Outcome.

1. It will detect if there is light around, since the dogs are supposed to go to the backyard only during the daytime. 

2. It will detect if the dogs are barking (this part was kind of tricky - I had to play with the sensibility of the microphone so it could differentiate very loud from not very loud noises).

3. The Servo Motor acts as a door latch  and if the microphone hears the barks (or very loud noises) it will rotate 90. 

4. The door will be open, and the dogs will be able to push it so they can go out. A notification will be sent. 

5. I included a button so the latch can be closed again. 

While I was doing this project I realised that probably the microphone was not the most effective idea to detect if the dogs are ready to go out, since there might be other loud noises around. Therefore, if I was to continue to develop this solution, I would probably try this solution and also a limit switch to react to the dogs' push and see which one works best.