There was a time when LED light bulbs were a premium product that commanded a premium price mainly due to limited supply and simple marketing tactics. But now is not the time, as you can pick up an LED bulb at any store for a buck or two. So why on earth would you go to the effort of making your own light bulb?
for [DiodeGoneWild], the answer is simple: it’s about being in rhythm. Circadian rhythms, ie. We all know how bad light towards the blue end of the spectrum is for our sleep cycles, because it tricks our lizard brains into thinking it’s dawn. But even if you choose an LED bulb with a warm, or reddish, color temperature, the phosphor LEDs that are commonly used still emit a lot of UV light.
[DiodeGoneWild]A first attempt at a design, in the first video below, eschews most phosphor LEDs in favor of a mix of yellow, red and yellow-green LEDs to get a warm spectrum. He used the housing and base from an expired light bulb to enclose his custom circular PCB, the fabrication of which was a real treat using a hand drill as a lathe and a Dremel to machine centering tracks on the cladding. So was the power supply — a dropping capacitor and a bridge rectifier and a filtering cap. We like the discharge resistor across the cap and the fusible resistor in the main body — it’s nice to see the safety aspect right from the start. And what’s not to like about using a DVD as a makeshift spectroscope?
We see that [DiodeGoneWild] Just dropped a second design, this time with much smaller bulbs and relatively more phosphor LEDs.