2025-11-21 08:00:48
If you’ve ever used an NE602 or similar IC to build a radio, you might have noticed that the datasheet has a “gilbert cell” mixer. What is that? [Electronics for the Inquisitive Experimenter] explains them in a recent video. The gilbert cell is a multiplier, and multiplying two waveforms will work to mix them together.
At the heart of the gilbert cell is essentially three differential amplifiers that share a common current source. The video shows LTSpice simulations of the circuits as he explains them.
One reason these work well on ICs is that they require very closely-matched transistors. In real life, it is hard to get transistors that match exactly. But when they are all on the same slab of silicon, it is fairly straightforward.
What we really like is that after simulating and explaining the circuit, he explains why multipliers mix signals, then builds a real circuit on the bench using discrete transistors and matched transistor arrays. There is a bit of trigonometry in the explanation, but nothing too difficult.
Of course, the most common application of differential amplifiers is the op amp. The NE602 is out of production, sadly, but if you can find any, they make dandy receivers.
2025-11-21 05:00:47
Once upon a time, owning a calculator watch was the epitome of cool. Well, for a very specific subset of the population with our own definition of “cool” anyway. The only thing cooler than wearing a calculator watch? Making a calculator watch, of course! If you do it as part of developing your own SDK for a popular RISC V microcontroller, all the better. That’s what [Miroslav Nemecek] did with his Antcalc watch, which is one of the demo projects for the CH32Lib SDK, which is currently under development at version 0.35 as this is written.
As you might guess, CH32LibSDK is targeting the super-cheap CH32 series of RISC V microcontrollers. Perhaps because the SDK is so early in development, there’s not much documentation outside of the example projects. The examples are all worth looking at, but our tipster wanted us to cover the Antcalc calculator watch specifically.
The Antcalc watch uses the SOP16-packaged CH32V002A4M6 to drive a small OLED display while taking input in Reverse Polish Notation from a dozen small buttons. We’re not sure how the cool kids feel about RPN these days, but that’s got to be worth extra nerd cred. Using a RISC V chip doesn’t hurt in that department, either.
For something so small– 30 mm x 55 mm–it’s looks like a decent little calculator, with 10 registers holding a mantissa of 21 digits and exponents up-to +/-99 in binary coded decimal. Seven layers on the dozen-key input pad mean most of the scientific functions you could ask for are available, along with the ability to record and replay upto 10 macros. There are also ten memory slots, all of which go into the chip’s onboard flash so are non-volatile during a battery swap. (Of which many will be necessary, since this appears to run on a single coin cell.)
If you get bored of wrist-mounted calculating, you could always repurpose this microcontroller to play MOD files on your wrist. Some people couldn’t imagine ever getting bored by a wrist-mounted calculator, and just for them we have this teardown of a beautiful 1975 model and a this article on the history of the calculator watch.
Thanks to [James Bowman] for the tip.
2025-11-21 03:30:58
When you’re like [Wes] from Watch Wes Work fame, you don’t have a CNC machine hoarding issue, you just have a healthy interest in going down CNC machine repair rabbit holes. Such too was the case with a recently acquired 2001 Milltronics ML15 lathe, that at first glance appeared to be in pristine condition. Yet despite – or because of – living a cushy life at a college’s workshop, it had a number of serious issues, with a busted Z-axis drive board being the first to be tackled.
The identical servo control board next to it worked fine, so it had to be an issue on the board itself. A quick test showed that the H-bridge IGBTs had suffered the typical fate that IGBTs suffer, violently taking out another IC along with them. Enjoyably, this board by one Glentek Inc. did the rebranding thing of components like said IGBTs, which made tracking down suitable replacements an utter pain that was eased only by the desperate communications on forums which provided some clues. Of course, desoldering and testing one of the good IGBTs on the second board showed the exact type of IGBT to get.
