I’ve wanted a precision adder for a while. I’ve played with the one in the Disting a little, but that’s on other duties pretty much permanently, so I decided to make one.
I found a schematic on the Fishboy Tech blog and went through my spares box and found that I had everything I needed already.
The blog post was using fancy prototyping boards, so I ignored the layout and designed my own on regular stripboard.
It has 3 inputs; A, B and C. A and B are just added to the output directly, but C is switched with a 5v offset and is scalable with the pot on the front panel before being added in.
I’m not sure how precise it is due to the components used, but I’ll be quantising the output anyway, so that doesn’t worry me.