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All the Badges of DEF CON 26 (vol 1)

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Two or three years back you would see a handful of really interesting unofficial badges at DEF CON. Now, there’s a deluge of clever, beautiful, and well executed badges. Last weekend I tried to see every badge and meet every badge maker. Normally, I would publish one megapost to show off everything I had seen, but this year I’m splitting it into volumes. Join me after the break for the first upload of the incredible badges of DC26!

Telephreak Eleven Badge

The Telephreak party at DEF CON is a gathering of a tight knit group of phone phreakers who spend the Sunday of DC having a good time. You can find them in advance of the party by looking for the Telephreak badge which is usually one of the more interesting offerings. This year’s badge is no exception.

The screen on this badge is one of the best looking full-color screens I’ve seen on any badge. Photos are traded wirelessly between badges. One really interesting tidbit is that the badges are traded over a mesh network (badge to badge) and with each transfer, depending on the proximity and signal quality, the photos will degrade. Think of it like sending a fax of a fax of a fax. Very fitting for the phreakers!

The badge itself is sporting an ATmega328 and a 915 MHz packet radio. 140 of these wer produced all by hand. I thought the auxiliary hardware @dominotree had with him was really interesting as well. He’s using a Teensy and a wireless module to “seed” new images. Read more about the badge on spun.io.

Brotherhood of Steel Watch

If you wear it, does that make it a badge? No matter the answer, here’s an interesting one I bumped into at the hardware hacking village. It’s called the “Brotherhood of Steel” since it’s based on the Pip-Boy from Fallout.

As you expect from the wrist-mount mult-tasker, this does a little bit of everything. It’ has those red bubble displays for displaying information, with four toggle switches and a d-pad. With the case off you can see the laser diode, Adafruit GPS, and Honeywell compass. It’s running on an NXP ARM controller fed by 400 mAh LiPo that’s nestled between the PCB and the lower portion of the case.

Car Hacking Village Badge

The Car Hacking Village badge gets a shout-out for the most TSA unfriendly. I checked my in my luggage after reading some Tweets that this badge looks like a wrench that is beyond the allowable size by airport security. At least one of these was pulled out and shown off in the airport!

One end is an incredibly densely packed matrix of LEDs. The double-row that rings the outside of the board are purple. but the grind inside is RGB — 320 total 0404 parts laid out on a standard 4-layer board! What’s exceptionally interesting to me is that the scanning is being done with five 595 shift registers which you can see in a row just to the left of the LEDs. There are three microcontrollers on the board, all NXP; the s32, k22, and s99. In addition to blinking, you get ODB-II which lets you hack CAN bus using a scripting language, along with USB, and an SD card.

This is the 4th year that they’ve done the car hacking village badge. There was some adversity this year as their original PCB supplier dropped the job and only told them three days before delivery. Looks like everything came out just fine though!

Add-Ons By TwinkleTwinkie

This certainly was the year that badges got their own badges. The entrance of the 2×2 pin add-on standard meant there were a ton of people making simple yet interesting things to hang off of a pin socket. TwinkleTwinkie is hands-down the most prolific of add-on producers. You should definitely check out his Hackaday.io page, but above you can see some of my favorites like Big Green, Krusty the It, and Mad Cat. I also heard a story that Twinkle used to work in the printing industry which is why the half-tone art looks so great.

DeLorean Add-On

I have no idea of the back story on this one, but who could resist snapping a picture of a DeLorean add-on? This also shows off the add-on totems that were used to show off add-ons without a badge. They simply provided ~3 V of power via a pair of batteries.

LineCon Badge

The Linecon badge is a stunning example of half-tone art on a PCB. Despite the fairly low quality/resolution often face with PCB silk screen, this technique can deliver great looking boards.

The board is driven by an STM32, using an IR sensor to count the number of times you dart your finger into the hole in the board. Yep, just about as fun as linecon — the art of standing in line waiting for the official DEF CON badge. There is also USB available for serial puzzles and unlocks.

I really like the positioning of the three batteries on the back. Usually you just see a single 3-cell holder but this technique spreads the weight and bulk out. The OLED screen on board is your typical 64×128, and around the edges of the badge there are 30 APA102 RGB LEDs for bling.

uBadge

I would call this the “micro” badge, but I think Joe Fitz is actually pronouncing it the “you” badge. At any rate, the letter u indicates it is a small badge and I can confirm that this is trolling at its finest. Joe’s badge is based on the Digispark, providing an ATtiny85 which you can plug into a USB cord and program yourself. The bulk of the “badge” is the add-on header itself.

Speaking of the add-ons, Joe made up for the badge trolling with an impressive set of “arms” that extend the add-on header and allow more than one to be powered by the uBadge. Joe panelized these in a 10×10 grid, and populated 11 panels. That’s a lot of badges so make sure you ask him for one next time you see him.

Maneki Neko

This is one of two badges I saw this year that includes motors. The Maneki Neko badge’s name includes the words for lucky cat in Japanese. It will hang from a lanyard, using the 12-segment displays to look at you and blink. When it’s time to wave, the eyes turn to asterisks and the left paw waves a few times.

