Solar Calculator

I am not absolutely certain, but I think I invented the world's first solar calculator. Take a look:

Note the red wires barely visible exiting the battery compartment at the top right edge of the calculator. These wires connect the solar cells to the battery terminals inside the calculator.

This photo shows the six silicon solar cells, arranged in two columns of three. They are covered with silicone rubber. The red wires are clearly visible, and there is a very thin copper wire (ground) which is not visible going from the center of the two columns of cells to the "middle" contact of the battery compartment.

The calculator is a Teal LC811, serial number 159240. I bought it at the Disco-Mart near 39th St. in Portland, Oregon in 1973 and added the solar cells to it immediately. (I am an inventor at heart). The solar cells are 200 MA (gross overkill!) "satellite" cells, and 6 are needed because the calculator used two watch batteries. Interestingly, the batteries were "tapped" in the middle, providing +1.5 and -1.5V (CMOS, anyone?) so I had to do the same with the solar cells.

The calculator was one of the first consumer Liquid Crystal Display (LCD) calculators, which are the only designs that are practical to power with room light. I was very interested in photovoltaic cells when I saw it and I immediately wondered if it could be run directly from cell output. I put this together before I had ever seen a commercial solar calculator...

Yes, it still works. No, I never patented it so I will not send money to your charitable cause.... ;-)


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David Butcher
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