Vintage Digital Frequency Meter Teardown

July 19, 2023 by Al Williams 4 Comments

You think of digital displays as modern, but the idea isn’t that new. We had clocks, for example, with wheels and flip digits for years. The Racal frequency counter that [Thomas Scherrer] is playing with in the video below has columns of digits with lamps behind them. You just need the right plastic and ten lightbulbs per digit, and you are in business. Easy enough to accomplish in 1962.

Inside the box was surprising. The stack of PC boards looks more like a minicomputer than a piece of test gear. There were a few novel items inside, too, ranging from a glass-encapsulated crystal to an interesting method of selecting the line voltage.

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Tearing Down And Improving A Professional Power Supply

July 11, 2023 by Al Williams 11 Comments

[OZ2CPU] has an HP power supply that is about 30 years old. It looks brand new, though, and has three outputs and includes tracking for the adjustable positive and negative supply. After a quick demo of the unit’s features, he tears it all down so we can see inside. You can catch the video below.

Some similar supplies offer a 10-turn adjustment knob, but this one doesn’t. Inside is a beefy transformer and quite a few through-hole components. There was room to change the main adjusted pot to a 10-turn unit, so he made the mod.

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Inside Digital Calipers

June 22, 2023 by Al Williams 51 Comments

If you do any kind of machining, 3D printing, or PCB layout, you probably have at least considered buying a pair of calipers. Old-fashioned ones had a dial and were mechanical devices, but lately, digital ones have become quite affordable. We keep meaning to tear a set of ours apart to see what’s inside, but thanks to [learnelectronics], we don’t have to — the video below provides a fascinating look at what’s inside a cheap pair of Harbor Freight calipers.

Honestly, it doesn’t seem like it would be that hard to figure out how far down a bar you are. The trick is the caliper has to be super accurate. Oddly enough, the cheap calipers examined use capacitors as a sensing element.

There is a long flexible PCB stuck to the sliding part with conductive pads. The display unit is also a printed circuit and manages the battery, the display, and the other half of the capacitive sensor. If you want a more detailed explanation of how the sensor actually works, check out capsense.com. If you note, the pattern on the sliding part has traces that look like a square wave, and half have a different phase than the other half. These are the sine plates and the cosine plates. A 100 kHz signal flows through the capacitor, and it is possible to read the direction of travel and the amount of travel easily.

The calipers are very accurate, but it’s possible to improve them. A more practical project is to make them communicate with the outside world.

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What’s In A Slip Ring?

June 19, 2023 by Jenny List 20 Comments

We know that when [Big Clive] puts up another video, the chances are we’re in for another fascinating look into a piece of tech on his bench. The latest is a slip ring assembly, and he gives it a teardown to reveal its secrets.

For most of us, the only place we encounter a slip ring is in some electric motors or alternators when it provides a connection via a conductive ring and a graphite brush from a fixed component to a rotating one. But they also appear as components in their own right wherever a rotating assembly needs an electrical contact, and it’s one of these that [Clive] has on his bench. It’s a compact unit with an impressive six conductors, and its manufacturer boldly claims that it’s good for mains voltages. We’re going with the verdict in the video below the break. That’s wishful thinking, given the size of the unit.

Inside is a rotor with six brass rings and a couple of decent little bearings, while the other half of the unit is a set of gold-plated spring contacts. There is extensive use of potting, and the verdict is that this is a surprisingly good quality component for the eBay price. We look forward to our community finding inventive uses for them. Having a ready-made unit sure beats making your own.

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Teardown Of An Aircraft Video Symbol Generator

June 19, 2023 by Dave Rowntree 17 Comments

[Adrian Smith] recently scored an avionics module taken from a British Aerospace 146 airliner and ripped it open for our viewing pleasure. This particular aircraft was designed in the early 1980s when the electronics used to feed the various displays in the cockpit were very different from modern designs. This particular box is called a ‘symbol generator’ and is used to generate the various real-time video feeds that are sent to the cockpit display units. Various instruments, for example, the weather radar, feed into it, and it then reformats the video if needed, mixing in any required additional display.

