You’ve probably seen the videos of a grape — cut almost totally in half — in a microwave creates a plasma. A recent physics paper studies the phenomenon with a lot of high-tech gear and now the actual mechanism is known. [Veritasium] interviews the scientists and explains the grape plasma phenomenon in plain language. You can see the video below or read the paper directly.
Turns out the grape is about 1/10 of the microwave frequency and the refractive index of the grape at microwave frequencies might be as much as ten. A whole grape can get all the microwaves trapped inside, but two grapes — or two halves — that touch create fields strong enough to ionize the air.
Continue reading “Grape Plasma Explained”
The Jacob’s Ladder is an electrical device named after a biblical “ladder to Heaven”, consisting of a pair of vertically oriented conductors that spread apart vertically. These conductors are charged with high voltage, which creates the repeatedly climbing arc we’ve all come to know and love from science fiction movies of yesteryear.
[LOOK MUM NO COMPUTER] was on a scavenger hunt for electronic junk, and came across a microwave in a skip that was begging to be hacked. After kicking around a few ideas, it was decided that the microwave would donate its high voltage transformer to create a Jacob’s ladder. The transformer is first bolted down to a piece of wood, and creates some sparks on the bench when shorted. The output is then wired to a pair of copper pipes to create the classic effect.
Unfortunately, the device isn’t self starting, requiring the electrodes to be temporarily short circuited to generate the initial arc. We suspect that increasing the voltage may help things somewhat, either with another transformer in series or with a voltage multiplier.
It goes without saying that high voltage projects do bring certain risks to life and limb that should not be overlooked. If you’ve still got a thirst for danger, check out this home built X-ray machine. Video after the break.
Continue reading “Microwave Parts Become Quick and Nasty Jacob’s Ladder”
When I started working in a video production house in the early 1980s, it quickly became apparent that there was a lot of snobbery in terms of equipment. These were the days when the home video market was taking off; the Format War had been fought and won by VHS, and consumer-grade VCRs were flying off the shelves and into living rooms. Most of that gear was cheap stuff, built to a price point and destined to fail sooner rather than later, like most consumer gear. In our shop, surrounded by our Ikegami cameras and Sony 3/4″ tape decks, we derided this equipment as “ReggieVision” gear. We were young.
For me, one thing that set pro gear apart from the consumer stuff was the type of connectors it had on the back panel. If a VCR had only the bog-standard F-connectors like those found on cable TV boxes along with RCA jacks for video in and out, I knew it was junk. To impress me, it had to have BNC connectors; that was the hallmark of pro-grade gear.
I may have been snooty, but I wasn’t really wrong. A look at coaxial connectors in general and the design decisions that went into the now-familiar BNC connector offers some insight into why my snobbery was at least partially justified.
Continue reading “The BNC Connector and How It Got That Way”
Most hackers are rankled by those “Warranty Void If Broken” seals on the sides of new test equipment. Even if they’re illegal, they at least put the thought in your head that the space inside your new gear is off-limits, and that prevents you from taking a look at what’s inside. Simply unacceptable.
[Shahriar] has no fear of such labels and tears into just about everything that comes across his bench. Including, most recently, a $1.3 million 110-GHz oscilloscope from Keysight. It’s a teardown that few of us will ever get the chance to do, and fewer still would be brave enough to attempt. Thankfully he does, and the teardown video below shows off the remarkable engineering that went into this monster.
The numbers boggle the mind. Apart from the raw bandwidth, this is a four-channel scope (althought the unit [Shahriar] tested is a two-channel) that doesn’t split its bandwidth across channels. The sampling rate is 256 GS/s and the architecture is 10-bits, so this thing is dealing with 10 terabits per second. We found the extra thick PCBs, which are perhaps 32-layer boards, to be especially interesting, and [Shariar]’s tour of the front end was fascinating.
It all sounds like black magic at first, but he really makes the technology approachable, and his appreciation for fine engineering is obvious. If you’ve got even a passing interest in RF electronics you should check it out. You might want to brush up on microwave topics first, though; this Doppler radar teardown might help.