An STM32 controls the badge, driving the eyes and motor. There is a connector for an ESP8266 but that is up to the user to implement.

Continued in Volume Two

We’re all badged out for the moment. Join us soon for Volume 2!


Foreshadow: The Sky Is Falling Again for Intel Chips

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It’s been at least a month or two since the last vulnerability in Intel CPUs was released, but this time it’s serious. Foreshadow is the latest speculative execution attack that allows balaclava-wearing hackers to steal your sensitive information. You know it’s a real 0-day because it already has a domain, a logo, and this time, there’s a video explaining in simple terms anyone can understand why the sky is falling. The video uses ukuleles in the sound track, meaning it’s very well produced.

The Foreshadow attack relies on Intel’s Software Guard Extension (SGX) instructions that allow user code to allocate private regions of memory. These private regions of memory, or enclaves, were designed for VMs and DRM.

How Foreshadow Works

The Foreshadow attack utilizes speculative execution, a feature of modern CPUs most recently in the news thanks to the Meltdown and Spectre vulnerabilities. The Foreshadow attack reads the contents of memory protected by SGX, allowing an attacker to copy and read back private keys and other personal information. There is a second Foreshadow attack, called Foreshadow-NG, that is capable of reading anything inside a CPU’s L1 cache (effectively anything in memory with a little bit of work), and might also be used to read information stored in other virtual machines running on a third-party cloud. In the worst case scenario, running your own code on an AWS or Azure box could expose data that isn’t yours on the same AWS or Azure box. Additionally, countermeasures to Meltdown and Spectre attacks might be insufficient to protect from Foreshadown-NG

The researchers behind the Foreshadow attacks have talked with Intel, and the manufacturer has confirmed Foreshadow affects all SGX-enabled Skylake and Kaby Lake Core processors. Atom processors with SGX support remain unaffected. For the Foreshadow-NG attack, many more processors are affected, including second through eighth generation Core processors, and most Xeons. This is a significant percentage of all Intel CPUs currently deployed. Intel has released a security advisory detailing all the affected CPUs.

A Radar Module Teardown And Measuring Fan Speed The Hard Way

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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 …read more

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Track Everything, Everywhere with an IoT Barcode Scanner

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I’ve always considered barcodes to be one of those invisible innovations that profoundly changed the world. What we might recognize as modern barcodes were originally designed as a labor-saving device in the rail and retail industries, but were quickly adopted by factories for automation, hospitals to help prevent medication errors, and a wide variety of other industries to track the movements of goods.

Medication errors in hospitals are serious and scary: enter the humble barcode to save lives. Source: The State and Trends of Barcode, RFID, Biometric and Pharmacy Automation Technologies in US Hospitals

The technology is accessible, since all you really need is a printer to make barcodes. If you’re already printing packaging for a product, it only costs you ink, or perhaps a small sticker. Barcodes are so ubiquitous that we’ve ceased noticing them; as an experiment I took a moment to count all of them on my (cluttered) desk – I found 43 and probably didn’t find them all.

Despite that, I’ve only used them in exactly one project: a consultant and friend of mine asked me to build a reference database out of his fairly extensive library. I had a tablet with a camera in 2011, and used it to scan the ISBN barcodes to a list. That list was used to get the information needed to automatically enter the reference to a simple database, all I had to do was quickly verify that it was correct.

While this saved me a lot of time, I learned that using tablet or smartphone cameras to scan barcodes was actually very cumbersome when you have a lot of them to process. And so I looked into what it takes to hack together a robust barcode system without breaking the bank.

Source: IoTMaker.vn

A Barcode Reader to Make a Hacker Proud

Dedicated barcode scanners cost around $20 USD from banggood or DX and are an obvious solution, but that would be boring. I also wanted a more powerful device: a barcode scanner that could directly connect to the Internet so I could track things centrally online without any further hardware. While the idea was hardly unique, it still stuck with me. Recently, I saw a tiny barcode scanner module (Youku E1005) for sale for $17 USD with no datasheet, and I knew the game was on.

The scanner module itself was very compact, which lent itself well to making a convenient device. It had a generic unlabeled MCU, and a 12-pin ribbon cable connector. The vendor told me it supported Code 39 barcodes (true – but it actually supports many more!), and had USB and TTL output. It was time to puzzle the module out!

Dissecting Barcode Hardware

Not my finest soldering job.

Logically, some of the 12 pins were going to be power, ground, USB data lines, and TTL serial output. Typically these modules are used to build hand-held barcode scanners, so also require a trigger to be pressed to activate the scanner. The first step was to desolder the connector so I could get access to the pads underneath.

The next step was to identify power and ground. Ground was pretty easy since several components were connected to what was clearly a ground plane. The power pin was harder, but there was an IC that looked like a voltage regulator in a SOT-753 package. Given common pinouts, both the enable and the voltage input pins were connected to a single pad.

Having probable inputs for power and ground, I connected 3.3v to the circuit. Nothing happened, which is expected as I’ve yet to find the trigger pin that activates the device. The easiest thing to do was to quickly connect each remaining pad to ground and see if the trigger was of the ‘active-low’ variety. It turned out it was, and the LED of the device turned on to indicate it was ready to scan.

