The PIR Motion Sensor Detector Module HC-SR501 allows you to sense motion. It is almost always used to detect the motion of a human body within the sensor’s range. It is often referred to using “PIR”, “Pyroelectric”, “Passive Infrared” and “IR Motion” sensor. The module has an onboard pyroelectric sensor, conditioning circuitry, and a dome-shaped Fresnel lens. It has a delay time adjustment Potentiometer and sensitivity adjustment Potentiometer. Repeat Trigger Selection solderable Jumper is also available.

The Digital Light Dependent Resistor LDR Sensor Module is used to detect the presence of light / measuring the intensity of light. The output of the LDR module goes high in the presence of light and it becomes low in the absence of light. You can adjust the threshold (sensitivity) of the digital output by tuning the onboard variable resistor (potentiometer). Simple usage as it is the digital output, so you will know is the light present and decide what to do with it.LDR photoresistor sensor module comes with an M3 mounting hole for ease of attaching it to an object. Onboard, it provides an LDR, high sensitivity and commonly being used for light detection.