Wifi Fan

Electronics May 13, 2016

What is it?

I built a wifi fan out of a bifferboard. It also contains a USB flash drive for a filesystem, Realtek Wifi dongle, a DHT-11 temperature/humidity sensor, and some extra circuitry for power and controlling the fan.

The DHT-11 sensor speaks a...unique 1-wire serial protocol. I had to implement a driver for that, as the mainline linux one (commonly used with the much beefier raspberry pi) relies on GPIO interrupts, which the chip here doesn't support.

The fan talks over wifi to my MQTT broker, allowing it to be switched on and off, by publishing a '1' or '0' to the 'fan' topic.

A JSON object is also published to the 'sensor' topic, which can be subscribed to for temperature and humidity data from the sensor.

Thanks to the mosquitto command line clients, the whole thing hangs together with a number of bash scripts.

Below is a MQTT/websocket interface to the two topics: