Eyes in the back of your back

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[[User:rachel|Rachel]] and others are creating a vest that will allow the wearer to feel side-to-side movement behind them.  This will be done by a set of motion sensors connected to a touch display (of pager motors, at least initially).  The first prototype will have a one dimensional display so that up & down motion will not be detected, but this can probably be added later once some of the more pressing problems are solved.  We have not yet made a final determination on the prototype sensors but have had some success with ultrasonic rangefinders.
 
[[User:rachel|Rachel]] and others are creating a vest that will allow the wearer to feel side-to-side movement behind them.  This will be done by a set of motion sensors connected to a touch display (of pager motors, at least initially).  The first prototype will have a one dimensional display so that up & down motion will not be detected, but this can probably be added later once some of the more pressing problems are solved.  We have not yet made a final determination on the prototype sensors but have had some success with ultrasonic rangefinders.
  
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* [[EBB Notes 1]]
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* [[EBB Notes 2]]
  
 
== Current Status ==
 
== Current Status ==
Some functional if rough arduino code for a Parallax Ping))) module has been producedIt blinks an LED once per half second, with a larger duty cycle the closer an object is to the sensor.  The Ping))) module is large and somewhat cumbersome, and appears to be quite inaccurate at distances greater than about 2-3 feet.  There is a pair of MaxSonar-EZ1 modules in the Cyborg parts bin which look interesting to try as well.
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Parallax PING))) works but we don't like it so muchGot a Maxbotics MAXSonar EZ-1 functional in its analog mode, with LED standing in for motor (the shift register not yet integrated) but have failed at reading its serial out.
  
 
I (Rachel) have a fairly detailed mental model of the armature but have not made it yet.
 
I (Rachel) have a fairly detailed mental model of the armature but have not made it yet.
 
Code:
 
<pre>
 
/*
 
* Based on code found at http://arduino.cc/en/Tutorial/Ping
 
*/
 
 
int pin = 13;
 
int pingPin = 12;
 
int ledPin = 11;
 
double periodFactor = .5; // percent of one second
 
 
void setup()                    // run once, when the sketch starts
 
{
 
//  pinMode(pin, OUTPUT);      // sets the digital pin as output
 
  Serial.begin(9600);
 
  pinMode(ledPin, OUTPUT);
 
}
 
 
void loop()                    // run over and over again
 
{
 
  long duration, inches, 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);
 
  delayMicroseconds(2);
 
  digitalWrite(pingPin, HIGH);
 
  delayMicroseconds(5);
 
  digitalWrite(pingPin, LOW);
 
  delayMicroseconds(2);
 
 
  // 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
 
  inches = microsecondsToInches(duration);
 
  cm = microsecondsToCentimeters(duration);
 
 
  Serial.print(inches);
 
  Serial.print("in, ");
 
  Serial.print(cm);
 
  Serial.print("cm");
 
  Serial.println();
 
 
  pwm(duration);
 
}
 
 
void pwm(long microseconds)
 
{
 
  Serial.print(microseconds);
 
  Serial.println("ms");
 
 
  long offCycle = microseconds / 18;
 
  long onCycle = 1000 - offCycle;
 
  digitalWrite(ledPin, HIGH);
 
  delay(onCycle * periodFactor);
 
  digitalWrite(ledPin, LOW);
 
  delay(offCycle * periodFactor);
 
}
 
 
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;
 
}
 
</pre>
 
  
 
== Next Steps ==
 
== Next Steps ==
Next we'd like to see if the MaxSonar-EZ1 device has any better of a range than the Ping))).  Someone else has hooked it up to an arduino and posted code: http://www.flatline.net/journal/2007/12/02/arduino-reading-the-maxbotix-ultrasonic-rangefinder/
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* Try out IR sensor?  Daniela has lent us one, and I think there's some others in the bin plus of course the 900 PIR boards upstairs...
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* Buy the other US sensor I found?  Its specs beat out both the Maxbotics and the PING))).  Decide later.

Revision as of 07:48, 6 April 2009

or, Vibro Vest. Name suggestions encouraged!

Rachel and others are creating a vest that will allow the wearer to feel side-to-side movement behind them. This will be done by a set of motion sensors connected to a touch display (of pager motors, at least initially). The first prototype will have a one dimensional display so that up & down motion will not be detected, but this can probably be added later once some of the more pressing problems are solved. We have not yet made a final determination on the prototype sensors but have had some success with ultrasonic rangefinders.

Current Status

Parallax PING))) works but we don't like it so much. Got a Maxbotics MAXSonar EZ-1 functional in its analog mode, with LED standing in for motor (the shift register not yet integrated) but have failed at reading its serial out.

I (Rachel) have a fairly detailed mental model of the armature but have not made it yet.

Next Steps

  • Try out IR sensor? Daniela has lent us one, and I think there's some others in the bin plus of course the 900 PIR boards upstairs...
  • Buy the other US sensor I found? Its specs beat out both the Maxbotics and the PING))). Decide later.
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