Modeling The Classic 555 Timer On A Breadboard

Over the years, readers have often commented that microcontrollers (or more specifically, the Arduino) are overkill for many of the projects they get used in. The admonition that the creator “Should have used a 555” has become something of a rallying cry for those who think modern electronic hobbyists are taking the easy way out.

But what if you think even the lowly 555 timer is overkill? In that case, perhaps you’ll be interested in a recent blog post by [TheMagicSmoke], where the reader is walked through the process of creating an analog of the classic integrated circuit on a somewhat larger scale. Finally, we can replace that cheap and handy IC with a mass of wires and components.

Alright, so you’ve probably guessed that there’s no practical reason to do this. Outside of some theoretical MacGyver situation in which you needed to create a square wave using parts salvaged from devices laying around, anyway. Rather, the project is presented as a good way to become more confident with the low-level operation of electronic circuits, which is something we think everyone can agree is a good thing.

The components used include a 74S00 quad NAND gate, a LM358 dual operational amplifier, a 2N2222A transistor, and a handful of passive components. [TheMagicSmoke] not only explains how the circuit is constructed, but shows the math behind how it all works. Finally, an oscilloscope is used to verify it’s operating as expected.

We respect a hacker on a mission, just last month [TheMagicSmoke] put together a similar “back to basics” post on how to interface with an I2C EEPROM.

Back To Basics With An Arduino And An EEPROM

There are plenty of techniques and components that we use in our everyday hardware work, for which their connection and coding is almost a done deal. We are familiar with them and have used them before, so we drop them in without a second thought. But what about the first time we used them, we had to learn somewhere, right? [TheMagicSmoke] has produced just what we’d have needed then for one component that’s ubiquitous, the I2C EEPROM.

These chips provide relatively small quantities of non-volatile memory storage, and though they are not the fastest of memory technologies they have a ready application in holding configuration or other often-read and rarely written data.

Since the ST24C04 512-byte device in question has an I2C bus it’s a straightforward add-on for an Arduino Mega, so we’re shown the wiring for which only a couple of pull-down resistors are required, and some sample code. It’s not the most complex of projects, but it succinctly shows what you need to do so that you too can incorporate an EEPROM in your work.

If learning about I2C EEPROMs piques your interest, perhaps you’d like to read a previous look we made at them.

Decap ICs Without The Peril

There can be few of us who haven’t gazed with fascination upon the work of IC decappers, whether they are showing us classic devices from the early years of mass semiconductor manufacture, or reverse-engineering the latest and greatest. But so often their work appears to require some hardcore scientific equipment or particularly dangerous chemicals. We’ve never thought we might be able to join the fun. [Generic Human] is out to change all that, by decapping chips using commonly available chemicals and easy to apply techniques. In particular, we discover through their work that rosin — the same rosin whose smell you will be familiar with from soldering flux — can be used to dissolve IC packaging.

Of course, ICs that dissolved easily in the face of soldering wouldn’t meet commercial success, so an experiment with flux meets little success. Pure rosin, however, appears to be an effective decapping agent. [Generic Human] shows us a motherboard voltage regulator boiled in the stuff. When the rosin is removed with acetone, there among the debris is the silicon die, reminding us just how tiny these things are. We’re sure you’ll all be anxious to try it for yourselves, now, so take a while to look at the video below showing their CCC Congress talk.

The master of chip decapping is of course [Ken Shirriff], whose work we’ve featured many times. Our editor [Mike Szczys] interviewed him last year, and it’s well worth a look.

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Fun With Negative Resistance II: Unobtanium Russian Tunnel Diodes

In the first part of this series, we took a look at a “toy” negative-differential-resistance circuit made from two ordinary transistors. Although this circuit allows experimentation with negative-resistance devices without the need to source rare parts, its performance is severely limited. This is not the case for actual tunnel diodes, which exploit quantum tunneling effects to create a negative differential resistance characteristic. While these two-terminal devices once ruled the fastest electronic designs, their use has fallen off dramatically with the rise of other technologies. As a result, the average electronics hacker probably has never encountered one. That ends today.

