Sensor

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 “I1”		yes
  freq	Number	Milliseconds. The frequency in ms of data events.	25ms	no
  threshold	Number	Any. The change threshold (+/- value).	1	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

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.scale(0, 10).on("change", function() {
    console.log(this.value);
  });
});

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);
  });
});

API

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

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

• scale([low, high]) Same as scale(low, high).

• 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
  
  });

Events

• change The "change" event is emitted whenever the value of the sensor changes more then the threshold value allows. The "change" event has aliases that can be used to better reason about the program being written: "slide", "touch", "force", "bend".

• data The "data" event is fired as frequently as the user defined freq will allow in milliseconds. ("data" replaced the deprecated "read" event)

Examples

• Sensor Component
• Sensor - Photoresistor
• Sensor - Potentiometer
• Sensor - Force Sensitive Servo Controller
• Sensor - Slide Potentiometer
• Sensor - Slide Potentiometer Servo Controller