# This Block Of Rubber Can Count To Ten

Complex behaviors can arise from simple mechanics, and that’s demonstrated by a block of rubber that acts as a counter.

The block contains beams, and by controlling how the block is compressed, the vertical beams shift in a stable and consistent way, acting as a mechanical counter. It’s a straightforward implementation of the work of two physicists from the Netherlands: [Martin van Hecke] and [Lennard Kwakernaak].

This device brings flexures to mind, which are also examples of obtaining complex and useful behavior from seemingly simple objects. We’ve seen flexures used as latches and counters, and we’ve seen 3D printed flexures as a kind of linear actuator.

You can check out the research paper for more details on the rubber beam counter. [Kwakernaak] aims to create a much more complex structure with elements that interact across a plane instead of in a single direction. Such a device would, in effect, be a simple computer.

Watch the beam counter in action in the short video embedded below. See how the elements of the green rubber block move while constrained by an outer frame that helps control the force that is applied. The thin beams flip from left to right, one at a time with each press.

# Op-Amp Challenge: A Logic-Free BCD

Of digital electronics, a wise man once said that “Every idiot can count to one.” Truer words have rarely been spoken, because at the end of the day, every digital circuit is really just an analog circuit with the interesting bits abstracted away. And to celebrate that way of looking at things, we’re pleased to present this BCD to seven-segment converter that uses no logic chips.

With cheap and easily available chips that perform this exact job, it might seem a little loopy to throw 20 LM324 op-amps at the job. But as [gschmidt958] explains, this is strictly for the challenge, plus it made a nice entry in the recently concluded Op-Amp Challenge contest. His work began in simulation, exploring op-amp versions of the basic logic gates — NAND, AND, OR, and NOT — all of which rely on using the LM324s as comparators. There were real-world curveballs, of course, not least of which was running out of the 10k resistors used for input averaging. Another plot twist was running out of time to order a PCB, which required designing one using MS Paint and etching it at home.

The demo video below shows the circuit at work, taking the BCD output of a 74HC393 counter — clocked by a 555, naturally — and driving a seven-segment LED.  It’s honestly a lot of work for such a simple task, but there’s something satisfying about the whole project. We think [Widlar] would be proud.

# Automatic Coin Sorter Brings Order To Your Coin Jar

Few things hold as much promise as the old coin jar. Unfortunately, what’s generally promised is tedium, as one faces the prospect of manually sorting, counting, and rolling the accumulated change of cash transactions past. Unless, of course, you’ve got a fancy automatic coin sorter like this one.

True, many banks have automatic coin sorters, but you generally have to be a paying customer to use one. And there’s always Coinstar and similar kiosks, but they always find a way to extract a fee, one way or another. [Fraens] decided not to fall for either of those traps and roll his own machine, largely from 3D-printed parts. The basic mechanism is similar to that used in commercial coin counters, with an angled bowl rotating over an array of holes sized to fit various coins. Holes in the bottom of the feed bowl accept coins fed from a hopper and transport them up to the coin holes. The smallest coins fall out of the bowl first, followed by the bigger coins; each coin drops into a separate bin after passing through an optical sensor to count the number of each on an Arduino. Subtotals and a grand total of the haul are displayed on a small LCD screen. The video below shows the build and the sorter in operation.

[Fraens] built this sorter specifically for Euro coins, but it should be easy enough to modify the sorting slots for different currencies. It’s not the first coin sorter we’ve seen, of course, and while we applaud its design simplicity and efficient operation, it can’t hold a candle to the style of this decidedly less practical approach.

# To Turn An ATtiny817 Into A 150MHz Counter, First Throw Out The Spec Sheet

One generally reads a data sheet in one of two ways. The first is to take every spec at face value, figuring that the engineers have taken everything into account and presented each number as the absolute limit that will prevent the Magic Smoke from escaping. The other way is to throw out the data sheet and just try whatever you want, figuring that the engineers played it as safely as possible.

The latter case seems to have been the motivation behind pushing an ATtiny way, WAY beyond what the spec sheet says is possible. According to [SM6VFZ], the specs on the ATtiny817 show that the 12-bit timer/counter D (TCD) should be limited to a measly 32 MHz maximum frequency, above which one is supposed to employ the counter’s internal prescaler. But by using a 10-MHz precision frequency generator as an external clock, [SM6VFZ] found that inputs up to slightly above 151 MHz were countable with 1-Hz precision. Above that point, things started to drift, but that’s still pretty great performance from something cobbled together on an eval board in a decidedly suboptimal way.

