(180);
  4. delay(2000);

Control relay with TIP120

Control Omron G5LE-1 relay that requires 12V to switch the relay on and off. The relay it self is turning a 220VAC circuit on and off.

Using a potentiometer to control LED

You can easly control the current running through your LED by adding a potentiometer as part of your circuit.

To control the LED with Arduino programming you attach the potentiometer to your analog in and let your Arduino program decide how much to dim the LED depending on the input you get from the potentiometer.

The input from analogRead returns a value between 0 and 1023. The analogWrite takes values between 0 and 255. The code below show you have to convert your analog in value to make your LED shine as bright as possible when the potentiometer is fully on.

  1. int ledPin = 3;
  2. int potentiomenterInput = 0;
  3.  
  4. void setup()  {
  5.   pinMode(ledPin, OUTPUT);
  6. }
  7.  
  8.  
  9. void loop()  {
  10.  
  11.   potentiomenterInput = (analogRead(0)/4); // Divides input 0-1023 to resemble to 0-255
  12.  
  13.   analogWrite(ledPin, potentiomenterInput);  
  14.   // The delay can be change to get the desired dimming effect
  15.   delay(20);                            
  16. }