This is a followup of my previous post.
I have managed to integrate multiple sensors into a single system capable of sensing if the entrance door is locked/unlocked, if there is a motion inside the apartment and to record the temperature and humidity.

It all started with the status of the entrance door. I wanted a system capable of sensing the status of the lock, but to be able to work without any electrical contacts, since it may corrupt the sensor in time. So I have found an inductive (contactless) switch and I have placed it in the entrance door of my apartment. It is connected to one of my raspberry pi computers, and it sends the information about the state of the door lock to my main server.

You may wonder why are the headphones attached to the Pi. They emit the annoying sound of sine waveform, frequency of 3000Hz when the door is unlocked for more than one minute. That way I have a reminder that I need to lock the door.

The red LED is an indicator of the door lock status. If it is red, the door is locked. However, going to the door to see if it is locked or unlocked is not too attractive. I had to invent some way to know the door status without actually going to the door. That is why I have developed the Android application for it:

The lock icon goes red when the door is locked (the time is written below the icon), and goes green when the door is unlocked. The notification comes in real time thanks to the Google Cloud Messaging.

Next came the web portal. I wanted to have the history of door locking and unlocking. That is how I made this web page:

The red cell in the table indicates that there was some motion detected after the door has been locked. This is the proper introduction for the motion detection sensors: after adding door lock and temperature sensors, I wanted to add motion detection sensors inside the apartment. I have used HC SR-501 PIR motion detector: