In situations where your CV isn't expected to be comprehensive, it helps to think of it as telling a story. The purpose of the story is to get you an interview, to influence what is discussed in the interview, and ultimately, to get help get you the job.
Personal projects can suggest that you are more than your work history, or they can help people see a common theme in your work history that may not be obvious.
Personal projects can also be used to entice the interest of the reviewer. When reviewing a lot of applications, people will often do successive iterations to get to the short list of people to interview. The interviews themselves can be a chore. The chance to talk to you about an intriguing personal project might be enough to get you the interview over a slightly more (on paper) qualified candidate.
The idea that it doesn't count if you don't get paid is worth putting aside. An average employer just cares that its employees do what they are paid to do. A great employer knows that having employees who love, or at least like their work is good for both sides. At the very least, personal projects show that you don't just do electronics design because you get paid to do it, you do it because you like it.
So, what story do you want to tell? What is your audience going to be receptive to?