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73 lines
2.0 KiB
Plaintext
73 lines
2.0 KiB
Plaintext
/*
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Calibration
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Demonstrates one techinque for calibrating sensor input. The
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sensor readings during the first five seconds of the sketch
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execution define the minimum and maximum of expected values
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attached to the sensor pin.
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The sensor minumum and maximum initial values may seem backwards.
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Initially, you set the minimum high and listen for anything
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lower, saving it as the new minumum. Likewise, you set the
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maximum low and listen for anything higher as the new maximum.
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The circuit:
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* Analog sensor (potentiometer will do) attached to analog input 0
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* LED attached from digital pin 9 to ground
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created 29 Oct 2008
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By David A Mellis
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Modified 17 Jun 2009
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By Tom Igoe
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http://arduino.cc/en/Tutorial/Calibration
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*/
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// These constants won't change:
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const int sensorPin = 2; // pin that the sensor is attached to
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const int ledPin = 9; // pin that the LED is attached to
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// variables:
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int sensorValue = 0; // the sensor value
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int sensorMin = 1023; // minimum sensor value
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int sensorMax = 0; // maximum sensor value
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void setup() {
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// turn on LED to signal the start of the calibration period:
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pinMode(13, OUTPUT);
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digitalWrite(13, HIGH);
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// calibrate during the first five seconds
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while (millis() < 5000) {
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sensorValue = analogRead(sensorPin);
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// record the maximum sensor value
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if (sensorValue > sensorMax) {
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sensorMax = sensorValue;
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}
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// record the minimum sensor value
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if (sensorValue < sensorMin) {
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sensorMin = sensorValue;
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}
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}
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// signal the end of the calibration period
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digitalWrite(13, LOW);
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}
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void loop() {
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// read the sensor:
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sensorValue = analogRead(sensorPin);
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// apply the calibration to the sensor reading
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sensorValue = map(sensorValue, sensorMin, sensorMax, 0, 255);
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// in case the sensor value is outside the range seen during calibration
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sensorValue = constrain(sensorValue, 0, 255);
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// fade the LED using the calibrated value:
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analogWrite(ledPin, sensorValue);
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} |