Ripping Up A Rothult

NFC locks are reaching a tipping point where the technology is so inexpensive that it makes sense to use it in projects where it would have been impractical months ago. Not that practicality has any place among these pages. IKEA carries a cabinet lock for $20USD and does not need any programming but who has a jewelry box or desk drawer that could not benefit from a little extra security? Only a bit though, we’re not talking about a deadbolt here as this teardown shows.

Rothult has all the stuff you would expect to find in an NFC scanner with a moving part. We find a microcontroller, RFID decoder, supporting passives, metal shaft, and a geartrain. The most exciting part is the controller which is an STM32L051K8 processor by STMicroelectronics and second to that is the AS3911 RFID reader from AMS. Datasheets for both have links in the teardown. Riping up a Rothult in the lab, we find an 25R3911B running the RFID, and we have a link to that PDF datasheet. Both controllers speak SPI.

There are a couple of things to notice about this lock. The antenna is a flat PCB-mounted with standard header pins, so there is nothing stopping us from connecting coax and making a remote antenna. The limit switches are distinct so a few dabs of solder could turn this into an NFC controlled motor driver. Some of us will rest easy when our coworkers stop kidnapping our nice pens.

Rothult first came to our attention in a Hackaday Links where a commenter was kind enough to tip us off to this teardown. Thanks, Pio! If this whets your appetite for NFC, we have more in store.

Teardown: The Guts of a Digital Sentry

I have a home alarm system that has me wondering if I can make it better with my maker Kung-fu. Recently we had to replace our system, so I took the time to dissect the main controller, the remote sensors, and all the bits that make a home security system work.

To be precise, the subject of today’s interrogation is a Zicom brand Home Alarm that was quite famous a decade ago. It connects to a wired telephone line, takes inputs from motion, door, and gas sensors, and will make quite a racket if the system is tripped (which sometimes happened accidentally). Even though no circuits were harmed in the making of this post, I assure you that there are some interesting things that will raise an eyebrow or two. Lets take a look.

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Teardown: Nihon Kenko Magnetic Wave Tester

You never know what kind of wonders you’ll find on eBay, especially when you have a bunch of alerts configured to go off when weird electronic devices pop up. You may even find yourself bidding on something despite not being entirely sure what it is. Perhaps you’re a collector of unusual gadgets, or maybe it’s because you’ve committed to doing monthly teardowns for the hacker blog you work for. In any event, you sometimes find yourself in possession of an oddball device that requires closer inspection.

Case in point, this “Magnetic Wave Tester” from everyone’s favorite purveyor of high-end electronics, Nihon Kenko Zoushin Kenkyukai Corporation. The eBay listing said the device came from an estate sale and the seller didn’t know much about it, but with just a visual inspection we can make some educated guesses. When a strong enough magnetic field is present, the top section on the device will presumably blink or light up. As it has no obvious method of sensitivity adjustment or even a display to show specific values, it appears the unit must operate like an electromagnetic canary in a coal mine: if it goes off, assume the worst.

If you’re wondering what the possible use for such a gadget is, you’re not the only one. I wasn’t able to find much information about this device online, but the few mentions I found didn’t exactly fill me with confidence. It seems two groups of people are interested in this type of “Magnetic Wave Tester”: people who believe strong magnetic fields have some homeopathic properties, or those who think it will allow them to converse with ghosts. In both cases, these aren’t the kind of users who want to see a microtesla readout; they want a bright blinking light to show their friends.

So without further ado, let’s align our chakras, consult with the spirits, and see what your money gets you when you purchase a pocket-sized hokum detector.

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Restoring An HP LCZ Meter From The 1980s

We are fantastically lucky not only in the parts that are easily available to us at reasonable cost, but also for the affordable test equipment that we can have on our benches. It was not always this way though, and [NFM] treats us to an extensive teardown and upgrade of a piece of test equipment from the days when a hacker’s bench would have been well-appointed with just a multimeter and a 10MHz ‘scope.

The Hewlett Packard 4276A LCZ meter is, or perhaps was, the king of component testers. A 19″ rack unit that would comfortably fill a shelf, it has a host of functions and a brace of red LED displays. This particular meter had clearly seen better days, and required a look inside just to clean up connectors and replace aged batteries.

In the case is a backplane board with a series of edge connectors for a PSU, CPU, and analogue boards. Aged capacitors and those batteries were replaced, and those edge connectors cleaned up again. The CPU board appears to have a Z80 at its heart, and we’re sure we spotted a 1987 date code. There are plenty of nice high-quality touches, such as the individual 7-segment digits being socketed.

An after-market option for this equipment included a DC offset board, and incredibly HP publish its full schematic and a picture of its PCB in their manual. It was thus a simple process and quick PCB ordering to knock up a modern replica, with just a few component substitutions and single resistors replacing an HP specific encapsulated resistor pack.

