Posts Tagged ‘Sonar’

Arduino – Redefining the TV Remote

We use them every day, but has no one got bored of pressing buttons on a stick, it’s far too much effort pressing buttons! Surely there are better ways to control a device? After doing some work with my Nikon camera using IR to control it, I wanted to do the same with other devices. Check out the video at the bottom of this post…

However, unlike the Nikon remote, my Samsung TV remote has many many buttons so each IR sequence sent from the remote will be different. This can be a problem when you want to decode the signals, which while not impossible I am lazy, so thankfully Ken Shirriff has built a library to do just that and while its built for TV remotes you can decode an IR signal to its raw pulses using it. Essentially the library senses IR and notes each pulse and gap between pulses, Kens library saves a lot of time and its well coded – I’ll cover the basics of it in a bit.

My idea is to capture the IR sequences and then using the Arduino send them by using different inputs other than buttons. My first idea is to use my SRF05 distance sensor (You can use any distance sensor) and the premise being that different distances from the sensor send different signals to the TV. So rather than pressing a button you just wave your hand above the sensor. Of course this is slightly limited but since I only have 5 channels (yep – only 5!) so it turned out to be quite feasible.

There are drawbacks to this of course – the main one being that you can only define so many actions in the sensors dectection range. But there is plenty of range to do the basics, power, sound and channel and by constantly measuring distances we can even say the direction of movement, up to down and vice versa, can have an effect on what signal to send. For example moving your hand closer to the sensor will change the channel down.

So first of all you may want to read some of my other tutorials/projects concerning IR and the SRF-05 and Sharp IR (it should also work well).
Arduino Nikon IR Intervalometer Camera Remote
SRF-05
– contains handy wiring diagram!
Arduino and Sharp GP2Y0A02 Infrared distance sensor

(Other Arduino projects and tutorials)

OK, next take a look at Ken Shirrifs IR library and guide here:
http://www.arcfn.com/2009/08/multi-protocol-infrared-remote-library.html

Arduino TV Remote Components

Arduino
Breadboard
IR Diode
3pin (NPN) Phototransistor/ IR receiver (
Radio Shack 276-640 IR receiver, Panasonic PNA4602, Vishay TSOP4838 – or just get one out an old mouse)
SRF-05 (or any distance measuring device e.g. Sharp IR GP2Y0A02)
Jumper wires

Oh and stating the obvious but you’ll also need a T.V with working remote to steal the signals from – course you can use other remotes (stereos etc..)

The circuits themselves are very very easy to build, an IR LED to pin 3, a IR receiver to pin 11 and the SRF-05 I’ve plugged into pins 2 and 4. I have all of them in one breadboard and it works very well (see below).

Using Kens Arduino TV Remote Library

If you download the library and then unzip it to your Arduino/Libaries directory (older versions, I think its Arduino/hardware/libaries). The library assumes that your phototransistor/ IR receiver is on digital pin 11 and your IR diode is on digital pin 3. Typically you want a IR receiver with a 38Khz range – they seem to work best for me.

How to get our TV infrared/ remote codes

First of all use Ken’s IRrecvDump example (should be in your examples menu) load this into your Arduino and begin to capture your remotes codes. My Samsung wasn’t recognised so I used the Raw codes – there’s plenty of documentation on Ken’s site for this – it’s really simple, even I could figure it out. You need to note how many pulses etc.. it decodes in the raw signal which helpfully is outputted e.g. Raw (68):

Now we process the codes slightly and put them in an array for each one now that we have our codes and the information we need to use them – since mine are in the raw format I need to clean them up slightly ready to be put in my code – just adding commas etc…

Now we can test the remote codes to make sure you can control your TV

Now using the IRsendDemo example, altering it my case to send the raw signal, we can test the codes to make sure that we can control the T.V – just use the basic sketch to send the codes which I edited slightly just to use an array for the raw code. You can check out the library files themselves to see the functions.

