spectrum analyzer

52 Articles

Balancing A Motor With An Oscilloscope

June 18, 2022 by 17 Comments

With all things in life, one must seek to achieve balance. That may sound a little like New Age woo-woo, but if you think it’s not literally true, just try tolerating a washing machine with a single comforter on spin cycle, or driving a few miles on unbalanced tires.

Anything that rotates can quickly spin itself into shrapnel if it’s not properly balanced, and the DIY power tools in [Matthias Wandel]’s shop are no exception. Recent upgrades to his jointer have left the tool a bit noisy, so he’s exploring machine vibrations with this simple but clever setup. Using nothing but a cheap loudspeaker and an oscilloscope, [Matthias] was able to characterize vibrations in a small squirrel-cage blower — he wisely chose to start small to validate his method before diving into the potentially dangerous jointer. There was quite a lot to be learned from the complex waveforms coming back from the transducer, analysis of which was greatly helped by the scope’s spectrum analyzer function. The video below shows the process of probing various parts of the blower, differentiating spectral peaks due to electrical noise rather than vibration, and actually using the setup to dynamically balance the fan.

We’d rate this as yet another handy shop tip from [Matthias], and we’ll be looking out for the analysis of his jointer. Want to do the same but you don’t have an oscilloscope? No problem — an earbud and Audacity might be all you need.

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Character VFD Becomes Spectrum Analyzer

May 24, 2022 by 7 Comments

These days, streaming services are a great way to listen to music or podcasts on your computer or on the go. However, they lack one feature of the MP3 players and streamers of old: visualizations! [mircemk] is a fan of those, and has built a hardware spectrum analyzer that pumps with the music.

The build relies on a 20×2 character VFD display that looks great, with high brightness and excellent contrast. It can be easily driven from a microcontroller, as it has a controller on board compatible with the typical HD44780 command set. On Arduino platforms, this means the display can easily be driven with the popular LiquidCrystal library.

The Arduino Nano inside takes in the audio signal via its analog inputs. It then processes the audio with the fix_fft library, which runs a Fast Fourier Transform in order to figure out the energy level of each frequency bin in the audio spectrum for both the left and right channels. This data is then sent to the screen for display. It’s impressively fast and smooth, with the display dancing along with the beat nicely as [mircemk] tests it out with some tunes.

If it looks familiar, it’s because it’s an updated version of a prior project from [mircemk]. We saw it previously as a VU meter that pulsed with the beat, an altogether simpler visualization but still a cool one. Video after the break.

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Big Audio Visualizer Pumps With The Music

May 13, 2022 by 2 Comments

A spectrum analyzer is a great way to create exciting visuals that pulse in time with music. [pyrograf] wanted a big one as a display piece, so set about whipping up something of their very own.

An ESP32 microcontroller serves as the heart of the build, with its high clock rate and dual cores making it a highly capable choice for the job. Audio from a microphone is amplified and pumped into the ESP32’s analog input. Core 0 on the ESP32 then runs a Fast Fourier Transform on the input audio in order to determine the energy in each frequency band. The results of this FFT are then passed to Core 1, which is used to calculate the required animations and pipe them out to a series of WS2812B LEDs.

Where this build really shines, though, is in the actual construction. Big chunks of acrylic serve as diffusers for the LEDs which light up each segment of the spectrum display. Combine the big pixel size with a nice smooth 30 Hz refresh rate on the LEDs, and the result is a rather large spectrum analyzer that really does look the business.

We’ve seen some similar builds over the years, too. Video after the break.

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Pluto Spectrum Analyzer Uses Command Line

November 15, 2021 by 11 Comments

If you don’t care about shortwave frequencies, the PlutoSDR is a great deal. The device is supposed to be an evaluation board for Analog Device’s radio chips, but it does great as a software-defined radio that can receive and transmit and it even runs Linux internally. [SignalsEverywhere] shows how to use it as a spectrum analyzer that works from the command line in the video you can see below.

The software used is Retrogram. Despite the ASCII graphics, the program has many features. You can use simple keystrokes to change the center frequency, the sampling rate, the bandwidth, and more. You can run the software on a Linux host or compile a binary on the box or cross-compile using tools on the Raspberry Pi.

