I don't have time to complete this at the moment, so I'll just jot down a few details for posterity. The goal of the project is to create a bright ring light, adjustable and with long battery life, suitable for macro photography. For materials, I'll cannibalize a 12 V Milwaukee Li-Ion battery pack (and charger) that I found by the side of the road (unfortunately, the drill was beyond repair), and use 3 automotive ring-shaped headlights, purchased for a dollar or two each on Amazon.
I intend to preserve the portion of the battery casing that interfaces with the charger, so I can plug the macro light into the charger as if it were a stock battery. A three-piece 3D-printed casing (along with a donut-shaped a piece of acrylic, sanded for light-dispersion) will fit around this, and will be secured together with 5 socket-head cap screws. A 52 mm threaded filter-ring (for screwing the macro-light onto a camera) will be press-fit and glued in-place against a ridge in the center piece of the printed casing.
For dimming, the ring lights will be powered one, two, or three at a time with 12V DC, rather than by PWM or other modulation scheme, to avoid rolling-shutter artifacts.
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