As a treat we get a ringside seat for the set-up and alignment of the machine. The DC offset board gives the wrong voltage, which he traces to a voltage reference with a different tolerance to the original HP part. [NFM] makes some adjustments to resistor values, and is able to pull the voltage to the correct value. Finally we see the instrument put through its paces, and along the way have a demonstration of how capacitance of a ceramic capacitor can vary with voltage close to its working voltage. Even if you never have the need for an LCZ meter or never see an HP 4276A, this should be worth a watch. And if you now have an urge to find a bench full of similar treasures, take a look at our guide to old test equipment.

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Components Cut in Half Reveal their Inner Beauty

We rarely take a moment to consider the beauty of the components we use in electronic designs. Too often they are simply commodities, bought in bulk on reels or in bags, stashed in a drawer until they’re needed, and then unceremoniously soldered to a board. Granted, little scraps of black plastic with silver leads don’t exactly deserve paeans sung to their great beauty – at least not until you cut them in half to reveal the beauty within.

We’ve seen a little of what [Tube Time] has accomplished here; recall this lapped-down surface-mount inductor that [electronupdate] did a while back. The current work is more extensive and probably somewhat easier to accomplish because [TubeTime] focused mainly on larger through-hole components such as resistors and capacitors. It’s not clear how the sections were created, but it is clear that extreme care was taken to lap down the components with enough precision that the inner structures are clearly visible, and indeed, carefully enough that some, most notably the LED, still actually work. For our money, though, the best looking cross-sections are the capacitors, especially the electrolytic, for which [Tube Time] thoughtfully provides both radial and axial sections. The little inductor is pretty cool too. Some of the component diagrams are annotated, too, which makes for fascinating reading.

Honestly, we could look at stuff like this all day.

Thanks to [Stuart Rogers] for the tip.

How Much Apple Does A Hamburger Get You?

A while ago, [Skippy] bought a cheap knock-off of the Apple USB mains charger from an AliExpress seller, for the British low, low price of 89p. Normally we’d give you a dollar conversion, but since that’s coincidentally the price of the basic McDonalds hambuger in the UK we’ll go with the hamburger as a unit of conversion. And as any self-respecting hacker would, he subjected it to a teardown and gave it a few tests.

Surprisingly though its pins were a little long it was just within the BS1363 pin spacing specification, probably due to its external dimensions copying the Apple original. The emissions test he performed might surprise readers, as it gave the little device its first pass. Radiated RF emissions were well below the test threshold, a welcome sight for anyone who has had to test a device. Sadly the same could not be said for conducted emissions, and it was happily spraying RF to all and sundry from its connections.

Taking a look inside revealed the usual litany of frightening safety fails. There was no insulation between the mains pins and the circuit board, and a secondary capacitor was even touching one of the pins. Meanwhile another capacitor connecting both sides of the circuit was not of the required Y rating. These and a raft of others make the device illegal for sale in Europe without further tests, but to give some numbers to it all he subjected it to a screen test applying 600 VAC common mode to its pins and checking for leakage current through the device. This it failed, and indeed it did not recover from the test.

So in this case, the price of a hamburger definitely does not get you an Apple, nor even does it get you an equivalent. But of course, you knew that, because we’ve talked about fake Apple chargers and power supplies many times before.

Lithium Jump Starter Disassembly Is Revealing

High-capacity lithium batteries tend to make everything in life better. No longer must you interact with your fellow human beings if your car battery goes flat in the carpark. You can jump the car yourself, with a compact device that fits in your glovebox. [Big Clive] decided to pull one apart and peek inside, and it’s quite the illuminating experience.

The first thing to note is there is almost no protection at all for the lithium battery inside. The output leads connect the lithium pack inside directly to the car battery, save for some diodes in series to prevent the car’s alternator backcharging the pack. [Clive] demonstrates this by short circuiting the pack, using a copper pipe as a test load to measure the current output. The pack briefly delivers 500 amps before the battery gives up the ghost, with one of the cells swelling up and releasing the magic smoke.

The teardown then continues, with [Clive] gingerly peeling back the layers of insulation around the cells, getting right down to the conductive plates inside. It’s a tough watch, but thankfully nothing explodes and [Clive]’s person remains intact. If you’ve never seen inside a lithium cell before, this is a real treat. The opened pack is even connected to a multimeter and squeezed to show the effect of the physical structure on output.

It would be interesting to compare various brands of jump starter; we imagine some have more protection than others. Regardless, be aware that many on the market won’t save you from yourself. Be careful out there, and consider jumping your car with an even more dangerous method instead (but don’t). Video after the break.

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