Vermes
Advanced Member level 4
This device can be useful during bicycle trips, when you need power to supply a GPS, charge accumulators in a camera or a mobile phone. Photovoltaic cells are very popular for that purpose, but sunny days do not occur every day. A good solution for that problem is a hub which is both a dynamo.
Its main advantages are:
- low rolling resistance
- durability
- water resistance
Such a dynamo produces alternating current -6V -3W. It is sufficient to power a bicycle lighting, and to charge different devices necessary during a day trip.
Charger:
The charger consists of a classical power supply based on regulated stabilizer LM317. Diodes D1 to D4 adn Schottky diodes. The characteristic feature is a small capacity of the connector, so that a typical switching time is only about 100ps. Schottky diodes also have a smaller voltage drop in the direction of conduction.
C3 capacitor – 10uF causes greater than fivefold increase in ripple and impulse interference attenuation. Ripple attenuation coeficient of the output voltage LM317 will be about 80dB. With that additional capacitor, use protective diode D6, which should discharge the capacitor in case of short circuit of the system output. Diode D5 is a protection against too high output voltage – this may happen immediately after power is turned off. Then the diode becomes conductive and drains „reverse” current from the tip of the stabilizer.
Dynamo, Shimano -6V/3W
Power supply in the housing with a switch.
Link to original thread (useful attachment) – Rowerowa ładowarka - Zasilacz USB
