Chirping bird pendant

This tiny free-form soldering circuit by Jack Spiggle (aka NanoRobotGeek) is a masterpiece of miniaturisation. The key to this build is the KXOB25-02X8F-TB solar panel, which generates 5.5 volts in the bright Australian sunshine. As with Jack’s other builds, the solar panel charges a capacitor, which, when it’s full, activates the circuit – in this case, that’s four oscillators making a ‘chirp’ sound via a piezo speaker.

We can only imagine how hard it must be to perform free-form soldering on a circuit this small and get it so neat (Jack says that working with brass is a headache, as it conducts heat away from solder so quickly).