Circuit diagram and things you need:
The HC-SR505 PIR sensor is affordable and small in size but it is very sensitive. I place it near the air-con air flow( not directly at the cool air path), the LED light goes ‘on’ and ‘off’ repeatedly without object moving in its sensing area. And its sensitivity cannot be adjusted also its ‘on’ timing (approx. 6-10 seconds) is fixed.
An enclosure was made to hold this project together and making it look more like a finished product/ project.
Following this post, I will use a more expensive PIR motion sensor and see its performance. Will update again in another post. Meanwhile keep building and making. 🤙