Ultrasonic Radar & Robot

Given almost no budget and some salvaged parts, the aim is to try and build a robot hopefully more advanced than simple avoidance.

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Ignoring the cost of the arduino UNO, I'm planning on keeping the costs below £10 (about $17).
So far i've salvaged a couple of drive motors with gearboxes and wheels already attached.

Luckily China is an excellent source for very cheap (although not amazing quality) sensors, and parts. And so far i've got a basic sonar system set up using nothing more than an ultrasonic sensor, and servo costing little more than £1.

More photos to follow, next step mounting the sonar to the wheel base.

//Rangefinder Arduino code

//Ultrasonic Rangefinder
#include <PWMServo.h>
#include <NewPing.h>

PWMServo servo1;

unsigned int duration;

long timer;

#define svomin 10
#define svomax 150
#define svodormant 80

#define lmotor 1
#define rmotor 2

#define mStop 0
#define mForward 1
#define mReverse 2
#define mLeft 3
#define mRight 4

#define lmotorf 3
#define lmotorr 2
#define rmotorf 5
#define rmotorr 4

#define trigPin 14
#define echoPin 15
#define button1 16
#define avoid 17

#define maxdistance 100

long runTime = 0;
int robotState = mStop;
int mbm = 52;
int svo = svomin;
int count = svomax - svomin;
float distance[180];
int buttonState;
int lastButtonState = LOW;
int scanState = false;
int avoidState;
int lastAvoidState = LOW;
long lastDebounceTime = 0;
long debounceDelay = 50;

NewPing sonar(trigPin, echoPin, maxdistance);

void setup() {
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  pinMode(button1, INPUT);
  pinMode(avoid, INPUT);
  pinMode(lmotorf, OUTPUT);
  pinMode(lmotorr, OUTPUT);
  pinMode(rmotorf, OUTPUT);
  pinMode(rmotorr, OUTPUT);
  svo = svodormant;
  timer = millis() + mbm;
  scanState = false;

void loop() {
  int reading = digitalRead(button1);
  avoidState = digitalRead(avoid);
  if (scanState == true) {
  if (avoidState == LOW && scanState == false && robotState == mForward) {
    scanState = true;
    svo = svomin;
  if (reading != lastButtonState) {
    lastDebounceTime = millis();
  if((millis() - lastDebounceTime) > debounceDelay) {
    if(reading != buttonState) {
      buttonState = reading;
      if(buttonState == HIGH) {
        scanState = true;
        svo = svomin;
  lastButtonState = reading;
  if(timer < millis() && scanState==true) {    
    if(svo > svomax) { 
      for(int i=0;i<=count;i++) {
        Serial.println(distance[i], DEC); 
      scanState = false;
    if(svo==svomin) { delay(1000); }
    timer = millis() + mbm;
  if (runTime < millis()) {
    motor(lmotor, mStop);
    motor(rmotor, mStop);

void getDist2() {
  duration =;
  distance[svo-svomin] = duration/US_ROUNDTRIP_CM;
  if(duration==0) { distance[svo-svomin] = maxdistance; }

void smooth() {
  int p;
  float temp;
  float mean;
  for(int i=0;i<=count;i++) {
    for(int t=-4;t<=4;t++) {
      if(p>count) {
      if(p<0) {
      mean = mean + distance[p];  
    mean = mean / 9;
    distance[i] = mean;

void motor(int m, int d) {
  int mf;
  int mr;
  switch (m) {
    case lmotor:
      mf = lmotorf;
      mr = lmotorr;
    case rmotor:
      mf = rmotorf;
      mr = rmotorr;
      mf = 0;
      mr = 0;
  switch (d) {
    case mStop:
      digitalWrite(mf, LOW);
      digitalWrite(mr, LOW);
    case mForward:
      digitalWrite(mf, HIGH);
      digitalWrite(mr, LOW);
    case mReverse:
      digitalWrite(mf, LOW);
      digitalWrite(mr, HIGH);
      digitalWrite(mf, LOW);
      digitalWrite(mr, LOW);

