OWON Oscilloscope Teardown

January 15, 2020 by Al Williams 27 Comments

We sympathize with [learnelectronic’s] statement: “I’m ashamed. I may have bought another oscilloscope.” We get it and we enjoyed watching him tear down the OWON SDS1102. (Video, embedded below.) As you might guess, this is a 100 MHz, two-channel scope, and very similar to many other Chinese scopes you can get inexpensively.

The last ten minutes are so of the video below shows him removing the case. There’s only three little boards inside. One is clearly a power supply. The other two don’t have much on them. There’s a tiny RF shield over one part of the board, so you assume that’s the input section.

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Fail Of The Week: Thermostat Almost Causes A House Fire

January 8, 2020 by Dan Maloney 63 Comments

Fair warning: any homeowners who have thermostats similar to the one that nearly burned down [Kerry Wong]’s house might be in store for a sleepless night or two, at least until they inspect and perhaps replace any units that are even remotely as sketchy as what he found when he did the postmortem analysis in the brief video below.

The story begins back in the 1980s, when the Southern New England area where [Kerry] lives enjoyed a housing boom. Contractors rushed to turn rural farmland into subdivisions, and new suburbs crawled across the landscape. Corners were inevitably cut during construction, and one common place to save money was the home’s heating system. Rather than engage an HVAC subcontractor to install a complicated heating system, many builders opted instead to have the electricians install electric baseboards. They were already on the job anyway, and at the time, both copper and electricity were cheap.

Fast forward 40 years or so, and [Kerry] finds himself living in one such house. The other night, upon catching the acrid scent of burning insulation, he followed his nose to the source: a wall-mounted thermostat for his electric baseboard. His teardown revealed burned insulation, bare conductors, and scorched plastic on the not-so-old unit; bearing a 2008 date code, the thermostat must have replaced one of the originals. [Kerry] poked at the nearly combusted unit and found the root cause: the spot welds holding the wires to the thermostat terminal had become loose, increasing the resistance of the connection. As [Kerry] points out, even a tenth of an ohm increase in resistance in a 15 amp circuit would dissipate 20 watts of heat, and from the toasty look of the thermostat it had been a lot more than that.

The corner-cutting of the 1980s was nothing new, of course – remember the aluminum wiring debacle? Electrical fires are no joke, and we’re glad [Kerry] was quick to locate the problem and prevent it from spreading.

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See How Wildly Different Air Conditioners Can Be (On The Inside)

December 15, 2019 by Donald Papp 16 Comments

Air conditioners are easy to take for granted. From refrigerators to climate control, most of us would miss them dearly if they disappeared. That’s part of what draws [Josh Levine]’s interest in air conditioners, and he has provided an interesting tour of several different units and how different they can be, despite all working in basically the same way.

That white PCB is crucial (for running the bluetooth speaker and LED flashlight, that is.)

One way that air conditioners try to stand out is by being quiet, and the bulk of noise comes from the fans and the compressor. One unit (the Haier Serenity) aimed to be the quietest unit possible, but while this effort had mixed results at best it is still interesting to see [Josh] give a tour of the different ways they tried to reduce noise (YouTube, embedded below). Noise-limiting elements include the unusual step of using separate motors for the indoor and outdoor fans, and even little counterweights to ensure they are perfectly balanced, just like wheel weights on automobile tires.

Another notable air conditioner is the Zero Breeze, a portable unit that was the product of a Kickstarter campaign. Features included (either bizarrely or predictably, you be the judge) a bluetooth speaker and an LED flashlight. [Josh] more than half suspected the product would never actually ship, but was pleasantly surprised. Not only did it deliver, it turned out to be a pretty nice design with only a couple of mildly head scratching moments (YouTube, also embedded below).

There are a few more to check out in the roundup on [Josh]’s web site, which he also compares and contrasts with his own DIY unit which we featured in the past.

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A Magnetron Tear Down

December 5, 2019 by Al Williams 27 Comments

Microwave ovens are everywhere, and at the heart of them is a magnetron — a device that creates microwaves. [DiodeGoneWild] tore one apart to show us what was inside and how it works. If you decide to do this yourself, be careful. The magnetron may have insulators made of beryllium oxide and inhaling dust from the insulator even one time can cause an incurable lung condition.

Luckily, you can’t get a lung problem from watching a video. In addition to just seeing the guts of the magnetron, there are also explanations about how everything works with some quick sketches to illustrate the points.

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PixMob LED Wristband Teardown (Plus IR Emitters And How To Spot Them)

November 26, 2019 by Donald Papp 11 Comments

PixMob units are wearable LED devices intended for crowds of attendees at events like concerts. These devices allow synchronized LED effects throughout the crowd. [yeokm1] did a teardown of one obtained from a preview for the 2019 Singapore National Day Parade (NDP), and in the process learned about the devices and their infrastructure.

Suspected IR emitter for the PixMob units, mounted on a lighting tower (marked here in white).

