Mailbox notifier that sends and MQTT message when mail arrives (mailbox is opened). Uses a 6 volt solar panel and TP4056 charge controller to charge a 18650 battery. A door/window magnet sensor is connected to a Wemos D1 mini. MQTT message is send to my Home Assistant instance.

Parts:

• Wemos D1 mini
• wires
• breadboad
• 18650 battery (to give run time over night)
• solar panel - I used 6 volt, 3w size 145mm x 145mm https://www.amazon.com/dp/B081ZSXBJ4?ref=ppx_yo2ov_dt_b_product_details&th=1
• I used a plastic enclosure box I had on hand, although you could print a box
• 3D printed parts
• magnet door/window sensor, something like: https://www.amazon.com/Dairzitv-Surface-Sensor-Magnetic-Switch/dp/B09XL85C3Z/ref=sr_1_2_sspa?crid=3CCRGTCTQL5RK&keywords=magnetic+door+sensor&qid=1663961969&qu=eyJxc2MiOiI0LjQ0IiwicXNhIjoiNC40NyIsInFzcCI6IjQuMjEifQ%3D%3D&s=hi&sprefix=magnetic+door+sensor%2Ctools%2C109&sr=1-2-spons&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUEzUzhLMFlOWDBISklDJmVuY3J5cHRlZElkPUEwMTI0OTI3T08zWkkwM05SSlVEJmVuY3J5cHRlZEFkSWQ9QTA4OTUxNjE5STQwNTNLUUcwMlkmd2lkZ2V0TmFtZT1zcF9hdGYmYWN0aW9uPWNsaWNrUmVkaXJlY3QmZG9Ob3RMb2dDbGljaz10cnVl

Sends the MQTT messages via wifi, so make sure you have adequate coverage / range to your mailbox.