{"id":193,"date":"2011-06-02T21:23:52","date_gmt":"2011-06-03T01:23:52","guid":{"rendered":"http:\/\/hackaweek.com\/hacks\/?p=193"},"modified":"2011-08-19T21:01:36","modified_gmt":"2011-08-20T01:01:36","slug":"the-photophone","status":"publish","type":"post","link":"http:\/\/hackaweek.com\/hacks\/the-photophone\/","title":{"rendered":"The Photophone"},"content":{"rendered":"

In Februrary of 1880, Alexander Graham Bell and his assistant Charles Sumner Tainter invented a device that allowed the transmission of sound via a beam of light. It was called the Photophone<\/a>. Bell believed the Photophone was his most important invention! Indeed, 100 years later in the 1980s fiber optics came into widespread use. It is noted on a plaque that on June 3rd, 1880 the first wireless transmission of a telephone message using the Photophone took place. This year marks the 131st anniversary of this event. <\/p>\n

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Bell’s Photophone used crystalline selenium cells at the focal point of its parabolic receiver. My version uses a solar cell as the receiver. The transmitter is a mirror attached to a speaker aimed at the solar cell. The mirror is aligned so that it reflects the Suns rays onto the solar cell. The solar cell is mounted at one end of a black 4″ ABS pipe about 2 feet long. The light reflecting off the mirror is modulated by the vibrating speaker. The Solar cell receives this modulated wave of light and outputs a corresponding modulated voltage that can be fed into an amplifier and output through a speaker to produce audio. A 0.1 uF capacitor is connected in series between the solar panel and the amp. <\/p>\n

The whole project is quite simple and fun to build. Enjoy the video and.. as always, Keep On Hackin! <\/p>\n