How many 555 timers does it take to add up two 10 digit numbers? [Alan’s] 555 Adding Machine does it with 102 of them, he designed the machine as an extreme entry to the 555 contest and the original plan was to make it even more complicated. This machine uses the 555’s to implement a nine decade accumulator and multiplexer, all inputs are managed by an old school dial from a rotary phone which apparently provide nicely timed outputs. Addition and subtraction are achieved using 9s compliment arithmetic which he discusses in the video after the break, for anyone who wants to brush up on 9s compliment or 555 theory.

Alan’s website has some nice pictures (We’re particularly impressed by all that minimalistic soldering) including schematics, and a very nice 33 minute video in which he discusses in detail how the machine works and even offers some history on the Pascaline, which is mechanical calculator that works on similar principles.

## 6 thoughts on “Minimalistic 555 Adding Machine”

1. MrCung says:

Not sure I would call this “Minimalistic”, but hey it’s really cool.

He should have use 555 555 timers (or 227.5 556 timers, just chop one in half)

3. Hirudinea says:

That is very cool, needs nothing from a technical point of view but from just an asthetic point of view it needs a steampunk wooden and brass cabinet and nixie tubes, then it would be totally cool!

4. a steampunk wooden and brass cabinet and nixie tubes, then it would be totally cool!

5. Drone says:

You just “discovered” this one HaD? Man, you’re late to the party…

6. mike says:

this would actualy output to a nixie just perfectly, the nixie’s have a seperate segment for each digit, and this has a seperate LED for each digit