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ESP32 Spectrum Analyzer Taps Into Both Cores

December 10, 2020 by 16 Comments

We probably don’t need to tell the average Hackaday reader that the ESP32 is a powerful and extremely flexible microcontroller. We’ve seen some incredible projects using this affordable chip over the last few years, and by the looks of it, the best is yet to come. That’s because it always takes some time before the community can really figure out how to get the most out of a piece of hardware.

Take for example the Bluetooth audio player that [squix] was recently working on. Getting the music going was no problem with the esp32-a2dp library, but when he wanted to add some visualizations the audio quality took a serious hit. Realizing that his Fast Fourier transform (FFT) code was eating up too much processor power, it seemed like a great time for him to explore using the ESP32’s second core.

[squix] had avoided poking around with the dual-core nature of the ESP32 in the past, believing that the second core was busy handling the WiFi communication. But by using the FreeRTOS queue system, he wrote some code that collects audio data with one core and runs the actual FFT magic on the other. By balancing the workload like this, he’s able to drive the array of 64 WS2812B LEDs on the front of the Icon64 seen in the video after the break.

Even if you’re not terribly interested in running your own microcontroller disco, this project may be just the example you’ve been waiting for to help get your mind wrapped around multitasking on the ESP32. If you want to master a device with this many tricks up its sleeve, you’ll need all the help you can get.

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Product Review: The TinySA, A Shirt-Pocket Sized Spectrum Analyzer

November 9, 2020 by 39 Comments

I suppose most of us have had the experience of going to the mailbox and seeing that telltale package in the white plastic bag, the sign that something has just arrived from China. This happened to me the other day, and like many of you it was one of those times when I puzzled to myself: “I wonder what I bought this time?”

With so many weeks or months between the time of your impulsive click on the “Buy Now” button on AliExpress or eBay and the slow boat from China actually getting the package to your door, it’s easy enough to forget what exactly each package contains. And with the price of goods so low, the tendency to click and forget is all the easier. That’s not necessarily a good thing, but I like surprises as much as the next person, so I was happy to learn that I was now the owner of a tinySA spectrum analyzer. Time for a look at what this little thing can do.

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Second-Hand Television SHINEs, Takes Down Entire Village’s Internet

September 22, 2020 by 53 Comments

We occasionally get stories on the tips line that just make us want to know more. This is especially true with tech stories covered by the mass media, which usually leave out the juicy tidbits that would just clutter up the story for the majority of non-technical readers. That leaves us to dig a little deeper for the satisfying details.

The latest one of these gems to hit the tips line is the tale of a regular broadband outage in a Welsh village. As in, really regular — at 7:00 AM every day, the internet customers of Aberhosan suffered a loss of their internet service. Customers of Openreach, the connectivity arm of the British telco BT, complained about the interruptions as customers do, and technicians responded to investigate the issue. Nobody was able to find the root cause, and despite replacing nearly all the cables in the system, the daily outages persisted for 18 months.

In the end, Openreach brought in a crack team from their Chief Engineer’s office to investigate. Working against COVID-19 restrictions, the team set up a spectrum analyzer in the early morning hours, to capture any evidence of whatever was causing the problem. At the appointed hour they saw a smear of radio frequency interference appear, a high-intensity pulse of noise at just the right frequency to interfere with the village’s asymmetric digital subscriber line (ADSL) broadband service.

A little sleuthing led to the home of a villager and a second-hand TV, which was switched on every day at 7:00 AM. The TV was found to be emitting a strong RF impulse when it was powered up, strong enough to knock out the ADSL service to the entire village. Openreach categorized this as SHINE, or single high-level impulse noise. We’d never heard of this, but apparently it’s common enough that BT warns customers about it and provides helpful instructions for locating sources with an AM radio.

We’ll say one thing for the good people of Aberhosan: they must be patient in the extreme to put up with daily internet outages for 18 months. And it’s funny how there was no apparent notice paid by the offending television’s owner that his or her steady habit caused the outage. Perhaps they don’t have a broadband connection, and so wouldn’t have noticed the borking.

In any case, the owner was reportedly “mortified” by the news and hasn’t turned the TV on since learning of the issue. This generally seems to be the reaction when someone gets caught inadvertently messing up the spectrum — remember the Great Ohio Key Fob Mystery?

Thanks to [Kieran Donnelly] for spotting this for us.