Waterproof Temperature Probe (DS18B20)

The DS18B20 comes in both a cable, an SMD, and a transistor-style package. We're only covering the cable here, but for others see the Datasheet.

Connect it up - to 0v, 3.3v, and the data line to any free signal line of your Espruino device, with a 4.7k resistor between data and the 3.3v line. There seem to be two types of cabled sensor, and each has differently coloured wires. Both are covered below:

To use it (assuming you connected to pin A1), simply write the following on the right-hand side:

var ow =newOneWire(A1);var sensor =require("DS18B20").connect(ow);
setInterval(function(){
  console.log(sensor.getTemp());},1000);

And the current temperature will be displayed every second. Note that the first time getTemp is called, an incorrect temperature may be returned.

=27.625

MULTIPLE SENSORS

The DS18B20 communicates over a 1-Wire bus, which allows connecting multiple thermometers on the same data line.

To create an array containing three sensors, simply:

var ow =newOneWire(A1);var sensor1 =require("DS18B20").connect(ow,0);var sensor2 =require("DS18B20").connect(ow,1);var sensor3 =require("DS18B20").connect(ow,2);var sensors =[sensor1, sensor2, sensor3];

Alternatively, you can create the same array with a little help of the Array.map() function:

var sensors = ow.search().map(function(device){returnrequire("DS18B20").connect(ow, device);});

Now make a function that will be called repeatedly by Espruino:

setInterval(function(){
  sensors.forEach(function(sensor, index){
    console.log(index +": "+ sensor.getTemp());});},1000);