Visualizing RF Standing Waves

August 6, 2015 by Dan Maloney 14 Comments

Standing waves are one of those topics that lots of people have a working knowledge of, but few seem to really grasp. A Ham radio operator will tell you all about the standing wave ratio (SWR) of his antenna, and he may even have a meter in the shack to measure it. He’ll know that a 1.1 to 1 SWR is a good thing, but 2 to 1 is not so good. Ask him to explain exactly what a standing wave is, though, and chances are good that hands will be waved. But [Allen], a Ham also known as [W2AEW], has just released an excellent video explaining standing waves by measuring signals along an open transmission line.

To really understand standing waves, you’ve got to remember two things. First, waves of any kind will tend to be at least partially reflected when they experience a change in the impedance of the transmission medium. The classic example is an open circuit or short at the end of an RF transmission line, which will perfectly reflect an incoming RF signal back to its source. Second, waves that travel in the same medium overlap each other and their peaks and troughs can be summed. If two waves peak together, they reinforce each other; if a peak and a trough line up, they cancel each other out.

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Headphone Amp Features A Tiny CRT

July 7, 2015 by Adam Fabio 40 Comments

[ErikaFluff] needed an amp for her Grado open cans. Rather than build yet another boring black box, she built what may be the most awesome headphone amp ever by adding a tiny CRT which displays the current audio waveform. She packaged all this up in a customized Hammond box which makes it look like it just rolled off the line from some audiophile studio.

The amplifier in this case is based upon the CMoy, a common headphone amp design. [ErikaFluff] added a MOSFET on the output to drive his relatively low impedance (32 ohm) Grado headphones with reasonable volume. The CRT is from an old video camera viewfinder. Before LCDs were advanced and cheap enough to include in video cameras, CRTs were the only show in town. These tiny black and white screens use high voltage to scan an electron beam across a phosphor screen just like their bigger brethren.

Since she was going with an oscilloscope style vector scan rather than the raster scan the screen electronics were originally designed for, [ErikaFluff] had to create her own horizontal and vertical deflection circuits. Horizontal scan is created by a 555 timer generating a sawtooth wave at 75 Hz. Vertical deflection is via an LM386 driving a hand wound impedance matching transformer. The high voltage flyback transformer and its associated driver circuit were kept from the original CRT, though repackaged to make them as small as possible.

You might think that having a few thousand volts next to a sensitive audio amplifier would cause some noise issues. We also worried a bit about shorts causing unexpected shock treatments through the wearer’s ears. [ErikaFluff] says there is no need to for concern — the signal is fed to the CRT circuit through optocouplers. The audio circuit is also electrically split from the CRT and runs on a virtual ground. Judicious amounts of shielding tape keeps the two circuits isolated.

This may not be the most practical project, but we think it’s pretty darn cool. The response over on Reddit’s electronics subreddit seems to be positive as well. We hope [ErikaFluff] is sitting down when this post gets published!

UController Code Profiler Debugs Your Microcontroller

July 6, 2015 by Bryan Cockfield 7 Comments

When working on digital circuits that operate at high frequencies it helps to have some special tools on hand. Things like oscilloscopes and logic analyzers are priceless when something isn’t working right. Another great tool would be this hardware-based profiler that [Mike] came up with while he was working on another project.

The profiler connects to USB and shows up as a serial port. Normally [Mike] used a set of LEDs to get information about how his microcontrollers work, but for this project that wasn’t enough. The uController Code Profiler can provide the main loop running time, time functions and sections of code, keep track of variables, and a few other tasks as well, all with nanosecond resolution.

The source code isn’t provided but a hex file is available, along with a schematic and an include file, if you want to try this one out on your next project. Like this homemade logic analyzer, this could be a powerful tool in your microcontroller arsenal. Simply include the file with various pieces of your code to get it up and running!

Hackaday Links: June 28, 2015

June 28, 2015 by Brian Benchoff 12 Comments

The iBookGuy is using CPU heatsinks to cool microwave dinners. It’s an old Pentium II heatsink and a modern fan, cobbled together into a device that can quickly and effectively cool down a microwave dinner. I have several heatsinks from some old Xeon servers in my kitchen, but I don’t use them to cool food; I use them to defrost food. It’s very effective, and now I need to get some data on how effective it is.

[juangarcia] is working on a 3D printable PipBoy – the one in the upcoming Fallout 4. The extra special edition of Fallout 4 include a PipBoy that works with your cellphone, but if you want one before November, 3D printing is the way to go.

[Collin] over at Adafruit is teaching Oscilloscope Basics. Note the use of the square wave output to teach how to use the controls. Also note the old-school DS1052E; the Rigol 1054Z is now the de facto ‘My First Oscilloscope’

[Donovan] has one of those V212 toy quadcopters. The remote has a switch that controls a bunch of lights on the quad. This switch can be repurposed to control a small camera. All it takes is some wire, an optocoupler, and a bit of solder. Very cool. Video here.

I go to a lot of events where hackers, devs, and engineers spend hours banging away on their laptops. The most popular brand? Apple. The second most popular brand for savvy consumers of electronics? Lenovo, specifically ThinkPad X- and T-series laptops (W-series are too big, and do you really need a workstation graphics card for writing some node app?). They’re great computers, classic works of design, and now there might be a ThinkPad Classic. With a blue Enter key, 7-row keyboard, a multi-color logo, ThinkLights, a bunch of status LEDs, and that weird rubberized paint, it’s a modern realization of what makes a ThinkPad great. Go comment on that Lenovo blog post; the designer is actually listening. Now if we could just get a retina display in a MacBook Air (the one with ports), or get manufacturers to stop shipping displays with worse than 1080 resolution…

Need a fan guard? Know OpenSCAD? Good. Now you have all the fan guards you could ever want. Thanks [fridgefire] for sending this one in.

Increasing The Brightness Of A Philips LivingColors Lamp

June 12, 2015 by Rick Osgood 6 Comments

[Martin] recently purchased a Philips LivingColors lamp. It’s a commercial product that basically acts as mood lighting with the ability to change to many different colors. [Martin] was disappointed with the brightness of his off-the-shelf lamp. Rather than spend a few hundred dollars to purchase more lamps, he decided to modify the one he already had.

[Martin] started by removing the front cover of his lamp. He found that there were four bright LEDs inside. Two red, one green, and one blue. [Martin] soldered one wire to the driver of each LED. These wires then connected to four different N-channel MOSFET transistors on a piece of protoboard.

After hooking up his RIGOL oscilloscope, [Martin] was able to see that each LED was driven with a pulse width modulated signal. All he had to do was connect a simple non-addressable RGB LED strip and a power source to his new driver board. Now the lamp can control the LED strip along with the internal LEDs. This greatly extends the brightness of the lamp with minimal modifications to the commercial product. Be sure to check out the video below for a complete walk through. Continue reading “Increasing The Brightness Of A Philips LivingColors Lamp” →

Controlling A Rigol With Linux

June 6, 2015 by Brian Benchoff 19 Comments

The Rigol DS1052E is the de facto oscilloscope for any tinkerer’s bench. It’s cheap, it’s good enough, and it’s been around for a long time; with the new 1054 zed model out now, you might even be able to pick up a 1052E on the cheap.

[wd5gnr1] came up with a really interesting piece of software that allows a Linux system to control most of the functions on this popular scope. With just a USB cable, you can read and log all the measurement of the scope, save waveforms in CSV format, and send data to gnuplot and qtiplot.

Since the 1052E has been around for such a long time, there’s a bunch of software out there that takes advantage of the nifty USB port on the front of this scope. If you need a cheap spectrum analyzer, here ‘ya go, and tools for the .WFM files native to this scope even exist for Windows. [wd5gnr1] even says his tool can probably be ported to Windows, but ‘just use Linux.’

Nerdalert: German TV Producers’ Amazing Vectorscope Animations

March 14, 2015 by Elliot Williams 21 Comments

German weekend late-night comedy show “Neo Magazin Royale” has a bunch of super-nerds behind the screens in the production studio. This is apparently what they do when they’re (not) working: making test screens that render as multiple animations on their test equipment.

While others out there are limited to displaying cool graphics on oscilloscopes, these guys have vectorscopes and waveformer monitors. A vectorscope is like an oscilloscope in X-Y mode, but with one screen that decodes the color space and one screen for the audio (in stereo). A waveform monitor that plots out the brightness levels of a test image. Normal studio techs use these to calibrate their colors, brightness, and audio levels.

Apparently, these guys programmed a custom test screen that would: a) encode a small animation of a 20-sided die spinning around the show’s logo in the color channel b) encode the show’s logo in the left and right sound channels, and c) their production company’s logo in the screen’s brightness.

At the end of the video, the director Patrick (in the glasses) admits that they’ve spent about three months working on this project and everyone starts laughing. “And who gets anything from this? Nobody!” says the show’s host.

One way to rectify that, though. Post the source code!