After replacing said IGBTs, as well as an optocoupler and other bits and pieces, the servo board was good as new. Next, the CNC lathe also had a busted optical encoder, an unusable tool post and a number of other smaller and larger issues that required addressing. Along the way the term ‘pin-to-pin compatible’ for a replacement driver IC was also found to mean that you still have to read the full datasheet.
Of the whole ordeal, the Glentek servo board definitely caused the most trouble, with the manufacturer providing incomplete schematics, rebranding parts to make generic replacements very hard to find and overall just going for a design that’s interesting but hard to diagnose and fix. To help out anyone else who got cursed with a Glentek servo board like this, [Wes] has made the board files and related info available in a GitHub repository.
2025-11-21 02:00:02
It’s likely that Hackaday readers have among them a greater than average number of people who can name one special thing they did on September 23rd, 2002. On that day a new web browser was released, Phoenix version 0.1, and it was a lightweight browser-only derivative of the hugely bloated Mozilla suite. Renamed a few times to become Firefox, it rose to challenge the once-mighty Microsoft Internet Explorer, only to in turn be overtaken by Google’s Chrome.
Now in 2025 it’s a minority browser with an estimated market share just over 2%, and it’s safe to say that Mozilla’s take on AI and the use of advertising data has put them at odds with many of us who’ve kept the faith since that September day 23 years ago. Over the last few months I’ve been actively chasing alternatives, and it’s with sadness that in November 2025, I can finally say I’m Firefox-free.
It was perhaps inevitable that Firefox would lose market share when faced with a challenger from a player with the economic muscle of Google. Chrome is everywhere, it’s the default browser in Android and ChromeOS, and when stacked up against the Internet Explorer of fifteen years or so ago it’s not difficult to see why it made for an easy switch. Chrome is good, it’s fast and responsive, it’s friendly, and the majority of end users either don’t care or don’t know enough to care that it’s Google’s way in to your data. When it first appeared, they still had the “Don’t be evil” aura to them, even if perhaps behind the warm and fuzzy feeling it had already worn away in the company itself.
If Firefox were destined to become a minority player then it could still be a successful one; after all, 2% of the global browser market still represents a huge number of users whose referrals to search engines return a decent income. But the key to being a success in any business is to know your customers, and sitting in front of this particular screen it’s difficult to escape the conclusion that Mozilla have lost touch with theirs. To understand this it’s necessary for all of us to look in the mirror and think for a moment about who uses Firefox.
A quick straw poll in my hackerspace revealed a majority of Firefox users, while the same straw poll among another group of my non-hackerspace friends revealed none. The former used Firefox because of open-source vibes, while the latter used Edge or Safari because it came with their computer, or Chrome on their phone and on their desktop because of Google services. Hackaday is not a global polling organisation, but we think it’s likely that the same trend would reveal itself more widely. If you’re in the technology space you might use Firefox, but if you aren’t you may not even have heard of it in 2025. It’s difficult to see that changing any time soon, to imagine some killer feature that would make those Chrome, Safari, and Edge users care enough to switch to Firefox.
To service and retain this loyal userbase then, you might imagine that Mozilla would address their needs and concerns with what made Phoenix a great first version back in 2002. A lightweight and versatile standards-compliant and open-source web browser with acceptable privacy standards, and without any other non-browser features attached to it. Just a browser, only a browser, and above all, a fast browser.
Instead, Mozilla appear to be following a course calculated to alarm rather than retain these users. Making themselves an AI-focused organisation, neglecting their once-unbeatable developer network, and trying to sneak data gathering into their products. They appear now to think of themselves as a fad-driven Valley startup rather than the custodians of a valuable open-source package, and unsurprisingly this is concerning to those of us who know something about what a browser does behind the scenes.
