Author: Al Williams

4349 Articles

A Transistor? Memory? Wait, It’s Both!

December 18, 2022 by 13 Comments

What do you get if you cross graphene, hexagonal boron nitride, and tungsten diselenide? Well, according to researchers at Hunan University, you get a field effect transistor that can act as both a switching element or a memory cell. The partial floating-gate field-effect transistor or PFGFET uses 2D van der Waals heterostructures to deal with isolated atomic layers. The paper in Nature is unfortunately behind a pay wall, but you can read a summary over on [TechExplore].

The graphene acts as the gate, and the transistor can be switched between n-type behavior and p-type behavior. It can also be configured as a switching element or as a memory element similar to an EEPROM cell.

One advantage of having configurable transistor types is that a single transistor structure can produce CMOS or complementary circuits. Traditionally, a CMOS IC has two different transistor structures and often producing one of them requires extra effort.

The configuration takes place by applying a control voltage pulse. A negative control voltage produces a p-type FET and a positive voltage configures the same transistor as an n-type. If you don’t have access to the paper, the figures available online offer a good bit of insight into the device’s design.

If you want to learn more about ordinary MOSFETs, we talk about them often. You can also get the skinny on CMOS from [Bil Herd].

Robot Dog Has Animal Magnetism

December 18, 2022 by 7 Comments

Robot “dogs” are all the rage lately, but you probably haven’t seen one that can climb up a wall. Researchers in Korea have made one that can, assuming the wall is made out of a metal that a magnet can stick to at least. The robot, MARVEL or magnetically adhesive robot for versatile and expeditious locomotion, might be pressing its luck on acronyms, but it is pretty agile as you can see in the video below. Tests showed the robot walking on walls and ceilings. It can cross gaps and obstacles and can even handle a curved storage tank with paint and rust.

The robot weighs 8 kilograms (17.6 pounds), can carry 2 – 3 kg of payload, and operates without a tether. Each foot contains both an electropermanent magnet and magnetorheological elastomers. If you haven’t seen them before, an electropermanent magnet, or EPM, is a magnet that can be turned on or off electronically. The elastomer is a polymer containing ferromagnetic particles that can alter the material’s properties in response to a magnetic field.

EPMs have two parts. One part is a simple permanent magnet. The other is a soft core easily magnetized by a surrounding coil. If you magnetize the soft core to oppose the permanent magnet, the fields cancel out, effectively turning off the magnet. If you magnetize it the other way, it reinforces the field.

This is better than an electromagnet in this application because turning the magnet on or off only requires a brief pulse. If you want your robot to hang out on the ceiling with Spider Man indefinitely, you don’t have to worry about draining your batteries while keeping an electromagnet engaged.

Overall, an interesting robot. Most wall-climbing robots we’ve seen are pretty lightweight. We don’t see nearly as many that can have the feeling of clinging to the ceiling.

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Say The Magic Word, And The TinySA Goes Ultra

December 17, 2022 by 15 Comments

We’ve looked at the TinySA spectrum analyzer in the past. However, the recent Ultra edition offers an increase in range from 800 MHz to 6 GHz. How does it work? [IMSAI Guy] tells us in a recent video that you can watch below. In addition to an increased frequency range, the new device offers a larger display and enhancements to the signal generator and bandpass filtering. It also has an optional LNA. All this, of course, is at a price since the Ultra sells at a little more than twice the original unit’s price. Still, $120 or so for a 6 GHz spectrum analyzer isn’t bad.

For some reason, you have to put a passcode in to enable the Ultra mode, although the passcode appears to be common knowledge and available on the device’s wiki. You can presume they could, at some point, make this feature or others require a paid passcode, but for now, it is just a minor inconvenience. Reminds us of a certain oscilloscope that’s become quite popular in our community.

One thing you should be aware of, however, is that the Ultra mode uses a mixer to downconvert the incoming signal to the ordinary 800 MHz range. That means, as you can see in the video, that the local oscillator puts out some signal at the input. The level is relatively low, but still something to be aware of if you are trying to make a precision measurement.

