Anonymous
Mar 11, 2026
Rating: 5/5
Reliable motion detection
Using this to trigger an LED strip in my hallway. The response time is instant, and the build quality feels solid despite the low cost.
Description
Reviews
| Brand | - |
| Category | Robotics / STEM Teaching Tools / Sensors |
| Origin | - |
| Model Number | HC-SR501 |
| Operating Voltage | DC 4.5V - 20V |
| Detection Distance | Up to 7 meters |
| Detection Angle | < 120 degrees cone angle |
| Trigger Mode | L (Repeatable) / H (Non-repeatable) |
| Delay Time | Adjustable from 5s to 300s |
| Blockade Time | Default 2.5s (adjustable) |
| PCB Dimensions | 32mm x 24mm |
| Lens Type | Fresnel Lens included |
| Output Signal | 3.3V High / 0V Low |
Anonymous
Mar 11, 2026
Rating: 5/5
Reliable motion detection
Using this to trigger an LED strip in my hallway. The response time is instant, and the build quality feels solid despite the low cost.
Anonymous
Mar 08, 2026
Rating: 4/5
Good value but needs calibration
Great little module for the price. It took a minute to calibrate the sensitivity knobs to avoid false triggers from my ceiling fan, but once set, it has been reliable.
Anonymous
Mar 08, 2026
Rating: 5/5
Essential for robotics class
Bought five of these for our university robotics project. They are consistent, easy to wire, and the documentation online is plentiful. Highly recommend for students.
Anonymous
Mar 06, 2026
Rating: 5/5
Exceeded expectations
I was worried about the detection angle being too narrow, but it covers my entire doorway perfectly. Very happy with this purchase.
Anonymous
Mar 05, 2026
Rating: 4/5
Works as expected
Standard PIR sensor performance. The jumper settings for repeatable vs non-repeatable mode are clearly marked on the board. Just remember it needs a warm-up period after power-on.
Anonymous
Mar 02, 2026
Rating: 5/5
Perfect for Arduino projects
This sensor works flawlessly with my Arduino Uno. The detection range is accurate, and the delay adjustment potentiometer makes it very versatile for different lighting applications.
Q: Is the Fresnel lens removable for custom optics?
A: Yes, the white dome Fresnel lens can be gently removed if you wish to use a different lens or expose the raw pyroelectric element for specific experimental setups.
Q: Can this sensor detect motion through glass or thin walls?
A: No, PIR sensors detect infrared radiation emitted by bodies. Glass and most solid walls block IR radiation, so the sensor requires a direct line of sight to detect motion effectively.
Q: How long does the sensor need to stabilize after powering on?
A: The sensor typically requires an initial calibration period of about 30 to 60 seconds after being powered on. During this time, the LED may flash, and detection might be inconsistent.
Q: Does this module work directly with 5V Raspberry Pi GPIO pins?
A: Yes, the HC-SR501 operates between 4.5V and 20V, and its output is 3.3V high, which is safe for Raspberry Pi GPIO inputs without needing a level shifter.
Q: What is the difference between L and H trigger modes?
A: In 'H' (Non-repeatable) mode, the output stays high only for the set delay time after motion stops. In 'L' (Repeatable) mode, the timer resets every time new motion is detected, keeping the output high as long as movement continues.