Inner Workings of the PlayJack LED Ping Pong Table and Paddles
If you were at SXSW 2018 hopefully you were able to stop by the BEYOND WORDS booth to check out the PlayJack LED Ping Pong Table. Although we have been primarily using PlayJack for live music events, the objective of bringing the ping pong table was to demonstrate the concept of PlayJack in a simple and fun way for SXSW participants to try for themselves.
Inside each handle is an Arduino Pro mini, a NRF24L01+ transceiver, a piezo disc and a small quadcopter battery. These are the main components for all the PlayJack prototypes at the moment. They are simple, but effective. Using basic radio signals instead of wifi or bluetooth to communicate means there is no setup time or latency when using these devices. Just turn on and play.
The focus when designing the prototypes was to keep it compact and robust at a low cost. All the parts we use are small, cheap and readily available. This setup has proven to be reliable and is small enough that I was able to fit it all into the handle of a ping pong paddle. The Arduino we use is the Arduino Pro Mini regulated for 3.3v. This is important because the the NRF24L01+ can burn out if you power it with 5V. Additionally, the lipo batteries we use don’t go much higher than 4.2V at full charge.
For assembly I mounted the piezo disc, radio transceiver, and Arduino on one side, and then the battery, power switch and charging port on the other side of the handle. This paddle also has three 2N7000 MOSFETs, one to control each color of the 5V RGB tape wrapped around the edge of the paddle. Even though the battery was putting out around 4V, brightness or power was never an issue. To close it up 3D printed covers were made and taped to the wooden handle with a little electrical tape. After that I made laser cut end caps and and wrapped the entire handle with grip tape to make it look and feel like a normal ping pong paddle.
For the table we decided to build onto an existing foldable ping pong table we bought off of Amazon. The main differences between the paddles and the table is that the paddles have a piezo disc to measure vibrations while the table controller has a TIP122 transistor to control the LED strips. Because space is less of an issue on the table, we are able to have a power adapter and battery pack to supply 12V so we went with the brighter 12V SMD5050 RGD LED tape. We only used green for our demonstration so the table controller was wired to only control the green channel on the LED tape to make trouble shooting easier if problems came up while we were using it nonstop at SXSW. Thankfully we didn’t run into any issues. Despite limiting the controller to only green, the table itself was wired with generic RGB connectors with each side of the table running as separate circuits. Changing controllers to control each side of the table’s LEDs independently or to use RGB colors only takes a few seconds.
Since we were coming from Tokyo we had to make the table portable, so all the LED wiring has breaks in it so the table can fold up and be taken on a plane. (This is also why the table was so small) The controller and battery pack are mounted under the table along with the power adapter so it can be used in any environment!
That’s the gist of it at the moment. We are considering adding some more lighting to and maybe a sound element to it similar to what we did with our version of Othello. If you are interested in seeing more of PlayJack watch the video below!
Playjack site: playjack.jp
Konel site: konel.jp
