I've been trying to make a decimal calculator using binary adders that feed into 3 x 7 segment displays. I cant find an efficient way to do this. If someone could point me to the correct resources, or maybe show a circuit that you made that is similar, that would be greatly appreciated.
closed as too broad by brhans, Dwayne Reid, winny, Dmitry Grigoryev, Finbarr Nov 14 '18 at 14:05
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If you're doing this with discrete IC's, like 74xx series, you need a binary-to-BCD converter. Searching on that phrase turns up the DM74185 [http://www.utm.edu/staff/leeb/DM74185.pdf] (the companion DM74184 goes the other way). BCD is Binary Coded Decimal -- 4 bits per digit, encoding 0-9. Then the outputs of those can go to BCD-to-7 segment converters, to the display.
For a 3-digit display (0-999), that's 10 binary bits, and you would need 5 or 6 of them. The data sheet shows how they get cascaded together.
However, further search on those part number comes up a little light, so those chips might not be common anymore.
In modern times, you would build a calculator with a microcontroller. But if you want a hardware learning experience, you could do this on an FPGA, like the Go Board [https://www.nandland.com/goboard/introduction.html]. You would use Verilog or VHDL to describe the circuit you want. It's not like programming a microcontroller; you're describing a circuit that gets "wired up" in the FPGA, just as if you built it from gates. But there is a significant learning curve for the tools and methods.