Why does my 8-bit adder say 1+3=6?

I have chained together the following full adder design given by the minecraft wiki eight times so that I can add together two 8-bit signals.:

For some odd reason the return of all the adders gives me 00000110 when I have inputted 00000011 and 00000001 respectively on the two input lines.

Is there something wrong with my design? Or am I just doing something really dumb?

Solution 1:

Looking through the circuit, it looks like it should work

I went ingame and made one module of it, and cloned it 4x times, so it can add 4 bit numbers

  red    | 3 | 0011
+ blue   | 1 | 0001
= purple | 4 | 0100

Looking into how to get results like yours, I found that you might be missing a redstone torch, or either of two redstone dusts

Removing one of the dusts causes the issue you're seeing

This produces your current result

  red    | 3 | 0011
+ blue   | 1 | 0001
= purple | 6 | 0110