Point Abino Lighthouse Joule Thief Flasher

Point Abino Lighthouse Model - 3D PRINT

The original design was going to use a PICAXE-08M2 microcontroller (MCU). With an MCU, I can control the exact light time and flash duration. I've experimented with an intelligent RGB LED and could reproduce almost any color of light. But, alas, the one restraining limitation was the power source. Being a tiny model, the power source would have to be external. So, I changed the criterion for the light and settled for a rough approximation of the light.

Searching the internet for a solution, I stumbled across a circuit that fit the use perfectly.

The ubiquitous Joule Thief circuit, and one that flashes the LED.

The Joule Thief circuit is known for its miserly power usage and voltage boost. That means the battery will last a long time (the circuit works just fine with nearly dead batteries) and provide a voltage boost to light higher voltage white LEDs. This particular circuit has a great advantage: it is super simple, with a minimum number of active and passive components. See the schematic for the parts list.

The original circuit used an air core inductor. To minimize the size, I selected a high permeability ferrite toroid core - Fair-Rite 2673002402. I used #30 wire-wrap with 12 turns for the red primary and 6 turns for the two secondaries. Note the phasing of the winding as per the schematic. Get it wrong, and the circuit will not work.

Does this circuit create RF interference? You bet it does. Just hold an AM radio near the circuit to hear the gorgeous harmonics sweeping across the band. Using a toroid minimizes the effect, and a small distance away, it can't be heard on the radio.