Introduction Sometimes you want to hide a PIR sensor behind a plastic cover for aesthetics or protection. But many plastics block infrared, rendering the sensor useless. This article explains what works and what doesn’t. Why Most Plastics Block IR Common…

Introduction If your property is near a road with buses or a railway line, passing large vehicles may trigger your PIR sensors. These vehicles are large, warm, and moving – perfect targets for a PIR sensor. Why It Happens Buses…

Introduction After a power outage, some PIR sensors fail to resume normal operation. They may stay stuck in one state or not detect motion. This article explains why and how to fix it. Why It Happens 1. Warm-Up Period Required…

Introduction Moving curtains or blinds near a window can cause PIR sensors to false-trigger. The moving fabric creates changing IR patterns that mimic human motion. Why It Happens Curtains move in the wind from an open window or HVAC vent.…

Introduction Refrigerators and air conditioners cycle on and off, causing temperature changes and electrical noise that can trigger PIR sensors. This is a common problem in home automation. How They Cause False Triggers 1. Temperature Changes When a refrigerator compressor…

Introduction Raspberry Pi is a popular platform for PIR sensor projects, but many users report problems. This article covers the specific issues with Raspberry Pi and how to solve them. Common Issues 1. 3.3V Logic (Same as ESP32) Raspberry Pi…

Introduction Many modern microcontrollers like ESP32, Raspberry Pi Pico, and STM32 use 3.3V logic. Traditional PIR sensors like HC-SR501 are designed for 5V. Connecting them directly can cause problems. The Problems 1. Power Supply Voltage HC-SR501 requires at least 4.5V…

Introduction Insects and spiders are a surprisingly common cause of PIR sensor false triggers. A crawling insect near the lens can look like a warm moving object to the sensor. How Insects Cause False Triggers Direct Contact An insect crawling…

Introduction Outdoor PIR sensors often false-trigger during rain or snow. This is a common complaint, especially with inexpensive sensors. Understanding why helps in finding solutions. Why Rain and Snow Cause False Triggers Water Droplets on Lens Water absorbs infrared strongly.…

Introduction Just as cold weather affects PIR sensors, high temperatures can also cause problems. When ambient temperature approaches human body temperature (37°C), the contrast between a person and the background disappears, making detection difficult or impossible. Why High Temperature Causes…