Passive infrared Sensors, often known as PIR sensors, are used to detect motion within the specific sensor range. These sensors are inexpensive, small, and require low power.
An Overview of HC-SR501 Sensor
HC-SR501 PIR module has a wide range of input voltage from 4V to 12V. But, we recommend it to use 5Volts. Further, it can efficiently detect the movement of objects or humans. The sensor possesses two operating modes, repeatable and non-repeatable. It can easily cover a distance of about 120 degrees within 7 meters. The sensor works in operating temperatures from -20 degrees to 80 degrees Celsius. Also, it consumes minor power. Hence, favorable to manage. The sensor operates in two modes that are repeatable and default non-repeatable modes. The sensor has a potentiometer to adjust the sensitivity and time.
Internal Structure
The sensor comprises two different materials, one is the pyroelectric crystal which detects the heat signatures of any living organism and the other is a Fresnel lens of white color that wides the range of the sensor. If you remove that lens you may find the Pyroelectric sensor inside which is covered with a protective metal.
Working Principle
After the sensor gets connected, there will be one-minute initialization. And, during the initialization, the module will output 0 to 3 times at intervals. Then the module will go into standby mode. To avoid misoperation, keep the interference of any light source and other sources away from the surface of the module.
Features and Specifications of HC-SR501
Features
- Automatic infrared detection (LHI778 probe design)
Output goes high when objects enter the sensing range, and automatically returns to low when an object leaves - Optional photosensitive control
- Optional temperature compensation
- Trigger mode jumper
- L: Non-repeatable / delay mode: sensor goes low after the delay, regardless of the presence of the object.
- H: Repeatable: sensor stays high as long as any object is detected during the delay time.
- Wide operating voltage range
- Micro-amp power
- Output high signal: easy to achieve docking with the various types of circuits.
- Infrared technology (LHI778 probe design)
- high sensitivity | high reliability
- widely used especially for battery-powered products.
Specifications
- Product Type: HC–SR501 Body Sensor Module
- Adjustable delay
- Adjustable sensing range
- Input voltage: DC 4.5-20V
- Static current: 50ua
- Sensing range: Max 7
- Input voltage: DC 4.5-20V
- Static Current: <50uA
- Level output: High 3.3 V / Low 0V
- Trigger: L cannot be repeated trigger / H can be repeated trigger
- Delay time: 5-200s
- Block time: 2.5s
- Board Dimensions: 32mm*24mm
- Angle Sensor: <100 cone angle
- Operation Temp: -15-+70 degrees
- Lens size sensor: Diameter: 23mm
Pinouts of HC-SR501
| Pin Number | Pin Name | Description |
| 1 | Vcc | Input voltage pin, range from 4.5V- 12V. Usually, use 5V. |
| 2 | High/Low Output (Dout) | Digital pulse high (3.3V when motion is detected), digital low (0V), when idle(no motion detected) |
| 3 | Ground | Needs to connect the ground of the system |
Applications of HC-SR501
Intruder Alarms
The sensitive Intruder Alarm is a safety purpose circuit that gives a warning or signal alert when an intruder enters a home, museum, office, bank, or any other place. It prevents robbery and heists. This effective alarm can easily detect the person, even the shadow of someone is enough to activate the circuit.
Industrial and Home Automation
Since the HC-SR501 detects movement, and gestures, and gives signals according to the output component attached to the circuit, therefore, can be used in industrial and home automation systems for safety purposes.
