PLEASE NOTE: This site is no longer being actively maintained. For frequently updated BeagleBone resources please visit

Read Temperature and Control a Buzzer


In this tutorial you will learn how to measure temperature and control a simple buzzer alarm circuit, access Cloud9 (the BeagleBone's coding interface), load and run a script.  This project introduces the analog read function to measure a temperature sensor, and presents a typical control application.

Note: This tutorial uses a BeagleBone set up specifically for our BeagleBone Black Tinkerer Workshop. The BeagleBone Black you will use in the Tinkerer Workshop will be set up with a Display and a Keyboard with a trackball mouse, and the JavaScript Files will be saved to the board. The BeagleBone will be running Angstrom, which come pre-loaded when you get the board. If you are not in a Tinkerer Workshop and want to do these projects, you can find a guide on how to attach a keyboard with a trackball mouse and a display here. You will also need to add the JavaScript files, which can be found here, to the following directory on the BeagleBone Black: /var/lib/cloud9/workshop

Parts List

Wiring DiagramProject 5 - Fritzing wiring diagram

Step 1

Wire the components as shown. Note the orientation of the Transistor (3-leads) E-B-C
Note: The face of the transistor is flat.

Step 2

Plug the DC power jack into the BeagleBone Black to power the device.

Step 3

Once the system is ready, click on BEAGLEBONE-workshop icon to open the Chromium browser and then start the Cloud9 IDE BeagleBone.local:3000 (

Step 4

In the Cloud9 workshop folder click on the file Project5.js to open the BoneScript program that will control the LED and make it blink.
The code should look like this:

var b = require('bonescript');

var analogPin = "P9_36";
var buzzerPin = "P8_13";
var ledRed = "P9_14";
var ledGreen = "P8_19";
var ledYellow = "P9_16";
var volume = "0.2";
var value = 0;

// configure pins
b.pinMode(buzzerPin, b.OUTPUT);
b.pinMode(ledRed, b.OUTPUT);
b.pinMode(ledGreen, b.OUTPUT);
b.pinMode(ledYellow, b.OUTPUT);

setInterval (inputHandler, 500);

function inputHandler() {     // read thermistor value
   value = b.analogRead(analogPin);
   value = Math.round(((value*10)-4.5)*4000);
   if (value < 100) value = 100;
   console.log (value);

loop();  //beep at interval of thermistor value

function loop() {
   b.analogWrite(buzzerPin, volume);
   setTimeout(function(){b.analogWrite(buzzerPin, b.LOW);}, 50);
   setTimeout(loop, value);
   if (value > 1000) b.digitalWrite(ledGreen,b.HIGH);
   else b.digitalWrite(ledGreen,b.LOW);
   if (value > 200 && value < 1000) b.digitalWrite(ledYellow,b.HIGH);
   else b.digitalWrite(ledYellow,b.LOW);
   if (value < 200) b.digitalWrite(ledRed,b.HIGH);

Step 5

Now press Run at the top of the Cloud9 interface. If this says "Debug", select "Run" from the drop down under this button.
Cloud 9 BeagleBone Black Run Button
The script should now run. You can make the buzzer sound by warming the thermistor up by pinching it between your fingers.