First Prototype
We are developing a system to help blind people sense their surroundings beyond the range of a standard walking cane. Using low-cost, open source, wearable electronics we hope to produce a set of technologies and methodologies that can be easily replicated and customized by others.
The prototype below uses under $100 in parts, using an Arduino board, a vibration motor and an ultrasonic range finder to translate a single point of depth data into varying intensities of tactile output. A similar system could be mass produced for under $40.
Here’s the source code:
//
// Touch Optics
// v.1
// http://touchoptics.wordpress.com
//
// Do we want debugging on serial out? 1 for yes, 0 for no
int DEBUG = 1;
const int motorPin = 9;
const int pingPin = 7;
boolean ascending = true;
void setup()
{
pinMode(motorPin, OUTPUT);
if (DEBUG) {
Serial.begin(9600); // Set serial out if we want debugging
}
}
void loop()
{
long cm = getPingCentimeters(pingPin);
analogWrite(motorPin,map(cm,0,200,255,0));
delay(100);
}
long getPingCentimeters(int pin)
{
// establish variables for duration of the ping,
// and the distance result in inches and centimeters:
long duration;
// 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);
return microsecondsToCentimeters(pulseIn(pingPin, HIGH));
}
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;
}
