TritiLED

These tiny lights shine clearly in the dark, glowing for over two and a half years on a single CR2032 battery.

The pushbutton selects the run time, from 1 year to 7 years (approximately). To change the runtime, remove the battery and wait about 10 seconds for the capacitor to drain. Then reinsert the battery and press the button to cycle through brightnesses (and by extension lifetime). Wait a second and the selected runtime will blink several times, then set until the battery is removed.

What are these for?

Tritium lights are cool. This is a known fact. However, they are expensive, potentially hazardous, and not suitable for a lot of applications. That's where the TritiLED comes into play; it's relatively low cost, safe (as long as you don't eat the battery) and easily attached to anywhere you need a permanent light with a magnet or some double sided foam-tape. I have them around my apartment marking off the corners of tables so I suffer less late-night bumps.

How does it work?

This entire project was built with efficiency as its main objective. The LED is chosen for ideal visual registration in low light, and the 60Hz pulse circuitry is configured to provide a regulated pulse that uses a minimum amount of power without any visible flickering.

The circuit is essentially a single shot boost regulator, being driven by a microcontroller to pulse at a specified rate. The driver MOSFET is opened for a single cycle before being released, resulting in a brief flow of current through the inductor, which stores energy. Once the MOSFET is closed the voltage across the inductor spikes, activating the LED and releasing the stored energy as light with very little electrical loss.