I made the similar project, but cheaper cost (in total) and can be used for industrial environment here: https://www.hackster.io/phpoc_man/phpoc-monitoring-door-open-via-facebook-messenger-49603eSystem Architecture
- One pin to GND.
- Another pin to A0.
Follow 12 steps (see red square)
1. Create Applet.
2. Set trigger.
3. Search "Webhooks" and click Webhooks.
4. Choose "Receive a web request."
5. set Event Name is "door_open" and click "Create trigger" button.
6. Click "+that" button to create the action.
7. Search "Facebook Messenger" and click.
8. Choose Action "Send message". It needs to connect to Facebook for the first time.
9. Create the content of message and then click "Add ingredient" button.
10. Choose "OccurredAt". This is time of door open.
11. Click "Create action" button.
12. Click "Finish" button
Now Applet is created.Get Webhooks Key
Go to this link https://ifttt.com/maker_webhooks
Click "Documentation" to see the Webhooks Key.
Copy the Webhook Key and put it in Arduino code.LibraryThe Best Arduino Starter Kit for Beginner
If you are looking for an Arduino kit, see The Best Arduino Kit for Beginners