/*
 * IRremote: IRsendDemo - demonstrates sending IR codes with IRsend
 * An IR LED must be connected to Arduino PWM pin 3.
 * Version 0.1 July, 2009
 * Copyright 2009 Ken Shirriff
 * http://arcfn.com
 */

#include 

IRsend irsend;

// just added my own array for the raw signal
unsigned int powerOn[68] = {4450,4500,550,1700,500,1750,500,1750,500,600,550,600,500,600,550,600,500,600,550,1700,550,1700,550,1700,500,600,550,600,500,600,550,600,500,650,500,600,550,1700,500,650,500,600,550,600,500,600,550,600,500,600,550,1700,550,600,500,1700,550,1700,550,1700,550,1700,500,1750,500,1750,500};

void setup()
{
  Serial.begin(9600);
}

void loop() {

      // altered the code just to send/test my raw code
      irsend.sendRaw(powerOn,68,38);
      delay(100);

}

Add the distance sensor

This is actually the hardest bit and it’s not that hard really I just used my previous work and adapted it and wrote a few statements concerning the detected distance. You just have to spend some time debugging and getting your values right to ensure that your commands are only sent at the right time and that it doesn’t get confused. My code is still a little buggy if you’re not used to how to move your hand but it does work well once you’re used to it.

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/*
    http://luckylarry.co.uk
    Larrys alternative TV remote - oops no buttons!
    Sends signals to TV based upon sensor readings

    Makes use of Kens Shirriffs IRremote library
    An IR LED must be connected to Arduino PWM pin 3.
    Version 0.1 July, 2009
    Copyright 2009 Ken Shirriff
    http://arcfn.com

    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program.  If not, see .
*/

#include
IRsend irsend;

const int numReadings = 5;   // set a variable for the number of readings to take
int index = 0;                // the index of the current reading
int total = 0;                // the total of all readings
int average = 0;              // the average
int oldAverage = 0;           // the old average
int echoPin = 2;              // the SRF05's echo pin
int initPin = 4;              // the SRF05's init pin
unsigned long pulseTime = 0;  // variable for reading the pulse
unsigned long distance = 0;   // variable for storing distance

// setup my arrays for each signal I want to send
unsigned int powerOn[68] = {4450,4500,550,1700,500,1750,500,1750,500,600,550,600,500,600,550,600,500,600,550,1700,550,1700,550,1700,500,600,550,600,500,600,550,600,500,650,500,600,550,1700,500,650,500,600,550,600,500,600,550,600,500,600,550,1700,550,600,500,1700,550,1700,550,1700,550,1700,500,1750,500,1750,500};
unsigned int soundUp[68] = {4450,4500,550,1700,550,1700,500,1750,500,600,550,600,500,600,550,600,500,600,550,1700,550,1700,550,1700,500,650,500,600,550,600,500,600,550,600,500,1750,500,1700,550,1700,550,600,500,600,550,600,500,600,550,600,500,600,550,600,550,600,500,1700,550,1700,550,1700,550,1700,500,1750,500};
unsigned int soundDown[68] = {4400,4550,500,1750,500,1700,550,1700,550,600,500,600,550,600,500,600,550,600,500,1750,500,1750,500,1700,550,600,500,650,500,600,550,600,500,600,550,1700,550,1700,500,600,550,1700,550,600,500,600,550,600,500,600,550,600,500,600,550,1700,550,600,500,1750,500,1750,500,1700,550,1700,550};
unsigned int channelUp[68] = {4400,4550,500,1700,550,1700,550,1700,550,600,500,600,550,600,500,600,550,600,500,1750,500,1700,550,1700,550,600,500,600,550,600,500,650,500,600,550,600,500,1700,550,600,550,600,500,1700,550,600,500,650,500,600,550,1700,500,600,550,1700,550,1700,550,600,500,1700,550,1700,550,1700,550};
unsigned int channelDown[68] = {4450,4500,500,1750,500,1750,500,1700,550,600,500,650,500,600,550,600,500,600,550,1700,500,1750,500,1750,500,600,550,600,500,600,550,600,500,600,550,600,500,650,500,600,550,600,500,1700,550,600,500,650,500,600,500,1750,500,1750,500,1750,500,1700,550,600,500,1750,500,1750,500,1700,550};

void setup() {
  // make the init pin an output:
  pinMode(initPin, OUTPUT);
  // make the echo pin an input:
  pinMode(echoPin, INPUT);
  // initialize the serial port:
  Serial.begin(9600);
}

 void loop() {

    // loop for a number of readings on the SRF-05 to get an average to smooth the results. Much like all my other examples
    for (index = 0; index<=numReadings;index++) {
      digitalWrite(initPin, LOW);
      delayMicroseconds(50);
      digitalWrite(initPin, HIGH);
      delayMicroseconds(50);
      digitalWrite(initPin, LOW);
      pulseTime = pulseIn(echoPin, HIGH);
      distance = pulseTime/58;
      total = total + distance;
      delay(10);
   }
    // store the previous reading
    oldAverage = average;
    // store the current reading
    average = total/numReadings;
    // debug to check for spikes in the sensor etc..
    Serial.println(average);