PixMob hardware has been known to change over time. This version has two RGB LEDs (an earlier version had only one), an unmarked EEPROM, an unmarked microcontroller (suspected to be the Abov MC81F4104), and an IR receiver module. Two CR1632 coin cells in series power the device. [yeokm1] has made the schematic and other source files available on the teardown’s GitHub repository for anyone interested in a closer look.

One interesting thing that [yeokm1] discovered during the event was the apparent source of the infrared emitter controlling the devices. Knowing what to look for and reasoning that such an emitter would be mounted with a good view of the crowd, [yeokm1] suspected that the IR transmitter was mounted on a lighting tower. Viewing the tower through a smartphone’s camera revealed a purplish glow not visible to the naked eye, which is exactly the way one would expect an IR emitter to look.

Sadly, there wasn’t any opportunity to record or otherwise analyze the IR signals for later analysis but it’s possible that the IR protocol might be made public at some point. After all, running custom code on an earlier PixMob board was made possible in part by asking the right people for help.

Restoring A Rusty Rebar Cutter

October 27, 2019 by Dan Maloney 16 Comments

We’ve all probably come across hunks of junk that used to be tools, long-neglected and chemically welded into a useless mass of solid rust. Such items are available for a pittance at the local flea market, or more likely found in an old barn or rotting on a junk pile. They appear to be far beyond salvage, but with the proper application of elbow grease and penetrating lubricants, even a nasty old seized-up rebar cutter can live again.

We honestly almost passed up on the video below when it came across our feed. After all, a rebar cutter is a dead-simple device, and half the fun of restoration videos like those made by [my mechanics] is seeing all the parts removed, restored, and replaced. But it ended up being far more interesting than we expected, and far more challenging too.

The cutter was missing its original handle and looked for all the world like it had been cast from a solid piece of iron oxide. [my mechanics] was able to get the main pivot bolts free with a combination of leverage, liberal application of penetrating oil, drilling, and the gentle persuasion of a hydraulic press.

These efforts proved destructive to both bolts, so new ones were made on the lathe, as were a number of other parts beyond saving. New cutters were fabricated from tool steel and a new handle was built; before anyone comments on anyone’s welding skills, please read [Jenny]’s recent article on the subject.

The finished product is strikingly dissimilar to the starting lump of oxidized junk, so there’s going to to be some debate in calling this a “restoration” in the classical sense. The end result of a [my mechanics] video is invariably a tool or piece of gear that looks far better than it did the day it was made, and any one of them would get a place of honor on our shelf. That said, he’d probably be swiftly shown the door if he worked at the Smithsonian.

Whatever you want to call these sort of videos, there are tons of them out there. We’ve featured a few examples of the genre, from the loving rehabilitation of classic Matchbox cars to rebuilding an antique saw set. They’re enough to make us start trolling garage sales. Or scrap yards.

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What The Scale? Mouse Teardown Throws Up A Few Surprises

October 13, 2019 by Anool Mahidharia 35 Comments

[Eric Weinhoffer] and his colleagues did a great comparative tear down of the MX Master 3 and the MX Master 2S mice from Logitech. Tear down’s are great fun and often end up teaching us a lot. Looking at the insides of a product can tell us a great deal about how to solve certain problems, or avoid pitfalls. Opening up two versions of the same product provides an even greater wealth of useful information on how product design evolves based on lessons learned from the earlier versions. Logitech is no greenhorn when it comes to Mice design, so the MX Master 2S was already almost perfect. But looking at the Master MX 3 shows where the earlier version fell short of expectations and how it could be improved upon.

These mice have intelligent scroll wheels, which can rotate in either “detente” or “freewheel” modes. Detente allows slower, precise scrolling, while freewheeling allows rapid scrolling. The two mice models have completely different, and interesting, methods of achieving these actions. The older version has a rubber-coated wheel and uses a motor, which turns a cam. This forces a detent ball onto the inside of the wheel for detent mode and releases it for free mode. Once the rubber wears off, the mouse is pretty much headed for the dumpster. The new metal wheel does away with the rubber coating as well as the noisy, slow, and prone to wear-and-tear motor assembly. The actuation is now done using a bi-stable electromagnet. A 25 V pulse magnetizes the coil which sits inside the wheel and it pulls on little metal teeth on the inside rim of the wheel. This gives a noiseless detente feel, without any physical contact. A second 25 V spike de-magnetizes the coil, allowing the scroll wheel to spin freely.

[Eric] points out several incremental changes in design which have resulted in improved ergonomics. He also uncovers a few nuggets of useful information. The use of interchangeable mold inserts help make molds last longer while still offering the flexibility to make changes in the molded part. It’s interesting to see special components being used for withstanding vibration and high-G forces. Some of these insights can be useful for those moving from prototyping to production. There’s one puzzling feature on the new PCB that [Eric] cannot figure out. There is a 15 mm scale screen-printed over the blue tooth antenna. If you have an answer on its purpose, let us know in the comments below.

If you are left-handed (which makes 10% of us), you’re out of luck with these right-handed mice and might like to sign one of the several online petitions demanding lefty versions.