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Sensor Technology Tasks

Triggering and modulating events

Task 8 Name: Triggering and modulating events Set: w5i Due: Monday 19th December 2016 Weighting: assessable (10%) Courses: stech
Prev Task: Investigating sensors - Make your own sensor - Make your own arduino Next Task: Advanced sensors
Task Summary All stech tasks

Real-life examples of triggering and modulating events.

Incidentally, a good reading list here: https://itp.nyu.edu/physcomp/resources/books/

A real life example

Ultrasound Ping Code for Arduino

// Gagglina v01
// 110301
// Based on GaggleSingle v003
// Now works via one routine
// just the one ping, for testing...

int myDel = 5;

void setup()

void loop()
//  ping(3);
//  ping(4);
//  ping(5);
//  ping(6);
//  ping(7);
//  ping(8);
//  ping(9);
//  ping(10);

void ping(int pingPin)
  long duration;
  float cm;

  // The PING))) is triggered by a HIGH pulse of 2 or more microseconds.
  // We give a short LOW pulse beforehand to ensure a clean HIGH pulse.
  pinMode(pingPin, OUTPUT);
  digitalWrite(pingPin, LOW);
  digitalWrite(pingPin, HIGH);
  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);
  Serial.print(", ");
 //  Serial.print(", ");
  // Serial.println(myDel);
  // convert the time into a distance
  cm = microsecondsToCentimeters(duration);

  Serial.print("a: "); 
  // control the rate via a pingPin
  // these need ranging, so there's are ranges of difference between one 'range' and another.
  // if (pingPin == 8) { myDel = map(duration, 0, 15000, 500, 20) ; }

long microsecondsToInches(long microseconds)
  // According to Parallax's datasheet for the PING))), there are
  // 73.746 microseconds per inch (i.e. sound travels at 1130 feet per
  // second).  This gives the distance travelled by the ping, outbound
  // and return, so we divide by 2 to get the distance of the obstacle.
  // See: http://www.parallax.com/dl/docs/prod/acc/28015-PING-v1.3.pdf
  return microseconds / 74 / 2;

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;

Here is a working Max patch: http://rhoadley.org/courses/tech_resources/stech/tasks/triggers/triggering.zip

to top of page The Task

  • This is not a weighted task.
  • You might like to consider how best to control the things you want to control with the things you want to control them.

    Added Value

  • Completing the basics of the task will get you a basic pass mark. Try to develop other ways of implementing or extending the task for bonus marks up to 70 and beyond.
  • Clearly, I don't want you to submit your Arduinos. You need to submit sufficient appropriate documentary evidence that you've completed your task. The most obvious way to do this is to submit some sort of video of your task working. If you can't do this, take photos. Bear in mind that you'll get extra marks for 'added value', so try to adapt and make your project more interesting. Simply repeating what we've already done will get minimal marks (if it works).


  • Zip or Stuff your patches, demos, etc. into one file called your_student_number_"triggers" (e.g. 0504335_triggers.zip), include a readme with your name and student number and, if necessary, how to use or just open the patch.
  • Keep a copy of the task and submit to the i-Centre on Monday 19th December 2016