[jyl]

In need of a simple electrical circuit.

My bicycle has a generator hub, with two contacts, hot and ground. When riding at 10+ mph, it produces 6 volts AC and will drive two LED headlights wired in parallel. Voltage and frequency are speed dependent. At 7 mph it produces 5 volts, at 5 mph 3 volts. When the bicycle is stationary, such as at a stoplight, the hub produces 0 volts, obviously.

Goal 1: to incorporate a rechargeable battery or super capacitor in the circuit, so that one (or if possible both) of the lights will stay illuminated for a few minutes when the bicycle is stationary.

Goal 2: to switch power from both lights to only one light, when the hub voltage drops below 5 volts, then to switch power back to both lights, when hub voltage rises above 5 volts.

Goal 3: to do this with common electrical components, all analog stuff, that even I can solder together.

Goal 4: to fit this all in a very small, weatherproof box (ideally about Altoid tin size) that can be mounted to the underside of my front rack.

Any ideas?