Hardware, IoT

Monitoring Temperature and Humidity in the House

In our house, we sometimes have problems with mold in outer corners, so four months ago we built a series of inexpensive IoT sensors for monitoring temperature and humidity. Our devices are made from just three components: WeMos D1 Mini (lite) microcontroller Si7021 temperature and humidity sensor 3x AA Ni-MH rechargable batteries Because we wanted to build around 10 sensors, we had to watch out a bit for the price tag on the components.  We ended up at around 9 € per device, with 50% of the cost beeing the batteries. We chose the Si7021 sensor because judging from this excellent review of common temperature sensors, it was better than the commonly used DHT22 and came in 2nd place behind the more expensive BME280. For the power supply of the devices it was clear that we were going to run them on rechargable battery using deep sleep.  Andreas Spiess made an…