Motion Detector
I needed a way to know if a person was approaching somewhere so I made this motion detector. It uses a PIR sensor to detect movement and sends an SMS to a predetermined phone number. It worked flawlessly with only a few false positives.
First Version
The first version was put together in limited time. Its powered externally by a 9V battery. The top breadboard is the power supply, stepping the voltage down to 5V for the Arduino microcontroller and 3.3V for the sms module. It had limited battery life with no way to know if the battery had run out.
Second version
This improved version uses an 18650 battery internally for power and a boost converter to step it up to 5V for the Arduino. It has a power switch and usb-c charging port accessible from outside. It featured a battery percentage reading whenever it send an SMS and a low battery warning SMS. Its battery life and size were significantly improved over the original version.
I want to improve this project even further by creating a PCB for it, and using a flat lithium battery and an ATtiny85 as a microcontroller in order to make it even more compact and power efficient.