Not for playing tennis!

This is a "smart" replacement for the classic tennis-ball-hanging-from-the-garage-ceiling-so-you-know-when-to-stop trick.

Embedded inside is an MPU-6050 accelerometer/gyro and 8 LEDs with current limiters. These are connected through the cable to an arduino pro mini which runs a sketch based on Jarzebski's libraries.

When the car's windshield disturbs the tennis ball, the lights flash, letting you know the car is far enough in for the door to be closed. Positioning of the tennis ball is crucial.

The arduino will do other things, like monitor the state of the garage door, and relay the various events to the home automation system I'm working on.

I printed the bottom at an angle, with supports, so that the little tabs come out ok. Was moderately successul (see screen shot).

I hot-glued some weights in the bottom to help it hang properly.

https://playground.arduino.cc/Main/MPU-6050
https://github.com/jarzebski/Arduino-MPU6050