Robotic Ping-Pong Ball Launcher

youmagine

This is something I made for a Cub Scout "Invention Convention" pack meeting. At one station, we taught kids to use TinkerCAD (www.tinkercad.com), an extremely easy-to-learn, highly useful, free online CAD package that I used to design 3D printed parts for this project, both to learn and show kids how you can do something engineering-like with it. At another station, we taught kids to program these simple robots using a graphical programmer for Arduino called Modkit. You can find the link for the Arduino programming software at http://www.modkit.com/micro, which is free at this writing. Side note, at the third station, we taught them to solder a simple flashlight circuit, and I'm happy to say that I was the only person burned (and then only slightly) by a 9-year-old handling a soldering iron. No cub scouts were harmed in making these flashlights. I didn't feel that I could get the resolution needed for the servo horns, so I just hot glued the servo horns to the 3D printed pieces. Something else not obvious from the picture is that I placed a small triangular piece of foam behind the bottom end of the ping-pong-throwing arm. This makes the arm throw at about a 45-degree angle without causing any sharp impacts. There are attached pictures showing the circuit, but there's one important note: The Arduino will not provide enough current to drive the two servos, so I added a separate power supply for those. Before doing that, the servos would cause the Arduino to reboot randomly. Because of where I soldered the servos (on the 5V supplied from the Arduino), I needed to cut that trace or expect letting the magic smoke out of the chip. So, I suggest cutting the 5V trace as I did, and as shown in the picture, or soldering the servos in a different spot. For the 5V servo power supply, I used a 3-pin keyed header so I wouldn't accidentally plug it in backwards. You could also cut off the end of the wall wart and solder it down. Note that to power the Arduino as a whole, I used the USB cable since I needed that anyway to program the Arduino. In terms of wiring, I put the servos on pins 10 and 11 and the switch on pin 7, but these were mostly arbitrary.