Getting to know the SIM800L module's components, power requirements, and pinout, as groundwork for using it practically with Arduino.
Wiring the digital DS18B20 temperature sensor over the 1-Wire protocol, and why the pull-up resistor matters.
Wiring the BMP180 sensor to measure atmospheric pressure, temperature, and altitude over the I2C protocol with Arduino.
A quick rundown of four essential sensors: the LDR light sensor, PIR motion sensor, infrared receiver, and tilt sensor.