Making Sense of It All

Pin Function
2 VCC
3 GND
5 TX
12 Trigger

The final step was to find the TTL output. That turned out to be pretty easy now that I could force the device to scan barcodes. I took an arbitrary barcode and scanned it while looking at different pins on my oscilloscope. When I found output, I captured it so I could determine the baud rate later on. The final pinout I found is to the right. The flat cable connector pads were fairly dense, so I soldered wires to components connected to the relevant pads rather than the pads themselves where possible.

After scanning a barcode and capturing the output on my oscilloscope, I saw that the duration of the shortest peak was just over 100μs. That translates to a frequency of a little under 10000 bits per second. The closest common baudrate is 9600 baud, so that is likely our TTL baudrate. Now, we have all the information we need to connect the barcode scanner module to a microcontroller, in our case an ESP8266 running NodeMCU.

The first peak has the shortest duration in the sequence, at about 105μs. A reasonable baud rate to try is the closest common one to 1s/105μs = 9523 baud, which is 9600 baud.

Our code will be very simple: Change the UART speed to 9600 baud, and when any data is received concatenate what comes in for the next 150 milliseconds and print it out. Remember to set the baud rate of your development tool (e.g. ESPlorer) to 9600 as well.

 -- Setup UART and print something so we know it's working uart.setup(0, 9600, 8, uart.PARITY_NONE, uart.STOPBITS_1, 0)
print("Scanning") -- Set up a couple of variables so they're not nil data = ""
datac = "" -- This function prints out the barcode data and clears all variables so the scanner can read a new barcode. If you wanted to send the data over MQTT, your code would replace the print statement here. function finish() print(datac) data = "" datac = ""
end -- This function concatenates all data received over 150 milliseconds into the variable datac. The scanner sends the data in multiple parts to the ESP8266, which needs to be assembled into a single variable. uart.on("data", 0, function(data) tmr.alarm(0,150,0,finish) datac = datac .. data
end, 0) 

This worked quite nicely and was able to read various types of barcode without issue. It would be very easy to connect this to a server on the Internet, either directly via MQTT, or using an Internet of Things dashboard. It would even be possible to implement encryption and authentication if you needed.

Custom Tricks Now Open Up To Us

An interesting fact is that the NodeMCU is capable of executing serial input, so make sure that feature is turned off (the 0 at the end of the uart.setup line). Otherwise someone will promptly drop by with the barcode to the right. The usual precautions apply to the backend as well. You could even filter out problematic characters at the hardware level, which would be nice. Of course if you’re clever this could be a feature and not a vulnerability.

I didn’t have a particular use case for this barcode scanner in mind, but it would be nice to see someone implement it in a cloud Point-of-Sale system for small merchants in Asia to track inventory in a primarily cash-based economy. In effect that would be very similar to the original use of barcode scanners – minus the expensive POS system.

Finally, while at a local convenience store, I saw the perfect project case for this sitting on a shelf. I bought it, and it was filled with candy! Sometimes we live in the best of all possible worlds:

Fun fact: all my hacks are sugarfree and do not cause tooth decay. The case also comes in an extra cool variety, but I’m saving that for another day.

Rover V2 Handles Stairs as Easily as the Outdoors

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Rover V2 is an open-source, 3D-printable robotic rover platform that has seen a lot of evolution and development from its creator, [tlalexander]. There are a number of interesting things about Rover V2’s design, such as the way the wheel hubs themselves contain motors and custom planetary gearboxes. This system is compact and keeps weight down low to the ground, which helps keep a rover stable. The platform is all wheel drive, and moving parts like the suspension are kept high up, as far away from the ground as possible. Software is a custom Python stack running on a Raspberry Pi that provides basic control.

The Rover V2 is a full mechanical redesign of the previous version, which caught our attention with its intricate planetary gearing inside the wheel hubs. [tlalexander]’s goal is to create a robust, reliable rover platform for development that, thanks to its design, can be mostly 3D printed and requires a minimum of specialized hardware.

Don’t Forget Your Mints When Using This Synthesizer

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While synthesizers in the music world are incredibly common, they’re not all keyboard-based instruments as you might be imagining. Especially if you’re trying to get a specific feel or sound from a synthesizer in order to mimic a real instrument, there might be a better style synth that you can use. One of these types is the breath controller, a synthesizer specifically built to mimic the sound of wind instruments using the actual breath from a physical person. Available breath controllers can be pricey, though, so [Andrey] built his own.

To build the synthesizer, [Andrey] used a melodica hose and mouthpiece connected to a pressure sensor. He then built a condenser circuit on a custom Arduino shield and plugged it all into an Arduino Mega (although he notes that this is a bit of overkill). From there, the Arduino needed to be programmed to act as a MIDI device and to interact with the pressure sensor, and he was well on his way to a wind instrument synthesizer.

The beauty of synthesizers is not just in their ability to match the look and sound of existing instruments but to do things beyond the realm of traditional instruments as well, sometimes for a greatly reduced price point.