It is likely that I am preaching to the choir here, but it’s important that there be a plurality of browsers in the world. And by that I mean not just a plurality of front-ends, but a plurality of browser engines. One of the reasons Phoenix appeared all those years ago was to challenge the dominance of Microsoft Internet Explorer, the tool by which the Redmond software company were trying to shape the online world to their tune. If you remember the browser wars of that era, you’ll have tales of incompatibilities seemingly baked in on purpose to break the chances of an open Web, and we were all poorer for it. Writing Javascript with a range of sections to deal with the quirks of different browser families is now largely a thing of the past, and for that you have the people who stuck with Firefox in the 2000s to thank.
The fear is that here in 2025 we are in an analogous situation to the early 2000s, with Google replacing Microsoft. Such is the dominance of Google Chrome and the WebKit-derived Blink engine which powers it, that in effect, Google have immense power to shape the Web just as Microsoft did back in the day. Do you trust them to live up to their now-retired mission statement and not be evil? We can’t say we do. Thus Firefox’s Gecko browser engine is of crucial importance, representing as it does the only any-way serious challenger to Blink and WebKit’s near-monopoly. That it is now tied to a Mozilla leadership treating it in so cavalier a manner does not bode well for the future of the Web.
So I’ve set out my stand here, that after twenty-three years, I’m ready to abandon Firefox. It’s not a decision that has been easy, because it’s important for all of us that there be a plurality of browsers, but such is the direction being taken by Mozilla that I am not anxious to sit idly by and constantly keep an eye out for new hidden privacy and AI features to turn off with obscure checkboxes. In the following piece I’ll take a look at my hunt for alternatives, and you may be surprised by the one I eventually picked.
2025-11-21 00:30:39
[Zack], in addition to being a snappy dresser, has a thing for strange 3D printing filament. How strange? Well, in a recent video, he looks at filaments that require 445 C. Even the build plate has to be super hot. He also looks at filament that seems like iron, one that makes you think it is rubber, and a bunch of others.
As you might expect, he’s not using a conventional 3D printer. Although you might be able to get your more conventional printer to handle some of these, especially with some hacking. There is filament with carbon fiber, glass fiber, and more exotic add-ons.
Most of the filaments need special code to get everything working. While you might think you can’t print these engineering filaments, it stands to reason that hobby-grade printers are going to get better over time (as they already have). If the day is coming when folks will be able to print any of these on their out-of-the-box printer, we might as well start researching them now.
If you fancy a drinking game, have a shot every time he changes shots and a double when the Hackaday Prize T-shirt shows up.
2025-11-20 23:00:30
If you take a look around you, chances are pretty good that within a few seconds, your eyes will fall on some kind of electrical connector. In this day and age, it’s as likely as not to be a USB connector, given their ubiquity as the charger of choice for everything from phones to flashlights. But there are plenty of other connectors, from mains outlets in the wall to Ethernet connectors, and if you’re anything like us, you’ve got a bench full of DuPonts, banana plugs, BNCs, SMAs, and all the rest of the alphabet soup of connectors.
Given their propensity for failure and their general reputation as a necessary evil in electrical designs, it may seem controversial to say that all connectors are engineered to last. But it’s true; they’re engineered to last, but only for as long as necessary. Some are built for only a few cycles of mating, while others are built for the long haul. Either way, connectors are a great case study in engineering compromise, one that loops physics, chemistry, and materials science into the process.
While there’s a bewildering number of connectors available today, most have at least a few things in common. Generally, connectors consist of one or more electrically conductive elements held in position by an insulating body of some sort, one that can mechanically attach to another body containing more conductive elements. When the two connectors are attached, the conductive elements come into physical contact with each other, completing the circuit and providing a low-resistance path for current to flow. The bodies also have to be able to separate from each other when the connections need to be broken.
