It’s A TV-Scope-Guitar Amplifier!

October 26, 2019 by 8 Comments

Guitar amplifiers are a frequent project, and despite being little more than a simple audio amplifier on paper, they conceal a surprising quantity of variables in search of a particular sound. We’ve seen a lot of them, but never one quite like [Nate Croson]’s CRT TV guitar amplifier. The LM386 doesn’t just drive the speaker, he’s also using it to turn the TV into a crude oscilloscope to form a visualisation of the sound.

The video showing this feat is below the break, and it puts us in a quandary due to being short on technical information. He’s driving the horizontal coils with the TV’s 50 Hz sawtooth field timebase, and the vertical ones with the audio from the LM386. We aren’t sure whether he’s rotated the yoke or whether the connections have been swapped, but the result is certainly impressive.

So given that there’s not quite as much technical detail as we’d like, why has this project captured our interest? Because it serves as a reminder that a CRT TV is a bit more than a useless anachronism, it’s a complex analogue device with significant and unique hacking potential. The older ones in particular provide endless possibilities for modification and circuit bending, and make for a fascinating analogue playground at a very agreeable price. It’s worth pointing out however that some of the voltages involved can make them a hazardous prospect for the unwary hacker. If you’re interested though, take a look at our dive into an older model.

Continue reading “It’s A TV-Scope-Guitar Amplifier!” →

Worried About Bats In Your Belfry? A Tale Of Two Bat Detectors

October 17, 2019 by 33 Comments

As somebody who loves technology and wildlife and also needs to develop an old farmhouse, going down the bat detector rabbit hole was a journey hard to resist. Bats are ideal animals for hackers to monitor as they emit ultrasonic frequencies from their mouths and noses to communicate with each other, detect their prey and navigate their way around obstacles such as trees — all done in pitch black darkness. On a slight downside, many species just love to make their homes in derelict buildings and, being protected here in the EU, developers need to make a rigorous survey to ensure as best as possible that there are no bats roosting in the site.

Perfect habitat for bats.

Obviously, the authorities require a professional independent survey, but there’s still plenty of opportunity for hacker participation by performing a ‘pre-survey’. Finding bat roosts with DIY detectors will tell us immediately if there is a problem, and give us a head start on rethinking our plans.

As can be expected, bat detectors come in all shapes and sizes, using various electrickery techniques to make them cheaper to build or easier to use. There are four different techniques most popularly used in bat detectors.

 

  1. Heterodyne: rather like tuning a radio, pitch is reduced without slowing the call down.
  2. Time expansion: chunks of data are slowed down to human audible frequencies.
  3. Frequency division: uses a digital counter IC to divide the frequency down in real time.
  4. Full spectrum: the full acoustic spectrum is recorded as a wav file.

Fortunately, recent advances in technology have now enabled manufacturers to produce relatively cheap full spectrum devices, which give the best resolution and the best chances of identifying the actual bat species.

DIY bat detectors tend to be of the frequency division type and are great for helping spot bats emerging from buildings. An audible noise from a speaker or headphones can prompt us to confirm that the fleeting black shape that we glimpsed was actually a bat and not a moth in the foreground. I used one of these detectors in conjunction with a video recorder to confirm that a bat was indeed NOT exiting from an old chimney pot. Phew!

Continue reading “Worried About Bats In Your Belfry? A Tale Of Two Bat Detectors” →

Does This Timber Have The Right Timbre?

July 27, 2019 by 20 Comments

A hi-fi amplifier used to be a rite of passage for the home electronic constructor, back in the days when consumer electronics was still dominated by analogue entertainment. It’s unusual then to see [carbono.silício]’s stereo amplifier project, constructed in an open-wire circuit sculpture form on a log. You didn’t read that incorrectly, it’s built not on a breadboard but on a piece of Olea Maderensis, or Madiera Olive wood, complete with bark. This endangered tree was not felled, instead it was a piece blown down after a storm.

The circuit is slightly unusual for a project such as this, in that it uses a pair of LM386 audio amplifier chips. This isn’t an unusual component, but it’s one more commonly seen providing the amplification for a small speaker project than in a stereo hi-fi amplifier. But the construction is beautifully done, with very neatly routed wires, a single central volume knob, and a blue LED power light. A particularly nice touch are the aluminium electrolytic capacitors, we suspect having had their plastic sleeving removed.

We’ve had our share of stereo amp projects here, and some of them are surprisingly simple. We have even been known to partake of them ourselves.

Building A Slimline Portable NES

April 3, 2019 by 3 Comments

Emulation of classic consoles has long been a solved problem. It’s now possible to run thousands of vintage games on a computer the size of a stick of gum, and to do so with all the benefits emulation brings. [M-Parks] isn’t the biggest fan, however – and decided to build a slimline NES handheld instead. The goal was to produce a portable NES in as compact a package as possible.

