This round earring with a diameter of 31 mm has eight LEDs, a voltage regulator, an MSP430 microcontroller together with some passive components.

Project available in the following languages:

  • English
  • German / Deutsch
  • Spanish / Español
  • French / Français
  • Dutch / Nederlands


At Elektor, everything can turn into an electronic device.

This round shaped earring with a diameter of 31 mm basically includes eight LEDs, a voltage regulator, an MSP430 microcontroller and some passive components, and it's powered by a CR2032 battery. At this point there are two firmware versions available, but it's also possible to reprogram the device by means of the UART-interface. Current software versions include four different light patterns in both directions (clockwise and anticlockwise), switching between them with the pushbutton. It's about a low power design, and it needs only about 4.45 mA at 2.8 V (12 mW) when LEDs are multiplexed.

You may see this video during the development stages, taken while the program wasn't still complete.

This article was first published as Elektor.POST No. 1.


(We would like to thank Mr. Colin Mitchell for his comments and contribution!)

  • The text mentions that the current through the LEDs is limited by means of 100 Ω series resistors. The correct value is 220 Ω (as noted on the schematics).
  • Figure 2 caption may be hard to understand in the English version, please see the following: "only add a very small blob of solder to the board to prevent a short-circuit with other contacts".
  • The debouncing is indeed implemented by software and not by means of C5, as the text notes.