For as simple as that sounds, a lot of engineering goes into making connectors that are suitable for the job at hand. The intended use of a connector dictates a lot about how it’s designed, and in terms of connector durability, looking at the extremes can be instructive. On one end of the scale, we might have something like a Molex connector on a wiring harness in a dishwasher. Under ideal circumstances, a connector like that only needs to be used once, in the factory during assembly. If the future owner of the appliance is unlucky, that connector might go through one or two more mating cycles if the machine needs to be serviced at some point. Either way, the connector is only going to be subjected to low single-digit mating cycles, and should be designed accordingly
On the other end of the mating-cycle spectrum would be something like the USB-C connector on a cell phone. Assuming the user will charge the phone once a day, the connector might have to endure many thousands of mating cycles over the useful life of the phone. Such a connector has a completely different use case from a connector like that Molex, and very different design constraints. But the basic job — bringing two conductors into close contact to complete a low-resistance circuit, and allow the circuits to be broken only under the right circumstances — is the same for both.
But what exactly do we mean by “close contact”? It might seem obvious — conductors in each half of the connector have to touch each other. But keeping those conductors in contact is the real trick, especially in challenging environments such as under the hood of a car or inside a CNC machine, where vibration, dust, and liquid intrusion can all come together to force those contacts apart and break the circuit while it’s still in use.
To keep contacts together, engineers rely on one of the simplest mechanisms of all: springs. In most connectors, the contacts themselves are the sprung elements, although there are connectors where force is applied to the contacts with separate springs. In either case, the force generated by the spring pushes the contacts together firmly enough to ensure that they stay connected. This is the normal force, called so because the force is exerted perpendicular to the plane of contact when the connector is mated.
Traditionally, normal force in connector engineering is expressed in grams, which seems like an affront to the SI system, where force is expressed in Newtons. But fear not — “grams” does not refer to the mass of a contact, but rather is shorthand for “gram-force,” the force applied by one gram of mass in a one g gravitational field. So, an “80 gram” contact is really exerting 0.784 N of normal force. But that’s a bit clunky, especially when most connectors have normal forces that are a fraction of a Newton. So it ends up being easier to refer to the grams part of the equation and just assume the acceleration component.
The amount of normal force exerted by the contacts is a critical factor in connector design, and has to be properly scaled for the job. If the force is too low, it may increase the resistance of the circuit or even result in intermittent open circuits. If the force is too high, the connector could be difficult to mate and unmate, or the contacts could wear out from excess friction.
Since the contacts themselves are usually the springs as well as the conductors, getting the normal force right, as well as ensuring the contacts are highly conductive, is largely an exercise in materials science. While pure copper is an excellent conductor, it is not elastic enough to provide the proper normal force. So, most connectors use one of two related copper alloys for their contacts: phosphor bronze, or beryllium copper. Both are excellent electrical and thermal conductors, and both are strong and springy, but there are significant differences between the two that make them suitable for different types of connectors.
As the name implies, phosphor bronze is an alloy of phosphorus and bronze, which itself is an alloy of copper and tin. To make phosphor bronze, about 0.03% phosphorus is added to pure molten copper. Any oxygen dissolved in the copper reacts with the phosphorus, making phosphorus pentoxide (P2O5), which can be easily removed during refining. About 2% tin is added along with about 10% zinc and 2% iron to make the final alloy, which is easily cast into sheets or coil stock.
While far superior to pure copper or non-phosphor bronze for use in contacts, phosphor bronze is, at best, a compromise material. It’s good enough in almost all categories — strength, elasticity, conductivity, wear resistance — but not really great in any of them. It’s the “Jack of all trades, master of none” of the electrical contact world, which, coupled with its easy workability and low cost, makes it the metal of choice for the contacts in commodity connectors. If a manufacturer is making a million copies of a connector, especially ones that are cheap enough that nobody will cry too much if they have to be replaced, chances are good that they’ll choose phosphor bronze. It’s also the alloy most likely to be used for connectors intended for low mating-cycle applications, like the aforementioned dishwasher Molex.
