Today there are quite a number of wind-up DC power generation consumer products including radios, flashlights and even cell-phone rechargers. In 1998 this South African manufacturer designed a recharging and powering product that was unlike any other that had been produced to date.
It used not just a clock-type wind-up spring to power the radio, but it used a patented and proprietary circuity to store the power and use it only when the radio needed more power.
The heart of the system was a small DC motor, which when spun in reverse, became a nice, fairly efficient DC electrical generator. Due to patent restrictions, most of the wind-up consumer products today, use only the DC motor/generator for power (only works when you are cranking the gear-drive hand crank), or charges a small capacitor or rechargeable NiCad/NiMH battery set.
The original version of this product used a small capacitor to temporariy store the hand-cranked power. You would crank the handle about 30 times which would wind-up a large internal clock spring, which would then unwind as it spins the DC generator.
The difference with this product and any others was that it had a circuit that could read the amount of stored power in the capacitor and then discharge it to the radio circuit as needed (mostly dependent on the sound volume selected). This patented feature allowed a much longer play time for the radio compared to radios that were just powered directly by the hand-crank or from power stored in a battery or capacitor.
While this product was originally developed for the African remote village market, the manufacturer wanted to expand their markets to the U.S. consumer market where the wind-up radio could be used by anyone needing a radio that was not dependent on batteries. Intended markets were consumers who wanted a radio at the beach, on the boat, while camping, car-washing, gardening etc. An unintended market which caused a dramatic serge in sales, was the Y2K event where concerned radio users thought they needed an emergency radio (actually a valid market in case of storms, power outages, etc.) in case the Y2K publicized embedded chip failure (many computer chips were not originally programmed to recognize the year 2000 and it was thought that many microprocessor controlled consumer and industrial devices would stop working at midnight, December 1999).
So that the consumer would not have to constantly wind-up the radio every 30 minutes, the producer came to PHOTON TECHNOLOIGES with an idea:
Design, Develop and Integrate a small, efficient and inexpensive solar panel into the radio to allow the radio to be directly powered by the panel, with no need to continually rewind it.
Since the radio may be used in a shaded or less than direct sunlight environment, PHOTON TECHNOLOGIES chose an Amorphous Thin-Film solar panel rather than a traditional Crystalline (thin, delicate blue solar cells) since a Thin-Film panel, while not as powerful size for size, it offers a much better power response to lower light levels, especially when used indoors under artificial lighting (per solar powered calculators).
The radio was made of a high-impact plastic and was subject to dropping and outdoor abuse, therefore instead of the typicaly glass Thin-Film solar panel as is used in solar powered calculators, PHOTON TECHNOLOGIES chose a Plastic, Flexble Thin-Film solar panel that was produced in the United States.
The development and the matching of a small solar panel to the power needs of this radio product included considerable evaluation of the radio's circuit, it's speaker (a 4" speaker) and the various environmental conditions that the radion would be used in.
It was found that the circuit only drew about 10-20 mA at half volume, even driving the large 4" speaker. It was also found that the larger size speaker allowed the radio to "sound" louder that a similar radio circuit driving a smaller speaker which would consume more power with less sound output.
Since the radio would normally be used outdoors and may be subject to an occasional sprinkle of moisture (gardening, car washing, beach, etc.) the solar panel which was not rated as an "outdoors" panel to keep the cost down, was fitted into an inset molded tray which would protect it from impact. The inset area was then covered by a clear acrylic thin, stiff lens which first had a black band printed on its backside to cover the solar panel wiring, and then coated at the back edges with a strong acrylic adhesive which permenently glued the lens down to the face of the solar panel inset area. This offered a high degree of impact and moisture protection to the solar panel.
This radio product was a tremendous success and led to many wind-up associated products such as solar/wind-up flashlights and cell-phone chargers.
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