(Image credit: Future) Publishing Alerts to an MQTT Broker Thonny has a built-in Python package manager that we can use to install extra Open Thonny and click on Tools > Manage Packages. Connect your Raspberry Pi Pico W to your computer.ģ. Follow this guide to download and install the MicroPython firmware, and setup Thonny.Ģ. With this module, we can publish and subscribe to messages via a broker.ġ. Installing MQTT Client to Raspberry Pi Pico Wīefore we start the project, we first need to install the MQTT module for MicroPython. These sensors are approximately $8 via Amazon. It works in the exact same logic as PIR too, so we can swap this into a project without changing our code. It even works quite well through thin walls and cases. This sensor uses doppler radar to detect humans / moving creatures. These generally come in at $10 per sensor.įinally, if PIR sensors aren’t your thing, you can pick up an RCWL-0516 (front sensor in the above image) doppler sensor. A more expensive version, in a yellow plastic case, offers a more robust housing for the same sensor. A five-pack of these sensors is around $10 and well worth the investment. Other versions of this sensor are typically called “obstacle sensors,” and they provide a short range (up to 20 centimeters) detection system, often used with robots. I’ve used this hack at countless Raspberry Pi teacher training events. This version of the sensor is ideal for projects where you wish to detect movement in a large room, as the dome extends the sensor’s “field of vision.” Should this be too wide for you, a simple hack is to use a paper cup, create a hole in the bottom, and place the sensor inside so that it is pointing out of the wide end. They also come in many different forms, with the most common being a geodesic dome attached to a square of circuit board. They have two states: no motion detected (data pin pulled high), and motion detected (data pin pulled low). PIR (Passive Infrared) sensors are one of the most basic sensors you can use. The LED will be controlled by subscribing to an MQTT topic, where it listens for “on” and “off” messages. To demonstrate subscription, we will use an LED, connected to GPIO 17. This sensor will trigger when it detects movement, pulling an output pin low, which will trigger our code to send a message via MQTT. To demonstrate how to publish, we shall use a simple PIR sensor, connected to GPIO 16 as an input. We are going to be using one circuit to demonstrate both aspects of MQTT (publish and subscribe). We will publish live data from a PIR sensor, and then control an LED using messages sent to a Pico W. In this how-to, we will learn how to publish and subscribe to MQTT data feeds using the Raspberry Pi Pico W and a free public MQTT broker service from HiveMQ. An analogy would be YouTube, which acts as a broker for creators publishing their content, and subscribers watching. They can be another Raspberry Pi Pico W, a laptop, or a data center processing scientific data. Subscribers are those interested in receiving the data from the publishing device. Devices can publish information to MQTT via a broker, using topics to filter messages of a certain type. MQTT has two basic functions: publish and subscribe. But with MQTT we can effortlessly send and receive data with a Raspberry Pi Pico W, and use it with multiple devices across the globe. We’ve already covered how to control a Raspberry Pi Pico W via web services such as Anvil and sent live sensor data to Twitter via IFTTT.
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