What do you get when you cross a mixed-signal oscilloscope, a function generator, a multimeter, a power supply, and some programmable digital I/O in a box? Sounds like the set up to a very geeky joke, but it is actually National Instrument’s VirtualBench product. [Shahriar] has one and wanted to know what was inside, so he did a tear down.
RTL-SDR, the USB TV tuner turned software-defined radio is an amazing device, capable of listening to nearly anything from 25MHz to 1750MHz, fits in your pocket, and costs about $20. Even more astonishing is that it’s also a kinda-okay spectrum analyzer. [Kerry D. Wong] tested out one of these USB TV tuner, and the results are exactly what you would expect: it lacks a little precision, and sampling bandwidth is only a tiny bit terrible, but it does work.
A stock USB TV tuner doesn’t come with a connector that would normally be used for spectrum analysis. A BNC connector can be easily attached, as can a terminator to match the 75Ω impedance of the SDR. This isn’t really necessary; the frequencies being measured are low enough that you can get away without one.
As far as software goes, [Kerry] first pulled out the usual suspects of the SDR world; rtlsdr-scanner distorted the measured spectrum, as did a lot of other SDR receivers. Gqrx SDR was the first one that worked well, but the king of this repurposing of USB TV tuners was OSMOCOM. There’s a huge number of tools for spectrum analysis right out of the box with this package.
How did the RTL SDR fare as a spectrum analyzer? Feeding some stuff in from a signal generator, [Kerry] discovered the LO in the RTL SDR was off by a hair. Also, OSMOCOM only measures amplitude in dB, not the dBm found in every other spectrum analyzer ever made. By measuring a 0 dBm signal whatever value displayed can be shifted up or down.
So, does it work? Yes, it does. If, for some reason, you need a spectrum analyzer now, can you use this? Yep. Pretty cool.
Here’s something that’s just a design study, but [Ivan]’s Apple IIe phone is a work of art. You’re not fitting a CRT in there, but someone out there has a 3D printer, an old LCD, and a GSM module. Make it happen. See also: the Frog Design Apple phone.
[Arduino Enigma] created a touchscreen Enigma machine. Why haven’t we seen an Arduino Colossus yet?
The crew at Adafruit now have a Flying Toaster OLED, which means we now have flying toaster bitmaps for all your OLED/graphic display projects.
[Ian] had an old rackmount programmable voltage standard. This was the remote programmable voltage standard, without front panel controls. No problem, just get an Arduino, shift register, and a few buttons. Video right here.
Good, workable test gear is key to enabling our hobby. In this post we will discuss where to procure it at rock-bottom prices, what to look for, how to fix it, and how to tailor your laboratory practices around gear that may not be reliable.
We are lucky to be living in an era with plentiful high-quality test gear. Since the Second World War, surplus test gear has been in abundance at low costs enabling hobbyists, innovators, and academics to experiment and build great things. If you are willing to think before you measure you can save serious amounts of money and have a professional laboratory in your home.
Where to buy
The obvious answer is eBay, but the deals on test equipment are at the hamfests. Don’t be fooled by the name. Hamfests sell much more than amateur radio equipment. Hamfests are swap meets where hobbyists trade electronics of all kinds. Check out the ARRL hamfest calendar to find the next local one near you! I suggest you arrive early, however. The culture of hamfests tends to favor showing up as soon as the doors open and leaving about two hours before the official end. The early bird gets the worm!
Kyocera is vastly expanding their product lineup with the Shop Sink 3530. The perfect addition to your copiers, fax machines, and laser printers.
About a year and a half ago and with objections from the editorial staff, we did a Top 10 hacking fails in movies and TV post. The number one fail is, “Stupid crime shows like NCIS, CSI, and Bones.” A new show on CBS just topped this list. It’s named Scorpion, and wow. Dropping a Cat5 cable from an airplane doing an almost-touch-and-go because something is wrong with the computers in the tower. Four million adults age 18-49 watched this.
[Derek] found something that really looks like the Hackaday logo in a spacer of some kind. It’s been sitting on his shelf for a few months, and is only now sending it in. He picked it up in a pile of scrap metal, and he (and we) really have no idea what this thing is. Any guesses?
[Sheldon] has a teardown of a vintage voltage and current standard. Just look at those hand drawn traces on a single sided board. Beautiful.
[Art] has another, ‘what is this thing’. He has two of them, and he’s pretty sure it’s some sort of differential, but other than that he’s got nothing. The only real clue is that [Art] lives near a harbor on the N. Cali coast. Maybe from a navigation system, or a governor from a weird diesel?
So you have a Kinect sitting on a shelf somewhere. That’s fine, we completely understand that. Here’s something: freeze yourself in carbonite. Yeah, it turns out having a depth sensor is exactly what you need to make a carbonite copy of yourself.
[Stynus] has finished a unique decade resistance box which doesn’t use conventional rotary switches to select the appropriate resistors. These switches are old fashioned and expensive, so [Stynus] built this decade resistance box that uses a microcontroller and a series of relays to switch the resistors.
Simply selecting a resistance on the screen tells the microcontrollers which resistors need to be switched in order to provide the proper resistance. The box uses relays to do switching instead of transistors because the transistors don’t handle high frequency AC as well as the relays. The device is powered by an 18V transformer and rectifier and, as a bonus, [Stynus] got all of his parts on the cheap which made this a great solution to the expensive resistance decade box problem.
This is a very well-polished piece of test equipment. We’ve featured other decade resistance boxes but never one that was controlled by a microcontroller. All of the PCB layouts and the code for microcontroller are available on the project site if you have a desire to make your own.
If you’re not so daft as to think Arduino-based oscilloscopes and multimeters are actually useful for all but the simplest tests and measurements, you just might have some big iron sitting around your workbench from the likes of HP, or Tektronix. You might have noticed a strange port on the back of these machines, labeled GPIB or IEEE-488. This is the standard interface for these devices, and if you’ve ever priced out a USB to IEEE-488 converter, you can see why [Steven] thought it would be cheaper to build his own.
This build is an update to an earlier version we saw a few years ago. Since then, [Steven] has taken some advice from the community and replaced a bunch of resistors with proper GPIB line driver ICs, and generally cleaned up the firmware.
Because a USB to GPIB adapter is only one small part of the tools necessary to connect these old measurement devices to a modern computer, [Steven] has also been working on InstrumentKit. It’s a Python library that takes all the standardized instrument commands and wraps them up in an easy to use API. You can check out the docs for InstrumentKit here, or just look through the board files and firmware on the Github