The Square-Inch Project Rides Again!

Want to play a game? Your challenge is to do something incredible with a printed circuit board that measures no more than one inch by one inch. It’s The Return of the One Square Inch Project and it’s going to be amazing!

We can’t believe that it’s been three years! The original One Square Inch Project was a contest dreamt up by user [alpha_ninja] back in 2015, and we thought it was such a great idea that we ponied up some prizes. The entries were, frankly, the best we’ve ever seen. So we’re doing it again!

Last time around, the size constraint focused the minds and brought out the creativity in some of the best and brightest of What functionality or simply amusement can you pack into a square PCB that’s just a tad over 25 mm on a side? We’d like to see.

We’ll be featuring entries throughout the contest. We think geek ‘cred is the best reward but if you want something more to sweeten the pot here you go:

  • Grand Prize:

    • $500 Cash!
  • Four Top Entries Win Tindie Gift Certificates:

    • Best Project – $100
    • Best Artistic PCB Design – $100
    • Best Project Documentation – $100
    • Best Social Media Picture or Video – $100
  • Five Runner-Up Entries:

    • $100 OSH Park gift cards
Quadcopter in One Inch

Want some inspiration? Last time the winner was a quadcopter in one square inch, but there were tons of useful and amusing projects crammed into tight quarters, and many of them transcend their constraints. There were not one but two hi-fi sound cards: one for your laptop’s USB port and one for your microcontroller projects that is now officially supported by the Teensy Audio Library. Need a MPPT power converter for a small solar project? How about a plug-load meter that fits on a US mains plug or an I2C to WS2818 converter to make blinking easier?

There were breakout boards for nearly every imaginable chip, a radio downconverter from our own [Jenny List], and a great magnetic rotary encoder design. Key Pass, an Arduino in the size of a DIP-8, and of course a bat detector, a bubble display volt meter, a smart watch, and a capacitive touch wheel.

It’s been three years, and parts have gotten cheaper, smaller, and more capable. What’s newly feasible in a square inch that wasn’t way back in 2015? Show us what you got.

37 thoughts on “The Square-Inch Project Rides Again!

    1. We were thinking of one cubic inch this time, but then we started to worry that you’d expect an increase in dimensionality with every new contest, and we weren’t really sure how we’d even judge one-inch tesseracts…

      It’s worth noting that a number of winning entries were actually 25 mm x 25 mm. We put the calipers up to them and were like “good enough”.

    1. You can use a nice even 20 mm square if you want to :)
      Joking aside it would be interesting to the limit area instead of size could so people could make odd shaped boards that have limited area.

        1. Which means there were other things called “an inch” – so what? The current inch (from the current yard, 0.9144 m) is a mid-1900s thing. The centimeter (0.01 m) hasn’t changed since 1795.

          I mean, the US also has a survey inch, which is older, but that’s not the customary inch.

        1. You mean 25.4 mm, obviously. That was common industry usage, back in the 1930s (hence ‘industrial inch’) – but the official US definition of an inch didn’t become 25.4 mm until the ‘international yard’ definition in 1959. Up until then, an inch in the US was defined by the Mendenhall Order, which was actually a bit different (1/39.37 m), which we now call a “survey inch.”

          And as insane as something like this seems to metric nations (“everything’s in meters!”), the reason you still have these different definitions is because you have large-scale measurement efforts (US surveys) which already existed, so redoing them didn’t make practical sense. In fact, the US standards have been metric since the Mendenhall Order, but the problem was that the US chose 39.37 inches = 1 meter, and the UK chose 39.370113 (and that’s actually because the US standards went metric *first* – in the UK they kept their yard as the standard, and they had to keep remeasuring it). Those two values are on other sides of 1 inch = 25.4 mm , and so in the 1950s, the international agreement just said skip it, it’s 25.4 mm.

          1. Thanks for the correction and clarification.
            As an aside, a lot of antique rulers/yardsticks/etc. show a noticeable difference between the various makers’ definition of inch. Maybe that is why carpenters today will use only one ruler/tape measure.

            Also interesting is how the standard “volt” has been changed/clarified over the years…

          2. “Maybe that is why carpenters today will use only one ruler/tape measure.”

            That’s *absolutely* the reason why you use a single standard throughout. So long as your standard is stable, its accuracy isn’t that important for construction. The *stability* of the reference is more important than its actual value.

