High Voltage Switching With MOSFETs

June 10, 2018 by Al Williams 9 Comments

Using a MOSFET as a switch is generally pretty simple. Make the gate voltage sufficient with respect to the source and current flows through the channel. However, if you are switching higher voltages, you may need some additional circuitry to protect the device’s gate and possibly the microcontroller driving the whole thing, too. [Lewis] discusses high voltage switching in the latest in his series of videos dealing with MOSFETs. You can see the video below.

You’ll see in the video a breadboard setup driving a 50 V load and also a higher-voltage H-bridge. There are three major topics covered: Using an optoisolator, using a gate bleeder resistor, and using a zener diode to limit gate voltage.

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Hackaday Links: Benchoff Rants On Flying Cars

June 10, 2018 by Brian Benchoff 52 Comments

It’s time for Computex, and that means [Linus] has dropped something. I don’t know what, but he’s dropped something. It’s a meme or something at this point. What were the highlights? Asus announced Project Precog, a laptop with two screens. Yes, a touchscreen keyboard. It’s the 2018 version of the IBM Transnote or whatever that Microsoft thing was called. Why is it called Project Precog? Because AI or whatever. Unimaginative marketing is terrible. Intel is going to launch a 28-core CPU, and AMD is introducing a 32-core CPU. Awesome, core wars. And here’s RGB RAM because stuffing a case full of cold cathode lighting is sooo early-2000s.

Need a reverse engineering challenge? Here’s something from American Science and Surplus. It’s a 48 x 12 LED matrix, loaded up with driver ICs and power regulators. $20 a piece, so stock up and save.

Finally, the main event. The biggest story in aviation this week is that a media embargo has lifted on the Kitty Hawk Flyer. Kitty Hawk is a startup funded by Larry Page, CEO’d by Sebastian Thrun, and has received $6.5 M in funding. The Flyer, a one-man decacopter, was announced to the world through CNN Money and Casey Neistat. It should be noted that in the entire media landscape, these are the two outlets most ignorant of aviation: CNN needs no explanation, and Neistat flies quadcopters through the Hudson River Corridor at 1000 feet AGL. Additionally, Kitty Hawk is not exhibiting at AirVenture next month, which leads me to believe Kitty Hawk is trying to stay out of the aviation industry or simply doesn’t want knowledgeable people asking them questions. But I digress.

The Kitty Hawk Flyer is being promoted by the company as “a personal flying vehicle… to make flying part of everyday life” and a machine that will give you, “a world free from traffic”. It is being billed by CNN and Neistat as ‘a flying car’. Kitty Hawk is just fine with allowing the media to call it as such. Additionally, Sebastian Thrun is making claims about the Flyer that are disingenuous at best, outright illegal at worst, and should draw the ire of any investors.

In the CNN Money piece, Thrun claims the Flyer is capable of traveling at 100 miles per hour, which would be illegal. The Flier is certified as a Part 103 Ultralight, and under that regulation the Flyer “is not capable of more than 55 knots calibrated airspeed at full power in level flight.” The Flyer may also be overweight. The first version of the Flyer was basically a decacopter with a seat, and weighed in at 220 pounds. Part 103 regulations have a limit of 254 pounds, and it’s entirely possible there are more than 34 pounds of chassis and fiberglass on the latest version. I should also mention the safety training, while not required for a Part 103 ultralight, is insufficient: Casey Neistat’s underwater egress training was done in a Chuck E. Cheese-style ball pit. You can breathe in a ball pit, you can’t breathe underwater.

But legality aside, a Part 103 ‘flying car’ is just about the dumbest idea ever. You can’t use it to commute, and you’re welcome to call your local FSDO to confirm that. You’re not going to fly it in New York City or San Francisco because there are airports in the way. At best, this is a ‘flying ATV’ that you would take out on your farm; a toy for rich people. At worst, it’s the latest example of the Silicon Valley philosophy of ‘ignore laws and break things’.

Super Chromatic Peril Sensitive Sunglasses

June 10, 2018 by Brian Benchoff 25 Comments

The Joo Janta 200 super-chromatic peril-sensitive sunglasses were developed to help people develop a relaxed attitude to danger. By following the principle of, ‘what you don’t know can’t hurt you,’ these glasses turn completely opaque at the first sign of danger. In turn, this prevents you from seeing anything that might alarm you.

Here we see the beginnings of the Joo Janta hardware empire. For his Hackaday Prize entry, [matt] has created Nope Glasses. Is that meeting running long? Is your parole officer in your face again? Just Nope right out of that with a wave of the hand.

The Nope Glasses are two LCD shutters mounted in a pair of 3D printed glasses. On the bridge of the glasses is an APDS 9960 gesture sensor that tracks a hand waving in front of the glasses. Waving your hand down in front of the glasses darkens the shutters, and waving up makes them clear again. Waving left flashes between clear and dark, and waving right alternates each shutter.

In all seriousness, there is one very interesting thing about this project: how [matt] is attaching these LCD shutters to his glasses. This was done simply by taking a picture of the front and top of his glasses, converting those to 1-bit BMPs, and importing that into OpenSCAD. This gave him a pretty good idea of the shape of his glasses, allowing him to create an ‘attachment’ for his glasses. It’s great work, and we’d really like to see more of this technique.

Joe Grand Is Hiding Data In Plain Sight: LEDs That Look Solid But Send A Message

June 10, 2018 by Mike Szczys 19 Comments

Thursday night was a real treat. I got to see both Joe Grand and Kitty Yeung at the HDDG meetup, each speaking about their recent work.

Joe walked us through the OpticSpy, his newest hardware product that had its genesis in some of the earliest days of data leakage. Remember those lights on old modems that would blink when data is being transmitted or received? The easiest way to design this circuit is to tie the status LEDs directly to the RX and TX lines of a serial port, but it turns out that’s broadcasting your data out to anyone with a camera. You can’t see the light blinking so fast with your eyes of course, but with the right gear you most certainly could read out the ones and zeros. Joe built an homage to that time using a BPW21R photodiode.

Transmitting data over light is something that television manufacturers have been doing for decades, too. How do they work in a room full of light sources? They filter for the carrier signal (usually 38 kHz). But what if you’re interested in finding an arbitrary signal? Joe’s bag of tricks does it without the carrier and across a large spectrum. It feels a bit like magic, but even if you know how it works, his explanation of the hardware is worth a watch!

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Rubber Duck Debugging The Digital Way

June 10, 2018 by Dan Maloney 16 Comments

Anyone who slings code for a living knows the feeling all too well: your code is running fine and dandy one minute, and the next minute is throwing exceptions. You’d swear on a stack of O’Reilly books that you didn’t change anything, but your program stubbornly refuses to agree. Stumped, you turn to the only one who understands you and pour your heart out to a little yellow rubber duck.

When it comes to debugging tools, this digital replacement for the duck on your desk might be even more helpful. Rubber duck decoding, where actually explaining aloud to an inanimate object how you think the code should run, really works. It’s basically a way to get you to see the mistake you made by explaining it to yourself; the duck or whatever – personally, I use a stuffed pig– is just along for the ride. [platisd] took the idea a step further and made his debugging buddy, which he dubs the “Dialectic Ball,” in the form of a Magic 8-Ball fortune teller. A 3D-printed shell has an ATtiny84, an accelerometer, and an LCD screen. To use it, you state your problem, shake it, and read the random suggestion that pops up. The list has some obvious suggestions, like adding diagnostic print statements or refactoring. Some tips are more personal, like talking to your local guru or getting a cup of coffee to get things going again. The list can be customized for your way of thinking. If nothing else, it’ll be a conversation piece on your desk.

If you’re more interested in prognostication than debugging, we have no shortage of Magic 8-Ball builds to choose from. Here’s one in a heart, one that fits in a business card, and even one that drops F-bombs.

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Coming Back To Curving Bullets

June 10, 2018 by Brian McEvoy 23 Comments

What do you do when you have time, thousands of dollars worth of magnets, and you love Mythbusters? Science. At least, science with a flair for the dramatics. The myth that a magnetic wristwatch with today’s technology can stop, or even redirect, a bullet is firmly busted. The crew at [K&J Magnetics] wanted to take their own stab at the myth and they took liberties.

Despite the results of the show, a single magnet was able to measurably alter the path of a projectile. This won’t evolve into any life-saving technology because the gun is replaced with an underpowered BB gun shooting a steel BB. The original myth assumes a firearm shooting lead at full speed. This shouldn’t come as any surprise but it does tell us how far the parameters have to be perverted to magnetically steer a bullet. The blog goes over all the necessary compromises they had to endure in order to curve a bullet magnetically and their results video can be seen below the break.

Here we talk about shooting airplane guns so they don’t get mislead after leaving the barrel, and some more fun weaponry from minds under Churchill’s discretion.

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Fail Of The Week: Never Trust A Regulator Module

June 10, 2018 by Jenny List 47 Comments

[Ryan Wamsley] has spent a lot of time over the past few months working on a new project, the Ultimate LoRa backplane. This is as its name suggests designed for LoRa wireless gateways, and packs in all the features he’d like to see in a LoRa expansion for the Nano Pi Duo.

His design features a three-terminal regulator, and in the quest for a bit more power efficiency he did what no doubt many of you will have done, and gave one of those little switching regulator modules in a three-terminal footprint a go. As part of his testing he inadvertently touched the regulator, and was instantly rewarded with a puff of smoke from his Nano Pi Duo. As it turned out, the regulator was susceptible to electrical noise, and had a fault condition in which its input voltage was routed directly to its output. As a result, a component in the single board computer received way more than its fair share, and burned out.

If there is a moral to be extracted from this story, it is to never fully trust a cheap drop-in module to behave exactly as its manufacturer claims. [Ryan]’s LoRa board lives to fight another day, but the smoke could so easily have come from more components.

So that’s the Fail of The Week part of this write-up complete, but it would be incomplete without the corresponding massive win that is [Ryan]’s LoRa board itself. Make sure to take a look at it, it’s a design into which a lot of attention to detail has been put.