Skip to content

Sensor

Jump to bottom Edit New page
Rick Waldron edited this page Jul 5, 2017 · 41 revisions

The Sensor class constructs objects that represent a single analog sensor component attached to the physical board. This class is intentionally generic and will work well with many types of sensors, including (but not limited to):

  • Linear Potentiometer
  • Rotary Potentiometer
  • Flex Sensitive Resistor
  • Pressure Sensitive Resistor
  • Force Sensitive Resistor
  • Hall Sensor
  • Tilt Sensor
  • Photoresistor/Light Dependent Resistor

...And more, see examples

Parameters

  • pin A Number or String address for the Sensor pin (analog).

  • options An object of property parameters.

    Property Type Value/Description Default Required
    pin Number, String Analog Pin. The Number or String address of the pin the sensor is attached to, ie. "A0" or 0 mean the same thing. yes
    freq Number Milliseconds. The frequency in ms of data events. 25ms no
    threshold Number Any. The change threshold (+/- value). 1 no
    enabled boolean Whether to start emitting events right away (>= v0.9.12) true no

  • options (experimental) These options can be used with the Sensor class, but are considered experimental.

    Property Type Value/Description Default Required
    type String "digital", "analog". Specify that this is a sensor attached to a digital pin. Allows using a digital pin as the value of the pin option no

Shape

Property Name Description Read Only
id A user definable id value. Defaults to a generated uid No
pin The pin address that the Sensor is attached to No
threshold The change threshold (+/- value). Defaults to 1 No
boolean ADC value scaled to a boolean. Yes
raw ADC value (0-1023). Yes
analog ADC reading scaled to 8 bit values (0-255). Yes
constrained ADC reading constrained to 8 bit values (0-255). Yes
value ADC reading, scaled. Yes
freq The rate in milliseconds to emit the data event. Disables the event if set to null. (>= v0.9.12) No

Component Initialization

Analog Sensor (Most common case)

new five.Sensor("A0");

Digital Sensor (Less common, but supported experimentally)

new five.Sensor({
  pin: 2, 
  type: "digital"
});

// Can also be written as: 
new five.Sensor.Digital(2);

Common Options

//   - attached to pin "A0"
//   - emits data events every 250ms
//   - emits change events when the ADC value has changed by +5/-5
//
var temp = new five.Sensor({
  pin: "A0", 
  freq: 250, 
  threshold: 5
});

Usage

Analog Sensor

var five = require("johnny-five");
var board = new five.Board();

board.on("ready", function() {
  var sensor = new five.Sensor("A0");
  
  // Scale the sensor's data from 0-1023 to 0-10 and log changes
  sensor.on("change", function() {
    console.log(this.scaleTo(0, 10));
  });
});

Digital Sensor

var five = require("johnny-five");
var board = new five.Board();

board.on("ready", function() {

  var sensor = new five.Sensor.Digital(2);

  sensor.on("change", function() {
    console.log(this.value);
  });
});

If you prefer arrow functions...

var five = require("johnny-five");
var board = new five.Board();

board.on("ready", () => {
  var sensor = new five.Sensor("A0");
  
  // Scale the sensor's data from 0-1023 to 0-10 and log changes
  sensor.on("change", () => {
    console.log(sensor.scaleTo(0, 10));
  });
});

Digital Sensor

var five = require("johnny-five");
var board = new five.Board();

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

  var sensor = new five.Sensor.Digital(2);

  sensor.on("change", () => {
    console.log(sensor.value);
  });
});

API

  • scaleTo(low, high) (integer) Return the sensor's present value, scaled to a new value within the specified low/high range.

  • fscaleTo(low, high) (float) Return the sensor's present value, scaled to a new value within the specified low/high range.

    var sensor = new five.Sensor("A0");

sensor.on("change", function() {
  // this.value will reflect a scaling from 0-1023 to 0-180
  console.log(this.scaleTo(0, 180)); // integer
  console.log(this.fscaleTo(0, 180)); // float
});
    var sensor = new five.Sensor("A0");

sensor.on("change", () => {
  // this.value will reflect a scaling from 0-1023 to 0-180
  console.log(sensor.scaleTo(0, 180)); // integer
  console.log(sensor.fscaleTo(0, 180)); // float
});

  • scaleTo([low, high]) (integer) Return the sensor's present value, scaled to a new value within the specified low/high range.

  • fscaleTo([low, high]) (float) Return the sensor's present value, scaled to a new value within the specified low/high range.

    var sensor = new five.Sensor("A0");

sensor.on("change", function() {
  // this.value will reflect a scaling from 0-1023 to 0-180
  console.log(this.scaleTo([0, 180])); // integer
  console.log(this.fscaleTo([0, 180])); // float
});
    var sensor = new five.Sensor("A0");

sensor.on("change", () => {
  // this.value will reflect a scaling from 0-1023 to 0-180
  console.log(sensor.scaleTo([0, 180])); // integer
  console.log(sensor.fscaleTo([0, 180])); // float
});

  • scale(low, high) Scale the sensor's value to a new value within a specified range. scale(...) is deprecated, use scaleTo(...)

  • scale([low, high]) Same as scale(low, high). scale(...) is deprecated, use scaleTo(...)

  • booleanAt(barrier) Set a midpoint barrier value used to calculate returned value of the .boolean property. The barrier is based on the scaled value, not the raw value. Defaults to 50% (512 when unscaled).

    var sensor = new five.Sensor("A0");

// ADC readings less than 100 will result 
//  in the value of the `boolean` property being false.
// 
// ADC readings greater than 100 will result 
//  in the value of the `boolean` property being true.
// 
sensor.booleanAt(100);

  • within(range, handler) When value is within the provided range, execute callback.

    var sensor = new five.Sensor("A0");

sensor.within([ 100, 200 ], function() {
  
  // This is called when the sensor's value property falls within 100-200

});

  • enable() Start emitting "data" and "change" events, at a rate determined by the user defined freq in milliseconds. No-op if Sensor is already enabled. (>= v0.9.12)

  • disable() Stop emitting "data" and "change" events. No-op if Sensor is already disabled. (>= v0.9.12)

Events

  • change The "change" event is emitted whenever the value of the sensor changes more than the threshold value allows.
  • data The "data" event is fired as frequently as the user defined freq will allow in milliseconds. ("data" replaced the deprecated "read" event)

Collection

Sensor supports a Sensors collection class, which allows multiple Sensor instances to be controlled via a single instance object. Events emitted by instances of the Sensor class are forwarded through instances of the Sensors class. The handler receives the instance that emitted the event as the first parameter.

new five.Sensors([ 2, 3, 4, 5 ]);
new five.Sensors([ { pin: 2 }, { pin: 3 }, { pin: 4 }, { pin: 5 } ]);
new five.Sensors([ sensor1, sensor2, sensor3 ]);

Examples

The JavaScript Robotics Programming Framework

Add a custom sidebar
Clone this wiki locally