    // now the fun part...
    // if my distance is less than 5...
    if (average <= 5) {
      Serial.println("Power Off");
      // use Kens IR library to send my signal (array, number of items in array, Khz)
      irsend.sendRaw(powerOn,68,38);
      // these delays depend on how long it take my device to recognise the signal sent and to act - I don't want to send signals that aren't getting read etc..
      delay(5000);
      // otherwise if my hand is higher
    } else {
      // check to see if my hand is in the registered space above the sensor
      if (average <=20 && average >=10 && oldAverage >=10) {
        // the below statement is our sensitive the readings are so if the current and previous readings are different with a tolerance of +/- 1 we can look at the direction of movement
        if ((average != oldAverage)
        && (average+1 != oldAverage)
        && (average-1 != oldAverage)) {
          // if the current reading is higher than the previous, then my hand is moving upwards
          if (average > oldAverage) {
            Serial.println("Channel Up");
            irsend.sendRaw(channelUp,68,38);
            delay(2000);
          } else {
            // otherwise if it is below then my hand is moving downwards
            if (average < oldAverage && oldAverage <=20) {               Serial.println("Channel Down");               irsend.sendRaw(channelDown,68,38);               delay(2000);                        }                  }          // otherwise my hand must be stationary so check where it is.         } else {           // if my hand is stationary between 10 and 15 cms away from the sensor           if (average >= 10 && average <=15) {             Serial.println("Sound down");             irsend.sendRaw(soundDown,68,38);           } else {             // if my hand is a bit higher up...             if (average >= 16 && average <=20) {               Serial.println("Sound up");               irsend.sendRaw(soundUp,68,38);             }           }         }         }     }        // clear our index and total for the next reading just in case     if (index >= numReadings)  {
      index = 0;
      total = 0;
    }
}

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Arduino + Processing: Make a Radar Screen to Visualise Sensor Data from SRF-05 – Part 2: Visualising the Data

Arduino SRF 05 radar

This is where all the work is done to read an interpret the values from the servo and the sensor. If the readings are to erratic then you won’t have nice shapes. Also if you don’t allow enough time to the signals to be sent back then you’ll get false distance readings. So this code is only as good as your Arduino code and sensor setup.

Took me a few evenings to work this out to get it how I wanted, the hardest bit is the trigonometry involved which isn’t that difficult, everything else is done by loops and a few IF statements. I use the FOR loops alot because the all the elements can be displayed programmatically without having to write each rectangle, cirle and line to the screen with their own statement.

If you’re not familiar with Processing then head over to Processing.org. Processing is a tool/ IDE that lets you program and code graphics and animation, it’s free to use and pretty powerful – best part is it works hand in hand with Arduino in the same C/C++ style of code, letting us take data from Arduino and whatever’s plugged into it and then visualise it on screen, e.g. like a radar screen.

First we have to setup our variables, background and load in the serial port libraries to ensure we can read the data sent by the Arduino. We also have to include a function from the serial library called serialEvent() which listens for data being sent and allows us to read the data easily. We do some easy string work, splitting the serial port lines to get the servo position and sensor value.

Also we can setup the radar screen, drawing the text, measurements and display grid. With processing whats nearest the top of the draw() function is displayed first with everything subsequentally drawn on top of this. So our lines and text will be at the bottom of the function so it will always be visible. To draw the lines and measurements we use a FOR loop. The draw() function draws one frame, so we basically re-draw the frame 180 times – we use a couple of arrays to store the previous values to make it look continuous.

Now that we have those we can then begin to display the values on our screen. We use a FOR loop to loop through each item in our array, newValue and oldValue. These are setup to hold 181 items – 1 item per servo position with 1 extra just in case, we loop through these to constantly display the previous readings – if we were to use the servo position itself to iterate through the array then no previous data would be displayed since the servo position is always changing.

