This Supercapacitor and Solar-Powered Freeform Circuit Will Blink an LED Forever

We all know that perpetual motion devices are impossible, because of the first law of thermodynamics — energy can’t be created or destroyed, only transferred. But that doesn’t mean you can’t create a device that runs forever, or at least until the sun dies or the device itself fails. There are, of course, a great deal of devices that are powered by solar energy. Redditor Xancestor built one such device, which is a freeform LED circuit that is powered indefinitely by a supercapacitor and small solar panels.

Freeform circuits have been trending lately, and we’ve featured quite a few of them in the past. These tend to be more artistic than PCB, perf board, and breadboard circuits, so it makes sense that they tend to be less practical than many of the projects we cover. Without a need for practicality, the builders are free to express their creativity. In this case, the device’s only purpose is to blink an LED once every seven seconds, and to continue doing so as long as it is exposed to light — though the supercapacitor stores enough energy to keep it blinking through the night.

The circuit is made completely with discrete components, which are mostly resistors, capacitors, and a couple of transistors. There isn’t even a timer chip involved. Instead, the solar panels, which were salvaged from solar-powered calculators, slowly charge up the supercapacitor. That, in turn, charges up a “trigger” capacitor. Once that reaches the proper voltage, it discharges and switches on the circuit that connects the supercapacitor to the LED. That trigger capacitor is quickly depleted, and the circuit is switched back off. The process simply repeats indefinitely. Adjusting the resistor and capacitor values makes it possible to change the blinking interval. The freeform structure was constructed from brass rods, which gives the device a cool handcrafted aesthetic.