Exploring the PIR Sensor: Navigating HC-SR501's Capabilities.

We'll delve into the purposes for which the PIR sensor is used, its basic trigger operations, pin connection details, and technical specifications. Finally, we will examine some real-life applications. 

The Rg pull down resistor provides the required standby zero logic to the FET to makes sure that it stays completely switched OFF in the absence of an IR signal.  

Upon detection of a moving IR signal by the pair of sensing elements, a corresponding pair of high and low logic signals is generated. These signals undergo amplification by the FET and are then replicated at its output pin. The attached circuitry processes these pulses further. To enhance the filtration process, additional EMI stages, along with capacitors, are employed. This ensures the production of a clean set of pulses at the designated output pin of the PIR. 

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| Parameter                                        | Value                   |

|------------------------------------|--------------------------|

| Recommended Model              | D204B                              |

| Encapsulation Type                    | TO-5                                  | 

| IR Receiving Electrode            | 2x 1mm, 2 elements  |

| Window Size                                 | 5x3.8mm                          |

| Spectral Response                    | 5-14 μm                             |

| Transmittance                             | >= 75%                               |

| Signal Output [Vp-p]              | >3500mV                          |

| Sensitivity                                    | >=3300V/W               |

| Detectivity (D*)                         | ≥1.4 x 10^8 cmHz ½W     |

| Noise [Vp-p]                                | <70mV                   |

| Output Balance                        | <10%                    |

| Offset Voltage                          | 0.3-1.2V                |

| Supply Voltage                        | 3-15V                   |

| Operating Temperature     | -30-70˚C                |

| Stooge Temperature           | -40-80˚C                |

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Click here to view how the PIR Works