Should’ve Used A 555 — Or 276 Of Them

When asked to whip up a simple egg timer, most of us could probably come up with a quick design based on the ubiquitous 555 timer. Add a couple of passives around the little eight-pin DIP, put an LED on it to show when time runs out, and maybe even add a pot for variable timing intervals if we’re feeling fancy. Heck, many of us could do it from memory.

So why exactly did [Jesse Farrell] manage to do essentially the same thing using a whopping 276 555s? Easy — because why not? Originally started as an entry in the latest iteration of our 555 Contest, [Jesse]’s goal was simple — build a functional timer with a digital display using nothing but 555s and the necessary passives. He ended up needing a few transistors and diodes to pull it off, but that’s a minor concession when you consider how many chips he replaced with 555s, including counters, decoders, multiplexers, and display drivers. All these chips were built up from basic logic gates, a latch, and a flip-flop, all made from one or more 555s, or variants like the 556 or 558.

As one can imagine, 276 chips take a lot of real estate, and it took eleven PCBs to complete the timer. A main board acts as the timer’s control panel as well as serving as a motherboard for ten other cards, each devoted to a different block of functions. It’s all neat and tidy, and very well-executed, which is in keeping with the excellent documentation [Jesse] produced. The whole thing is wonderfully, needlessly complex, and we couldn’t be more tickled to feature it.

33 thoughts on “Should’ve Used A 555 — Or 276 Of Them

  1. I get the 555 fetish and coolness factor.

    But this is on the edge of resource waste and depletion. HaD Prize for environment conservation and this box, is a bit schizophrenic.Or I’m getting old?

      1. They soon will be if everybody starts making these…

        I mean, the effort is a brilliant one, and demonstrates an out-of-the-box application for the humble 555… definitely worth looking at for ideas… but I wouldn’t go replicating it verbatim. :-)

    1. I doubt the production of this device factors much in the lifetime resource use and emissions of an individual. But it seems likely it will be a significant part of their electronics learning curve.

      Might be better [educational value] per [resource] than many school books and toys.

    2. More of an ecological bomb than a modern smartphone the average joe swaps each year? I feel like any fake outrage is misplaced here. Game theory itself predicts change can only happen if there is a benefit in it.

      >”they will notice that their interests might at least sometimes be best served by getting the benefits from cooperation and not returning them”
      Q: Why do green activity Y if another country does less of harmful thing X in place of myself?

  2. Small fix for the documentation, and gates are NOT universal due to their inability to invert (and why inputs had to be bubbled upstream of the AND logic). NAND gates ARE universal in that regard.

Leave a Reply

Please be kind and respectful to help make the comments section excellent. (Comment Policy)

This site uses Akismet to reduce spam. Learn how your comment data is processed.