I'm continuing to dissect and learn from this old (1974) calculator. One thing that surprised my was that the pins of the main IC have both negative and positive voltages 0 to ±28V. Having worked mainly with ICs like the ATMEGA line, PIC controllers and other popular chips, the voltage surprised me.
- Am I correct in thinking that modern IC operate at lower voltages so they can pack in more transistors without over heating?
Inside view of circuit board of Sharp ELSI 8002 Calculator. The mystery IC: HD3623 has no online data sheet that I could find, but MK14 at eevblog pointed me to this data sheet showing how a similar calculator works.
When I once destroyed an ATMEGA128 with 12V, was the nature of the destruction heat that melted or burned the traces in the IC making it inoperable? But this old more robust IC must have thicker, more conductive traces.
Is that why it is so big despite doing comparatively less than smaller modern ICs?
There is one advantage to this beefy old IC: It can drive the VFD, which seems to have a -28V grid, directly. Maybe, I should look for a programmable IC that runs at higher voltages? Or would that be frustrating?
- Are there IC that meet this description that can be programmed by a novice?
Maybe I should use a logic level converter of some kind instead? I want to be able to repurpose the buttons and the display within the existing case. I like the form factor and quality of the calculator, I want to make it work with a modern micro controller.
Sharp ELSI 8002 calculator. I'm fairly certain that the VFD is the Futaba 9CT06, it's not super well documented, but I can make it do what I want using bench power, so having identified the pins I just need some kind of PWM... I think.
Maybe I should table this project until I've studied more! I've found some people with similar projects, but none with the same VFD.
I've put notes by my main questions for clarity.