Every Shop Needs A Giant Wooden Utility Knife

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Generally speaking, we don’t cover that many woodworking projects here at Hackaday. What’s the point? It’s bad enough that wood reminds us of the outside world, but it hardly ever blinks, and forget about connecting it to Wi-Fi. This doesn’t seem to bother you fine readers, so we have to assume most of you feel the same way. But while we might not always “get” large woodworking projects around these parts, we’re quite familiar with the obsession dedication required to work on a project for no other reason than to say you managed to pull it off.

On that note, we present the latest creation of [Paul Jackman], a supersized replica of a Stanley utility knife made entirely out of wood. All wooden except for the blade anyway, which is cut from 1/8″ thick knife steel. That’s right, this gigantic utility knife is fully functional. Not that we would recommend opening too many boxes with it, as you’re likely to open up an artery if this monster slips.

We can’t imagine there are going to be many others duplicating this project, but regardless [Paul] has done a phenomenal job documenting every step of the build on his site. From cutting the rough shape out on his bandsaw to doing all painstaking detail work, everything is clearly photographed and described. After the break there’s even a complete build video.

The most interesting part has to be all of the little internal mechanisms, each one carefully reproduced at perfect scale from different woods depending on the requirements of the component. For example [Paul] mentions he choose white oak for the spring due to its flexibility. Even the screw to hold the knife closed was made out of a block of wood on the lathe.

For whatever reason, people seem to enjoy building scaled up replicas of things. We’ve seen everything from LEGO pieces to gold bars get the jumbo treatment. We suppose it’s easier than the alternative: building very tiny versions of big things.

Before Sending A Probe To The Sun, Make Sure It Can Take The Heat

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This past weekend, NASA’s Parker Solar Probe took off for a journey to study our local star. While its mission is well covered by science literate media sources, the equally interesting behind-the-scenes information is a little harder to come by. For that, we have Science News who gave us a look at some of the work that went into testing the probe.

NASA has built and tested space probes before, but none of them were destined to get as close to the sun as Parker will, creating new challenges for testing the probe. The lead engineer for the heat shield, Elizabeth Congdon, was quoted in the article: “Getting things hot on Earth is easier than you would think it is, getting things hot on Earth in vacuum is difficult.” The team used everything from a concentrated solar facility to hacking IMAX movie projector lenses.

The extreme heat also posed indirect problems elsewhere on the probe. A rocket launch is not a gentle affair, any cargo has to tolerate a great deal of shock and vibration. A typical solution for keeping fasteners in place is to glue them down with an epoxy, but they’d melt where Parker is going so something else had to be done. It’s not all high technology and exotic materials, though, as when the goal was to verify that the heat shield was strong enough to withstand up to 20G of acceleration expected during launch, the test team simulated extra weight by stacking paper on top of it.

All that testing should ensure Parker can perform its mission and tell us a lot of interesting things about our sun. And if you got in on the publicity campaign earlier this year, your name is along for the ride.

Not enough space probe action for the day? We’ve also recently featured how creative hacking gave the exoplanet hunter Kepler a second lease on life.


Circuit VR: A Tale Of Two Transistors

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Last time on Circuit VR, we looked at creating a very simple common emitter amplifier, but we didn’t talk about how to select the capacitor values, or much about why we wanted them. We are going to look at that this time, as well as how to use a second transistor in an emitter follower (or common collector) configuration to stiffen the amplifier’s ability to drive an output load.

Several readers wrote to point out that I’d pushed the Ic value a little high for a 2N2222. As it turns out, at least one of the calculations in the comments was a bit high. However, I’ve updated the post at the end to explore what was in the comments, and talk a bit more about how you compute power dissipation with or without LTSpice. If you read that post, you might want to jump back and pick up the update.

Back to Our Program

As a reminder, the LT Spice circuit we started with appears below. You can download that file and others on GitHub.

Output Z

Last time, we went over the design equations and even looked at a spreadsheet for figuring out the values. That spreadsheet assumed you wanted to pick a few items including the normal collector current for the device. In some cases, though, your driving design goal will be a certain output impedance. In that case, pick RC accordingly, and go through the same steps but you’ll compute Ic instead of selecting it and skip step 4. You can use this same procedure when the actual load you are driving is the collector resistor, which isn’t uncommon.

It is easy to see that RC is the output impedance if you do a little logic. Remember, this amplifier inverts. So Q1 is as close to off as it is going to get when the input signal is large. Assume Q1 turned all the way off. What would the output circuit look like then? A voltage divider made up of RC and RL. Like any voltage divider, the maximum power in RL is going to occur when RL=RC. If you have more of an engineering mindset, you can think of it as the amplifier’s Thevenin equivalent is a voltage source with RC as the resistor. Or, if you are more graphical, think of a voltage divider with a 10V input and a 100 ohm “top” resistor (R1). If you try values for the bottom resistor (R2) ranging from 1 to 200, it looks like this:

The voltage in R2 keeps going up, but the current goes down. When R2 is 100 ohms, the power maxes out at about 250 mW. This is why you try to match, say, a transmitter with an antenna or speakers with an amplifier.

You might want to control input impedance as well. For the input impedance case, you would have to control the values of Re, R1, and R2 which is quite a bit harder without setting up a lot of simultaneous equations or just iterating. It also will depend on beta, which is notoriously unreliable. If the product of Re and beta is a large number, you can approximate it as R1 and R2 in parallel, and that’s often good enough.