For more mission-critical contacts, a different alloy is generally called for: beryllium copper. Also known as spring copper, beryllium copper contains up to about 3% beryllium, but for electrical uses, it’s usually around 0.7% with a little cobalt and nickel added in. Beryllium copper is everything that phosphor bronze is, and more. It’s stronger and springier, it’s a far better electrical conductor, and it also has a better ability to withstand creep under load. Also known as stress relaxation, creep under load is the tendency for a spring to lose its strength over time, which reduces its normal force. Phosphor bronze has pretty good stress relaxation resistance, but when it heats up past around 125°C, it starts to lose spring force — not ideal for high-power applications. Beryllium copper is easily able to withstand 150°C or more, making it a better choice for power connectors.
Beryllium copper also has a higher elastic modulus than phosphor bronze, which makes it easier to create small contacts that still have enough normal force to maintain good contact. Smaller is better when it comes to modern high-density connectors, so you’ll often see beryllium copper used in fine-pitch connectors. It also has better fatigue life and tends to maintain normal force over repeated mating cycles, making it desirable for connectors that specify cycle lives in the thousands. But just because it’s desirable doesn’t make it a shoo-in — beryllium copper is at least three times more expensive than phosphor bronze. That means it’s usually reserved for connectors that can justify the added expense.
No matter what the base metal is for connector contacts, chances are good that the finished contact will have some sort of plated finish. Plating is important because it protects the base metal from oxidation, as well as increasing the wear resistance of contacts and improving their electrical conductivity. Plating metals fall into two broad categories: noble (principally gold, with silver used sometimes for high-power connectors, as well as palladium, but only very rarely) and non-noble platings.
Noble metal finishes are quite common in high-density connectors, RF applications, and high-speed digital circuits, as well as high-reliability applications and connectors that are expected to have high mating cycles. But at the risk of stating the obvious, gold is expensive, so it’s used only on connectors that really need it. And even then, it’s very rare that the entire contact is plated. While that would be incredibly expensive — gold is currently pushing $4,000 an ounce — the real reason is that gold isn’t particularly solderable. So generally, selective plating is used to deposit gold only on the mating surfaces of contacts, with the tail of the contact plated in a non-noble metal to improve solderability.
Among the non-noble finishes, tin and tin alloys are the first choice. Aside from its excellent solderability, tin alloys do a great job at protecting the base metal from corrosion. However, the tin plating itself begins to oxidize almost immediately after it’s applied. This would seem to be a problem, but it’s easily addressed by using more spring force in the contacts to break through the oxide layer to fresh tin. Tin-plated contacts typically specify normal forces of 100 grams or more, while noble metal contacts can get by with 30 grams or less. Also, tin contacts require much thicker plating than noble metal finishes. Tin is generally specified for commodity connectors and anywhere the number of mating cycles is likely to be low.
Although corrosion is obviously something to be avoided, the real enemy when it comes to connector durability is metal-on-metal contact. The spring pressure between contacts unavoidably digs into the plating, and while that’s actually desirable in tin-plated contacts, too much of a good thing is bad. Digging past the plating into the base metal marks the end of the road for many connectors, as the base metal’s relatively lower conductivity increases the resistance of the connection, potentially leading to intermittent connections and even overheating. Again, noble metals perform better in this regard, at least in the long run, as their lower normal force reduces friction and results in a longer-lived contact.
There’s another metallurgical phenomenon that can wreak havoc on connectors: fretting. Fretting is caused by tiny movements of the contacts against each other, on the order of 10-7 meters, generally in response to low-g vibrations but also as a result of thermal expansion and contraction. Fretting damage occurs when the force of micromotions between contacts exceeds the normal force exerted between them. This leads to one contact sliding over the other by a tiny amount, digging a trench through the plating metal. In tin-plated contacts, this exposes fresh tin, which oxidizes instantly, forming an insulating surface. Further micromotions expose more fresh tin, which leads to more oxides. Eventually the connection fails due to high resistance. Fretting is insidious because it happens even without a lot of mating cycles; all it takes is a little vibration and some time. And those are the enemies of all connectors.