void robotStop() {
  motor(lmotor, mStop);
  motor(rmotor, mStop);
  runTime = 1000;
  robotState = mStop;

void robotForward() {
  motor(lmotor, mForward);
  motor(rmotor, mForward);
  runTime = 1000;
  robotState = mForward;

void robotReverse() {
  motor(lmotor, mReverse);
  motor(rmotor, mReverse);
  runTime = 1000;
  robotState = mReverse;

void robotLeft() {
  motor(lmotor, mReverse);
  motor(rmotor, mForward);
  runTime = 1000;
  robotState = mLeft;

void robotRight() {
  motor(lmotor, mForward);
  motor(rmotor, mReverse);
  runTime = 1000;
  robotState = mRight;

void robotThink() {
  if (avoidState == HIGH && scanState == false) {
  if (avoidState == LOW && scanState == false) {
  if (avoidState == LOW && scanState...
Read more »

  • 1 × Arduino Uno
  • 1 × HC-SR04 based Ultrasonic Distance Sensor
  • 1 × L9110S H Bridge Stepper Motor Dual DC Driver Controller Board Module for Arduino
  • 1 × IR Obstacle Avoidance Sensor Module
  • 2 × Salvaged motors and gearboxes

View all 7 components

  • FreeBasic Reciever Code

    sad_ken05/03/2015 at 11:25 0 comments

    'Freebasic Rangefinder Reciever Code
    #Include ""
    Using fb
    ScreenRes 800,600,32
    Const TRUE = 1
    Const FALSE = 0
    Const maxdistance = 100          'Maximum distance we want to read
    Const factor = 250 / maxdistance     'scale factor for drawing bars
    Const minang = 10            'Starting angle, as a cheap servo was used moving to 0 causes problems
    Const maxang = 150            'Set to keep view in front of robot
    Const totalang = maxang-minang
    Const angfactor = 1
    Const pi = 3.14159265359
    Dim As UByte rec_Data
    Dim As UByte bounce
    Dim As UByte datastart
    Dim As uByte fin, gotang, gotmessage
    Dim As ubyte serialData
    Dim As String message, marker
    Dim As Integer ang, i
    Dim As Double distance
    Declare Function radang(ang As Double) As Double
    Declare Sub draw_line(ang As Integer, distance As Double)
    fin = FALSE
    gotang = FALSE
    gotmessage = FALSE
    datastart = TRUE
    Open com "COM14:57600,N,8,1,BIN,CS0,DS0" As 1        'Opens communication with serial port (in this case bluetooth)
    Sleep 100
    Circle (400,300),255,RGB(196,0,0),,,,F
    Line (0,301)-(800,600),RGB(0,0,0),bf
       If MultiKey(SC_ESCAPE) Then fin = TRUE
       If LOC(1) > 0 Then
          If datastart = TRUE Then 
             Circle (400,300),255,RGB(196,0,0),,,,F
             Line (0,301)-(800,600),RGB(0,0,0),bf
             datastart = FALSE 
          End If
          Get #1, ,serialData
       If serialdata <> 10 Then message = message & Chr(serialdata)     'start to decode the information coming in
       If serialdata = 10 Then 
          'Print message
          If Left(message,5) = "BEGIN" Then                 'Start of data stream
             datastart = TRUE
             Print "TADA"
          If Left(message,1) = "S" Then                     'Angle Data
             ang = Val(Right(message,Len(message)-1)) - 10
             gotang = TRUE
          If Left(message,1) = "V" Then                     'Distance Data
             distance = Val(Right(message,Len(message)-1))
             gotmessage = TRUE
          message = ""
       If gotang = TRUE And gotmessage = TRUE Then                 'draw line on display if both angle and data recieved
          gotang = FALSE
          gotmessage = FALSE
          If ang = 0 Then 
       For i = 0 To 250 Step 50
          Circle (400,300),i,RGB(255,255,255),radang(20),radang(160)
          marker = Str(Int(i/factor))
          Draw String (400-(4*Len(marker)),290-i), marker, RGB(255,255,255)
       Next i
       Line (399-totalang,350)-(401+totalang,400),RGB(0,0,255),b
    Loop Until fin = TRUE
    Close #1
    End 0
    Sub draw_line(ang As Integer, distance As Double)
       Dim As Double x1,y1,x2,y2, fdist, anginc, i, inc, ang2
       Dim As Integer x3, c, d
       If distance = 0 Then distance = maxdistance
       Static lastdist As Double
       ang2 = 360 - ang - ((180-(totalang))/2)
       fdist = distance * factor
       inc = (lastdist - distance) /500
       x1 = 400
       y1 = 300
       x3 = ((totalang-ang)*2)+ (400-(totalang))
       c = (255-((distance/maxdistance) * 255))
       If c < 0 Then c = 0
       If c > 255 Then c = 255
       For i = -1 To 0 Step 0.002
          d = c + (inc*i)
          If d > 255 Then d = 255
          x2 = ((fdist + (inc*i)) * Cos(radang(ang2 + i))) + x1
          y2 = ((fdist + (inc*i)) * Sin(radang(ang2 + i))) + y1
          Line (x1,y1)-(x2,y2),RGB(0,0,0)
          Line (x3 + i,350) - (x3 + i,400),RGB(d,d,d)
       Next i
       lastdist = distance
    End Sub
    Function radang(ang As Double) As Double
       Dim rad As Double
       rad = ang * (pi/180)
       Return rad
    End Function