Thoughout we need to calculate the X and Y co-ordinates of each servo position and sensor distance reading. To get these values we use trigonometry using sine and cosine and converting the servo position to a radian using the sensor reading as the distance from the center from which to draw the point. To learn more about this and to save me writing it up check out this tutorial at Processing.org.

The Sketch
Below is the code used to create the radar screen, it has comments to help explain. Everything used is an in built function of the Processing language and you can find the reference for the functions that I use in the reference section on the Processing.org website. So methods such as fill(), stroke(), rect(), line() etc…

/*
luckylarry.co.uk
Radar Screen Visualisation for SRF-05
Maps out an area of what the SRF-05 sees from a top down view.
Takes and displays 2 readings, one left to right and one right to left.
Displays an average of the 2 readings
Displays motion alert if there is a large difference between the 2 values.
*/
import processing.serial.*;     // import serial library
Serial myPort;                  // declare a serial port
float x, y;                       // variable to store x and y co-ordinates for vertices
int radius = 350;               // set the radius of objects
int w = 300;                    // set an arbitary width value
int degree = 0;                 // servo position in degrees
int value = 0;                  // value from sensor
int motion = 0;                 // value to store which way the servo is panning
int[] newValue = new int[181];  // create an array to store each new sensor value for each servo position
int[] oldValue = new int[181];  // create an array to store the previous values.
PFont myFont;                   // setup fonts in Processing
int radarDist = 0;              // set value to configure Radar distance labels
int firstRun = 0;               // value to ignore triggering motion on the first 2 servo sweeps

/* create background and serial buffer */
void setup(){
  // setup the background size, colour and font.
  size(750, 450);
  background (0); // 0 = black
  myFont = createFont("verdana", 12);
  textFont(myFont);
  // setup the serial port and buffer
  myPort = new Serial(this, Serial.list()[1], 9600);
  myPort.bufferUntil('n');
}

