Mystery Box Gives Up Its Patented Secrets

January 31, 2021 by Al Williams 21 Comments

[CuriousMarc] likes to go to surplus stores even though there are fewer of them around. On a recent trip, he found a box that had some parts he thought would work for a temperature controller project. It was marked Dial-A-Level and proudly proclaimed that it had a patent pending. The box was from the 1970s and [Marc] was wondering what the device was meant to do.

The device was a bit of a puzzle since it had three oddly-marked probe inputs. A search through the patent database revealed the device was a “capacitance probe for detecting moisture with very long cables.” The idea was to create a capacitor at the end of the cable and use the liquid as a dielectric. The sensor creates a 10 kHz sine wave it uses to excite the probe and an op amp measures the relative capacitive reactance of the probe versus a reference capacitor. The rest of the circuit is a comparator that reacts when the level is at a threshold.

We love seeing the old hand-drawn boards from that era. Component designations are in copper and there’s no solder mask visible. There was a clever application of a silicon controlled rectifiers and a relay to create a type of flip flop, that [Marc] explains.

Interestingly, the company that made the device, Expo Instruments, is still around and [Marc] contacted them. The actual patent holder replied and was amazed that [Marc] had possession of this antique. You can only wonder if anything you build today will wind up on whatever passes for YouTube three or four decades from now.

Capacitive sensing is quite versatile. Of course, there are many other ways to sense liquid level, too.

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How Does A Circuit Breaker Break?

January 26, 2021 by Al Williams 32 Comments

Even if you aren’t an electronics person, you probably have a working knowledge of circuit breakers. When the lights go out, you find the circuit breaker and flip it back to the on position. Most people understand, too, that the breaker will trip if you overload the circuit with too many things plugged in or with an accidental short circuit. But how does this common device actually work? Keep in mind, circuit breakers need to be super reliable and have been around long enough that you can imagine they are pretty low tech. [Learn Engineering] has a very clear video about what goes on inside a circuit breaker that’s worth the eight minutes to watch. You can see the video below.

The handle is a mechanical engineering marvel, using two springs and a special design so that even a tiny force will cause it to snap to the off position. That takes care of a human tripping it. However, you have two other cases where you want to turn it off: overload and short circuit.

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Q Multiplier — Er… Multiplies Q

January 18, 2021 by Al Williams 13 Comments

If you are below a certain age, you’ve probably never heard of a Q multiplier. This is a device that increases the “Q” of a radio receiver’s intermediate frequency and, thus, provide a higher selectivity. If you enjoy nostalgia, you can see inside a 1960s-era Heathkit QF-1 Q multiplier in [Jeff’s] informative video, below.

The Q multiplier was a regenerative amplifier that operated at just below the oscillation point. This provided very high amplification for the frequency of interest and less amplification for other frequencies. Some radios had a stage like this built-in, but the QF-1 was made to add into an external radio. For some Heathkit receivers, there was a direct plug to tap into the IF stage for this purpose. Othe radios would require some hacking to get it to work.

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LEDs From Dubai: The Royal Lights You Can’t Buy

January 17, 2021 by Al Williams 103 Comments

[Clive] had an interesting video about LED lights from Philips. You can’t buy them unless you live in Dubai. Apparently inspired by the ruler of Dubai, Sheikh Mohammad Bin Rashid Al Maktoum, who wanted more efficient and longer-lasting bulbs. The secret? A normal LED bulb uses an LED “filament” at 1 watt each. The Dubai bulbs run at about a fourth of that which means they need more LEDs to get the same amount of light, but they should last longer and operate more efficiently.

After exploring the brightness and color of different lamps, [Clive] tears one up and finds some surprises inside. The LEDs get over 200V each and the driver circuit has a lot of pairs of components, possibly to keep the size small for the high voltages involved, although it could be to improve reliability, [Clive] wasn’t sure.

By reducing the power, [Clive] was able to count that each LED strip contains 21 LEDs. He also notes some of the oddities in construction that appear to be for reliability and ease of manufacturing. We aren’t sure how that compares to the construction of conventional bulbs. The circuit includes a bridge rectifier and a linear current regulator using a MOSFET.

The bulbs cost a bit more, but if you factor in the probable long life, their total cost over time should be reasonable. Overall, it is interesting that a nice design came from what amounts to government regulation. Of course, there is a price: in exchange for the development of the bulbs, Philips has the exclusive right to make and sell the bulbs for the next several years. They expect to sell 10 million lamps by the end of 2021, although they are only available, currently, in Dubai.

