MQTT with BeagleBone and ESP8266 – MQTT on ESP8266 with Relay

After the article about the connection with the temperature and humidity sensor

MQTT with BeagleBone and ESP8266 – MQTT on ESP8266 with temperature sensor

in this article we set the esp8266 to run a relay. Here is how we connect the relay to the ESP module

nodemcu relay

In this example too we will consider the option of putting the nodemcu in sleep. To have the node back form the sleep the system has to reboot and  it is necessary to connect the PIN D0 (GPIO16) to RST PIN as specified in the nodemcu documentation

Nodemcu sleep

Let us take a look at the lua code; It consists of init.lua and relay.lua files.

We analyze now the main points of each file

  • init.lua

In the file we set the the parameters to access the wifi network, the address and port of the MQTT broker  and the file to be run on the ESP after wifi connection to the access point is estabilished. If the ESP doesn’t acquire the network address the system is restarted.

  • relay.lua

The relay.lua file manages the relay, the subscription on MQTT broker with submission of the data. Global parameters have been set to manage the topic, the waiting time in tmr.alarm. There are in particular the following topics

  • /home/relay1/status : Status topic. The status is sent at the start and at  request from the command topic /home/relay1/command.
  • /home/relay1/monitor: Status of the esp sent periodically to this topic.
  • /home/relay1/command: Other clients can send commands to the esp:
    • Restart: Restarts the esp.
    • Sleep n: Put to sleep for n seconds the esp.
    • ON: Turn on the  relay.
    • OFF: Turn off the  relay.
    • Status: Request of tthe relay status (ON or OFF).

There are various service functions to manage all. The comments in the code describe each feature.

In the next article we will set up the webserver on Beaglebone and the websocket configuration for Mosquitto always on the Beaglebone

MQTT with BeagleBone and ESP8266 – WebServer and MQTT WebSocket