We’d imagine this result could lead to some interesting projects, since the undocumented limit for this timer puts it well within range of multiple amateur radio allocations. Even if it doesn’t prove useful, that’s OK — just seeing how far things can be pushed is cool too. And it’s not like this is the first time we’ve caught [SM6VFZ] persuading an ATtiny to do unusual things, either.

# Empty Spools Make Useful Tools, Like Counters

What’s the deal with getting things done? There’s a Seinfeld anecdote that boils down to this: get a calendar, do a thing, and make a big X on each day that you do the thing. Pretty soon, you’ll thirst for chains of Xs, then you’ll want to black out the month. It’s solid advice.

[3D Printy] likes streaks as well, and made several resolutions at the beginning of 2022. As the first of 30 videos to be made throughout the year, they featured this giant 3D printed counting mechanism (video, embedded below) that uses empty filament spools, some 3D prints, and not much else. These are all Hatchbox spools, and it won’t work for every type, but the design should scale up and down to fit other flavors.

This isn’t [3D Printy]’s first counter rodeo — he’s made several more normal-sized ones and perfected a clever carryover mechanism in the process, which is of course open-source. So each spool represents a single digit, and there are printed parts in the core that make the count carry over to the next spool. Whereas the early counters used threaded rod, this giant version rides on 2.5 mm smooth rod, so the spools can slide apart easily. But how does everything stay together? A giant elastic band made of TPU filament, of course — because the answer is always in the room.

Check out the video after the break, and stay for the 900%-sped-up assembly at the end.

# Rŏ̽ta: Counting, With Style

Rǒta counts things. That’s it, really — what a cheap little mechanical counter does with a thumb press, or what you can do by counting on your fingers and toes, that’s pretty much all that Rǒta does. But it does it with style.

OK, that’s being a bit unfair to [Kevin Santo Cappuccio] — Rǒta has a few more tricks up its sleeve than simple counting. But really, those functions are just icing on the cake of how this little gadget looks. Rǒta was built around the unbeatable combination of a rotary telephone dial mechanism and a trio of Nixie tubes. The dial looks like it might have come from an old pay phone, all shiny and chrome and super robust looking. The Nixies sit atop the dial on a custom PCB, and everything, including the high-voltage supply for the tubes, is enclosed in a 3D printed case with a little bit of a Fallout vibe.

But what does this thing do? Actually, quite a lot. It’ll count up and down, using whatever number you dial into it. You can either increment from zero, or enter any three-digit number as the starting count. It keeps track of the score of your golf game, if that’s your thing, and it’s also got a stopwatch function. You can even dial up a display of the current battery voltage. It takes some ingenuity to use just the dial for all these functions, but that’s as easy as dialing the operator used to be — dialing 0 puts it in menu mode, allowing you to access any of the functions printed on the card in the center of the dial. It’s pretty clever — check out the video below.

Is it particularly useful? Perhaps not. But when has that ever been a measure of the worth of a project? Something like this rotary cellphone might be more useful, but sometimes looking great is good enough.

# A Nixie Clock, The Hard Way

Notice: no vintage Hewlett Packard test equipment was harmed in the making of this overly complicated Nixie clock. In fact, if anything, the HP 5245L electronic counter came out better off than it went into the project.

We mention the fate of this instrument mainly because we’ve seen our fair share of cool-looking-old-thing-gutted-and-filled-with-Arduinos projects before, and while they can be interesting, there’s something deeply disturbing about losing another bit of our shared electronic heritage. To gut this device, which hails from the early 1960s and features some of the most beautiful point-to-point backplane wiring we’ve ever seen, would have been a tragedy, one that [Shahriar] wisely avoided.

After a bit of recapping and some power supply troubleshooting, the video below treats us to a tour of the Nixie-based beauty. It’s a wonderful piece, and still quite accurate after all these decades, although it did need a bit of calibration. Turning it into a clock non-destructively required adding a little bit of gear, though. Internally, [Shahriar] added a divide-by-ten card to allow the counter to use an external 10-MHz reference. Externally, an ERASynth++ programmable signal generator was used to send a signal to the counter from 0 Hz to 23,595.9 kHz, ramping up by 100 Hz every second.

The end result is the world’s most complicated 24-hour clock, which honestly wasn’t even the point of the build at all. It was to show off the glorious insides of the counter, introduce us to some cool new RF tools, and as always with [Shahriar]’s videos, to educate and inform. We’ve always enjoyed his wizardry, from his look into automotive radars to a million-dollar scope teardown, and this was another great project.