ReflectanceArray

The ReflectanceArray class constructs an array of analog (digital arrays are not currently supported) reflectance sensors like the QTR-8A from Pololu.

Parameters

• pins An array Numbers or Strings for the analog sensor pins.

• emitter The pin where the emitter LED is attached. For these arrays, there is one pin that controls all of the emitters.

  new five.ReflectanceArray({
    emitter: 13,
    pins: ["A0", "A1", "A2", "A3", "A4", "A5"]
  });

• options An object of property parameters.

  Property	Type	Value/Description	Default	Required
  pins	Array of Numbers, Strings	["A*", ...]. The pins that the sensors are connected to		yes
  emitter	Number, String	Digital Pin. The pin that the light emitter is connected to		yes
  freq	Number	Milliseconds. The frequency in ms of data events.	25ms	no

Shape

Property Name	Description	Read Only
id	A user definable id value. Defaults to a generated uid	No
pins	The pin addresses that the sensors are attached to	No
isOn	Are the emitters on?	Yes
isCalibrated	Does the array have calibration data?	Yes
isOnLine	Is the array currently tracking a line? isCalibrated===true	Yes
sensors	An array of sensor objects that represent each sensor in the array.	Yes
calibration	The current calibration data.	Yes
raw	An array of raw values from all the sensors.	Yes
values	If calibrated, an array of calibrated values (between 0 and 1000). If not calibrated, raw data (between 0 and 1023).	Yes
line	If calibrated, a value between 0 and (n-1)*1000+1. For example, 6 sensors will have a line between 0 and 5001.	Yes

Component Initialization

Analog

new five.ReflectanceArray({
  emitter: 13,
  pins: ["A0", "A1", "A2"], // any number of pins
  freq: 25
});

Usage

const { Board, ReflectanceArray } = require("johnny-five");
const board = new Board();

board.on("ready", () => {

  const eyes = new ReflectanceArray({
    emitter: 13,
    pins: ["A0", "A1", "A2"], // any number of pins
    freq: 25
  });

  eyes.on('data', () => console.log("Raw Values: ", eyes.raw ));
  eyes.on('line', () => console.log("Line Position: ", eyes.line));

  eyes.enable();
});

API

• enable() Turn the light emitters on.

  const eyes = new five.ReflectanceArray({
    emitter: 13,
    pins: ["A0", "A1"]
  });
  
  eyes.enable();

• disable() turn the light emitters off

  const eyes = new five.ReflectanceArray({
    emitter: 13,
    pins: ["A0", "A1"]
  });
  
  eyes.disable();

• calibrate() Read all of the sensors and store the min/max values. Used to calculate calibrated values and line values. You should call calibrate() multiple times.

  const eyes = new five.ReflectanceArray({
    emitter: 13,
    pins: ["A0", "A1"]
  });
  
  for (var i = 0; i < 100; i++) {
    eyes.calibrate();
  }

• calibrateUntil(predicate) A convenience function that will call calibrate until a predicate function returns true. This allows you to decide when calibration is done. This trigger may be user input, time, or execution count. You decide.

  const eyes = new five.ReflectanceArray({
    emitter: 13,
    pins: ["A0", "A1"]
  });
  
  let calibrating = true;
  eyes.calibrateUntil(() => !calibrating);
  
  // calibrate for one second
  setTimeout(() => calibrating = false, 1000); 

• loadCalibration(calibration) Prime the array with calibration data. This allows you to load calibration data from a file. You can get it from the device using the calibration after it has been calibrated.

  const eyes = new five.ReflectanceArray({
    emitter: 13,
    pins: ["A0", "A1"]
  });
  
  eyes.loadCalibration({
    min: [37, 39],
    max: [1010, 1015]
  });

Events

• data The "data" event is fired as frequently as the user defined freq will allow in milliseconds. It includes an array of the RAW data from the sensors.

• calibratedData The "calibratedData" event is fired as frequently as the user defined freq will allow in milliseconds. It also requires that the device has been calibrated. It includes an array of calibrated values between 0 and 1000.

• line The "line" event is fired as frequently as the user defined freq will allow in milliseconds. It also requires that the divide has been calibrated. It is a single value between 0 and (n-1)*1000+1. An array with 6 sensors will yield a value between 0 and 5001.

Examples

• Line Follower
• Line Follower Video