Continue reading “Tearing Into a $1.3 Million Oscilloscope”
Deep inside your smartphone are a handful of interesting miniature electromechanical devices. The accelerometer is a MEMS device, and was produced with some of the most impressive industrial processes on the planet. Sometimes, these nanoscale devices are produced with plasma etching, which sounds about as cool as it actually is. Once the domain of impossibly expensive industrial processes, you can now plasma etch materials in a microwave.
Of course, making plasma in this way is nothing new. If you cut a grape in half and plop it in a microwave, some really cool stuff happens. This is just the 6th grade science class demonstration of what a plasma is, and really it’s only a few dissociated water, oxygen, and nitrogen molecules poofing in a microwave. To do something useful with this plasma, you need a slightly more controlled environment.
The researchers behind this paper used a small flask with an evacuated atmosphere (about 300 mTorr) placed into a microwave for a few seconds. The experiments consisted of reducing graphene oxide to graphene, with the successful production of small squares of graphene bonded to PET film. Other experiments changed the optical properties of a zinc oxide film deposited onto a glass microscope slide and changing a PDMS film from being hydroscopic to hydrophobic.
While the results speak for themselves — you can use a microwave to generate plasma, and that plasma can change the properties of any exposed material — this is far from a real industrial process. That said, it’s good enough for an experiment and another neat technique in the home lab’s bag of tricks.
If you have even the slightest interest in microwave electronics and radar, you’re in for a treat. The Signal Path is back with another video, and this one covers the internals of a simple 24-GHz radar module along with some experiments that we found fascinating.
The radar module that [Shahriar] works with in the video below is a CDM324 that can be picked up for a couple of bucks from the usual sources. As such it contains a lot of lessons in value engineering and designing to a price point, and the teardown reveals that it contains but a single active device. [Shahriar] walks us through the layout of the circuit, pointing out such fascinating bits as capacitors with no dielectric, butterfly stubs acting as bias tees, and a rat-race coupler that’s used as a mixer. The flip side of the PCB has two arrays of beam-forming patch antennas, one for transmit and one for receive. After a few simple tests to show that the center frequency of the module is highly variable, he does a neat test using gimbals made of servos to sweep the signal across azimuth and elevation while pointing at a receiving horn antenna. This shows the asymmetrical nature of the beam-forming array. He finishes up by measuring the speed of a computer fan using the module, which has some interesting possibilities in data security as well as a few practical applications.
Even though [Shahriar]’s video tend to the longish side, he makes every second count by packing in a lot of material. He also makes complex topics very approachable, like what’s inside a million-dollar oscilloscope or diagnosing a wonky 14-GHz spectrum analyzer.
Continue reading “A Radar Module Teardown And Measuring Fan Speed The Hard Way”
[Kerry Wong] comes across the coolest hardware, and always manages to do something interesting with it. His widget du jour is an old demo board for a digital RF attenuator chip, which can pad a signal in discrete steps according to the settings of some DIP switches. [Kerry]’s goal: forget the finger switch-flipping and bring the attenuator under Arduino control.
As usual with his videos, [Kerry] gives us a great rundown on the theory behind the hardware he’s working with. The chip in question is an interesting beast, an HMC624LP4E from Hittite, a company that was rolled into Analog Devices in 2014. The now-obsolete device is a monolithic microwave integrated circuit (MMIC) built on a gallium arsenide substrate rather than silicon, and attenuates DC to 6-GHz signals in 64 steps down to -31.5 dBm. After a functional check of the board using the DIP switches, he whipped up a quick Arduino project to control the chip with its built-in serial interface. It’s just a prototype for now, but spinning the encoder is a lot handier than flipping switches, and once this is boxed up it’ll make a great addition to [Kerry]’s RF bench.
If this video puts you in an RF state of mind, check out some of [Kerry]’s other videos, like this one about temperature-compensated crystal oscillators, or the mysteries of microwave electronics.
Continue reading “Digital Attenuator Goes from Manual to Arduino Control”