MadSci Network: Engineering

Re: What is the deal with the calculator chips ??

Date: Sun May 20 21:33:29 2001
Posted By: Karl Kolbus, Staff, Data processing, Mequon Consulting Corp.
Area of science: Engineering
ID: 989203384.Eg

Hi No Name,

While I admire your spirit of adventure, I think a little basic 
electronics education would serve you better than what you are planning on 

To begin with, I'm not sure I understand what you mean by 2 inputs. The 
only 'inputs' a calculator has is the keypad. If the pins you refer to are 
in a user-accessible compartment, they almost surely are the battery 
connectors, and serve only to power the unit.

Even if you were able to get it apart, I'm afraid you would be 
disappointed. Nowdays, calculators are built on one single 'chip' which 
has on it all the circuitry. These chips are designed and built to perform 
a specific function, i.e. a calculator, and wouldn't be of any use to you 
in building a different kind of circuit such as a clock or appliance 
controller, or anything else for that matter.

I suggest you purchase a book like the "CMOS Cookbook", by Don Lancaster, 
ISBN # 0-7506-9943-4, which will provide you with a basic understanding of 
transistors, CMOS technology and basic electronics. You will learn about 
oscillators, timers, shift registers, flip-flops, etc., and will then be 
able to select the proper chips to design all kinds of usefull circuits.

If it makes you feel any better, I took apart my Father's battery-powered, 
vacuum tube, portable radio when I was your age, or younger. What I ended 
up with was a box full of parts, and had no clue what each of them did. My 
Father was so mad, he made me spend all my free time at the library 
learning what each part did, and then re-assemble the radio! Hopefully, 
you won't have to learn that way!
You may also want to visit the following sites and check out 
their "Application Notes" for understanding and designing different 
circuit elements.

National Semiconductor -
Texas Instruments -

Good luck!   

Your Not-So-Mad scientist,

Karl Kolbus

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