Top view of the symbol generator instrument rack

There are many gold-plated chips on these boards, which indicates these may be radiation-hardened versions of familiar devices, most of which are 54xx series logic. 54xx series logic is essentially the same functionally as the corresponding 74xx series, except for the much wider operating temperature range mandated by military and, by extension, commercial aviation needs. The main CPU board appears to be based around the Intel 8086, with some Zilog Z180 compatible processors used on the two video display controller boards. We noted the Zilog Z0853604, which is their counter/timer/GPIO chip. Obviously, there are many custom ASICs produced by Honeywell as well as other special order items that you’ll never find the datasheet for. Now there’s a challenge!

Finally, we note the standard 400 Hz avionics-standard power supply, which, as some may know, is the standard operating frequency for the AC power system used within modern aircraft systems. The higher frequency (compared to 50 or 60 Hz) means the magnetic components can be physically smaller and, therefore, lighter for a given power handling capability.

We see a lot of avionics teardowns, likely because they’re fascinating. Here’s some more British military gear, an interesting RF distance measuring box from the 1970s, and finally, some brave soul building their own avionics gear. What could possibly go wrong?

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A Peek Inside A 747 Fuel Gauge

June 11, 2023 by Matthew Carlson 28 Comments

It isn’t that often that we civilians get the chance to closely examine the fantastic internals that make up the modern marvels of avionic engineering. Luckily for us, [Glen] got his hands on a 747 fuel gauge and tore it down for our benefit. Not only does he tear it down, but he also builds a controller to display values.

Unlike your typical automotive fuel gauge that reports the distance from the top of the tank to the fuel level, this gauge reports the number of pounds of fuel. The fact that the indicator pictured above can go all the way to 95,000 pounds of fuel hits home the sheer scale of the fuel tanks on a 747 compared to your Volvo. Of course, where this gets interesting is the teardown with the metal sleeve removed. A 400 HZ AC servo motor moves the pointer and counter through the gearing with the help of a feedback potentiometer. The resistance tolerance is only 3%, as there are adjustment knobs on the back. But the linearity spec is only 0.06%, putting this part in a different grade from most pots.

One of the indicators was in worse shape than the others, so [Glen] got to work tapping into the internals of the gauge to drive the motor directly. A custom AC power supply repurposed from another project provided power, and a Raspberry Pi Pico was the PID controller. For [Glen], it isn’t all roses. Unfortunately, a noisy spot around 22,500 prevents accurate placement around there.

The code is up on GitHub, and we love having a gauge on the desk to show whatever value we like. If you are curious about more 747 instruments, this retro control unit might interest you.

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Gesture Sensor Teardown Reveals Intel Heritage

June 9, 2023 by Al Williams 5 Comments

A few years ago, there was a rush of products on the market to detect motion. The idea being you could interact with your computer like they do on science fiction movies, with giant expressive hand motions in the air. Most of these were aimed at desktop computer users but one company, YouSpace, wanted to bring this technology to retail stores. [IMSAI Guy] got one of their sensor devices and decided to see what was inside it. You can see, too, in the video below.

The device appeared to have a laser inside, which motivated the teardown. We aren’t sure exactly what YouSpace had planned, but you can see their now-defunct website on the Wayback machine. The use cases listed didn’t really help us get a clear picture, so maybe that was part of the problem.

Getting into the device was the first challenge. Like many modern smartphones, there didn’t appear to be any fasteners, so you simply had to pry the case apart. Inside the case: a tiny circuit board and a metal assembly containing the laser and cameras that were easy to remove. The main PCB appears to be an Intel off-the-shelf board that was in many Intel RealSense products, and currently go for about $50 on eBay. The camera assembly looks a bit like an Intel D430, so it is possible the entire thing was off-the-shelf hardware. Even the little connector board is, technically, a D400 Interposer.

The peek into the structured light project under the microscope was interesting. We expected it would look different, and [IMSAI Guy] clearly didn’t expect its appearance either. The chip was made to beam a known pattern that the cameras would use to deduce the shape of the surfaces it hits.

If you can find these on the surplus market, they would probably be a good deal if you need this hardware which is typically pretty expensive. Just beware, though. Intel announced in late 2021 they were “winding down” RealSense. We don’t know if there will be third-party support in the future or if the whole product line will just be orphaned.

We’ve seen the occasional project that uses structured light. The technique can be very precise.

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