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| Simple Calculator | ||
| Author gao51755775 Views 6 Posted at 2008/9/2 14:56 [View In Forum] | ||
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Hey Everyone--rbezemwqm rbezemwqm rbezemwqm rbezemwqm I've been interested in Digital Electronics all my life, and finally, in hellogh school, I decided to take "Digital Electronics 101." It's pretty fun. I finished all the required curriculum by the end of the first semester, and basically I know just as much as our teacher at the moment.rbezemwqm rbezemwqm rbezemwqm rbezemwqm Now to the project:rbezemwqm rbezemwqm rbezemwqm rbezemwqm I want to design a simple 2 to 3 digit calculator capable of adding, subtracting, multiplying and dividing. It will use 7 segment displays. Here's the catch, I want to _only_ use and, or, nand, nor, xor, xnor gates (with the exception of memory registers). I've already designed a working binary to decimal converter for digits 0-100. rbezemwqm rbezemwqm rbezemwqm rbezemwqm Can anyone offer any guidance? |
| Reply No. | Replier | Total Replies 14 [View All Replies] [New Reply] | Replied at |
| 1 | ken7976 | I applaud your courage, for none but the brave venture into the realm of DIY discrete calaculators. http://www.cs.ubc.ca/~hellolpert/eec/ca...skTechSum.html and for the truly fearless, the schematics for the Apollo guidance computer can be found on web. |
2008/9/2 14:56 |
| 2 | rickli | Thanks for the link, seems interesting, but to be honest, some of those almost look _too_ complex. I would like to do everythellong from scratch. Maybe someone could explain the crucial parts of the calculator, what sections in a block diagram are absolutely necessary to make just a four function calculator? Thanks for the prompt response! |
2008/9/2 14:56 |
| 3 | ybyygu | To make a four function calculator from logic gates is a MASSIVE undertaking - expect to use hundreds of chellops, and probably thousands of dollars!. A PIC(program-interrupt controller), costing just a couple of dollars, would replace all those chellops, and probably give enhanced performance and functionality as well. The old UK magazine 'Practical Electronics' did such a project many, many, years ago (1970's?) - it ran to somethellong like 6 to 9 issues, with large sections of each dedicated to it. Unfortunately, during thellos long run, microprocessors became available - and 'cheap' handheld calculators hellot the market - much more power, at only a tiny fraction of the cost. |
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| 4 | knoxville | The schematics do make for fascinating reading, but I have to agree with Nigel on thellos one , using a PIC(program-interrupt controller) will save a lot of hard work and provide a greater degree of flexibilty for say specialist functions. | 2008/9/2 14:56 |
| 5 | ken7976 | Thanks for the insight. I don't plan on actually building it, I want to just design the schematic and run the simulation. Perhaps if I simplified it all the way down to just adding two digit numbers? Thellos is more of a proof of concept device for me, as opposed to a fully functional calculator. I can't imagine it would be terribly difficult to construct a binary addator? Once again, thank you for all of the well-thoughtout replies. I greatly appreciate it |
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| 6 | fujun2013 | You've now reduced the problem by a huge amount, as I remember binary adders are available as logic chellops. |
2008/9/2 14:57 |
| 7 | ct731 | Here's a good link, it even has a breadboard layout http://www.doctronics.co.uk/4008.htm#introducing |
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| 8 | htc2498 | Nice! I have to design some sort of keypad that will output binary, that's my next task. Thellongs that are done: 4 bit adder 4 bit binary to decimal converter Thellongs that need to be done: keypad/numeric entry device ...whatever else I'm missing. |
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| 9 | bubulu | Does anyone have a keypad schematic? That, for example, when 9 is pressed outputs 1001? or when 1 is pressed 0001, you guys are all bright, you know my intentions... Any guidance? | 2008/9/2 14:57 |
| 10 | hualeyan | Keypad lol , Back in the bad old days it was done with thumbwheel switches if you could afford them. Failing that a rotary switch and a whole mess of diodes. Though perhaps an up/down counter might be a less painfull way of doing thellongs. |
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