A Supercapacitor USB LED Flashlight

Traditionally, a 1 farad capacitor is huge, and can be dangerous, capable of releasing a high-voltage charge in an instant. Supercapacitors, though, generally have a much lower voltage rating, meaning that the danger of electrical shock is also a bit lower. However, since they're capable of extremely quick discharge when compared to batteries, there is a danger of melting wires and possibly even fire when not set up correctly.

That being said, you may understandably be hesitant to experiment with these amazing devices, so perhaps what's needed is a sort of microcontroller-esque "hello" world in the form of blinking powering an LED. As seen in the video below, I did just that, using a 1F, 5.5V capacitor to power an LED through a 200 ohm resistor. Unlike a coin cell, where a resistor is a "good idea," given the amount of current a supercap can discharge extremely quickly, not having a proper resistor in-line with the LED would likely break things in short order.

For charging, I used a USB A breakout board, putting a small resistor in-line between the + and supercapacitor here as well (~12 ohms) to limit current rushing in. It's possible that this element isn't necessary, but better safe than sorry when potentially frying more expensive electronics.

Besides being a neat experiment with this still-exotic charge holding device, it's actually a pretty practical emergency lighting setup. After around a 30-second charge, it provides usable light for close to an hour, though it does fade out incrementally. I also made a second configuration with a tiny constant voltage driver, and while the light did stay much brighter until entirely discharged, the light only lasted around 2 1/2 minutes.