In order to actually open a door, we will need some help from the inside. Servomotors are the most common motors used in robotics and they are very easy to operate. There are two kinds of servomotors, there are the standard ones that only rotate 180 degrees and there are the continuous rotation servos that can rotate as much as you want in both directions. The trade-off with continuous rotation servos is that they are less precise. For this project, we will be using a standard servo since we only need to turn 45 degrees and the standard servo is usually more precise than the continuous rotation servo. Again, this depends on the kind of door you have. There is no such thing as a universal door, and you might need to modify the design of this project a bit depending on the door you have. In the next section of this chapter, we will take a closer look at the doors I used for this project, but first let's just take a quick look at how to operate the motor.

As servomotors...