Arduino + Processing – Make a Radar Screen – Part 3: Visualising the Data from Sharp Infrared Range Finder

Arduino Sharp IR radar

So I had some luck with getting the Sharp Infrared range finder working and I’ve now plugged this on to my servo rig to see if I get better results on my radar styled display.

Check out how to use the Sharp IR range finder here

Few things to bare in mind, whilst the code is pretty much the same there are a few subtle differences. Firstly for better readings the Arduino code has a longer delay – but since we’re not allowing for a sonar ping there’s not much noticeable difference.

Next we’re expecting integer values in the processing code so when sending values to over the serial port we cast them from float to integer.

Because the IR sensor has a different range I’ve altered the display to measure only up to 150cm. And becasue of this range limitation, if there is any value recorded outside of this range then we need to handle it to avoid seeing spikes and the same for any value under 20cm we need to also handle this.

To make the display more readable I keep the same size screen and area (radius of 300) and then multiply the sensor values by 2 to magnify them a bit more.

Other than it, it’s basically the same code as before and when we look at the image comparison now between what the sensor records and what is physically there we see a far better match, in some cases it’s a little to accurate.


Arduino sketch

Radar Screen Visualisation for Sharp GP2Y0A02 IR range finder
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
float total = 0;              // the total of all readings must be a float to allow totaling of float values
int average = 0;              // the average
int IRpin = 1;                // analog pin for reading the IR sensor
/* setup the pins, servo and serial port */
void setup() { 
  // initialize the serial port:
/* begin rotating the servo and getting sensor values */
void loop() { 
  for(leftRightPos = 0; leftRightPos < 180; leftRightPos++) {  // going left to right.                                
      for (index = 0; index<=numReadings;index++) {            // take x number of readings from the sensor and average them
        float volts = analogRead(IRpin)*0.0048828125;          // value from sensor * (5/1024) - if running 3.3.volts then change 5 to 3.3
        float distance = 65*pow(volts, -1.10);                 // worked out from graph 65 = theretical distance / (1/Volts)S -
        total = total + distance;                              // update total
    average = (int) total/numReadings;                         // create average reading CAST TO INT!! remove the decimal places
    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                                
    for (index = 0; index<=numReadings;index++) {
      float volts = analogRead(IRpin)*0.0048828125;            // value from sensor * (5/1024) - if running 3.3.volts then change 5 to 3.3
      float distance = 65*pow(volts, -1.10);                   // worked out from graph 65 = theretical distance / (1/Volts)S -
      total = total + distance;
    average = (int) total/numReadings;  
    if (index >= numReadings)  {           
      index = 0;           
      total = 0;     

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Processing sketch

Radar Screen Visualisation for Sharp GP2Y0A02
Maps out an area of what the GP2Y0A02 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);
  // setup the serial port and buffer
  myPort = new Serial(this, Serial.list()[1], 9600);

/* 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]*2)); // create x coordinate
      y = radius + sin(radians((180+i)))*((oldValue[i]*2)); // create y coordinate
      vertex(x, y);                     // plot vertices
  endShape();                           // end shape
  /* second sweep */
    for (int i = 0; i < 180; i++) {
      x = radius + cos(radians((180+i)))*(newValue[i]*2);
      y = radius + sin(radians((180+i)))*(newValue[i]*2);
      vertex(x, y);
  /* average */
    for (int i = 0; i < 180; i++) {
      x = radius + cos(radians((180+i)))*(((newValue[i]+oldValue[i])/2)*2); // create average
      y = radius + sin(radians((180+i)))*(((newValue[i]+oldValue[i])/2)*2);
      vertex(x, y);
  /* if after first 2 sweeps, highlight motion with red circle*/
  if (firstRun >= 360) {
      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]*2);
          y = radius + sin(radians((180+i)))*(newValue[i]*2);
          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++){
    stroke(0, 255-(30*i), 0);
    ellipse(radius, radius, (100*i), (100*i)); 
    fill(0, 100, 0);
    text(Integer.toString(radarDist+25), 380, (305-(radarDist*2)), 50, 50); // change this to measure up to 150cm
  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++) {
    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);
    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. */
  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", 540, 380, 250, 50);
  fill(0, 100, 0); 
  text("Screen Key:", 100, 50, 150, 50);
  text("First sweep", 115, 70, 150, 50);
  text("Second sweep", 115, 90, 150, 50);
  text("Average", 115, 110, 150, 50);
  ellipse(29, 113, 10, 10); 
  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);
        If our values are outside either end of the sensors range then convert them to the max/min for a better display without the spikes
        if (value > 150) {
          value = 150; 
        if (value < 20) {
          value = 20;
    	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 */
    	if (firstRun > 360) {
    	  firstRun = 360; // keep the value at 360 

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Part 1: Setting up the Circuit and Outputting Values
Part 2: Visualising the Data


  • Hey larry,
    really nice post! I gave it a go with IR and it works brilliantly! Im trying this again but with a stepper motor for 360° rotation but I’m having problems with sending the steps over to serial.print. Do you have any idea how I could solve this?

