Picotemp is a simple home temperature monitor based on a Raspberry Pi Pico. The pico with a SHT40 reports the ambient temperature and humidity via an LED and over a serial connection. If the data is recorded over the serial connection, I include some optional analysis code in python that can produce plots for a basic localhost HTML monitoring page.
The pico circuit contains:
- Raspberry Pi Pico
- Adafruit SHT40 Humidity & Temperature Sensor Package
- Tricolour LED
- 3 - 1K Ohm resistors
The circuit is summarized in the following diagram.
As written and connected as above, the tricolour LED will glow,
- Blue: <20°C
- Blue-Green: 20-21°C
- Green: 21-22°C
- Green-Red: 22-23°C
- Red: >23°C
Set up your build environment as described in the Pico Getting Started Datasheet. As a brief, incomplete summary:
- Download and install build tools & pico-sdk
- Set up the pico-sdk environment variable
- Create build directory and
cd cmake ..make -j4- Connect pico via USB in BOOTSEL mode
- Drag and drop created readtemp.uf2 file onto pico
The serial connection with the Pico can be read using minicom,
minicom -b 115200 -D /dev/ttyACM0 -C env.log -O timestamp
This will produce output like,
[Timestamp] [Temperature] [Humidity]
which can be parsed by analysis.py.
Running web/server.py in the background will start a localserver that will show figures of the last 6, 24, and 72 hours of environmental data. I suggest adding a cronjob that runs analysis.py every 15 or so minutes to update these plots automatically.
The result is a simple local webpage as in the image below.