/* draw the screen */
void draw(){
  fill(0);                              // set the following shapes to be black
  noStroke();                           // set the following shapes to have no outline
  ellipse(radius, radius, 750, 750);    // draw a circle with a width/ height = 750 with its center position (x and y) set by the radius
  rectMode(CENTER);                     // set the following rectangle to be drawn around its center
  rect(350,402,800,100);                // draw rectangle (x, y, width, height)
  if (degree >= 179) {                  // if at the far right then set motion = 1/ true we're about to go right to left
    motion = 1;                         // this changes the animation to run right to left
  }
  if (degree <= 1) {                    // if servo at 0 degrees then we're about to go left to right
    motion = 0;                         // this sets the animation to run left to right
  }
  /* setup the radar sweep */
  /*
  We use trigonmetry to create points around a circle.
  So the radius plus the cosine of the servo position converted to radians
  Since radians 0 start at 90 degrees we add 180 to make it start from the left
  Adding +1 (i) each time through the loops to move 1 degree matching the one degree of servo movement
  cos is for the x left to right value and sin calculates the y value
  since its a circle we plot our lines and vertices around the start point for everything will always be the center.
  */
  strokeWeight(7);                      // set the thickness of the lines
  if (motion == 0) {                    // if going left to right
    for (int i = 0; i <= 20; i++) {     // draw 20 lines with fading colour each 1 degree further round than the last
      stroke(0, (10*i), 0);             // set the stroke colour (Red, Green, Blue) base it on the the value of i
      line(radius, radius, radius + cos(radians(degree+(180+i)))*w, radius + sin(radians(degree+(180+i)))*w); // line(start x, start y, end x, end y)
    }
  } else {                              // if going right to left
    for (int i = 20; i >= 0; i--) {     // draw 20 lines with fading colour
      stroke(0,200-(10*i), 0);          // using standard RGB values, each between 0 and 255
      line(radius, radius, radius + cos(radians(degree+(180+i)))*w, radius + sin(radians(degree+(180+i)))*w);
    }
  }
  /* Setup the shapes made from the sensor values */
  noStroke();                           // no outline
  /* first sweep */
  fill(0,50,0);                         // set the fill colour of the shape (Red, Green, Blue)
  beginShape();                         // start drawing shape
    for (int i = 0; i < 180; i++) {     // for each degree in the array
      x = radius + cos(radians((180+i)))*((oldValue[i])); // create x coordinate
      y = radius + sin(radians((180+i)))*((oldValue[i])); // create y coordinate
      vertex(x, y);                     // plot vertices
    }
  endShape();                           // end shape
  /* second sweep */
  fill(0,110,0);
  beginShape();
    for (int i = 0; i < 180; i++) {
      x = radius + cos(radians((180+i)))*(newValue[i]);
      y = radius + sin(radians((180+i)))*(newValue[i]);
      vertex(x, y);
    }
  endShape();
  /* average */
  fill(0,170,0);
  beginShape();
    for (int i = 0; i < 180; i++) {
      x = radius + cos(radians((180+i)))*((newValue[i]+oldValue[i])/2); // create average
      y = radius + sin(radians((180+i)))*((newValue[i]+oldValue[i])/2);
      vertex(x, y);
    }
  endShape();
  /* if after first 2 sweeps, highlight motion with red circle*/
  if (firstRun >= 360) {
    stroke(150,0,0);
    strokeWeight(1);
    noFill();
      for (int i = 0; i < 180; i++) {
        if (oldValue[i] - newValue[i] > 35 || newValue[i] - oldValue[i] > 35) {
          x = radius + cos(radians((180+i)))*(newValue[i]);
          y = radius + sin(radians((180+i)))*(newValue[i]);
          ellipse(x, y, 10, 10);
        }
      }
  }
  /* set the radar distance rings and out put their values, 50, 100, 150 etc.. */
  for (int i = 0; i <=6; i++){
    noFill();
    strokeWeight(1);
    stroke(0, 255-(30*i), 0);
    ellipse(radius, radius, (100*i), (100*i));
    fill(0, 100, 0);
    noStroke();
    text(Integer.toString(radarDist+50), 380, (305-radarDist), 50, 50);
    radarDist+=50;
  }
  radarDist = 0;
  /* draw the grid lines on the radar every 30 degrees and write their values 180, 210, 240 etc.. */
  for (int i = 0; i <= 6; i++) {
    strokeWeight(1);
    stroke(0, 55, 0);
    line(radius, radius, radius + cos(radians(180+(30*i)))*w, radius + sin(radians(180+(30*i)))*w);
    fill(0, 55, 0);
    noStroke();
    if (180+(30*i) >= 300) {
      text(Integer.toString(180+(30*i)), (radius+10) + cos(radians(180+(30*i)))*(w+10), (radius+10) + sin(radians(180+(30*i)))*(w+10), 25,50);
    } else {
      text(Integer.toString(180+(30*i)), radius + cos(radians(180+(30*i)))*w, radius + sin(radians(180+(30*i)))*w, 60,40);
    }
  }
  /* Write information text and values. */
  noStroke();
  fill(0);
  rect(350,402,800,100);
  fill(0, 100, 0);
  text("Degrees: "+Integer.toString(degree), 100, 380, 100, 50);         // use Integet.toString to convert numeric to string as text() only outputs strings
  text("Distance: "+Integer.toString(value), 100, 400, 100, 50);         // text(string, x, y, width, height)
  text("Radar screen code at luckylarry.co.uk", 540, 380, 250, 50);
  fill(0);
  rect(70,60,150,100);
  fill(0, 100, 0);
  text("Screen Key:", 100, 50, 150, 50);
  fill(0,50,0);
  rect(30,53,10,10);
  text("First sweep", 115, 70, 150, 50);
  fill(0,110,0);
  rect(30,73,10,10);
  text("Second sweep", 115, 90, 150, 50);
  fill(0,170,0);
  rect(30,93,10,10);
  text("Average", 115, 110, 150, 50);
  noFill();
  stroke(150,0,0);
  strokeWeight(1);
  ellipse(29, 113, 10, 10);
  fill(150,0,0);
  text("Motion", 115, 130, 150, 50);
}

