PING))) Ultrasonic Distance Sensor + controller

adreal

Hello!

I am new to PING))) so I would like to get an advice for choosing the best controller for the sensor. I need to detect people from 0.5-4 meters outputing an array of distances via USB. The final array would be "date&time - distance". Sensor will be used indoors. The controller will be powered by PC PSU or optional adapter.

Best,
Martti

Duane Degn

I'd suggest using a controller you know how to use.

If you haven't used a controller before, I think the Propeller it the most useful.

Here's code I wrote for a QuickStart board using a Ping and 4 digit 7-segment LED display.

CON
  _clkmode = xtal1 + pll16x
  _xinfreq = 5_000_000
  PING_Pin = 0                                          ' I/O Pin For PING)))
 
  _DebugBaud = 9600                                     ' Debug Baud Rate
                                        

VAR
  long  range, rangeOld
    
OBJ
  Debug  : "FullDuplexSerial"
  ping : "ping"
  
PUB Start
  Debug.Start(-1, 1, 0, _DebugBaud)
  
  'Debug.str(string("PING))) Demo"))
  waitcnt(clkfreq / 10 + cnt)
  Debug.tx("z")
  Debug.tx(0)
  repeat                                                ' Repeat Forever                             
    rangeOld := range
    range := ping.Millimeters(PING_Pin)                 ' Get Range In Millimeters
    if rangeOld <> range
      Debug.tx("v")                                       
      Debug.dec(range)
    waitcnt(clkfreq / 10 + cnt)                         ' Pause 1/10 Second

The objects used a freely available and I'll post the code as an archive if you'd like.

Duane

Ohmware

How is your project coming along? I am attempting a similar project and it might be fun to compare notes.

For my initial experiments I am using a Freetronics Eleven controller board (an Arduino clone). Wether I stick with that will depend on how sophisticated the controller software ends up needing to be, but for now it is working fine and I had an Arduino sketch up and running in about 5 min. (Mostly because there was already an example using a PING))) sensor that I could modify.)

So far I have found the PING))) to be fairly noisy, so I will need some sort of filter on the output. I haven't collected any data yet but I am hoping to when I get back from holiday in a couple of weeks.

/* Ping))) Sensor
  
   This sketch reads a PING))) ultrasonic rangefinder and returns the
   distance to the closest object in range. To do this, it sends a pulse
   to the sensor to initiate a reading, then listens for a pulse 
   to return.  The length of the returning pulse is proportional to 
   the distance of the object from the sensor.
     
   The circuit:
    * +V connection of the PING))) attached to +5V
    * GND connection of the PING))) attached to ground
    * SIG connection of the PING))) attached to digital pin 7


   http://www.arduino.cc/en/Tutorial/Ping
   
   created 3 Nov 2008
   by David A. Mellis
   modified 30 Jun 2009
   by Tom Igoe
   modified 19 Nov 2011
   by Kaelin Colclasure
 
   This example code is in the public domain.


 */


// this constant won't change.  It's the pin number
// of the sensor's output:
const int pingPin = 7;


const long maxDistance = 300; // Max range 3m per data sheet
long lastDistance = 0;


void setup() {
  // initialize serial communication:
  Serial.begin(9600);
  pinMode(13, OUTPUT);
}


void loop()
{
  // establish variables for duration of the ping, 
  // and the distance result in inches and centimeters:
  long duration, distance;


  // The PING))) is triggered by a HIGH pulse of 2 or more microseconds.
  // Give a short LOW pulse beforehand to ensure a clean HIGH pulse:
  pinMode(pingPin, OUTPUT);
  digitalWrite(pingPin, LOW);
  delayMicroseconds(2);
  digitalWrite(pingPin, HIGH);
  delayMicroseconds(5);
  digitalWrite(pingPin, LOW);


  // The same pin is used to read the signal from the PING))): a HIGH
  // pulse whose duration is the time (in microseconds) from the sending
  // of the ping to the reception of its echo off of an object.
  pinMode(pingPin, INPUT);
  duration = pulseIn(pingPin, HIGH);


  // convert the time into a distance
  distance = microsecondsToCentimeters(duration);
  
  if (distance > maxDistance)
    distance = -1;
  
  if (distance != lastDistance) {
    Serial.print(distance);
    Serial.print("cm");
    Serial.println();
    lastDistance = distance;
    if (distance == -1)
      digitalWrite(13, LOW);    // set the LED off
    else
      digitalWrite(13, HIGH);   // set the LED on
  }
  
  delay(300);
}


long microsecondsToCentimeters(long microseconds)
{
  // The speed of sound is 340 m/s or 29 microseconds per centimeter.
  // The ping travels out and back, so to find the distance of the
  // object we take half of the distance travelled.
  return microseconds / 29 / 2;
}

Mike Green

The PING))) itself is actually not noisy at all. Perhaps you have a noisy power source or you're using long wires to connect your controller with the PING))) or ...

If, by noisy, you mean that the readings vary widely, remember that the PING))) responds to the first echo received. If you have a complex environment out there, there may be secondary echoes that, depending on the air temperature, air currents, object movement, etc., may return with sufficient amplitude to trigger the PING))) and give you what effectively looks like noise. In that case, some filtering of the distance measurements would indeed be in order. You could exclude values outside of the range you expect, maybe adjust the acceptable range based on relatively long-term trends.

Ohmware

Thanks Mike, I will take a closer look at my test setup when I get back. I thew the circuit together hastily on a breadboard connected to a Freetronics Eleven (Arduino clone) and using the USB power source plugged into an open low-power USB plug on my computer keyboard. I will definitely look at the power side of the equation. The wires between the controller and the ping were not more than 4" long… Is that enough to be a concern? (I would not have thought so, but I am primarily a software guy.)

Ohmware

Just as a follow-up… The problems with spurious readings pretty much vanished when I plugged a wall wart into my Arduino to supply the power instead of relying on the current from the USB port. Thanks again Mike for the troubleshooting tips!