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Teardown: Tap Trapper

January 14, 2021 by Tom Nardi 46 Comments

The modern consumer is not overly concerned with their phone conversations being monitored. For one thing, Google and Amazon have done a tremendous job of conditioning them to believe that electronic gadgets listening to their every word isn’t just acceptable, but a near necessity in the 21st century. After all, if there was a better way to turn on the kitchen light than having a recording of your voice uploaded to Amazon so they can run it through their speech analysis software, somebody would have surely thought of it by now.

But perhaps more importantly, there’s a general understanding that the nature of telephony has changed to the point that few outside of three letter agencies can realistically intercept a phone call. Sure we’ve seen the occasional spoofed GSM network pop up at hacker cons, and there’s a troubling number of StingRays floating around out there, but it’s still a far cry from how things were back when folks still used phones that plugged into the wall. In those days, the neighborhood creep needed little more than a pair of wire strippers to listen in on your every word.

Which is precisely why products like the TA-1356 Tap Trapper were made. It was advertised as being able to scan your home’s phone line to alert you when somebody else might be listening in, whether it was a tape recorder spliced in on the pole or somebody in another room lifting the handset. You just had to clip it onto the phone distribution panel and feed it a fresh battery once and awhile.

If the red light came on, you’d know something had changed since the Tap Trapper was installed and calibrated. But how did this futuristic defender of communications privacy work? Let’s open it up and take a look.

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Is Your Echo Flex Listening?

January 14, 2021 by Al Williams 42 Comments

We are always surprised that Amazon or Google doesn’t employ Kelsey Grammer — TV’s Frasier — as a spokesman for their smart home devices. After all, his catchphrase was, “I’m listening…” Maybe they don’t want to remind you that the device could, theoretically, be sending everything you say to them or a nefarious hacker or government agency. Sure, there’s a mute button and it lights up a red LED.

But if you are truly paranoid, that’s not enough. After all, the same people want to eavesdrop on you would be happy to fake a red light. [Electronupdate] had the same thought and decided to answer the question: does the mute button really mute your microphone? The answer required not only some case opening and analysis, but there was even some IC decapsulation.

We were impressed with the depth of the analysis. The tiny SMD parts are marked confusingly, and if you are really paranoid you don’t believe them anyway. But looking at the actual circuit die is pretty unambiguous. The parts in question turned out to be a Schmitt trigger, a flip flop, and a NAND gate.

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Starlink Satellite Dish X-Rayed To Unlock RF Magic Inside

January 11, 2021 by Tom Nardi 15 Comments

When [Kenneth Keiter] took apart his Starlink dish back in November, he did his best to explain the high-level functionality of the incredibly complex device in a video posted to his YouTube channel. It was a fascinating look at the equipment, but by his own admission, he wasn’t the right person to try and explain the nuances of how the phased array actually functioned. But he knew who could do the technology justice, which is why he shipped the dismembered dish over to [Shahriar Shahramian] of The Signal Path.

Don’t be surprised if you can’t quite wrap your head around his detailed analysis after your first viewing. You’ll probably have a few lingering questions after the second re-watch as well. But that’s OK, as [Shahriar] still has a few of his own. Even after cutting out a section of the dish and putting it under an X-ray, it’s still not completely clear how the SpaceX engineers managed to cram everything into such a tidy package. Though there seems to be no question that the $500 price for the early-access hardware is an absolute steal, all things considered.

The layered antenna works on multiple frequencies.

Most of the video is spent examining the stacked honeycomb construction of the phased antenna array, which as expected, holds a number of RF secrets if you know what to look for. Put simply, there’s no such thing as an insignificant detail to the trained eye. From the carefully sized injection molded spacer sheet that keeps the upper array a specific distance from the RF4-like radome, to the almost microscopic holes that have been bored through each floating patch to maintain equalized air pressure through the stack up, [Shahriar] picks up on fascinating details which might otherwise seem like arbitrary design decisions.

But a visual inspection will only get you so far. Eventually [Shahriar] has to cut out a slice of the PCB so he can fit it into the X-ray machine, but don’t feel too bad, the dish was long dead before he got his hands on it. While he hasn’t yet completed his full analysis, an initial examination indicates that each large IC and the eight chips surrounding it make up a 16 channel beam forming module. Each channel is further split into two RX and TX pairs, which provides the necessary right and left hand polarization. That said, he admits there’s some room for interpretation and that further work would be necessary before any hard conclusions could be made.

Between this RF analysis and the initial overview provided by [Kenneth], we’ve already learned a lot more about this device than many might have expected considering how rare and expensive the hardware is. While we admit it’s not immediately clear what kind of hijinks hardware hackers could get into once this device is fully understood, we’re certainly eager to find out.

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