Note that in the above circuit example I just put a large resistor in as the load so it didn’t affect things much. But what if that resistor had been a 16-ohm speaker, perhaps?

Back to Capacitors

So why are capacitors important? Because the transistor needs a very specific set of DC voltages on its terminals and connecting an input or output to it is going to perturb that. However, we can isolate the circuit from any DC effects using a capacitor on the input and the output. That means we can’t amplify very low-frequency signals well — the capacitors will act like large resistors. But at higher frequencies, it won’t be any problem. You can see that in the simulation where some capacitors guard the inputs and the outputs.

If you want to see the effect in a less distracting way, check out this simulation. Here an input signal is riding a DC level. A voltage divider sets another DC level. With a capacitor between them, the circuit essentially shifts the input to a new DC level, like this:

The reactance of the capacitor, of course, depends on the frequency, according to 1/(2*π*f*C). That means the higher the capacitance, the lower the reactance at a given frequency. In this case, the 100 Hz signal sees the 10 uF capacitor as about 160 ohms of reactance. At 47uF, that drops to about 34 ohms. At 1 kHz, that will divide both of those values by another 10 (16 and 3.4 ohms).

Gain

The emitter resistor essentially introduces negative feedback which reduces our dependence on beta and makes things generally more stable. However, it also limits gain. If you suppose you have RE as a short-circuit — 0 ohms — you might think you could get infinite gain. But, in fact, you really just get a small internal resistance that is temperature- and current-dependent. At room temperature, though, it is generally just a few ohms at most. It would still increase the gain quite a bit if we could just short the emitter — in theory, up to the beta of the transistor. But without the negative feedback, we get all the other undesirable features we tried to avoid.

However, just as we use capacitors to isolate the input and output, why can’t we use a capacitor to short the signal to ground even if the DC path is through the resistor? As it turns out, you can. Try adding a capacitor across RE and watch the output go higher. Below, you can see the same output with a 47 uF capacitor across RE. Look at the scales. That 0.2V input signal now produces an output of over 5V, peak-to-peak. That’s a gain of about 25, or 5 times the DC gain.

Gain with bypass cap

The effect varies on the value of the capacitor and, of course, the frequency. Here’s the output with 10uF, 47uF, and 100 uF capacitors (first graph, below). The second graph shows the effect versus frequency. You typically want the reactance of the capacitor to be about 1/10th of the emitter resistance at the frequency where you will accept a 3dB drop off.

Three values of bypass cap Three different frequencies

Note that the capacitor works so well, that at some frequencies, we go beyond the allowable gain and clip (see the last graph). Depending on your design goals, you may need to be careful with that.

Selecting Coupling Capacitors

To know what value to assign the coupling capacitors, you need to know the impedance of the amplifier. That’s fairly easy to estimate, but with LT Spice we can do better. If you look at V2, you know it is putting out 50 mV and you can measure the current drawn from it. Ohms law will tell you that .05 divided by that current must be the resistance V2 “sees.” With C1 set ridiculously high (1F) and V2’s internal resistance set to zero, the circuit draws about 1.75 mA from V2. That’s about 28.6 ohms. So if you know the 3dB frequency you want you simply have to compute the capacitance using the familiar 1/(2*π*f*R) formula. Assume we want 10 kHz as the 3dB point. Since R is 28.6 you need at least 0.6 uF of capacitance. Of course, you can also reverse the formula and determine what your 3 dB point should be given a certain value of capacitor.

Here’s a little WolframAlpha tip. If you try to do the above calculation, you get the answer in scientific notation: 5.56 x 10-7. Sure, you can just shift the decimal point two to the right to get the exponent to -9… or is that to the left? However, you can also just add the words “engineering form” to your query, and you’ll get the answer to the nearest exponent that’s a multiple of 3.

Output Loading

The other problem you’ll often see is that you need to drive a low impedance load which can limit your gain since matching that impedance will prevent you from using a large RC. One answer is to use an output transistor as an emitter follower or common collector amplifier. This is a very simple setup where the input to the base appears practically unchanged on the emitter. So the gain of the stage is nearly 1. That might not seem like a great thing until you realize that the output impedance of such an amplifier is roughly the source impedance divided by beta. Remember, lower output impedance is good because you can drive a wider range of load.

Suppose your RC in the main amplifier is 1600 ohms and you would like to drive a 16-ohm speaker. If the emitter follower beta is 100, the effective impedance seen from the main amp will be 1.6K ohms and the output impedance of the stage will be very low. But because in this case, the emitter resistor is probably the load itself, you won’t want to put a capacitor in the output because it would block the path to ground.

Have a look at this design:

This is very nearly the same amplifier as before, but there’s no coupling capacitor on the output. In addition, the component values changed a bit. When Q1 is turned off, the maximum voltage will go to the load and this will transfer the most power when RL=RC so the output impedance at Q1 is 1600 ohms. This is a poor match for a 16 ohm speaker, but Q2 can get us in the neighborhood in the emitter follower configuration. It is true that beta isn’t reliable, so the match probably won’t be perfect, but it should be good enough for most purposes.

