Can anyone figure out how to make this circuit?

commathe

I want something that can take in some number of logic highs and output how many there are as a binary number.

Lets say I have 4 separate 1-bit inputs. I want to convert this two a two-bit binary output. If all four inputs are high, then I want to put out 11, if three are high then output 10, if two are high 01, if none are high 00.

Here's where I am getting really stuck though: it needs to be able to do it no matter which inputs are high or low. ANY two inputs have to make it put out 01. ANY 1 input results in 01 out.

synaesthesia · Posted: Wed Sep 10, 2014 12:13 am Post subject:

You could do it straight forward and calculate the terms for the two binary output digits you want. This will likely result in a rather complex circuit with lots of gates.
However, instead of using logic gates you could try to break the two boolean functions down into terms with only two inputs and use 4052 chips to implement it FPGA style. The analog mux inputs could be hard-wired to Vdd/Vss to implement the truth table and the two inputs select the output from it.
Another approach is to do it the analog way. Add the input bits with a resistor network and evaluate the resulting output voltage using comparators.
From your description it is not clear to me what exactly the output should be. There are 0 to 4 HIGHs possible, but with two binary digits you can only represent the numbers 0 to 3. If you can describe what you intend to do with that function, there may be more ideas.

commathe · Posted: Wed Sep 10, 2014 12:28 am Post subject:

PHOBoS

synaesthesia · Posted: Wed Sep 10, 2014 10:09 am Post subject:

If you don't mind using chips in the TSSOP24 package, you could just use two 4067 ICs like this. (Showing only the wiring for the truth table that PHOBoS built so far)

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commathe

RingMad · Posted: Thu Sep 11, 2014 11:54 am Post subject:

Nothing useful to say about the circuit, but just an old classic joke to add...

There are 10 types of people in the world: Those who understand binary, and those who don't... Smile

James.

Cynosure · Posted: Sat Sep 13, 2014 9:06 am Post subject:

Use an lm3914 for your comparators. Then you can have 2 modes of opteration by switching between the line and dot display modes.

commathe · Posted: Sun Sep 14, 2014 12:25 pm Post subject: