Junkbox Constant Current Source Helps With Kelvin Sensing

November 7, 2018 by 3 Comments

Is it ironic when a YouTube channel named “The Current Source” needs to build a current source? Or is that not ironic and actually just coincidental?

Regardless of linguistic considerations, [Derek], proprietor of the aforementioned channel has made and disassembled a few current sources in his day. Most of those jobs were for one-off precision measurements or even to drive a string of LEDs in what he describes as a pair of migraine-inducing glasses. Thankfully, The junk box current source presented in the video below is more in service of the former than the latter, as his goal is to measure very small resistances in semiconductors using Kelvin clips.

The current source uses a 24-volt switch-mode power supply and the popular LM317 adjustable voltage regulator. The ‘317 can be configured in a constant current mode by connecting the chip’s adjustment pin to the output through a series resistance. A multiturn pot provides current adjustment, although the logarithmic taper is not exactly optimal for the application. We spotted a pair of what appear to be optoisolators in the build too, but there’s no schematic and no discussion of what they do. [Derek] puts the final product to use for a Kelvin measurement of a 0.47-Ω 1% resistor at the end of the video.

We’re glad to see [Derek] in action; you may recall his earlier video about measuring his own radiation with a Geiger counter after treatment for thyroid cancer. Here’s hoping that’s behind him now.

Continue reading “Junkbox Constant Current Source Helps With Kelvin Sensing” →

Teardown Of A (Relatively) Cheap Thermal Camera

November 7, 2018 by 32 Comments

The cost of tools and test equipment has largely been on the downward trend for years, making it now more affordable than ever to get into the hacking and making scene. This is particularly visible with something like the venerable oscilloscope: a piece of equipment that was near unobtainium for the home hacker a decade ago, you can now get digital pocket scope for as little as $20 USD. But there are still pieces of gear which haven’t quite hit the sort of prices we’d like to see.

A perfect example are thermal imaging cameras. The cheap ones are usually so low resolution they might as well just be thermometers, but the higher resolution ones can cost thousands. [Rob Scott] recently wrote in to tell us about a very promising middle ground, the HTI HT-A1. But he didn’t just point it out to us, he also tore it down and laid its internal’s bare for our entertainment. Now that’s our kind of introduction.

[Rob] walks us through the disassembly of the device, which is made unnecessarily difficult due to the fact that half the screws are hidden under a glued on screen bezel. That means a heat gun, a thin tool, and patience are in order if you want to get inside the device. It’s bad enough they use these kinds of construction techniques on modern smartphones, but at least they’re so thin that we can understand the reasoning. Why this chunky thing needs to resort to such measures is beyond us.

Eventually he cracks the HT-A1 open and is greeted with a single double-sided PCB. The top side is pretty much bare except for the buttons and the LCD display, and the flip side is largely just a breakout for a quad-core Allwinner A33 daughterboard. [Rob] theorizes this is to keep costs down by allowing reuse of the modular A33 board on other devices. Given the A33’s use in so many cheap tablets, it’s also possible HTI simply purchased these daughterboards as a drop-in component and designed their own board around it.

There’s not much else inside the HT-A1 beyond the rechargeable battery pack and thermal camera, both attached to the device’s rear panel. [Rob] noticed that the date on the thermal camera PCB is a full two years older than the date on the main PCB, leading one to wonder if HTI might have gotten a good deal on a bunch of these slightly outdated sensors and spun up a whole device around them.

The HT-A1 is high enough resolution that you can actually pick out individual components on a PCB, and at $400 USD is approaching a reasonable price point for the individual hacker. Which is not to say it’s cheap, but at least you get a useful tool for your money. We wouldn’t suggest you buy this device on a whim, but if you do a lot of diagnostic work, it might pay for itself after a couple repairs.

If that’s still a little too rich for your blood, we’ve covered a handful of DIY options which might better fit your budget.