Here’s the output:

Compare that with the output of the original amplifier driving a 16-ohm load. You’ll need to reduce the input drive down to 50mV, but even then the output from the original circuit will be very disappointing.

Of course, Q2 is going to need to be a power transistor. You won’t be able to quite get all 15V on the base of Q2, but you could get close. After the emitter drop, you could have a Ve of about 14V and that’s a little less than 900 mA or around 13 plus watts. Picture a big device with a heat sink. Luckily, the simulation doesn’t care. But, of course, that’s also one of the dangers of simulation is that you can overstress the models and they don’t care.

The End?

As much as we’ve talked about the common collector amplifier, there’s a lot more to it. What if the collector load is a tuned circuit? Or the emitter bypass? You can construct lots of things including multistage amplifiers using this as a building block.

By the way, you might think that bipolar transistors are old-fashioned compared to FETs, but they do have their uses. Also, all of these amplifier configurations have corresponding FET designs. The ideas are the same but, of course, the design equations are a bit different. FETs operate on voltages and there are other peculiarities. For example, some types of FETs are normally on, so you’ll need a negative bias voltage to get them to turn off. FETs — especially MOSFETs — have very high input impedance which makes input circuits easy to design. However, they also introduce capacitance which can be tricky at higher frequencies. But that’s a topic for a future Circuit VR.

Turning Cheap WiFi Modules Into Cheap WiFi Swiss Army Knives

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When the ESP8266 was released, it was sold as a simple device that would connect to a WiFi network over a UART. It was effectively a WiFi modem for any microcontroller, available for just a few bucks. That in itself is awesome, but then the hackers got their hands on it. It turns out, the ESP8266 is actually a very capable microcontroller as well, and the newest modules have tons of Flash and pins for all your embedded projects.

For [Amine]’s entry to the Hackaday Prize, he’s using the ESP8266 as the ultimate WiFi Swiss Army knife. The Kortex Xttend Lite is a tiny little WiFi repeater that’s capable of doing just about anything with a WiFi network, and with a bit of added hardware, can connect to Ethernet as well.

The hardware on this board sports an ESP8266-07S module, with two free GPIO pins for multiple functions. There’s a USB to UART in there, and a voltage regulator that’s capable of outputting 600mA for the slightly power hungry radio. There’s also an integrated battery management and charge controller, allowing this board to charge an off-the-shelf lithium cell and run for hours without any wires at all.

So, what can this board do? Just about everything you would want for a tiny little WiFi Swiss Army knife. There’s traffic shaping, port mapping, packet sniffing, and even support for mesh networking. There’s also an SMA connector on there, so grab your cantennas — this is a great way to extend a WiFi network, too.

This is a well-designed and well-executed project, and what makes this even more amazing is that this was done as one of [Amine]’s high school projects. Yes, it took about a year to finish this project, but it’s still amazing work for [Amine]’s first ‘high-complexity’ design. That makes it an excellent learning experience, and an awesome entry to this year’s Hackaday Prize.

The Wonderful World of USB Type-C

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Despite becoming common over the last few years USB-C remains a bit of a mystery. Try asking someone with a new blade-thin laptop what ports it has and the response will often include an awkward pause followed by “USB-C?”. That is unless you hear “USB 3” or maybe USB 3.1. Perhaps even “a charging port”. So what is that new oval hole in the side of your laptop called? And what can it really do? [jason] at Reclaimer Labs put together a must-read series of blog posts in 2016 and 2017 plumbing the depths of the USB 3.1 rabbit hole …read more

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A Tiny Steering Wheel You Can Print

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Racing games are a great way to test drive that Ferrari you can’t quite afford yet, and the quality of simulations has greatly improved in the last 30 or so years. While there are all manner of high-quality steering wheels to connect to your PC or home console, many gamers still choose to play using a typical controller, using the thumbstick for steering. What if there was something in between?

What we have here is a tiny steering wheel you can print for an Xbox One controller, that mounts to the controller frame and turns rotational motion into vaguely linear horizontal motion on the thumbstick. It does come with some pitfalls, namely blocking a button or two and it also obscures some of the D-pad. However, for those of you driving in automatic mode without using the buttons to shift gears, this could be a fun device to experiment with. Files to print your own are available on Thingiverse.

It’s a neat hack, and there’s plenty of room to take the idea further and personalise it to suit your own tastes. While you’re there, why stop at steering? You could make your own custom buttons, too!

[via Gizmodo, thanks to Itay for the tip!]

Radio Antenna Mismatching: VSWR Explained

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If you have ever operated any sort of transmitting equipment, you’ve probably heard about matching an antenna to the transmitter and using the right co-ax cable. Having everything match — for example, at 50 or 75 ohms — allows the most power to get to the antenna and out into the airwaves. Even for receiving this is important, but you generally don’t hear about it as much for receivers. But here’s a question: if a 100-watt transmitter feeds a mismatched antenna and only delivers 50 watts, where did the other 50 watts go? [ElectronicsNotes] has a multi-part blog entry that explains what happens on a mismatched transmission line, including an in-depth look at voltage standing wave ratio or VSWR.