  • Many Updates, One Log

    sad_ken08/05/2014 at 11:24 0 comments

    Ok, so the first couple of images i posted showed no more than a sensor on a servo.  Since then i've put together a wheelbase (not the most efficient setup, but it serves a purpose for the moment), added a bluetooth connection, and an IR avoidance sensor.  

    The wheelbase is made from a couple of motors and gearboxes salvaged from an old robot toy.  Sadly these are massively power hungry, and so the drive batteries don't last very long at all.  

    I've used an uber cheap HC-06 bluetooth module from ebay for wireless communication, and although it was fussy at the start, it seems to stream the data nicely.  Sadly however i've not figured out a way of putting it to sleep when it's not in use, causing more of a power drain on the system.  Coupled with the cheap servo the arduino is also drawing it's fair share of current (although from a different set of batteries from the motors).   

     Next step is definitely to sort out the power issues.  Hopefully starting with the control side, and shutting down both the servo, bluetooth, and possibly even the ultrasonic sensor when they are not needed. 

View all 2 project logs

Enjoy this project?



zafer wrote 05/02/2015 at 20:58 point

Hello dude, are you still working on this project?  'Cause i've problem with my project. I'am working on arduino based sonar with stepper motor and hc-sr04 ultrasonic sensor, i wrote the codes on arduino and i am trying to processing radar screen on MatLab but it doesn't work. After 5-10 degree scanning, the scanner bar is missing every time. Can you send me your arduino codes for this project?

  Are you sure? yes | no

sad_ken wrote 05/03/2015 at 07:41 point

I've not done anything to this for a while, my drive wheels were pretty poor so progress stalled.  Im happy to send you the code i have though.  My recieving code was written in freebasic, it is probably quite messy but hopefully you'll get the idea. 

I'll try and dig out the code later today when i'm on a laptop, and post it here.

  Are you sure? yes | no

davedarko wrote 08/05/2014 at 21:59 point
+skull for the Johnny 5 theme :)

  Are you sure? yes | no

sad_ken wrote 08/06/2014 at 08:39 point
Thanks, I couldn't resist the addition after someone suggested it on the original photo.

  Are you sure? yes | no

Eric Hertz wrote 12/10/2015 at 03:20 point

Hah, just came across this for the first time and as soon as I saw that image I thought "I bet davedarko would dig this"... well, I thought that *after* digging it, myself ;)

  Are you sure? yes | no

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