/* get values from serial port */
void serialEvent (Serial myPort) {
  String xString = myPort.readStringUntil('n');  // read the serial port until a new line
    if (xString != null) {  // if theres data in between the new lines
        xString = trim(xString); // get rid of any whitespace just in case
        String getX = xString.substring(1, xString.indexOf("V")); // get the value of the servo position
        String getV = xString.substring(xString.indexOf("V")+1, xString.length()); // get the value of the sensor reading
        degree = Integer.parseInt(getX); // set the values to variables
        value = Integer.parseInt(getV);
        oldValue[degree] = newValue[degree]; // store the values in the arrays.
        newValue[degree] = value;
        /* sets a counter to allow for the first 2 sweeps of the servo */
        firstRun++;
        if (firstRun > 360) {
          firstRun = 360; // keep the value at 360
        }
  }
}

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The end result
Here’s a video below of it all working! There is an issue to bare in mind with the SRF-05 and thats that it works best as a static range finder, it emits a conical wave which will bounce back off of anything small or large and has a wide detection field of vision so it may pick up something that’s not directly in front of it. As you can see by the below image the detection range is so wide that it doesn’t truly see all the gaps as its detected something else in its field of vision.

sonar-topdown

If there are less objects it works fine… time to look at other sensors I think – anyway here’s the video below just showing it working on my screen.

Part 1: Setting up the Circuit and Outputting Values
Part 3: Visualising the Data from Sharp Infrared Range Finder

Arduino + Processing – Make a Radar Screen to Visualise Sensor Data from SRF-05 – Part 1: Setting up the Circuit and Outputting Values

arduino servo SRF05

First things first, we need to build our circuit. This is the easy bit! We’ll be using the Arduino to control a servo that will rotate our sensor around 180 degrees. The Arduino will then send the value from the distance sensor along with the current angle of the servo to the serial port.

Before proceeding please take a moment to check out some of my other work with the SRF-05 and servos if you’re unfamiliar with either.
Arduino SRF-05 Tutorials
Arduino Servo Tutorials

I’m building this with the SRF-05 ultrasonic range finder/ distance sensor, but because this has a fairly wide field of detection it’s not very precise – I think I’ll end up trying a different range finder maybe an IR one as the SRF-05 works best as a static sensor/ detector, anyway…

Arduino Radar Parts list

SRF05 Ultrasonic range finder
Arduino Deumilanove w/ ATMEGA328
Breadboard / Prototyping board
Jumper/ Connector wires
1x Servo (has to need no more than 5v supply)
You’ll also need some way to mount the sensor to the servo.

Arduino Radar Servo Circuit

Straight forward, we have the Arduino providing power to the breadboard and we have the servo and the SRF-05 sharing this power. Then we have the servo output pin going to Arduino digital pin 9 and the SRF-05 pins going to digital pin 2 and 3. You’ll notice that in my pictures I have 2 servos – I’m just using the bottom one of the pair to rotate the sensor round. On your servo you’ll need to figure out a way to mount the sensor on to the servo wheel – I used a lot of blu-tac! You’ll also see I’ve mounted my sensor vertically so that the when the servo moves there’ll be less interference with recieving values – placing the sensor horisontally seemed to give differences of up to and sometimes over 5cm between the first and second readings.

My servos do tend to move a bit so I’ve used more blu-tak/ modelling clay to hold them down and in place – if the servos move other than the way they’re meant to then it means dodgy readings.

SRF05 pin layout
arduino-servo-SRF05
Simple rig to rotate sensor 180 degrees

Arduino SRF05 Radar Sketch

The hardest bit – rotate the servo from left to right, then right to left and for every degree of movement take a series of readings and send them to the serial port. We’ll want to produce an average reading value for consistancy. Unfortunately with this ultrasound sensor we have to be quite slow to make sure we’re getting accurate values and we have to allow time for the signal to come back each time and register in order to produce the average value.

We do the rotation using a for loop to count to 180 and for each iteration we move the servo by +1 or -1 depending on which way we’re going – if you’ve hacked your servos then you can do a full 360 loop. During this loop we do another FOR loop to count to 10/ numReadings and for each iteration we add the distance measured to the total and after 10 readings we get our average by dividing the total by the number of readings. Then reset the total and the counter to start again for the next servo position. Finally before finishing the  the FOR loop for the servo we output the servo position and average reading to the serial port each with a preceeding character for us to later use to identify the values when reading the serial port in Processing. The last line is using println which will start a new line for the next set of values – each reading has its own line in the serial buffer makign it much easier to get our values back out.

