Something’s Rotating In The State Of Denmark: A Clock

January 4, 2023 by 15 Comments

If you visit the Copenhagen City Hall, you’ll see an ornate mechanical clock. By itself, this is unremarkable, of course. There are plenty of ornate clocks in city halls around the world, but this one has a fascinating backstory that starts with a locksmith named Jan Jens Olsen. Unfortunately, Jens didn’t actually complete the clock before his death. It would take 12 years to put together the 15,448 individual parts. However, he did manage to see most of the clock that he had been designing for 50 years put together.

Jens was 60 when he started constructing the clock, but the story starts when he was only 25. In Strasbourg, the young locksmith saw an astronomical clock with a perpetual calendar in a cathedral. He was fascinated and returned several times to study the mechanism. Around the age of 30, Jens had moved to watchmaking and had a keen interest in astronomy — he was a founding member of the Danish Astronomical Society. Perhaps it was the combination of these two interests that made it inevitable that he would want to build a precise astronomically-correct clock.

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A Homebrew SMD Vise Built From Scrap Wood

January 4, 2023 by 23 Comments

We don’t see too many wooden projects around these parts, but when [olikraus] turned a few pieces of scrap lumber into a functional SMD vise, how could we not take notice? The idea is simple. Two pieces of wood with slots in them hold the PCB. Two other pieces form an arm with an adjustable needle that can hold down tiny parts while you solder. Magnets hold each piece to a metal working surface. Simple and elegant.

We might have 3D printed some of the pieces, but then again, you have to be careful where your soldering iron goes if you go that route. The other advantage to using wood is that you can easily grab a few pieces of scrap and have a different-sized vice in just a few minutes.

There are a few improvements we might suggest. For example, a thumbscrew to fix the needle would be welcome. It seems like you could make the part that holds the needle smaller, too, to help you get your soldering iron into the same area. But it looks workable with no changes at all.

Working with scrap wood isn’t glamorous, but it does make for quick and easy functional builds. A number of the holes and bolts here could even be replaced with glue if you don’t mind the time for it to set.

Of course, you could mix and match this with other designs. We like the “dollar store PCB holder,” but it would work well with the arm from this project. We couldn’t help but think of the SMD beak when we saw this project.

All About USB-C: Resistors And Emarkers

January 4, 2023 by 16 Comments

If you’ve been following along our USB-C saga, you know that the CC wire in the USB-C cables is used for communications and polarity detection. However, what’s not as widely known is that there are two protocols used in USB-C for communications – an analog one and a digital one. Today, let’s look at the analog signalling used in USB-C – in part, learn more about the fabled 5.1 kΩ resistors and how they work. We’ll also learn about emarkers and the mysterious entity that is VCONN!

USB-C power supply expects to sense a certain value pulldown on the CC line before it provides 5 V on VBUS, and any higher voltages have to be negotiated digitally. The PSU, be it your laptop’s port or a charger, can detect the pulldown (known as Rd) because it keeps a pullup (known as Rp) on the CC line – it then checks if a voltage divider has formed on CC, and whether the resulting voltage is within acceptable range.

If you plug a device that doesn’t make a pulldown accessible through the CC wire in the cable, your device will never get power from a USB-C port, and would only work with a USB-A to USB-C cable. Even the smarter devices that can talk the digital part of USB-C are expected to have pulldowns, it’s just that those pulldowns are internal to the USB-C communication IC used. A USB-C port that wants to receive power needs to have a pulldown.

This part is well-known by now, but we’ve seen lack-of-resistor failures in cheap devices aplenty, and the colloquial advice is “add 5.1 kΩ resistors”. You might be afraid to think it’s so simple, but you’d be surprised. Continue reading “All About USB-C: Resistors And Emarkers” →

Squeezing A Minimalist 6502 Retrocomputer Onto A Single Breadboard

January 4, 2023 by 11 Comments

Over the years, and especially lately, we’ve seen tons of single-board retrocomputer builds. That’s fine with us — the more, the merrier. But they all start to run together a bit, with little to distinguish between them. Not so this about-as-compact-as-possible 6502 computer that fits on a single breadboard.

Now, when you do the math, it seems like there’s no way that [Anders Nielsen] would have been able to fit even a minimal chipset onto a standard solderless breadboard. The 40-pin 6502 alone takes up nearly two-thirds of the connections available; add in equally large but necessary chips like the 6522 interface adapter, ROM and RAM chips, and some support ICs, and one breadboard isn’t going to cut it. Luckily, some frugal engineers at MOS back in the 70s came up with the 6507, a variant on the 6502 in a 28-pin DIP. The other key to this build is the 6532 RAM-I/O-timer chip or RIOT, which puts a tiny amount of RAM and some IO lines on a single 40-pin DIP. Along with a 28-pin ROM, a 14-pin hex inverter, and a little crystal oscillator, the entire chipset just barely fits on a single breadboard.

