What is it?

This is a simple circuit using a LMC555CTP timer to supply a clock pulse to a TI SN74LV163ARGYR binary counter that controls three dual FFB3904 FETs to sequentially light a pair of small LX0404SIUPG rbg leds that make up the eyes of an electronic owl. The pendant is designed to be worn so it is 3 - 5 V battery powered, and made as small as possible so the action is programmed without a microcontroller. At just 14 mm x 14 mm, this pendant packs a lot of electronic circuitry on both sides. This design should be fascinating for the technogeeks and hardware mavens, but the glowing eyes of the owl will mesmerize and appeal to the fashion sense of stylish girls and daring men. The circuit sequentially activates the rgb leds and the RC network add some delay so the colors persist. I am still tuning the resistors to get the most pleasing intensities of the red, green, and blue leds all of which have a different forward voltage and require a specific resistance for color balance. There is an on-board Murata PVZ2A474 470K potentiometer which controls the rate of the sequence from ~0.5 Hz to ~5 Hz. The user can change the rate at which the colors change to suit the occasion. There is a small switch for off/on operation.

Why did you make it?

I programmed an Arduino Pro Mini to use PWM to run through the colors of the rainbow with an RGB led and found the effect both soothing and fascinating to watch. I wanted a super small wearable that could approximate the effect. Of course, it would be possible to design a very small board with an AVR or ATTiny processor and reproduce the effect but it was a challenge to design a circuit that could approximate the effect without a microcontroller, used fairly inexpensive components, and was as small as possible. Also, my daughter's school mascot is an owl so I made it for her so she could impress her friends.

What makes it special?

It turned out beautifully and worked the first time I put it together. It is really a piece of electronic jewelry that will turn heads and cause constant comment. Guys, your girlfriends and wives will both love one! Men, do you dare wear electronic jewelry? Order the board from OSH Park and assemble your own, or order the fully assembled and tested electronic owl from me and see how beautiful and enchanting electronic jewelry can be!

Bad video below but you can get an idea of the effect. The 1K current limiting resistors on the rgb leds are really too small; I am experimenting with 10K, 4K7, and 2K2 on the R, G, B, respectively, in order to reduce the high intensity you see in the video, balance the colors so red doesn't dominate, and reduce power consumption so a small coin cell battery can allow hours of continuous use.