I made a simple HAT (Hardware Attached on Top) for the Raspberry Pi to read multiple DS18B20 temperature sensors — it was surprisingly easy. I used the measured temperatures to control a fan using Home Assistant.
Temperature and auxiliary sensor (RS-485), AVR
Temperature sensor with serial RS-485 interface. Two additional sensors can be connected using 3-pin headers on the circuit board. Uses an AVR ATmega8 microcontroller.
Temperature and humidity sensor (RS-232), AVR
I rebuilt an existing interface module — to be a stand-alone temperature and humidity sensor, with serial RS-232 interface. Uses an AVR ATmega8 microcontroller.
Temperature and light sensor with signalling LEDs (RS-232), AVR
I rebuilt an existing interface module — to be a stand-alone temperature and light sensor, with serial RS-232 interface and some signal LEDs. Uses an AVR ATmega8 microcontroller.
Temperature and light sensor, with LEDs — AVR serial module
Light intensity and temperature sensors; with white, green, yellow, red and blue signal LEDs and a buzzer. RS-232 communication. Uses an AVR ATmega8 microcontroller.