Ultrasonic sensor

Posted on March 29, 2014 by ellen

The following code outputs the distance:

#define echoPin 11 // Echo Pin
#define trigPin 12 // Trigger Pin
 
long duration, distance; // Duration used to calculate distance
 
void setup() {
 Serial.begin (9600);
 pinMode(trigPin, OUTPUT);
 pinMode(echoPin, INPUT);
}
 
void loop() {
 digitalWrite(trigPin, LOW); 
 delayMicroseconds(2); 
 
 digitalWrite(trigPin, HIGH);
 delayMicroseconds(10); 
 
 digitalWrite(trigPin, LOW);
 duration = pulseIn(echoPin, HIGH);
 
 //Calculate the distance (in cm) based on the speed of sound.
 distance = duration/58.2;
 
 Serial.println(distance);
 
 delay(50);
}

Decision maker with LEDs

Posted on November 25, 2012 by ellen

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.

int timeShowRandom = 1000;
int timeShowDecision = 3000;
int timeBlink = 50;
int buttonPin = 3;
 
int buttonPress = false;
int randomNumber;
int previousNo = 0;
int timePassed = 0;
 
void setup() {     
  // Set button pin
  pinMode(buttonPin, INPUT);
  // Set output pins  
  pinMode(12, OUTPUT);
  pinMode(11, OUTPUT);
  pinMode(10, OUTPUT);
 
}
 
void getRandomNo() {
  int rand = random(10,13);
  if(rand == previousNo) {
    getRandomNo();
  } else {
    randomNumber = rand;
    previousNo = randomNumber;
  }
}
 
void loop() {
  // Check if button is pressed
  if(digitalRead(buttonPin) == HIGH && buttonPress == false) { 
     buttonPress = true;
  } if(buttonPress == true && timePassed <= timeShowRandom) {
    getRandomNo(); // Get random pin number
    digitalWrite(randomNumber, HIGH);
    delay(timeBlink);  
    digitalWrite(randomNumber, LOW); 
    delay(timeBlink);  
    timePassed = timePassed + (timeBlink * 2);
  } else if(buttonPress == true) {
    digitalWrite(random(10,13), HIGH); // Set random pin on
    delay(timeShowDecision); // For x seconds
    buttonPress = false; // Set button to be enabled again 
    timePassed = 0;
  } else {
    // Reset all output pins
    digitalWrite(10, LOW);
    digitalWrite(11, LOW);
    digitalWrite(12, LOW);
  }     
}

Detect switch on digitalread

Posted on June 1, 2012 by ellen

const int buttonPin = 3; 
int buttonState = 0;    
 
void setup() {
  Serial.begin(9600);   
  pinMode(buttonPin, INPUT);     
}
 
void loop(){
  buttonState = digitalRead(buttonPin);
  Serial.println(buttonState);
}

Flexi force sensor

Posted on May 29, 2012 by ellen

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

int fsrReading; 
 
void setup(void) {
  Serial.begin(9600);   
}
 
void loop(void) {
  fsrReading = analogRead(A0);
  Serial.print("Analog reading = ");
  Serial.println(fsrReading);
 
  delay(100);
}

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

Arduino Ethernet Shield hooked up to LED message display

Posted on January 18, 2012 by ellen

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.

int stringToInt(String thisString) {
  String letters = " !’#$%&’()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[/]^_`abcdefghijklmnopqrstuvwxyz{|}~";
  
  int newstr = 32 + letters.indexOf(thisString);
  
  return newstr;
}
 
String generateMessage(String inputString) {
  
  byte checksum = 0×74;
  int i;
  
  for(i = 0;i < inputString.length();i++) {
      String currentChar    = inputString.substring(i,i+1);
      int asciiChar         = stringToInt(currentChar);
      checksum = checksum ^ asciiChar;
  }
  
   String hexStr =  String(checksum, HEX); 
   hexStr.toUpperCase();
   
   String message = "<ID00><L1><PA><FE><MA><WC><FE>" + inputString + hexStr + "<E>";
   return message;
   
}
 
String myString = "My led display message here";
 String mess = generateMessage(myString);
  Serial.print(mess);

Download my Arduino library on Github to try this out.

Control servo motor

Posted on January 9, 2012 by ellen

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.

Servo servoMotor;
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.

myservo.write(90);
delay(2000); 
myservo.write(180);
delay(2000);

Control relay with TIP120

Posted on October 26, 2011 by ellen

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.

Transistor controls other power source

Posted on October 26, 2011 by ellen

PNP transistor

Posted on October 22, 2011 by ellen

Turn the LED on with this code:

void setup() {                
  pinMode(13, OUTPUT);     
}
 
void loop() {
  digitalWrite(13, HIGH); // Turn on LED
  delay(5000);
  digitalWrite(13, LOW); // Turn off LED
  delay(5000);       
}

DC motor

Posted on September 27, 2011 by ellen

You will need:
- DC Motor
- Power diode
- TIP 120

Turn the motor on with this code:

void setup() {                
  pinMode(8, OUTPUT);     
}
 
void loop() {
  digitalWrite(8, HIGH); // Turn on motor
  delay(5000);
  digitalWrite(8, LOW); // Turn off motor
  delay(5000);       
}