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Espruino Pico and DHT22 example

by shedboy71
written by shedboy71

In this example we use the DHT22 (or AM2302) humidity/temperature sensor and the Arduino UNO board to read data and print it out to the serial monitor.

The DHT22 is better than the DHT11 because it has a wider range of measurement, 0 to 100% for humidity and -40°C to +125°C for temperature. Also it has a digital output that provides greater data accuracy.

AM2302

The AM2302 is a wired version of the DHT22, in a large plastic body, so they are the same device. Connect the red 3.3V power, the yellow wire to your data input pin and the black wire to ground.

 

Schematic

This is the pin connections

Device Pin – AM2302 colour Espruino Pico
1 (Vcc) – Red wire 3.3
2 (S)  – Yellow wire B3
3 (GND) – Black wire GND

 

pico and am2302_schem

Code

This example simply logs out temperature and humidity to the console every second

[codesyntax lang=”javascript”]

setInterval(function() {
  var dht = require("DHT22").connect(B3);
  dht.read(function (a){
    console.log("Temperature is "+a.temp.toString());
    console.log("Humidity is "+a.rh.toString());
  });
}, 1000);

[/codesyntax]

Link

AM2302 DHT22 temperature and humidity sensor for arduino

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Espruino

Espruino Pico and LDR example

by shedboy71
written by shedboy71

A light-dependent resistor is a light-controlled variable resistor. The resistance of a photoresistor decreases with increasing incident light intensity; in other words, it exhibits photoconductivity. A photoresistor can be applied in light-sensitive detector circuits, and light- and dark-activated switching circuits.

A photoresistor is made of a high resistance semiconductor. In the dark, a photoresistor can have a resistance as high as several megohms (MΩ), while in the light, a photoresistor can have a resistance as low as a few hundred ohms. If incident light on a photoresistor exceeds a certain frequency, photons absorbed by the semiconductor give bound electrons enough energy to jump into the conduction band. The resulting free electrons (and their hole partners) conduct electricity, thereby lowering resistance. The resistance range and sensitivity of a photoresistor can substantially differ among dissimilar devices. Moreover, unique photoresistors may react substantially differently to photons within certain wavelength bands.

As you can see later in the schematics its easy to connect one of these to an Espruino Pico, you only require an LDR and a 10k resistor so that this could easily be constructed on a breadboard. I used the following module

ldr

ldr

Schematics and Layout

 

pico and ldr_schem

pico and ldr_bb

 

Code

A simple code example, we will switch on and off the on board LED 1 depending on the value that’s read. So vary the light to the LDR and see what happens.

Type the following into the Espruino web ide and the Send to your Espruino

[codesyntax lang=”javascript”]

setInterval(function() {
  var light = analogRead(A5);
  console.log(light);
  //the value is between 0 and 1
  if(light >= 0.5)
  {
    digitalWrite(LED1, 0); //led off
  }
  else
  {
    digitalWrite(LED1, 1); //led on
  }
}, 1000);

[/codesyntax]

 

Links
20PCS x 5528 Light Dependent Resistor LDR 5MM Photoresistor

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