    • Well you got another option: hack a servo for continous rotation – never done it myself but might be useful.

      Anyway, not done too much with stepper motors, so apologies if I’m wrong.

      Have a look at:

      So first create a stepper motor object – are you using a bipolar stepper? If so I can help you out with the H-bridge/ motor controller chip 🙂

      If you’ve got all that done and can control the stepper then we just need to calculate the steps per revolution the motor will have – might already be in your tech specs.

      If you’ve got that then you should be able to use the Arduino stepper motor libraries and then send number of steps over the serial port?

  • Hi,

    Came across your stuff online and loved it.

    I am an artist only beginning to use arduino

    You can see examples of my work here-

    As you can see, I have been making some basic drawing and painting
    machines and so far I have been using some very basic software that turns
    a PC into a CNC machine, communicating to a driver box and powering
    stepper motors.

    I am now keen to make the pieces more interactive and am trying to make a
    painting machine that will paint according to the movements of the viewer,
    using a web cam to monitor the viewer and an arduino micro controller to
    move the stepper motors in real time.

    I have spoken to a friend of mine who has some experience of arduino who
    was able to find some processing code that would turn movements on a web
    cam into a drawing on the computer screen-

    It needs a plugin to be added to processing, from the JMyron site

    We were thinking that we should be able to tweak this to drive some
    stepper motors, at least i hope my friend will be able to. Trouble is he
    has little experience of stepper motors. The motors I have are like the
    ones here-

    I have got the motors kind of working through the arduino, all though they move very slow. I am desperately trying to find some way of translating the processing code for JMyron into x and y coordinates to move the the stepper motors. I have an art exhibition opening next week and have 3 pieces that all rely on this working. I have bitten off more than I can chew so any help you can offer would be amazing!

    Any advice you have would be greatly appreciated.

    Thanks for your time.


    • Hey Rhys,

      Tall order! Umm… well I this wold be my logic:

      Get image from jMyron
      Map/scale the camera image to your Processing screen/document area
      Translate the position of the jMyron item to a set of shapes/quads/lines and then produce co-ordinates from these – not sure how many points of reference you want but for example a hand you could split to several items.
      Then you pass the x, y and z of each object made from the jMyron to Arduino via the serial port.

      That probably makes it sound easier than it is. How precise do the movements need to be? and what do you want to detect – I guess you want to map the movement of a hand to alter the positions of the acid sprayer?

      What I would do instead is have a look at this:

      And build a kind of touch screen that will detect a users hand/ fingerprints from infrared (can convert the webcam easy enough)

      Not quite as fluid as monitoring a users hand but probably easier to achieve (Or not).

      Sorry not much use here – not done anything like this yet.

  • Hey, tried to use your processing code and i get a host of syntax errors. im new to processing and i really don’t know how to fix the code. when i try to run i get “syntax error, maybe a right parenthesis?” on this line, if (degree >= 179) { . using linux if that matters. thanks

    • Looks like I had a site bug thats messed up a lot of my code 🙁 should be fixed now

  • Hi Larry,
    I just bought a Sharp IR sensor for my project. The Arduino code is working fine. I got the data from the serial monitor. But for the Processing, the radar screen does not move at all. I used the code that you provided. I tried to find out if I can change the serial port number in the Processing program, but I can’t find it. So, do you have any idea what is the possible problem?

  • Hey, Larry

    I’ve built an infrared range finder from an infrared led and phototransistor and I can only get up to like 20 centimeters. Which is fine for me but im trying to change the processing code to reflect this and I can’t figure out how to change the numbers on the grid to go from like 5 centimeters to 20 any help would be greatly appreciated.

    Thanks, Cody

  • Hello!

    I want to change the distance values to frequency function. (Instead of voltage)

    Somebody can help??


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