            Which is, in fact, the entire reason why the world went metric. Not because “base 10 is awesome” or some crazy idea that making people memorize random prefix names is smart. The reason the world went metric is because the international prototype meter was more stable than any of the other references. The meter itself (the *unit*) is remarkably stupid – they thought basing it off of the circumference of the Earth was somehow intelligent, when in fact they couldn’t even measure it right. So, in fact, the meter itself is totally arbitrary.

            Would’ve been way better off if they had just decided 1 gram = 1/24 avoirdupois oz (which is where it got its name), make density of water still 1 g/cm^3, and define the meter that way. Then at least only *length* would’ve been slightly different between the two systems, conversions from kg to pound would’ve been easy (it would’ve been 1 kg = 1000/384 pounds). And it would’ve brought the damn meter *closer* to a yard (would’ve been 1 meter is roughly 37.24 inches.

            Hell, if they had decided 1 gram = 1/(24*16) livre de Paris (French pound when they came up with the metric system), it would’ve been even *better* – in that case 1 meter would have been 36.3 inches, everyone might have shifted sooner, and in fact, if they had kept inches, feet, etc. as fractions of *that* meter, the “speed of light = 1 ft/ns” would’ve been *even more* accurate.


      1. My experience with inches/meters in PCB stuff is mixed. Board outlines are often on a metric grid, but of course pin spacings for DIP parts are on 0.1″. Drill sizes is truly a matter of luck — my experience is that when I specify imperial, the fab only has metric bits, and vice-versa.

        The good news is that none of it matters. :)

        1. The smaller you go, the more metric it gets.
          Pitch sizes of 1mm, 0.8mm and 0.5mm are pretty common for high pin count mezzaine and board to board connectors. Most FFC and ZIF connectors in smaller pitch sizes are metric too, and BGA ball grids as well as QFN pad pitch in metric grids are very common these days. In the world of passive components a lot of people still use the old denomination, like 0603, but as our CAE librarian in the company i managed to get everything renamed to the metric style (1608) over the last few years, and our engineers seem to be OK with it.

        2. Recently I’ve changed all holes in pcb to align with metric drills, (metric-based) manufacturer wanted drill file with inch units and then incorrectly translated them back into metric drills and all holes were too small. Even manufacturers have problems with those dang thou’s.

  1. It should be a fun contest, it was last time. But I’d rather see a 50mm version. That board size is very cheap from China and has room for much more interesting creations. The 1 square inch rule makes it more an academic exercise than making anything useful.

    1. Au contraire! The 25 mm x 25 mm format brought out a lot of very nice designs that, while they could also be used free-standing, could be easily integrated into a bigger design. And if you’re going to be doing that, it’s a great bonus to have the designer have put extra effort into shrinking the design.

      You can fit four of these on a 50 mm x 50 mm. :)

      But point taken, too. The tiny size limits the scope of the project from the beginning, and it’s entirely arbitrary.

    2. When I started thinking “What ideas do I have that would make sense here?” one of the first things that came to mind was an application where one square inch was too big! I don’t know if I’ll be able to pull this off in the allowed time constraints, but I happen to need to shrink a device down to a 10 mm wide PCB with no overhangs on the sides. Two applications that come to mind that need really tiny PCBs are sensors – where you might want something you can thread into a half inch diameter hole – and toys / scale models, where you may need to squeeze sound effects or motor controls into a tiny package.

      1. My interpretation would be different. To me, the whole flex circuit has to fit (unfolded) into the 25.4 x 25.4 mm square. Otherwise it’s like having multiple stacked PCBs, and we’re headed toward the cubic inch criterion.

    1. “The total printed circuit boards required for a single copy of an entry must fit completely within a 1 inch by 1 inch square. (It may also be smaller.)”
      “Jumper wires and component connections in the air are allowed.”
      “Components choices are not restricted; components may be overhanging.” What about their in-air connections?
      Zero is smaller than one, so it seeems legal. Is it fair too? IDK.
      Anyway, if you build something cool, I will give a like to it. I like dead bug electronics. ;-)

      1. Right. The components are allowed to overhang the edges of the PCB, so you can glue chips to the PCB, with 90% of their area overhanging, and use flying wires to connect the off-board pins.

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