Displays We Love Hacking: SPI And I2C

December 21, 2023 by Arya Voronova 17 Comments

I’ve talked about HD44780 displays before – they’ve been a mainstay of microcontroller projects for literal decades. In the modern hobbyist world, there’s an elephant in the room – the sheer variety of I2C and SPI displays you can buy. They’re all so different, some are LCD and some are OLED, some have a touchscreen layer and some don’t, some come on breakouts and some are a bare panel. No matter which one you pick, there are things you deserve to know.

These displays are exceptionally microcontroller-friendly, they require hardly any GPIOs, or none extra if you already use I2C. They’re also unbelievably cheap, and so tiny that you can comfortably add one even if you’re hurting for space. Sure, they require more RAM and a more sophisticated software library than HD44780, but with modern microcontrollers, this is no problem at all. As a result, you will see them in almost every project under the sun.

What do you need for those? What are the requirements to operate one? What kind of tricks can you use with them? Let’s go through the main aspects.

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Cheap Computer PSU Puts On Weight With Box Of Iron

December 12, 2023 by Tom Nardi 42 Comments

Humans are funny creatures. For whatever reason, when handling a piece of electronics, we tend to equate heft with value. If something feels too light, it gives the impression of being cheap or inferior. As such, it’s not unheard of for gadgets to include a little chunk of metal that serves no purpose other than to add weight.

But a recent discovery by the aptly named [RedditCringe990] really takes things to a new low. Upon opening up the cheap power supply that came with their computer case, they noticed an odd little box that didn’t appear to have any electrical connection to the rest of the device. After unscrewing it from the metal body of the power supply and pulling the bottom panel off, they found it was packed full of iron filings.

At some level, you have to appreciate the attention to detail here. At first glance, especially if you were peeking through the PSU’s air vents, you could be forgiven for thinking the box was some kind of transformer. It’s even got some alphanumeric gibberish written on the side to help complete the look. Makes us wonder how many of these things might actually have gone undetected by less curious PC-builders.

As you might expect, the weighted box is only one of the issues with this particular PSU. As pointed out by fellow Redditor [Hattix], even the functional components are worthy of suspicion. There’s no protection on the input or output, no safety capacitor, and (unsurprisingly) no regulatory marks.

We’d say the thing might still be useful as a boat anchor, but now that the box of iron fillings has been removed, it’s probably not even heavy enough. Stay safe out there, folks.

New Part Day: Flush-mount Touchscreen For Retro PC Build

December 11, 2023 by Donald Papp 19 Comments

I recently had the opportunity to purchase an early version of a new display, and it happened to be just the thing I needed to make a project work. That display is the Elecrow 11.6″ CrowVision touchscreen slated for release in 2024. Preorders are being accepted on Crowd Supply.

I had an idea for a retro-inspired PC build that was just waiting for a screen like this. I’ll talk about the display and what’s good about it, then showcase the build for which it was the missing piece. If you’ve got a project waiting for something similar, maybe this part will provide what you need or at least turn on some new ideas.

What Is It?

The CrowVision 11.6″ 1366 x 768 touchscreen has an HDMI input, USB output for touch data, and accepts 12 V DC. It’s made to interface easily with a Raspberry Pi or other SBC (single-board computer).

Personally I consider a display like this to be the minimum comfortable size for using desktop type applications in a windowed environment. Most displays in this space are smaller. But aside from that, what helps make it useful for embedding into a custom enclosure is the physical layout and design.

Since I was looking for the largest display that could be flush-mounted in an enclosure without a lot of extra space around the display’s sides, it was just what I needed. The integrated touchscreen is a nice bonus.

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When Is A 6502 Not Quite A 6502?

December 9, 2023 by Jenny List 20 Comments

We all know that fake chips are a risk when it comes to buying parts on eBay or from Chinese markets such as AliExpress. It’s a simple enough scam, take a cheap chip and mark it as an expensive one, pocket the difference. It’s happened in several different forms, with everything from completely different devices through cheaper equivalents to incredibly, chips purpose fabricated to emulate better-known ones. We have a chance to see such a scam in action via [LinuxJedi], with a 6502 that wasn’t quite as it seemed.

The chip in question was a Rockwell 65C02 destined for an Acorn Atom, and when installed it failed to deliver the expected power consumption saving. Unsurprisingly when tested it turned out to be a fake, in this case a run-of-the-mill 6502 with new markings. The interesting part for Hackaday readers comes in the physical clues. The too-bright markings started to dissolve with a bit of acetone. A deeper investigation revealed the date and wafer codes did not agree with the branding. A new chip was secured which also turned out to be a fake, though in this case a real 65C02 rated for a lower clock speed than marked.