Due to the efficiencies of the modern on-line marketplace, these rare beasts of the diode world are not completely unobtainable. Although new-production diodes are difficult for individuals to get their hands on, a wide range of surplus tunnel diodes can still be found on eBay for as little as $1 each in lots of ten. While you’d be better off with any number of modern technologies for new designs, exploring the properties of these odd devices can be an interesting learning experience.

For this installment, I dug deep into my collection of semiconductor exotica for some Russian 3И306M gallium arsenide tunnel diodes that I purchased a few years ago. Let’s have a look at what you can do with just a diode — if it’s the right kind, that is.

[Note: the images are all small in the article; click them to get a full-sized version]

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A Datasheet Manifesto For The 21st Century

Selecting electronic components can be a frustrating process, one of trawling through the websites of distributors such as DigiKey, Mouser, or RS, and then poring over manufacturer data sheets. These documents produced as detailed guides to the technical specifications of a device contain enough to give an engineer everything they need to incorporate it into their designs.

Unfortunately many datasheets fall short of the ideal, and have instead become marketing documents designed to “win the socket”. This is a problem that vexes Boldport’s [Saar Drimer], and he has written a personal manifesto outlining his vision to make the world of datasheets a better place.

It’s a common-sense designer’s wishlist, and it’s one we could completely get behind. Chief among his desires are web-readable datasheets as well as the ubiquitous PDFs, with full data in human and machine readable forms instead of tiny printed graphs and tables. He also makes a plea for better UX testing to combat the scourge of the inaccurate pad layout, to which we’d add providing footprints ready-made for all popular CAD packages. These and the rest of his manifesto would be a game-changer, and wouldn’t displace the existing paper or PDF sheet for those who still use them. Whether or not the manufacturers will take heed is anyone’s guess, but to have such an ideal laid out is a start.

If you’re not familiar with [Saar]’s work, you’re in for a treat. Boldport produce some of the most beautiful artistic PCBs, and we’ve featured them before more than once.

Thanks to our colleague [Ted Yapo] for the header image.

Component Shelf Life: How To Use All That Old Junk

There are two types of Hackaday readers: those that have a huge stock of parts they’ve collected over the years (in other words, an enormous pile of junk) and those that will have one a couple of decades from now. It’s easy to end up with a lot of stuff, especially items that you’re likely to use in more than one design; the price breakpoints at quantities of 10 or 100 of something can be pretty tempting, and having a personal stock definitely speeds the hacking process now that local parts shops have gone the way of the dinosaur. This isn’t a perfect solution, though, because some components do have shelf-lives, and will degrade in some way or another over time.

If your stash includes older electronic components, you may find that they haven’t aged well, but sometimes this can be fixed. Let’s have a look at shelf life of common parts, how it can be extended, and what you can do if they need a bit of rejuvenation.

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Characterising A Potentiometer With A Stepper Motor

Potentiometers, or variable resistors, are a standard component that we take for granted. If it says “10k log” on a volume pot, than we fit and forget. But if like [Ben Holmes] you are modelling electronic music circuitry, some greater knowledge is required. To that end he’s created a rig for characterising a potentiometer to produce a look-up table of its values.

It’s a simple enough set-up in which a voltage controlled current source feeds the pot while an Arduino with a motor controller turns it through a stepper motor, and takes a voltage reading from its wiper via an analogue pin. Probably most readers could assemble it in a fairly short time. Where it becomes interesting though is in what it reveals about potentiometer construction.

Audio potentiometers are usually logarithmic. Which is to say that the rate of change of resistance is logarithmic over the length of the track, in an effort to mimic the logarithmic volume response of the human ear in for example a volume control. If you are taught about logarithmic pots the chances are you’re shown a nice smooth logarithmic curve, but as he finds out in the video below that isn’t the case. Instead they appear as a set of linear sections that approximate to a logarithmic curve, something that is probably easier to manufacture. It’s certainly useful to know that for [Ben]’s simulation work, but for the rest of us it’s a fascinating insight into potentiometer manufacture, and shows that we should never quite take everything for granted.

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