• EEVblog #389 – Casio Calculator Investigation

    Measuring the current consumption of some solar powered Casio calculators.
    And a look at an unusual chip mounting technique.
    Solar Power Hope

    Be Sociable, Share!

      About EEVblog

      Check Also

      EEVblog #821 – Mailbag

      EEVblog #821 – Mailbag

      More Mailbag! Extended Teardown Video HERE Forum HERE SPOILERS: Military Mystery Item Teardown – UPDATE: ...

      • tchicago

        I remember taking apart a similar Casio calculator (~1985), and it too had a glass-packaged diode inside. What was interesting is that this diode’s die actually emitted some dim red light when the solar panel was sufficiently lit. My guess is that this diode was actually a Zener diode to limit the voltage, and the technology it was made with was somewhat similar to LEDs. So it emitted some light when the voltage was high enough for it to start doing its job.

        • Martin

          I had a sharp elsi-mate pocket solar calculator that had the same idea, glass/ceramic package LED, which lit up, it fascinated me. I actually drilled a hole through the aluminium case so I could see it.

          Still have the calculator somewhere :-)

      • baljemmett

        The two rebadged Tandy models look like the fx-115 family — the older one may be an fx-115M; that was the first scientific calculator I remember playing with, c.1985-ish. Around 1990 my father upgraded to the later fx-115N (or maybe V, but I think that was mid-90s instead) which added the fourth row of function buttons and moved the solar cell to under the display. It took a dive into the sink one day, which is when I discovered the innards were one chip on a flexible sheet as you show here…

        If the older one only has eight digits rather than ten it could be an fx-85 series instead — I think the M/N/V suffices are the same for both. Or I could be miles off with my recollection, but Google Image Search shows it’s at least plausible!

        • baljemmett

          (Actually, I could be mistaken about the M suffix — just found an auction for the original fx-115 without suffix and it looks identical to the fx-115M, so can’t really tell from the outside which it’s likely to be!)

      • i80386


      • bob

        That Tandy looks like an Casio FX100

        BTW here’s a calc database


      • http://e-motion.lt elektrinis


      • viktor


        ( Yes, in respect to Feynman )

      • Anders

        What about the memory lcd from Sharp: http://www.sharpmemorylcd.com/memorylcd.html Consumption is in the nano-amp range.

        This application note: http://cdn.energymicro.com/dl/an/pdf/an0048_efm32_energy_friendly_display.pdf describes how to achieve a fully working wrist-watch application with less than 5uA total consumption with mcu + dot matrix lcd.

      • Nick

        They actually uses LED type packages here, http://www.datamath.org/Sci/Modern/JPEG_TI-30X-IIS_2004.htm#SR16

      • Pingback: ccn2785xdnwdc5bwedsj4wsndb()

      • Pingback: c5e7nstcc78e4x5cn7w4567465()

      • Pingback: xcmwnv54ec8tnv5cev5jfdcnv5()