We liked the very clean graphics showing how different load mismatches affect the transmission line. We also liked how he tackled return loss and reflection coefficient.

There was a time when driving a ham radio transmitter into a bad load could damage the radio. But if the radio can survive it, the effect isn’t as bad as you might think. The post points out that feedline loss is often more significant. However, the problem with modern radios is that when they detect high VSWR, they will often reduce power drastically to prevent damage. That is often the cause of poor performance more so than the actual loss of power through the VSWR mechanism. On the other hand, it is better than burning up final transistors the way older radios did.

Measuring VSWR without a transmitter is a bit trickier. A network analyzer can do it. While that used to be a pretty exotic piece of gear, it has become much more common lately.

Bench Power Supply Packs a Lot into a DIN-Rail Package

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We’re not sure why we’ve got a thing for DIN-rail mounted projects, but we do. Perhaps it’s because we’ve seen so many cool industrial control cabinets, or maybe the forced neatness of DIN-mounted components resonates on some deep level. Whatever it is, if it’s DIN-rail mounted, chances are good that we’ll like it.

Take this DIN-mounted bench power supply, for instance. On the face of it, [TD-er]’s project is yet another bench supply built around those ubiquitous DPS switching power supply modules, the ones with the colorful displays. Simply throwing one of those in a DIN-mount enclosure isn’t much to write home about, but there’s more to this project than that. [TD-er] needed some fixed voltages in addition to the adjustable output, so a multi-voltage DC-DC converter board was included inside the case as well. The supply has 3.3, 5, and 12 volt fixed outputs along with the adjustable supply, and thanks to an enclosed Bluetooth module, the whole thing can be controlled from his phone. Plus it fits nicely in a compact work area, which is a nice feature.

We haven’t seen a lot of DIN-rail love around these pages — just this recent rotary phase converter with very tidy DIN-mounted controls. That’s a shame, we’d love to see more.

An Achievable Underwater Camera

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We are surrounded by sensors for all forms of environmental measurement, and a casual browse through an electronics catalogue can see an experimenter tooled up with the whole array for a relatively small outlay. When the environment in question is not the still air of your bench but the turbulence, sand, grit, and mud of a sea floor, that pile of sensors becomes rather useless. [Ellie T] has been addressing this problem as part of the study of hypoxia in marine life, and part of her solution is to create an underwater camera by encasing a Raspberry Pi Zero W and camera in a sturdy enclosure made from PVC pipe. She’s called the project LoBSTAS, which stands for Low-cost Benthic Sensing Trap-Attached System.

The housing is simple enough, the PVC has a transparent acrylic disk mounted in a pipe coupler at one end, with the seal being provided at the other by an expansion plug. A neopixel ring is mounted in the clear end, with the Pi camera mounted in its centre. Meanwhile the Pi itself occupies the body of the unit, with power coming from a USB battery bank. The camera isn’t the only sensor on this build though, and Atlas Scientific oxygen sensor  completes the package and is mounted in a hole drilled in the expansion plug and sealed with silicone sealant.

Underwater cameras seem to have featured more in the earlier years of Hackaday’s existence, but that’s not to say matters underwater haven’t been on the agenda. The 2017 Hackaday Prize was carried off by the Open Source Underwater Glider.


When Every Last Nanoamp Matters

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You can get electricity from just about anything. That old crystal radio kit you built as a kid taught you that, but how about doing something a little more interesting than listening to the local AM station with an earpiece connected to a radiator? That’s what the Electron Bucket is aiming to do. It’s a power harvesting device that grabs electricity from just about anywhere, whether it’s a piece of aluminum foil or a bunch of LEDs.

The basic idea behind the Electron Bucket is to harvest ambient radio waves just like your old crystal radio kit. There’s a voltage doubler, a rectifier, and as a slight twist, a power management circuit that would normally be found in battery-powered electronics.

Of course, this circuit can do more than harvesting electricity from ambient radio waves. By connecting a bunch of LEDs together, it’s possible to send a few Bluetooth packets around. This is pretty impressive — the circuit is using LEDs as solar cells, which normally produce about 50nA of current at 0.5V in direct sunlight. By connecting 12 LEDs in parallel and series, it manages to harvest just enough energy to run a small wireless module. That’s impressive, and an interesting entry to the Power Harvesting Challenge in this year’s Hackaday Prize.

How The 8087 Coprocessor Got Its Bias

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Most of us have been there. You build a device but realize you need two or more voltages. You could hook up multiple power supplies but that can be inconvenient and just not elegant. Alternatively, you can do something in the device itself to create the extra voltages starting with just one. When [Ken Shirriff] decapped an 8087 coprocessor to begin exploring it, he found it had that very problem. It needed: +5 V, a ground, and an additional -5 V.

His exploration starts with a smoking gun. After decapping the chip and counting out all the bond wires going to the various pads, he saw there was one too many. It wasn’t hard to see that the extra wire went to the chip’s substrate itself. This was for providing a negative bias to the substrate, something done in some high-performance chips to get increased speed, a more predictable transistor threshold voltage, and to reduce leakage current. Examining where the bond wire went to in the circuitry he found the two charge pump circuits shown in the banner image. Those worked in alternating fashion to supply a -5 V bias to the substrate, or rather around -3 V when you take into account voltage drops. Of course, he also explains the circuits and dives in deeper, including showing how the oscillations are provided to make the charge pumps work.

If this is anything like [Ken’s] previous explorations, it’ll be the first of a series of posts exploring the 8087. At least that’s what we hope given how he’d previously delighted us with a reverse engineering of the 76477 sound effects chip used in Space Invaders and then went deeper to talk about integrated injection logic (I2L) as used in parts of the chip.

PC in an SNES Case is a Weirdly Perfect Fit

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For better or for worse, a considerable number of the projects we’ve seen here at Hackaday can be accurately summarized as: “Raspberry Pi put into something.” Which is hardly a surprise, the Pi is so tiny that it perfectly lends itself to getting grafted into unsuspecting pieces of consumer tech. But we see far fewer projects that manage to do the same trick with proper x86 PC hardware, but that’s not much of a surprise either given how much larger a motherboard and its components are.

So this PC built into a Super Nintendo case by [NoshBar] is something of a double rarity. Not only does it ditch the plodding Raspberry Pi for a Mini-ITX Intel i5 computer, but it manages to fit it all in so effortlessly that you might think the PAL SNES case was designed by a time traveler for this express purpose. The original power switch and status LED are functional, and you can even pop open the cart slot for some additional airflow.

[NoshBar] started by grinding off all the protruding bits on the inside of the SNES case with a Dremel, and then pushed some bolts through the bottom to serve as mounting posts for the ASUS H110T motherboard. With a low profile Noctua CPU cooler mounted on top, it fits perfectly within the console’s case. There was even enough room inside to add in a modified laptop charger to serve as the power supply.

To round out the build, [NoshBar] managed to get the original power slider on the top of the console to turn the PC on and off by gluing a spring-loaded button onto the side of the CPU cooler. In another fantastic stroke of luck, it lined up almost perfectly with where the power switch was on the original SNES board. Finally, the controller ports have been wired up as USB, complete with an adapter dongle.

[NoshBar] tells us the inspiration for sending this one in was the Xbox-turned-PC we recently covered, which readers might recall fought back quite a bit harder during its conversion.

Simple ESP8266 Weather Station using Blynk

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Today’s hacker finds themself in a very interesting moment in time. The availability of powerful microcontrollers and standardized sensor modules is such that assembling the hardware for something like an Internet-connected environmental monitor is about as complex as building with LEGO. Hardware has become elementary in many cases, leaving software as the weak link. It’s easy to build the sensor node to collect the data, but how do you display it in a useful and appealing way?

This simple indoor temperature and humidity sensor put together by [Shyam Ravi] shows one possible solution to the problem using Blynk. In the video after the break, he first walks you through wiring the demonstration hardware, and then moves on to creating the Blynk interface. While it might not be the ideal solution for all applications, it does show you how quickly you can go from a handful of components on the bench to displaying useful data.

In addition to the NodeMCU board, [Shyam] adds a DHT11 sensor and SSD1306 OLED display. He’s provided a wiring diagram in the repository along with the Arduino code for the ESP8266, but the hardware side of this demonstration really isn’t that important. You could omit the OLED or switch over to something like a BME280 sensor if you wanted to. The real trick is in the software.

For readers who haven’t played with it before, Blynk is a service that allows you to create GUIs to interact with microcontrollers from anywhere in the world. The code provided by [Shyam] reads the humidity and temperature data from the DHT11 sensor, and “writes” it to the Blynk service. From within the application, you can then visualize that data in a number of ways using the simple drag-and-drop interface.

We’ve seen Blynk and ESP8266 used to control everything from mood lighting to clearance-rack robotic toys. It’s a powerful combination, and something to keep in mind next time you need to knock something together in short order.

OMEN Alpha: A DIY 8085-Based Computer

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[Martin Malý] has put together a sweet little 8085-based single board computer called OMEN. He needed a simple one for educational purposes, and judging by the schematic we think he’s succeeded.

Now in its fourth iteration, it has a 32K EEPROM, 32K of memory, one serial and three parallel ports. In the ROM he’s put Tiny BASIC and Dave Dunfield’s MON85 Serial Monitor with Roman Borik’s improvements. His early demos include the obligatory blinking LED, playing 8-bit music to a speaker, and also a 7-segment LED display with a hexadecimal keyboard. There is also a system connector which allows you to connect a keyboard, a display, and other peripherals. Of course, you can connect serially at up to 115200 baud, making it very easy to compile some assembly on a PC and use the monitor to paste the hex into the board’s memory and run it. Or you can just jump into the Tiny BASIC interpreter and have some nostalgic fun. He demos all this in the video below.

He’s given enough detail for you to make your own and he also has the boards available in kit form on Tindie for a very reasonable price. With some minimal soldering skills, you can be back in the ’80s in no time.

Part of [Martin’s] interest in these vintage computers stems from his having grown up in the ’80s in Eastern Europe when it was impossible for him to have a computer of his own. We’re glad then that he wrote up his experience with home computers behind the iron curtain as well as the peripherals.

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