/*
luckylarry.co.uk
Radar Screen Visualisation for SRF-05
Sends sensor readings for every degree moved by the servo
values sent to serial port to be picked up by Processing
*/
#include             // include the standard servo library
Servo leftRightServo;         // set a variable to map the servo
int leftRightPos = 0;         // set a variable to store the servo position
const int numReadings = 10;   // set a variable for the number of readings to take
int index = 0;                // the index of the current reading
int total = 0;                // the total of all readings
int average = 0;              // the average
int echoPin = 2;              // the SRF05's echo pin
int initPin = 3;              // the SRF05's init pin
unsigned long pulseTime = 0;  // variable for reading the pulse
unsigned long distance = 0;   // variable for storing distance

/* setup the pins, servo and serial port */
void setup() {
  leftRightServo.attach(9);
  // make the init pin an output:
  pinMode(initPin, OUTPUT);
  // make the echo pin an input:
  pinMode(echoPin, INPUT);
  // initialize the serial port:
  Serial.begin(9600);
} 

/* begin rotating the servo and getting sensor values */
void loop() {
  for(leftRightPos = 0; leftRightPos < 180; leftRightPos++) {  // going left to right.
    leftRightServo.write(leftRightPos);
      for (index = 0; index<=numReadings;index++) {            // take x number of readings from the sensor and average them
        digitalWrite(initPin, LOW);
        delayMicroseconds(50);
        digitalWrite(initPin, HIGH);                           // send signal
        delayMicroseconds(50);                                 // wait 50 microseconds for it to return
        digitalWrite(initPin, LOW);                            // close signal
        pulseTime = pulseIn(echoPin, HIGH);                    // calculate time for signal to return
        distance = pulseTime/58;                               // convert to centimetres
        total = total + distance;                              // update total
        delay(10);
      }
    average = total/numReadings;                               // create average reading

    if (index >= numReadings)  {                               // reset the counts when at the last item of the array
      index = 0;
      total = 0;
    }
    Serial.print("X");                                         // print leading X to mark the following value as degrees
    Serial.print(leftRightPos);                                // current servo position
    Serial.print("V");                                         // preceeding character to separate values
    Serial.println(average);                                   // average of sensor readings
  }
  /*
  start going right to left after we got to 180 degrees
  same code as above
  */
  for(leftRightPos = 180; leftRightPos > 0; leftRightPos--) {  // going right to left
    leftRightServo.write(leftRightPos);
    for (index = 0; index<=numReadings;index++) {
      digitalWrite(initPin, LOW);
      delayMicroseconds(50);
      digitalWrite(initPin, HIGH);
      delayMicroseconds(50);
      digitalWrite(initPin, LOW);
      pulseTime = pulseIn(echoPin, HIGH);
      distance = pulseTime/58;
      total = total + distance;
      delay(10);
    }
    average = total/numReadings;
    if (index >= numReadings)  {
      index = 0;
      total = 0;
    }
    Serial.print("X");
    Serial.print(leftRightPos);
    Serial.print("V");
    Serial.println(average);
   }
}

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Part 2: Visualising the Data
Part 3: Visualising the Data from Sharp Infrared Range Finder

Arduino – Sonic range finder with SRF05

SRF05

A guide to using the SRF05 Distance Sensor with Arduino in order to calculate distances from objects. In this case I’m also altering the output of an LED with PWM according to how close an object is to the sensor. So the nearer you are the brighter the LED.

So if we start with the SRF05, it’s an IC that works by sending an ultrasound pulse at around 40Khz. It then waits and listens for the pulse to echo back, calculating the time taken in microseconds (1 microsecond = 1.0 × 10-6 seconds). You can trigger a pulse as fast as 20 times a second and it can determine objects up to 3 metres away and as near as 3cm. It needs a 5V power supply to run.

Adding the SRF05 to the Arduino is very easy, only 4 pins to worry about. Power, Ground, Trigger and Echo. Since it needs 5V and Arduino provides 5V I’m obviously going to use this to power it. Below is a diagram of my SRF05, showing the pins. There are 2 sets of 5 pins, 1 set you can use, the other is for programming the PIC chip so don’t touch them!

