Misc Hacks

4138 Articles

The Printing Of Pi

June 5, 2023 by 15 Comments

It really isn’t necessary, but there is some geek cred to learning pi to some bizarre number of digits. One way to do that is via a piem — a mnemonic device that is easy to remember and gives you the digits. Don’t know any? [Roni Bandini] has you covered with the PiemPi machine. It prints a random piem on a thermal printer and calculates each digit on the fly. You can watch the machine in action in the video below.

Unfortunately, the Raspberry Pi Zero inside doesn’t have enough language skills to ensure the thing makes sense, so you get word salad that may or may not have any real meaning. For example, [Roni] quotes astronomer [Sir James Jeans’] phrase: “How I want a drink, alcoholic, of course, after the heavy lectures involving quantum mechanics.” Before the advent of calculators, we always used: “May I have a large container of coffee today?” In each case, you count the number of letters in each word to get the digits. However, some of the piems you can see from the machine start off with phrases like: “# leon a yahoo execution im actual total pit eagle detector christmas…”

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This Vending Machine Is For The Birds

June 5, 2023 by 13 Comments

The early bird may get the worm, but [Stephen Chasey’s] birds only get to eat if they are smart. He’s created a vending machine for bird feeding. While this is a classic and simple exercise for a microcontroller, [Stephen’s] design is all op amps and 555 timers. The feeder comes on when it detects a warm body and waits for something to drop through a hole. Birds don’t have coins, so the hole will accept anything that will trigger the IR sensor within. In response, it dispenses a few peanuts. Rodents and squirrels won’t figure out the machinery, and so they can’t pilfer the peanuts meant for the pigeons — or other birds, even if they don’t start with the letter P.

A PIR sensor detects a warm body. A 555 keeps the system going for about 24 seconds after the last PIR event. Pairs of IR LEDs and phototransistors act as sensors that look through heat shrink tubing, which is, apparently, IR transparent. When a virtual coin drops through the hole, one of the sensors picks it up and starts another 555, which turns on a vibration motor. Another sensor watches for a nut to drop, which stops the motor. It also will time out after 11 seconds.

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Secret Bookshelf Door Uses Hidden Fingerprint Scanner

May 30, 2023 by 4 Comments

What is it that compels us about a secret door? It’s almost as if the door itself and the promise of mystery is more exciting than whatever could lay beyond. In any case, [Scott Monaghan] is a lover of the form, and built his own secret door hidden in a bookshelf, as all good secret doors should be.

The door is activated by pulling down on the correct book. This then reveals a fingerprint scanner. Upon presenting the right digit, the door will elegantly swing open to reveal the room beyond. Secret door experts will note there’s an obvious tell due to the light spilling through the cracks, however [Scott] reports that the finishing stages of the build solved this issue. The door was also fitted with a manual release for easier daily use.

Details are light, but the basics are all there. Really all you need is a cheap hardware store door opener, a secret activation lever or authentication method, and a well-hinged bookcase to achieve this feat yourself. We’ve seen some other great secret doors before, too. Video after the break.

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Getting Into NMR Without The Superconducting Magnet

May 26, 2023 by 14 Comments

Exploring the mysteries of quantum mechanics surely seems like an endeavor that requires room-sized equipment and racks of electronics, along with large buckets of grant money, to accomplish. And while that’s generally true, there’s quite a lot that can be accomplished on a considerably more modest budget, as this as-simple-as-it-gets nuclear magnetic resonance spectroscope amply demonstrates.

First things first: Does the “magnetic resonance” part of “NMR” bear any relationship to magnetic resonance imaging? Indeed it does, as the technique of lining up nuclei in a magnetic field, perturbing them with an electromagnetic field, and receiving the resultant RF signals as the nuclei snap back to their original spin state lies at the heart of both. And while MRI scanners and the large NMR spectrometers used in analytical chemistry labs both use extremely powerful magnetic fields, [Andy Nicol] shows us that even the Earth’s magnetic field can be used for NMR.

[Andy]’s NMR setup couldn’t be simpler. It consists of a coil of enameled copper wire wound on a 40 mm PVC tube and a simple control box with nothing more than a switch and a couple of capacitors. The only fancy bit is a USB audio interface, which is used to amplify and digitize the 2-kHz-ish signal generated by hydrogen atoms when they precess in Earth’s extremely weak magnetic field. A tripod stripped of all ferrous metal parts is also handy, as this setup needs to be outdoors where interfering magnetic fields can be minimized. In use, the coil is charged with a LiPo battery for about 10 seconds before being rapidly switched to the input of the USB amp. The resulting resonance signal is visualized using the waterfall display on SDR#.

[Andy] includes a lot of helpful tips in his excellent write-up, like tuning the coil with capacitors, minimizing noise, and estimating the exact resonance frequency expected based on the strength of the local magnetic field. It’s a great project and a good explanation of how NMR works. And it’s nowhere near as loud as an MRI scanner.

Automatic Coin Sorter Brings Order To Your Coin Jar

May 24, 2023 by 20 Comments

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.

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The Art And Science Of Making Beautiful Transparent Ice

May 24, 2023 by 43 Comments

For most of us, ice isn’t something we’ve thought about in detail since our high school science classes. For most of us, we pour some tap water into the ice trays, slam it in the freezer, and forget about it. Then we lob the frozen misshapen cubes into a beer and enjoy a quite literally ice-cold beverage.

However, there’s so much more fun to be had with ice if you really get into it. If you’ve ever wondered how pretentious cocktail bars make their fancy ice spheres or transparent cubes, read on!

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The Wizard Of Semiconductors

May 22, 2023 by 19 Comments

If you have three hours and you want to learn the fundamentals of semiconductors, [Tiny Tapeout] has something for you: An introduction to SiliWiz. You’ll also need the SiliWiz software (or use it online), which resembles the kind of tools that chip designers use but is meant for students to use as a learning tool

Using SiliWiz, you create layers on a virtual device, and you can use Spice to view the results. The tutorial is meant to be high-level and is suggested for students aged 14 or over (but we liked it and we are quite a bit older than that). Some more advanced material is also available at the same site.

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