But what can this minimalist 6502 actually do? As you can see in the video below, anything a 555 timer can do, and maybe a little bit more. That’s not a dig, of course — [Anders] actually calls out his initial blinkenlight application as a little more than a glorified 555, and actually comes up with a marginally more complex application just to prove the point. The interesting part here is dealing with the constraints imposed by the limited resources available on this machine.

We’re looking forward to whatever comes next for this clever build. It’s hard to see how some of the plans [Anders] has for it will still fit on a single breadboard, though — these things tend to spread out as they go.

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Bypass Defective STDP9320 Video Controller On Wacom Cintiq Companion 2

January 4, 2023 by 8 Comments

Some products seem to have a part of two that’s pretty much guaranteed to end up dying on you. In the case of the 2015-vintage Wacom Cintiq Companion 2, this turns out to be the so-called Athena chip, which switches the display input between the HDMI port and internal display controller. This allows for use in both standalone mode (tablet), as well as companion mode, where it acts as a drawing tablet for a connected PC. When confronted with such a faulty device, [neutrino] found and applied a simple fix: bypassing the Athena chip altogether.

This fix is recommended by the Repair Preservation Group’s wiki page on the topic, noting that this will permanently disable its use as an external display without additional repairs to recreate the functionality of the removed chip. This STDP9320 (PDF) part by ST Microelectronics is described as a ‘Premium high resolution multimedia monitor controller with 3D video’ and contains a wide range of video scalers, a HDMI receiver, DisplayPort (including embedded DP) support. With this fix, the Cintiq Companion 2’s Intel CPU’s graphics core is directly connected to the display’s eDP input, along with a range of voltages and enable pins.

What the exact reason is for the STDP9320 dying after a few years with what appears to be some kind of internal power failure or short, but this bypass fix at least restores standalone functionality. Sourcing a replacement for this obsolete IC seems possible, but a big gamble. Sadly, it would seem that this Wacom device will no longer be a companion for much longer.

The Crawlspace Crawler

January 3, 2023 by 35 Comments

This crawlspace crawler FPV robot is a fairly simple build. [Jeff G] bought a boxy chassis kit with frame, motors, and wheels, mounted lights and camera, and we get to see it in action (video, embedded below).

As always, the details are where it’s at, and his overview covers most of the high points. [Jeff] went for relatively slow 60 RPM motors so that he’d have plenty of grunt. The FPV setup is particularly simple – he bought a cheap Flysky i6 transmitter and receiver, and an Eachine TX05 all-in-one camera and transmitter. An interesting choice was a USB UVC video receiver so he can watch the footage on a computer, tablet, or a cell phone, which means he didn’t have to shell out for expensive FPV goggles. We also love the sticks-and-zip-ties used as feelers, letting him know when he’s about to get stuck, but that also serve as a visual frame for the camera.

The FPV Contest just came to an end, and we’ll be announcing the winners soon! If you find any inspiration there for your own project, [Jeff]’s simple basis here should get you started on the right track.

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Fool A Drone With A Fixed Battery

January 3, 2023 by 21 Comments

Lithium-ion and lithium-polymer rechargeable batteries have given us previously impossible heights of electronics power and miniaturization, but there’s a downside they have brought along with them. When a battery pack has to contain electronics for balancing cells, it’s very easy for a manufacturer to include extra functions such as locking down the battery. Repair a battery, replace cells, or use a third-party battery, and it won’t work. [Zolly] has this with a DJI Mavic Mini pack, and shares with us a method for bypassing it.

The pack talks to the multi-rotor with a serial line, and the hack involves interrupting that line at the opportune moment to stop it telling its host that things are amiss. Which is a good start — but we can’t help hacing some misgivings around the rest of the work. Disconnecting the balance line between the two cells and fooling the Battery Management System (BMS) with a resistive divider seems to us like a recipe of disaster, as does bypassing the protection MOSFETs with a piece of wire. It may work, and in theory the cells can be charged safely with an external balance charger, but we’re not sure we’d like to have a pack thus modified lying around the shop.

It does serve as a reminder that BMS boards can sometimes infuriatingly lock their owners out. We once encountered this with a second-generation iBook battery that came back to life after a BMS reset, but it’s still not something to go into unwarily. Read our guide to battery packs and BMS boards to know more.

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