Arduinoと超音波距離センサー「HC-SR04」（秋月電子から購入） を使った電子工作の中に面白いものを見つけたので、作ってみた。
これは、「Sonic Radar」というもので、デバイスから超音波を発して、跳ね返ってきた音を受信し、その時間で距離を計測するというものである。PCの助けを借りると、モニター画面上に映し出された表示結果は、レーダー画像を見ているような雰囲気がある。
参考にさせて戴いたURLは、
「ROBOTIC TUTORIALS.COM」の中の、Ultrasonic based RADAR である。
ハードウェアの組立は、結線箇所も少なく簡単に出来る。ハードウェアの組立に関しては、多くの他のブログでも紹介記事があるので、参考にするとよい。
しかし、PCの画面に結果を表示するためには、Processingというソフトウェアの助けを借りなければならない。僕は、Processingに関する知識が今は無いので、ネット上にあるものを拝借して出来るものをいろいろ探し回ってみた。私の組上げたシステムで表示できるもは、なかなか見つからなかった。ようやく見つけたのが、このURLである。どちらのSketch も殆どオリジナルのままである。しかし、表示部分に文字の重なりなどの問題があったので、フォントの大きさを変えたり、表示位置を変更し使わせて戴いている。
（注記：Sketch の中で init pin と言っているのは Trig Pin の事である。 まずArduinoを起動してから、次に Processing を起動してやれば良い。Processing が起動したとき、Arduino側の動きが一瞬停まるが、直ぐに同期して、PCの画面上に画像を映し出してくれる。）
《 Arduino Sketch 》
#include
/*
code for arduino bord ultrasonic radar system.
*/
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 = 6; // the HC-SR04's echo pin
int initPin = 7; // the HC-SR04's Trig 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);
}
}
《 Processing 用のSketch》
/*
Radar Screen Visualisation for HC-SR04
Maps out an area of what the HC-SR04 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 arduinoport; // 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
arduinoport = new Serial(this, Serial.list()[0], 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, 250); // 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(200, 200, 200);
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(200, 200, 200);
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 Plot Graph ", 540, 380, 250, 50);
fill(0, 50, 250);
textSize(22);
text("SP ROBOTICS : RADAR ", 570, 480, 650, 200);
textSize(12);
fill(0);
rect(70, 60, 150, 100);
fill(255, 255, 0);
text("Screen Key:", 100, 50, 150, 50);
fill(0, 50, 250);
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 arduinoport) {
String xString = arduinoport.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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