Diode Calculator will not work

I've been working on a diode only (well, plus switches for input [numbers, yet there's only one pad! not one for each digit], resistors for various things, and LEDs for the display) calculator that could add two two digit numbers (xx+xx=xxx) for a while, putting countless hours into it.

I have deemed it impossible.

There's so many problems with a mass diode resistor network that is just won't work. As some and gates conduct then some other gate (like it's suppose to) conducts, and eventually causes a voltage divder (with the pull up/ pull down resistors) and the output gets wacky and there's no wway of amplifying the signal.

The diode adder is dead

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You can do this very easily if you incorporate transistors into your design. Use them to create "and", "or", & "not" gates. That is what you need to do, then work on combining those gates to build half-adder and full adder circuits. Then hook up input and output, and you're done! In the old days, this was called DTL or diode-transistor logic. Worked then. Works now.
guyfrom7up (author)  LittleHairyApe9 years ago
the whole point of the thing was to show that you can create a smart machine without any "smart parts" such as transistors and other switching items.
but the TOD explanation clearly indicates that only diodes and transistors were the only allowed semiconductors
Well transistors are sort of diode pairs. But it's really old news that you can't cascade diode logic gates, so I thought I'd "help" with my suggestion. That's settled engineering. Either that or you make a 10000 input diode ROM. Up to you.
forgesmith9 years ago
Post circuit. If someone here can find the problem and make it work, then you'll feel better because your concept was good. If no one can fix it, then you'll feel better since not only were you right about it being impossible but there's no one here so much smarter than you they made it work. Win - win! Post circuit now. You'll be sorry if you don't.
guyfrom7up (author)  forgesmith9 years ago
well its several pages of work... And my scanner wings scan it good since I made it on graph paper... If you are wondering why I did it on paper its because I can do it faster on paper and there's a ton of changes on every page Maybe last night I was just getting frusterated... I'll work more on it today with a new design.
If you are wondering why I did it on paper...

The absolute last thing you have to do is explain to an old(er) geek like me the advantages of using paper.


I'm curious how you went about designing it. It sounds like a really cool project, but I'm not sure a look up table is the best way to implement an adder. A binary adder should be a bit simpler and have a lower component count. I know you can build an adder from and/or gates so it should be possible make one out of just diodes. I have some experience in digital logic design and would be happy to take a look at your design and help figure it out. Good luck
guyfrom7up (author)  advancedMischief9 years ago
the only problem with the AND & the OR gates is what happens when they are in series/cascaded. Voltage dividers occur and then the output of the gate gets all messed up.

here's a link that explains it well:

I'm still working on this, trying to create some creative way of getting around it.
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