Michael Yim's Badge-Waving SAO Delivers a Double-Sided Programmable Persistence of Vision Display

Maker Michael Yim wants you to wave your badge like you just don't care — in order to reveal secret messages through persistence of vision (POV), with the suitably-named POV Display Simple Add-On (SAO).

"It's an accelerometer-based hand-waved POV display featuring front and back LEDs to create two 5 pixel × 12 character display[s]," Yim explains of the compact badge add-on. "The device uses an [Analog Devices] ADXL345 accelerometer to track motion, enabling the user to just wave the SAO to show a message. Users can customize the message displayed via I2C, allowing flexibility in creating unique text or patterns. The combination of front and back LEDs ensures visibility from multiple angles, making this a versatile and engaging display for any application."

As Yim says, the heart of the device is the Analog ADXL345, a low-power three-axis accelerometer. Five surface-mount LEDs are found on both the back and the front of the board, which features the standard SAO connector — meaning it can be linked to any SAO-compatible badge for power and to have its messages, stored in its on-board Padauk PFC232 microcontroller, modified over an I2C bus.

In use, it's like any other POV display — relying on the human eye's inability to properly track fast-moving lights to turn cleverly-programmed flickers into visible text or images that appear to hover, briefly, in mid-air. The accelerometer means that the display is as easy to use as possible: just wave your badge with connected SAO in the air, and the message will appear.

"To streamline the testing process, I put together a quick and simple testing rig using an Arduino Pro Micro, a tactile button, and a protoboard," Yim writes of his development and testing process. "This setup allows me to power the POV display and test its functionality efficiently."

More information on the project is available on Hackaday.io, where Yim has also released Eagle schematic and layout files for those looking to build their own.