Ask a Hackaday scribe who’s helped run the lightning talks at one of our events, and they’ll tell you that keeping the speakers on time is a challenge. Conversely if the staffer is trying to indicate to the speaker how much time they have left, it must be difficult from the podium to keep track while delivering your talk. Fortunately there’s [makeTVee] waiting in the wings with a solution, a cube whose faces each have a custom 5×7 LED matrix on them. The countdown is clear and unambiguous, and should provide no distractions.

The brains behind it all is a XIAO nRF52840 Sense board using the Zephyr RTOS, the LEDs are WS2812s on their own PCBs, and the party piece is only revealed at the end of the countdown. A tilt mechanism triggered by a servo releases a ball bearing down a track, where it hits a telephone bell and provides a very audible reminder to the speaker. The result saw action during the lightning talks at the Hackaday Europe event earlier in the year, but it’s taken a while for the write-up to make it online.