The video compares the device to an HP 8591E spectrum analyzer. It tops out at 1.8 GHz and runs about $2,500 new. Even on eBay, you can expect to pay between $500 and $1000 for one of these. The results seem to be comparable, for the most part.

We looked at the device’s predecessor back in 2020. We also did a full-blown review a little bit later.

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Mazda Patents Spinning Dorito To Extend EV Range

December 16, 2022 by 44 Comments

OK, so a Wankel engine doesn’t really use a Dorito as its cylinders, but it sure looks like one. The company has announced it will offer a range extender rotary engine for the MX-30 electric “crossover” vehicle, but [CarBuzz] dug into the patent papers to find out that it has some interesting twists.

The MX-30 is an EV with a relatively small 35.5 kWh battery. Like a hybrid vehicle, the car includes a small internal combustion engine that can charge the battery. It does not, however, directly drive the wheels at any time. The Wankel has several improvements, including a secondary port that allows more air into the combustion chamber when the engine has to produce high power. But there’s a problem…

The secondary port is great when you are pushing hard, but at low speed, it produces inefficiency. To combat that, Mazda includes a valve to seal off the second port when it doesn’t make sense to open it. But that’s not the strange part. The strange part is that the engine also has its own electric assist motor that runs off the main battery.  That’s right. The battery you are charging provides some energy to operate the electric assist motor to help the engine that is charging the battery. If that makes your head spin like the Wankel’s rotor, you aren’t alone.

The assist motor can assist or retard the output shaft during the intake stroke. This can optimize the intake to the combustion chamber. Of course, this will cause odd movement in the engine’s output, but since it doesn’t drive the car, who cares? The battery isn’t going to mind if the output isn’t smooth.

The Wankel shows up in a lot of odd places. We’ve seen Wankel air compressors. Despite detractors, there have been many improvements in the design over the years.

Ask Hackaday: Will Your 2030 Car Have AM Radio?

December 9, 2022 by 171 Comments

Car makers have been phasing out AM radios in their cars for quite some time. Let’s face it, there isn’t much on AM these days, and electric vehicles have been known to cause interference with AM radios. So why have them? For that matter, many aftermarket head units now don’t even have radios at all. They play digital media or stream Bluetooth from your phone. However, a U.S. Senator, Edward J. Markey, has started a letter-writing campaign to the major car makers urging them to retain the AM radio in their future vehicles.

So does that mean AM lives? Or will the car makers kill it off? The letter requests that the companies answer several questions, including if they plan to discontinue AM or FM radios in the near future and if they support digital broadcast radio.

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Build A Better Mousetrap… But It Better Be Better!

December 8, 2022 by 22 Comments

As creative problem solvers, we like to “think outside the box,” and we should strive for that. But what happens if your strange idea isn’t kept in check by cooler heads? There is a real danger — especially if you work alone — to falling so in love with your idea, that you lose sight of what it really means to be better.

Case in point. The self-parking car. Well, not the modern variant, which seems to work pretty well. But did you know that the self-parking car was invented in the 1930s and used an extra fifth wheel? Hard to imagine? See the video below. History tells us that the idea didn’t catch on.

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Transparent Metal (Hydroxide) Without Mr. Scott

December 7, 2022 by 24 Comments

There’s a famous scene in one of the Star Trek movies where Scotty, who has traveled to the past, teaches a metal company to create the transparent aluminum he needs to bring some whales back to the future. But [The Action Lab] shows that we already have see-through metal, just not aluminum. You can see a video about why metals are normally opaque.

The metal in question is sodium. Normally, it isn’t transparent, but molten sodium hydroxide does turn transparent after it — well, sort of explodes. Of course, sodium hydroxide isn’t really a metal, but then neither is the aluminum oxide that’s been touted as real transparent aluminum. Aluminum oxide also makes transparent gemstones like rubies. However, there is some — kind of — transparent aluminum at the end of the video.

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