Continue reading “Teardown Of A (Relatively) Cheap Thermal Camera” →

Rooting The Amazon Fire TV Cube With An Arduino

November 7, 2018 by 11 Comments

Amazon might not be happy about it, but at least part of the success of their Fire TV Stick was due to the large hacking and modification scene that cropped up around the Android-powered device. A quick search on YouTube for “Fire Stick Hack” will bring up a seemingly endless array of videos, some with millions of views, which will show viewers how to install unofficial software on the little media dongle. Now it looks like their latest media device, the Fire TV Cube, is starting to attract the same kind of attention.

The team at [Exploitee.rs] has recently taken the wraps off their research which shows the new Fire TV Cube can be rooted with nothing more than an Arduino and an HDMI cable you’re willing to cut apart. Of course, it’s a bit more complicated than just that, but between the video they’ve provided and their WiKi, it looks like all the information is out there for anyone who wants to crack open their own Cube. Just don’t be surprised if it puts you on the Amazon Naughty List.

The process starts by putting the device’s Amlogic S905Z into Device Firmware Upgrade (DFU) mode, which is done by sending the string “boot@USB” to the board over the HDMI port’s I2C interface. That’s where the HDMI cable comes in: you can cut into one and wire it right up to your Arduino and run the sketch [Exploitee.rs] has provided to send the appropriate command. Of course, if you want to get fancy, you could use an HDMI breakout board instead.

With the board in DFU mode in you gain read and write access to the device’s eMMC flash, but that doesn’t exactly get you in because there’s still secure boot to contend with. But as these things tend to go, the team was able to identify a second exploit which could be used in conjunction with DFU mode to trick the device into disabling signature verification. Now with the ability to run unsigned code on the Fire TV Cube, [Exploitee.rs] implemented fastboot to make it easier to flash their custom rooted firmware images to the hardware.

As with the Fire TV Stick before it, make sure you understand the risks involved when you switch off a device’s security features. They’re often there to protect the end user as much as the manufacturer.

Continue reading “Rooting The Amazon Fire TV Cube With An Arduino” →

Inventor Services – Maybe Right For You – Maybe

November 7, 2018 by 20 Comments

You’ve no doubt been exposed to the ads for various inventor services; you have an idea, and they want to help you commercialize it and get the money you deserve. Whether it’s helping you file legal paperwork, defending your idea, developing it into a product, or selling it, there’s a company out there that wants to help. So which ones are legit, which ones are scams, and what do you really need to make your millions?

Continue reading “Inventor Services – Maybe Right For You – Maybe” →

Lightsaber Uses Pogo Pins To Make Assembly A Breeze

November 7, 2018 by 9 Comments

There was an endless supply of fantastic projects at Supercon this year, but one whose fit and finish really stood out was [Scott]’s lightsaber. If you were walking around and saw someone with a very bright RGB device with a chromed-out handle hanging off their belt it was probably this, though it may have been hard to look at directly. On the outside, the saber looks like a well-polished cosplay prop, and it is! But when Scott quickly broke down the device into component pieces it was apparent that extra care had been put into the assembly of the electronics.

Like any good lightsaber replica the blade is lit, and wow is it bright. The construction is fairly simple, it’s a triplet of WS2812B LED strips back to back on a triangular core, mounted inside a translucent polycarbonate tube with a diffuser. Not especially unusual. But the blade can be popped off the hilt at a moments notice for easy transport and storage, so the strips can’t be soldered in. Connectors would have worked, but who wants flying wires when they’re disconnecting their lightsaber blade. The answer? Pogo pins! Scott runs the power, ground, and data lines out of the strips and into a small board with slip ring-style plated rings. On the hilt, there is a matching array of pogo pins to pass along power and data. The data lines from all the strips are tied together minimizing the number of connections to make, and the outer two power rings have more than one pin for better current-carrying capacity. A handy side effect is that there is nowhere on the blade where there aren’t LEDs; the strips go down to the very end of the blade where it meets the main board inside the hilt.