Things have come a long way in the handheld console modding scene in the last ten years. 3D printing has largely replaced vacuum forming, and it’s no different here. [M-Parks] modeled up a case and sent it off to be 3D printed in PLA, somewhat mimicking the general layout of the original Game Boy. It’s a little larger, but given that it accepts full-size original NES carts, it can only be so small.

A Retro-bit NES-on-a-chip console was used to provide the motherboard and cartridge connector for the build. Rounding this out is a power supply from Adafruit, an LM386 audio amplifier, as well as a digital volume control which is a nice touch.

While such a build may sound daunting to the absolute beginner, all it takes is a soldering iron, some hot glue, and a willingness to have a go. There’s nothing wild or groundbreaking about this build, but to dwell on that would be missing the point. [M-Parks] now has a portable NES to play on those long train rides, and learned some great skills doing it –  a solid result for any project!

If you’re keen on seeing another take, check out [Dave]’s build from a few years back.

 

State Of The Art Big Mouth Alexa Bass

February 7, 2019 by 9 Comments

Hackers seem intent on making sure the world doesn’t forget that, for a brief shining moment, everyone thought Big Mouth Billy Bass was a pretty neat idea. Every so often we see a project that takes this classic piece of home decor and manages to shoehorn in some new features or capabilities, and with the rise of voice controlled home automation products from the likes of Amazon and Google, they’ve found a new ingredient du jour when preparing stuffed bass.

[Ben Eagan] has recently completed his entry into the Pantheon of animatronic fish projects, and while we’ll stop short of saying the world needed another Alexa-enabled fish on the wall, we’ve got to admit that he’s done a slick job of it. Rather than trying to convince Billy’s original electronics to play nice with others, he decided to just rip it all out and start from scratch. The end result is arguably one of the most capable Billy Bass updates we’ve come across, if you’re willing to consider flapping around on the wall an actual capability in the first place.

The build process is well detailed in the write-up, and [Ben] provides many pictures so the reader can easily follow along with the modification. The short version of the story is that he cuts out the original control board and wires the three motors up to an Arduino Motor Driver Shield, and when combined with the appropriate code, this gives him full control over Billy’s mouth and body movements. This saved him the trouble of figuring out how to interface with the original electronics, which is probably for the better since they looked rather crusty anyway.

From there, he just needed to give the fish something to get excited about. [Ben] decided to connect the 3.5 mm audio jack of an second generation Echo Dot to one of the analog pins of the Arduino, and wrote some code that can tell him if Amazon’s illuminated hockey puck is currently yammering on about something or not. He even added a LM386 audio amplifier module in there to help drive Billy’s original speaker, since that will now be the audio output of the Dot.

A decade ago we saw Billy reading out Tweets, and last year we presented a different take on adding an Alexa “brain” to everyone’s favorite battery powered fish. What will Billy be up to in 2029? We’re almost too scared to think about it. Continue reading “State Of The Art Big Mouth Alexa Bass” →

Twelve Circuit Sculptures We Can’t Stop Looking At

January 15, 2019 by 25 Comments

Circuits are beautiful in their own way, and a circuit sculpture takes that abstract beauty and makes it into a purposeful art form. Can you use the wires of the circuits themselves as the structure of a sculpture, and tell a story with the use and placement of every component? Anyone can exercise their inner artist using this medium and we loved seeing so many people give it a try. Today we announce the top winners and celebrate four score of entries in the Hackaday Circuit Sculpture Contest.

Let’s take a look at twelve outstanding projects that caught (and held) our eye:

Continue reading “Twelve Circuit Sculptures We Can’t Stop Looking At” →

A Guide To Audio Amps For Radio Builders

June 11, 2018 by 14 Comments

For hams who build their own radios, mastering the black art of radio frequency electronics is a necessary first step to getting on the air. But if voice transmissions are a goal, some level of mastery of the audio frequency side of the equation is needed as well. If your signal is clipped and distorted, the ham on the other side will have trouble hearing you, and if your receive audio is poor, good luck digging a weak signal out of the weeds.

Hams often give short shrift to the audio in their homebrew transceivers, and [Vasily Ivanenko] wants to change that with this comprehensive guide to audio amplifiers for the ham. He knows whereof he speaks; one of his other hobbies is jazz guitar and amplifiers, and it really shows in the variety of amps he discusses and the theory behind them. He describes a number of amps that perform well and are easy to build. Most of them are based on discrete transistors — many, many transistors — but he does provide some op amp designs and even a design for the venerable LM386, which he generally decries as the easy way out unless it’s optimized. He also goes into a great deal of detail on building AF oscillators and good filters with low harmonics for testing amps. We especially like the tip about using the FFT function of an oscilloscope and a signal generator to estimate total harmonic distortion.

The whole article is really worth a read, and applying some of these tips will help everyone do a better job designing audio amps, not just the hams. And if building amps from discrete transistors has you baffled, start with the basics: [Jenny]’s excellent Biasing That Transistor series.

[via Dangerous Prototypes]