<< Continuation of Part 1

I come back from the shadows to continue my “smart air conditioner” 😄

In the previous post, we got working a small test sketch that let us control our air conditioner with an arduino mega. Now it is time to port that sketch to an ESP-01 to make use of its WiFi connection and compact size, which is not much inside the air conditioner unit.

As in my smart washing machine (that keeps working a year and a half later 😊), the idea here is to use MQTT for the communication between my small IoT server which has OpenHAB installed. For this MQTT communication, we will need the PubSubClient library.

#include <ESP8266WiFi.h>
#include <WiFiClient.h>
#include <PubSubClient.h>

.
.
.

void reconnect() {
  // Loop until we're reconnected
  while (!client.connected()) {
    // Attempt to connect
    if (client.connect(mqttClientId, mqttUser, mqttPassword)) {
      // Once connected, resubscribe
      client.subscribe(mqttPowerCommandTopic);
      client.subscribe(mqttModeCommandTopic);
      client.subscribe(mqttTempCommandTopic);
      client.subscribe(mqttSpeedCommandTopic);
    } else {
      // Wait 5 seconds before retrying
      delay(5000);
    }
  }
}

For managing the WiFi connections, I found a library that lets us configure a new WiFi connection, in case we change our WiFi password, without having to reprogram our board, which is great. It is called WiFiManager. In this case, we choose to open a protected WiFi connection in case of not being able to connect to the saved WiFi connection, and retry after 3 minutes (180 seconds).

<< Continuation of Part 2

Let’s start assembling the board that will control the state of the washing machine cycle. Four things are needed: the microcontroller, its power supply (the microcontroller works at 3.3 volts, and the power adapter we’re using works at 5v), the door lock detector and the actuation over the “start washing cycle” button.

As stated above, the ESP-01 needs 3.3 volts to work, a ground connection and needs to have pulled high (using a resistor, like a 10kohm one for example) the GPIO0 and GPIO2 pins in order to boot correctly. Apart from that, an output pin will actuate the start button and an input pin will detect the door lock state.

The 3.3 volts power can be obtained using, for example, an LM317T, a famous classic voltage regulator that, using a couple of resistors allows us to get a specific voltage. Using one of the many online calculators, we can calculate which resistors we need. In my case, I used this one.