This is fresh on the heels of another hack that used similar construction methods to build a “magic” wood lamp. [Nick] takes it a step further, though. His case is precisely machined in white oak and stuffed with the latest China has to offer: a bank of lithium-ion batteries, a DC-DC converter to power the amplifier, and a Bluetooth module. After some sanding, the speakers look professional alongside the blue light features hiding behind the polycarbonate rings.
Of course you’ll want to visit the project site for all the details of how [Nick] built his speaker case. He does admit, however, that the electronics are fairly inefficient and need a little work. All in all though, it’s a very refined set of speakers that’ll look great on a bookshelf or on a beach, workshop bench, or anyplace else that you could take them.
As a fresh-faced electronic engineering student while the first Gulf War was raging in a far-off desert, I learned my way through the different families of 74 logic at a university in the North of England. 74LS was the one to use, the story went, because it’s quick and doesn’t use much power. At the time, there was an upstart on the scene: 74HC. Now that’s really quick. New. Exotic, even.
Thus an association was formed, when you want a quick logic function then 74HC is the modern one to go for. It could have been a lifelong love affair, but over twenty years, after many factors of speed increases and some RF tricks with gates we wouldn’t have dreamed of back then, it’s over. There is a whole world of newer logic families to choose from, and while HC is still good at what it does, it’s well past time to admit that it may just have been superseded.
40673s, probably now worth more by weight than anything else on four legs. (Thanks are due to [Brandon Dunson] and Tanner Electronics) A tendency to cling to the past with logic families is pretty harmless. Like [Adam Fabio]’s TIP power transistors they’re pretty cheap, still very much in production, and still do most jobs demanded of them excellently. But what prompted this piece was a far more egregious example of an old component still being specified: the RCA 40673 dual-gate MOSFET. Launched in the mists of time when dinosaurs probably still roamed the earth, this static-sensitive four-pin TO72 found a home in a huge variety of RF amplifiers, oscillators, and mixers. It worked well, but as you might expect better devices came along, and the 40673 was withdrawn some time in the 1980s.
Unfortunately, nobody seems to have told a section of the amateur radio community about the 40673’s demise. Or perhaps nobody’s told them that many scrap analogue TV tuners of a certain age will yield a perfectly good newer replacement for free. Because even today, thirty years after the 40673 shuffled off this mortal coil, you can still find people specifying it. If you have a stash of them in your junk box, they’re worth a small fortune, and yours could be the bench with the throng of people at the next ham radio convention.
A different but equally annoying manifestation of the phenomenon comes when the device everyone likes to specify is not very old and very much still in production, but the designer hasn’t taken the time required to check for a cheaper alternative. Nobody ever got fired for buying IBM, they say, but perhaps they should be fired for specifying an AD8307 logarithmic amplifier in an amateur radio power meter. Don’t take this the wrong way, it’s a beautiful chip and probably a lot of work at Analog Devices has gone into laser-trimming resistors to make it perform to an extremely demanding specification. But eleven dollars for a chip? When a cursory search will turn up Maxim’s MAX9933 which does a perfectly good job in this application at well under two dollars? Someone isn’t doing their homework.
Sometimes there are components for which there are no perfect replacements. Germanium point-contact diodes, for example. 1N34As and OA91s are becoming like hen’s teeth these days, and though Schottky diodes can replace them in many applications, there are still a few places if you’re a radio person you’ll hanker for the original. There are suppliers on Alibaba who claim to manufacture 1N34s, but the pictures always look suspiciously like 1N4148s, and anyway who can find a home for a hundred thousand diodes? (Hang on, this is Hackaday. There will be someone out there with a hundred-thousand-diode project, you can count on it.)
OK, maybe germanium diodes are an edge case and the examples above have a radio flavour, but you get the picture. What the full-blown rant in the previous paragraphs has been building up to is this: a plea for designers to do their homework. Please try to design every project for the next two decades, and as though any extras in the component price come from your company’s bottom line. (We’ll make exceptions for building something for which the whole point is a retro circuit. An Apple I replica like the Mimeo 1 needs old logic chips for artistic purposes.)
Is there a vital electronic engineering skill that’s being lost here perhaps? Back when the Internet was the sole preserve of boffins and Tim Berners-Lee hadn’t yet plugged his hypertext ideas into it, we relied on catalogs. Big paper-bound books the size of telephone directories were our only window into the exciting world of electronic components. If you’re an American yours was probably from Radio Shack, but for most UK-based hackers and makers who couldn’t get their hands on a commercial account from RS or Farnell that meant the Maplin catalogue. Before they moved in a consumer-electronics direction, they were a component specialist whose catalogue with its distinctive spaceships on the cover could be bought at large newsstands.
It’s difficult to describe the impact of electronics catalogues in the ’70s and ’80s to someone who has known only the abundance of information from the WWW. These publications were our only window into the world of electronic components. They contained significant excerpts from semiconductor data sheets, and we read their wealth of information from cover to cover. We knew by heart what each device was capable of, and we eagerly devoured each new tidbit of information as it arrived.
In short, when we specified a component, we did so with a pretty good knowledge of all the components that were available to us.
By comparison, nowadays we can quickly buy almost any device or component in production from a multitude of suppliers. There are millions more devices available, and if RS or Farnell don’t have the part then Mouser or Digi-Key are sure to provide. The WWW allows us to find what we need in short order, and the miracle of global distribution means that we can have it delivered within 48 hours almost wherever we live.
CPC’s very aptly-named Big Book
Which means that all the new devices are available to us, but we’ve lost the ability to keep on top of them. We’ve become information rich, but knowledge poor. Printed catalogs still exist, but the sheer volume of information they contain forces brevity upon their entries and expands the size of the publication to the point at which it becomes an unwieldy work of reference. We therefore tend to stick with the devices and components we know, regardless of their cost or of whether they have been superseded, and our work is poorer for it.
We need to relearn the skill of inquisitiveness when it comes to the parts we use, and to rediscover the joy of just browsing, even if the medium is now a huge suppliers’ web site rather than a paper catalog. Otherwise we’ll still be looking at circuit diagrams containing 74LS logic and 40673 MOSFETs in the 2030s, and that can’t be a good thing!
There is of course also a slightly macabre alternative scenario. The highest online price we found for 40673s was over $30 each, so if a producer can make that kind of silly money then there’s a danger that RCA’s successors will see a business model in exhuming the corpse and re-animating it, thus ensuring that we’ll never be free of the undead. We need to make sure that doesn’t happen!
Maxim Integrated recently posted a series of application notes chronicling how there’s more going on than you’d think in even the simplest “passive” components. Nothing’s safe: capacitors, resistors, and even printed circuit boards can all behave in non-ideal ways, and that can bite you in the reflow-oven if you’re not aware of them.
You might already know that capacitors have an equivalent series resistance that limits how fast they can discharge, and an equivalent inductance that models departures from ideal behavior at higher frequencies. But did you know that ceramic capacitors can also act like voltage sources, acting piezoelectrically under physical stress?
For resistors, you’ll also have to reckon with temperature dependence as well as the same range of piezoelectric and inductance characteristics that capacitors display. Worse, resistors can display variable resistance under higher voltages, and actually produce a small amount of random noise: Johnson Noise that depends on the value of the resistance.
Finally, the third article in the series tackles the PCB, summarizing a lot of potential manufacturing defects to look out for, as well as covering the parasitic capacitance, leakage currents, and frequency dependence that the actual fiberglass layers themselves can introduce into your circuit.
When my Swiss cousin-in-law sent us her wedding invitation, I didn’t immediately think I’d get to see Hackaday.io user [antti.lukats‘] tiny FPGA projects as part of the deal. I’m really glad that I came to Switzerland for the wedding, and also got to be a part of an awesome meetup in Zurich’s Fablab. [Antti], who was at the meetup, is pictured above holding a small tube full of FPGAs, he’s a Hackaday Prize Best Product finalist with FPGA project DIPSY.
As is becoming the norm for Hackaday meetups, we ask people to bring projects. We then count all the people who want to present something and squeeze all the presentations into just about 90 minutes. Before and after the lightening talks, there’s always plenty of time to walk around and see individual projects, meet people and of course eat and drink.
A 14-year-old in Dallas, Texas has been arrested for bringing a clock to his school. [Ahmed Mohamed] could be any one of us. He’s a tinkerer, pulling apart scrap appliances and building projects from the parts. He was a member of the his middle school robotics team. The clock was built from a standard four digit seven segment display and a circuit board. [Ahmed] built the circuit inside a Vaultz hard pencil case like this one. He then did what every other experimenter, inventor, hacker, or maker before him has done: He showed off his creation.
Unfortunately for [Ahmed] one of his teachers immediately leapt to the conclusion that this electronic project was a “hoax bomb” of some sort. The police were called, [Ahmed] was pulled out of class and arrested. He was then brought to a detention center where he and his possessions were searched. [Ahmed] is now serving a three-day suspension from school. His clock is considered evidence to be used in a possible criminal case against him.
If this situation doesn’t get your blood boiling, then we don’t know what does. Not only is there a glaring racial issue here, but also an issue of allowing kids to bring their projects to school. We hope you’ll join us in expressing outrage at this whole debacle, as well as supporting [Ahmed] in any way you can. Let’s join together as a community to make sure a few small-minded individuals don’t break the spirit of this budding hardware hacker.
For anyone out there who would like to support [Ahmed]’s education even when his school won’t, [Anil Dash] is will be in contact with the family later today. We’re offering a gift card for the hackaday store and we would assume other contributions would also be welcome. -Ed.
What if there was a job where you built, serviced, and prepared science demonstrations? This means showing off everything from principles of physics, to electronic theory, to chemistry and biology. Would you grab onto that job with both hands and never let go? That was my reaction when I met [Dan Rosenberg] who is a Science Lecture Demonstrator at Harvard University. He gave me a tour of the Science Center, as well as a behind the scenes look at some of the apparatus he works with and has built.
[Marc] has an old Voigtländer Vito CLR film camera. The camera originally came with an analog light meter built-in. The meter consisted of a type of solar panel hooked up to a coil and a needle. As more light reached the solar panel, the coil became energized more and more, which moved the needle farther and farther. It was a simple way of doing things, but it has a down side. The photo panels stop working over time. That’s why [Marc] decided to build a custom light meter using newer technology.
[Marc] had to work within the confines of the tiny space inside of the camera. He chose to use a LM3914 bar display driver IC as the primary component. This chip can sense an input voltage against a reference voltage and then display the result by illuminating a single LED from a row of ten LEDs.
[Marc] used a photo cell from an old calculator to detect the ambient light. This acts as a current source, but he needed a voltage source. He designed a transimpedence amplifier into his circuit to convert the current into a voltage. The circuit is powered with two 3V coil cell batteries, regulated to 5V. The 5V acts as his reference voltage for the display driver. With that in mind, [Marc] had to amplify this signal further.
It didn’t end there, though. [Marc] discovered that when sampling natural light, the system worked as intended. When he sampled light from incandescent light bulbs, he did not get the expected output. This turned out to be caused by the fact that incandescent lights flicker at a rate of 50/60 Hz. His sensor was picking this up and the sinusoidal output was causing problems in his circuit. He remedied this by adding two filtering capacitors.
The whole circuit fits on a tiny PCB that slides right into position where the original light meter used to be. It’s impressive how perfectly it fits considering everything that is happening in this circuit.
For resistors, you’ll also have to reckon with temperature dependence as well as the same range of piezoelectric and inductance characteristics that capacitors display. Worse, resistors can display variable resistance under higher voltages, and actually produce a small amount of random noise: 
