A rundown of five more sensors: water flow, vibration, heart rate pulse, Hall effect magnetic sensor, and dust sensor.
Wire the LM35 correctly, convert ADC readings to Celsius using the actual reference voltage, and improve stability through averaging and calibration.
Understand the difference between a bare photoresistor and an LDR module, build the divider, read A0, and calibrate a stable switching threshold.
Trigger the HC-SR04, measure echo time, and calculate distance with a timeout, while accounting for target angle, surface and air temperature.