It’s evident that in-demand retro chips are likely to be an ever-greater minefield of fakes as time passes, and the number of survivors dwindles. It’s as well to be aware then and learn from any fakes like these posted online. It’s not the first fake chip we’ve brought you.

MOSFETs — The Hidden Gate

December 8, 2023 by Al Williams 11 Comments

How many terminals does a MOSFET have? Trick question since most have three leads, even though there are really four connections to the underlying device. It isn’t a conspiracy, though and [Aaron Lanterman] talks about how MOSFETs really work and why thinking of them as three-terminal devices can lead you astray in a recent video that you can watch below.

Like many people, [Aaron] points out the parallel between a triode vacuum tube and a MOSFET. That’s not surprising, since a solid-state tube was exactly what they were looking for when they developed the FET. Since tubes and FETs are both voltage controllers, it is easy to think of the gate as the grid, the source as the cathode, and the drain as the plate. But, [Aaron] shows this isn’t really a very accurate picture.

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Switching Converter For EEPROM Programmer Taxes Solderless Breadboard

December 8, 2023 by Dan Maloney 13 Comments

We all know that solderless breadboards have their limitations. All that stray capacitance can play hell with circuits, especially high-speed stuff, but they’re so darn useful that avoiding them in favor of some other prototyping method can be really hard. So we often just forge ahead, plugging in our parts and hoping for the best

A recent veteran of the breadboard battle is [Anders Nielsen], who kicked off a new project by prototyping this high-voltage boost converter on a breadboard, with mixed results. The project is a scratch-built programmer for old-school ROM chips, a task normally farmed out to a dedicated programmer, but where’s the sport in that? Besides, this is the future, and generating the 12 to 14 volts needed should be a snap. And it would be, except for the fact that his chosen chip, a MIC2288 switching boost regulator, is only available in an SMD package. Getting the chip and a few other SMD support components onto breadboard-compatible breakouts proved to be challenging, and getting it working once it was there was even more work.

A lot of the trouble was down to simple breadboarding errors, but the big problem was the input capacitance, which [Anders] had to fiddle with quite a bit to get the converter to 14 volts. The current maxes out at about 25 mA before the voltage starts dropping, which just might be enough to burn those old chips, so we’ll call this a provisional win and see what happens when he builds the rest of the programmer.

[Anders]’ experience here raises a good question: what’s the best way to prototype using fussy SMD components? PCBs are cheap enough that it’s tempting to go straight to one, but swapping parts in and out like he had to do here to get everything just right would be much harder that way. We’re not sure we know the answer, but we’re pretty sure we’ll hear your thoughts on that in the comments section.

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This Laser-Cut One-Piece Wedge Tenon Locks Wood Joints Tight

December 4, 2023 by Dan Maloney 24 Comments

Woodworkers have always been very clever about making strong and attractive joints — think of the strength of a mortise and tenon, or the artistry of a well-made dovetail. These joints have been around for ages and can be executed with nothing more than chisels and a hand saw, plus a lot of practice, of course. But new tools bring new challenges and new opportunities in joinery, like this interesting “hammer joint” that can be made with a laser cutter.

This interesting joint comes to us from [Jiskar Schmitz], who designed it for quick, solid, joints without the need for glue or fasteners. It’s a variation on a wedged mortise and tenon joint, which strengthens the standard version of the joint by using a wedge to expand the tenon outward to make firm contact with the walls of the tenon.

The hammer joint takes advantage of the thin kerf of a laser cutter and its ability to make blind cuts to produce a tenon with a built-in wedge. The wedge is attached to a slot in the tenon by a couple of thin connectors and stands proud of the top of the tenon. The tenon is inserted into a through-hole mortise, and a firm hammer blow on the wedge breaks it free and drives it into the slot. This expands the tenon and locks it tightly into the mortise, creating a fairly bulletproof joint. The video below tells the tale.

While the hammer joint seems mainly aimed at birch plywood, [Jiskar] mentions testing it in other materials, such as bamboo, MDF, and even acrylic, although wood seems to be the best application. [Jiskar] also mentions a potential improvement: the addition of a ratchet and pawl shape between the wedge and the slot in the tenon, which might serve to lock the wedge down and prevent it from backing out.

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