The hilt is filled with an assembly of 18650’s and a Teensy mounted with a custom shield, all fit inside a printed midframe. The whole build is all about robust design that’s easy to assemble. The main board is book-ended by perpendicular PCBs mounted to the ends, one at the top to connect to the blade and one at the bottom to connect to a speaker. Towards the bottom there is space for an optional Bluetooth radio to allow remote RGB control.

Scott is selling this as a product but also provides detailed instructions and parts lists for each component. Assembly instructions for the blade are here. The hilt is here. And pogo adapters are on OSH Park here. An overview of the firmware with links to GitHub is here. Check out a walkthrough of the handle assembly and blade attachment after the break!

Continue reading “Lightsaber Uses Pogo Pins To Make Assembly A Breeze” →

Linux Fu: Pimp Your Pipes

November 7, 2018 by 17 Comments

One of the best things about working at the Linux (or similar OS) command line is the use of pipes. In simple terms, a pipe takes the output of one command and sends it to the input of another command. You can do a lot with a pipe, but sometimes it is hard to work out the right order for a set of pipes. A common trick is to attack it incrementally. That is, do one command and get it working with the right options and inputs. Then add another command until that works. Keep adding commands and tweaking until you get the final results.

That’s fine, but [akavel] wanted better and used Go to create “up” — an interactive viewer for pipelines.

Pipe Philosophy

Pipes can do a lot. They match in with the original Unix philosophy of making each tool do one thing really well. Pipe is really good at allowing Linux commands to talk to each other. If you want to learn all about pipes, have a look at the Linux Info project’s guide. They even talk about why MSDOS pipes were not really pipes at all. (One thing that write up doesn’t touch on is the named pipe. Do a “man fifo” if you want to learn more for now and perhaps that will be the subject of a future Linux Fu.)

This program — called up — continuously runs and reruns your pipeline as you make changes to the pipe. This way, every change you make is instantly reflected in the output. Here’s the video, here’s a quick video which shows off the interactive nature of up.

Installing

The GitHub page assumes you know how to install a go program. I tried doing a build but I didn’t have a few dependencies. Turns out the easy way to do it was to run this line:

go get -u github.com/akavel/up

This put the executable in ~/go/bin — which isn’t on my path. You can, of course, copy or link it to some directory that’s on your path or add that directory to your path. You could also set an alias, for example. Or, like I did in the video, just specify it every time.

Perfect?

This seems like a neat simple tool. What could be better? Well, I was a little sad that you can’t use emacs or vi edit keys on the pipeline, at least not as far as I could tell. This is exactly the kind of thing where you want to back up into the middle and change something. You can use the arrow keys, though, so that’s something. I also wished the scrollable window had a search feature like less.

Otherwise, though, there’s not much to dislike about the little tool. If writing a pipeline is like using a C compiler, up makes it more like writing an interactive Basic program.

Shakespeare In A Zip In A RAR, Hidden In An Image On Twitter

November 7, 2018 by 10 Comments

Steganography involves hiding data in something else — for example, encoding data in a picture. [David Buchanan] used polyglot files not to hide data, but to send a large amount of data in a single Twitter post. We don’t think it quite qualifies as steganography because the image has a giant red UNZIP ME printed across it. But without it, you might not think to run a JPG image through your unzip program. If you did, though, you’d wind up with a bunch of RAR files that you could unrar and get the complete works of the Immortal Bard in a single Tweet. You can also find the source code — where else — on Twitter as another image.

What’s a polyglot file? Jpeg images have an ICC (International Color Consortium) section that defines color profiles. While Twitter strips a lot of things out of images, it doesn’t take out the ICC section. However, the ICC section can contain almost anything that fits in 64 kB up to a limit of 16 MB total.

The ZIP format is also very flexible. The pointer to the central directory is at the end of the file. Since that pointer can point anywhere, it is trivial to create a zip file with extraneous data just about anywhere in the file.

Continue reading “Shakespeare In A Zip In A RAR, Hidden In An Image On Twitter” →