While playing tennis, we saw a strange device on a racket from one visitor. After questioning, it turned out that he determines the force of impact and the position of the ball. However, it is not as accurate as we would like and was too cumbersome. Having looked through the Internet, we learned that such devices are developed by different companies and all have different disadvantages. And then it was decided to develop its own sensor, which would be as effective as possible and show only the really necessary information to the athlete in the application for a reasonable fee.