Design a Coil for a Specific Inductance

YouTuber [RimstarOrg], AKA Hackaday’s own [Steven Dufresne], shows how to make a DIY inductor for a specific inductance. This is obviously a great skill to learn as sometimes your design may call for a very accurate inductance that may be otherwise hard to find.

Making your own inductor may seem daunting. You will have to answer a few questions such as: “what type of core will I use?”, “how many turns does my coil need?”, or “how do I calculate these parameters to create the specific inductance I desire?”. [RimstarOrg] goes through all of this, and even has a handy inductance calculator on his website to make it easier for you. He also provides all the formulae needed to calculate the inductance in the video below.

Using a DIY AM Radio receiver, he demonstrates in a visual way how to tune an AM Radio with a wiper on his home-built coil. Changing the inductance with a wiper changes the frequency of the radio: this is a variable inductor,

This video is great for understanding the foundations of inductors. While you may just go to a supplier and buy yours, it’s always great to know how to build your own when you can’t find a supplier, or just can’t wait.

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The Art Of The Silicon Chip

If you have followed the group of reverse engineers whose work on classic pieces of silicon we feature regularly here at Hackaday, you may well be familiar with the appearance of the various components that make up their gates and other functions. What you may not be familiar with, however, are the features that can occasionally be found which have no function other than the private amusement of the chip designers themselves. Alongside the transistors, resistors, and interconnects, there are sometimes little pieces of artwork inserted into unused spaces on the die, visible only to those fortunate enough to own a powerful microscope.

Fortunately those of us without such an instrument can also take a look at these works, thanks to the Smithsonian Institution, who have brought together a gallery of them on the web as part of their chip collection. In it we find cartoon characters such as Dilbert, favourites from children’s books such as Waldo, and the Japanese monster Godzilla. There are animals, cows, a leopard, a camel, and a porpoise, and of course company logos aplenty.

In a sense, these minuscule artworks are what our more strident commenters might describe as Not A Hack, but to dismiss them in such a manner would be to miss their point. Even in an age of huge teams of integrated circuit designers working with computerized tools rather than the lone geniuses of old with their hand drafting, we can still see little flashes of individuality with no practical or commercial purpose and with no audience except a very few. And we like that.

Also take a look at the work of [Ken Shirriff] for a masterclass in IC reverse engineering.

A Few of Our Favorite Chips: 4051 Analog Mux

Raindrops on roses, and whiskers on kittens? They’re alright, I suppose. But when it comes down to it, I’d probably rather have a bunch of 4051, 4052, and 4053 analog multiplexers on the component shelf. Why? Because the ability to switch analog signals around, routing them at will, under control of a microcontroller is tremendously powerful.

Whether you want to read a capacitive-sensing keyboard or just switch among audio signals, nothing beats a mux! Read on and see if you agree.

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Reusing A Wire Bonded Chip

We will all at some point have opened up a device to investigate its internal workings, and encountered a blob of resin on the PCB concealing an integrated circuit. It’s usually a cost thing, the manufacturer has sourced the chip as bare silicon rather than in encapsulated form, and it has been bonded to the board with its connections made directly using fine wires. The whole fragile component is then hidden by a protective layer of resin.

Normally these chips are off-limits to we experimenters because they can not be removed from the board without damage, and we have no information such as a part number about their function. Today though we have a rare example of a wire bonded chip being reused courtesy of Reddit user [BarockObongle], who has incorporated the controller from a multi-game joystick into his handheld NES project by cutting a square of PCB containing the chip, and soldering lengths of wire to the PCB tracks.

Of course, he’s in the rare position of knowing the function of the chip in question, and having a ready application for it. But it’s probable that few of us have considered the possibility of taking a resin blob from its original board and using it in a different way, so even though this is quite a straightforward piece of work it is sufficiently unusual to be worth a look. Sadly we don’t have the rest of the build to see it in context, it would be nice to think we’ll be able to feature it when it is completed.

If you are interested in what goes on underneath the blob, have a look at SparkFun’s explanation. Or charge your laser.


Precision Pressure In A Piston

[Scott] is building a DIY yeast reactor for his aquarium. What’s a yeast reactor? [Scott] wants to pump carbon dioxide into his aquarium so his aquatic plants grow more. He’s doing this with a gallon of sugary, yeasty water bubbling into a tank of plants and fish. In other words, [Scott] is doing this whole thing completely backward and utilizing the wrong waste product of the yeast metabolism.

However, along the way to pumping carbon dioxide into his aquarium, [Scott] created a very high precision pressure sensor. It’s based on a breakout board featuring the MS5611 air pressure sensor. This has a 24-bit ADC on board, which translates into one ten-thousandths of a pound per square inch of pressure.

To integrate this pressure sensor into the aquarium/unbrewery setup, [Scott] created a pressure meter out of a syringe. With the plunger end of this syringe encased in epoxy and the pointy end still able to accept needles, [Scott] is able to easily plug this sensor into his yeast reactor. The data from the sensor is accessible over I2C, and a simple circuit with an ATmega328 and a character LCD displays the current pressure in the syringe.

We’ve seen these high-resolution pressure sensors used in drones and rockets as altimeters before, but never as a pressure gauge. This, though, is a cheap and novel solution for measuring pressures between a vacuum and a bit over one atmosphere.

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Afroman Makes A UHF Oscillator From A Potato

If you have ever worked with simple logic gates, there is a good chance that at some point you will have built a ring oscillator from a chain of inverters. With the addition of a resistor and a capacitor, you can easily make a square wave oscillator up into the megahertz range with standard logic chips.

[Afroman] received some rather special logic chips, from an unexpectedly named company, Potato Semiconductor. They specialise in making versions of common 74 series logic that smash the usual 100+ MHz barrier of the faster conventional 74 series chips, and extend their bandwidth up to over 1 GHz. Using one of their 74GU04 parts, he made a ring oscillator relying only on the stray capacitances of its gate inputs for its timing, and while he didn’t manage to achieve a GHz he did measure it at about 373 MHz. He took a look with a spectrum analyser, and as you might expect from a logic circuit found strong harmonics in the GHz range.

Now normally there would be no news in someone making a ring oscillator with a 7404. It really wouldn’t be a hack with a run-of-the-mill 74LS or 74HC part. But this Potato part is sufficiently unusual that it deserves a bit of attention in its own right. After all, we’re not used to logic chips that can work at those kinds of frequencies.

We’ve put his video below the break. Meanwhile, the Potato Semiconductor website makes for an interesting browse, and proves that there is plenty of life left in the venerable 74 series.

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Manual LCD Makes Information Display Tedious, Educational

The HD44780 is one of the first chips we learned about as a kid, and chances are good you’ve used one in your project at some point, and almost certain that you’ve interacted with one in your life. The character LCD is ubiquitous, easy to interface, and very robust. They come in sizes from 8 x 1 to 20 x 4 and even larger, but they almost all have the same pinout, and there are libraries in many embedded environments for interacting with them. [The 8-Bit Guy] decided to interface with one using just switches and a button, (YouTube, embedded) with the intent of illustrating exactly how to use them, and how easy they are.

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