Hardware Arduino – ESP32 Wemos Lolin – DS18B20
ESP32 Wemos Lolin
The WEMOS Lolin ESP32 board is used. It has a built-in OLED display, the SSD1306 with 128×64 pixels and I2C connection. The ESP32 is a common microcontroller with many features. He has, for example, Wi-Fi integrated. The board can be programmed with the Arduino IDE. Therefore you need to setup the ESP32 support for Arduino.
The DS18B20 is a temperature sensor with an accuracy of +/-0.5 ° C in the temperature range between -10°C and +85°C. The total measurement range is -55°C to 125°C. Multiple sensors can be connected in parallel, with cable length up to 100m. The solution offered here limits the number to 20 sensors. Each sensor has its own ID, for example: 0x28FF09703017042E. In the program, a shorter ID is calculated (in this case, 0x2C5B), which can be used to distinguish the individual sensors.
SD Card Board
An SPI board is used to describe an SD card. I couldn’t figure out an actual manufacturer about it. On the Internet or on Alibaba Express you will find similar-looking boards with the search term “SPI Read Micro.” The program stores the data once a minute. One file is generated per sensor per day, which is approx. 18 Kbyte. So in the year 64 Mbytes of data are collected with 10 sensors. I use here a standard 4GB Micro SD Card.