SRF05 pin layout

SRF05 Arduino Components

220 Ohm resistor (Red, Red, Brown, Gold)
SRF05 Ultrasonic range finder
LED
Arduino Deumilanove w/ ATMEGA328
Breadboard / Prototyping board
Jumper/ Connector wires
Optional 9V DC power supply or use the USB power for the Arduino

Arduino SRF05 Circuit

Very, very simple circuit, I’ve used the breadboard to share the GND connection and to add the LED which I could probably have done with out the breadboard. You’ll see the most complex thing is the code later on.

Arduino-SRF05

SRF05 Arduino Distance Sensor sketch

All the work is done here, I’ve added code that averages the distance readings to remove some of the jitter in the results as the SRF05 is calculating distances very rapidly and there can be a lot of fluctuation. Also I convert the time in microseconds to distance by dividing the time by 58.

Why 58? Well because if you take the time in microseconds for a pulse to be sent and received e.g. for 1 meter it takes about 5764 microseconds – at least from my wall anyway. If I divide this time by the distance in cm in I will get 57.64 so I just round this up – you can calculate distance in any other unit with this method.

Here I’ve also decided that for every cm under 255 my LED will get 1 step brighter. I’ve been lazy here for the sake of the sensors 3 metre range I didn’t see the point in making this any more complicated. Otherwise I would calculate the brightness on the percentile of proximity out of total range.

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// written at: luckylarry.co.uk
// variables to take x number of readings and then average them
// to remove the jitter/noise from the SRF05 sonar readings

const int numOfReadings = 10;                   // number of readings to take/ items in the array
int readings[numOfReadings];                    // stores the distance readings in an array
int arrayIndex = 0;                             // arrayIndex of the current item in the array
int total = 0;                                  // stores the cumlative total
int averageDistance = 0;                        // stores the average value

// setup pins and variables for SRF05 sonar device

int echoPin = 2;                                // SRF05 echo pin (digital 2)
int initPin = 3;                                // SRF05 trigger pin (digital 3)
unsigned long pulseTime = 0;                    // stores the pulse in Micro Seconds
unsigned long distance = 0;                     // variable for storing the distance (cm)

// setup pins/values for LED

int redLEDPin = 9;                              // Red LED, connected to digital PWM pin 9
int redLEDValue = 0;                            // stores the value of brightness for the LED (0 = fully off, 255 = fully on)

//setup

void setup() {

  pinMode(redLEDPin, OUTPUT);                   // sets pin 9 as output
  pinMode(initPin, OUTPUT);                     // set init pin 3 as output
  pinMode(echoPin, INPUT);                      // set echo pin 2 as input

  // create array loop to iterate over every item in the array

  for (int thisReading = 0; thisReading < numOfReadings; thisReading++) {
readings[thisReading] = 0;
 }
// initialize the serial port, lets you view the
 // distances being pinged if connected to computer
     Serial.begin(9600);
 } 

// execute
void loop() {
digitalWrite(initPin, HIGH);                    // send 10 microsecond pulse
delayMicroseconds(10);                  // wait 10 microseconds before turning off
digitalWrite(initPin, LOW);                     // stop sending the pulse
pulseTime = pulseIn(echoPin, HIGH);             // Look for a return pulse, it should be high as the pulse goes low-high-low
distance = pulseTime/58;                        // Distance = pulse time / 58 to convert to cm.
 total= total - readings[arrayIndex];           // subtract the last distance
readings[arrayIndex] = distance;                // add distance reading to array
total= total + readings[arrayIndex];            // add the reading to the total
arrayIndex = arrayIndex + 1;                    // go to the next item in the array
// At the end of the array (10 items) then start again
if (arrayIndex >= numOfReadings)  {
    arrayIndex = 0;
  }

  averageDistance = total / numOfReadings;      // calculate the average distance

  // if the distance is less than 255cm then change the brightness of the LED

  if (averageDistance < 255) {
    redLEDValue = 255 - averageDistance;        // this means the smaller the distance the brighterthe LED.
  }

  analogWrite(redLEDPin, redLEDValue);          // Write current value to LED pins
  Serial.println(averageDistance, DEC);         // print out the average distance to the debugger
  delay(100);                                   // wait 100 milli seconds before looping again

}

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Well this is going to make the sensor for a robot methinks. I'll alter this to control a servo so turn left or right when blocked, or perhaps to alter the speed of the motors. Or maybe I'll just give myself bat like senses, maybe even fight crime! Anyway below is the quick video of it in action: