In this scenario, you will learn how to remotely control fan speed using PWM and how to control servo angle using MQTT messages. This scenario is a practical extension to the scenario U4 where you learned, how to receive and handle MQTT messages.

Undergraduate / Bachelor / Engineering Students

We assume you already know how to:

• handle LCD screen to present information,
• connect to the existing WiFi network: internal.IOT,
• receive and handle MQTT messages using PubSubClient library
• additionally we will ask you to install and use an MQTT client of your choice. We suggest using MQTT Spy, but any MQTT client that will let you subscribe to the MQTT messages is OK. You connect it to the public IP of the MQTT broker (see below).

MQTT broker present in the internal.IOT network is also visible under public address. So whenever you subscribe to the MQTT message using VREL node that is connected to the internal.IOT network, you may publish to it using other devices connected to the internal.IOT, i.e. other VREL node or if you're physically present at SUT in the IOT laboratory room 320, then you can connect your mobile and laptop to the internal.IOT network and use “internal” IP address. However, if you're in a remote location, you can access the same broker under public IP as stated in the node description. When you publish an MQTT message using public IP, it will be delivered to the subscribers in the private internal.IOT network as well. Mind, to access MQTT broker you need to use IP, user and password (applies to both public and private IPs of the MQTT Broker). Refer to the node documentation for the latest information.

In this scenario, you will handle incoming MQTT messages (one for controlling fan, other for servo, opening and closing the flap. Parallelly you will present incoming messages on the LCD screen.

You should be able to remotely control fan rotation speed and flap angle (0..90 degrees), observe connection status and incoming MQTT messages for your device on the LCD screen.

Define some identifiers to separate and update AP's SSID and passphrase easily. To format lines for the LCD, we suggest using a char buffer of 20 characters (one full line) and some 2-3 integers for iterators and storing current PWM for servo and fan. Remember to declare the LCD control class in your code. You do not need to instantiate WiFi communication class - as you have only one interface here, it is singleton class you can refer directly using WiFi. Reading analogue input brings you an integer value.

Servo is controlled using GPIO pin D5 (GPIO14) while the fan is controlled using GPIO pin D8 (GPIO15). As servo we use is a small one, it is powered and controlled directly through the ESP8266 while in case of the FAN, it is controlled indirectly, using a transistor.

Write some extra information if i.e. some steps are optional otherwise cancel this paragraph (but do not remove header).

Describe activities done in Step 1.

…

Describe activities done in Step n.

Provide some result validation methods, for self assesment.

This section is to be extended as new questions appear.
When using the printed version of this manual please refer to the latest online version of this document to obtain the valid and up-to-date list of the FAQ. Provide some FAQs in the following form:
Question?: Answer.