Very simple question:

Discussion in 'General Electronics Chat' started by shawd, Oct 14, 2010.

  1. shawd

    Thread Starter New Member

    Sep 20, 2009
    14
    1
    I was taking apart a simple pocket calculator, interested in perhaps harvesting the solar cell(Texas Instruments: TI-1706SV) and i was looking at the circuit board and found where the solar cell was hooked up, but also i found a very tiny alkaline cell battery ( GP189 ). I was interested and fussed with it and took it out of its holding place, and then the calculator wouldn't work anymore. But i put the battery back in, and then it started working again. If calculators are supposed to run off solar cells, whats the extra battery in the board for? Is a calculator not able to run fully on a 1.5 volt solar cell?
    Thanks
    PS here is a pic i found online of it, (top picture) not exactly the same layout. theres only two wires in mine instead of the four shown in the pic, and they run from the solar cell, but the battery looks the same.
    http://www.datamath.org/BASIC/LCD_Modern/JPEG_TI-1706SV.htm#PCB
     
    Last edited: Oct 14, 2010
  2. marshallf3

    Well-Known Member

    Jul 26, 2010
    2,358
    201
    99% of all those supposedly "solar powered" calculators have a fake black cell looking window and a battery that usually lasts so many years you'd never know.

    It's false advertising.
     
  3. solissydney

    New Member

    Sep 21, 2010
    9
    0
    I believe it to be a capacitor. I once had a solar watch with such a capacitor in it.
    Ken
     
  4. someonesdad

    Senior Member

    Jul 7, 2009
    1,585
    141
    It's probably to back up stored data when the calculator is stored in a dark place. At least that was what was implied in the instructions for the cheap Sharp calculator I bought (I preferred it over the Casio equivalent because it maintained the calculation stack after being turned off).
     
  5. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    Texas Instruments is a quality Name-Brand. They would not use a fake solar panel. Your solar panel is probably defective.

    I had a calculator with the opposite problem. After a few years it was too dim in the evenings but was fine in bright light. Replacing the battery fixed it.
     
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