A Crystal Radio Amplifier In A Jar

August 11, 2013 by 20 Comments

The cool thing with crystal radios is that they are solely powered by the incoming radio waves. However, it usually means listening to your AM radio station with an earpiece and even then, depending on the antenna length, ground connection, and radio station, it can be quite hard to hear.

Even though it is cheating, [Steven] decided to make an amplifier for all the different crystal radios he had made over the years. His design, based on an LM386 amplifier was firstly tested on a breadboard and then permanently soldered onto a perfboard. To make the complete system easy to transport, he opted for a peanut butter jar where he embedded the speaker in the cap. The on/off switch and volume controls are mounted on the side, and easy alligator clips are used for the antenna connection.

The final result is not the one shown in the picture above as [Steven] painted the jar black, giving it a sweet look.

Goodbye Hackaday Subdomains

August 11, 2013 by 51 Comments

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We’re sure some of you will be sad that the LIFE and HANDMADE Hackaday subdomains are going away. Others will be happy, and many won’t realize they even existed.

We tried a little experiment in diversity this summer, launching the two outliers of our main focus (which is engineering oriented hacks). Each was interesting in their own way, with steady streams of readers and small conversations. But this diverted some of the attention away from what we do best, and that’s why we’re closing them down.

Handmade has already been absorbed. The features which highlighted craftsmanship and artful creations like blowing glass are tangentially interesting. We’ve imported all of the articles and will continue to feature this sort of content from time to time if it fits in with what our readers are normally after.

Life was a little bit outside of what we normally focus on. These sorts of hacks are interesting tidbits to have bouncing around your brain. But you probably won’t see them hitting our front page. Don’t let that discourage you though. If you’ve got a tip or trick to make daily life less mundane you can always let us know on the tips line. At worst we will ignore you. But you might end up seeing it in a Links post, which is our weekly Sunday column that showcases things which weren’t compelling enough for their own post.

Just to be clear for those that are really paying attention. We’re not cramming this content onto the front page with everything else. We’re phasing it out except for those things that go hand in hand with our lust for tech hacks of the highest caliber.

Building The Electronics For A Tesla Coil… And Watercooling Them

August 11, 2013 by 5 Comments

A few years ago [Patrick] was offered the Tesla coil of a friend of a friend. This was an opportunity too good for him to pass up.

He then began the creation of an Off-Line Tesla Coil (OLTC), where no supply transformer is used. The incoming mains supply is rectified and directly fed into the tank capacitor.

[Patrick] therefore had to build a huge capacitor bank and more importantly his own primary coil, made with a 1.6mm (0.064″) copper sheet to handle the immense current involved. Air cooling the electronics was sufficient until he started using his three phase input supply. As more power involves more heat, a waterblock was designed to cool the main transistor.

Patrick’s write-up is very detailed and worth the read. Once you’re finished with it, we advise you to browse through his website, where a lot more cool projects are described.

Wireless Marble Labyrinth Uses TI Dev Hardware

August 11, 2013 by 3 Comments

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There’s so much affordable dev hardware out there these days that you can do a lot without even touching a soldering iron. This is a prime example. Texas Instruments software Engineer [Jordan Wills] recently completed this wirelessly controlled marble labyrinth.

Marble mazes like this are a popular targets for electronic tinkering. We’ve seen smartphones used as the controller, and others that dispense chocolate candy. This time around [Jordan] stuck with the store-bought game to simplify the build. A coworker helped by swapping the two control knobs with servo motors. These interface with a Stellaris Launchpad that has a SensorHub booster pack (shield) and CC2533 radio transceiver module. The same hardware makes up the remote unit as well. This turns the remote into an air mouse by reading the gyroscope, accelerometer, and magnetometer from the booster pack.

He doesn’t specifically mention it in his project log, but we think the magnetometer is used to sync orientation between the base unit and the user remote. Even though the board for the base unit is mounted at 90 degrees compared to how you hold the remote, you should still be able to adjust for the readings in code, right?

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Bitbanging I2C By Hand

August 11, 2013 by 18 Comments

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Play around with electronics long enough, and eventually you’ll run into I2C devices. These chips – everything from sensors and memory to DACs and ADCs – use a standardized interface that consists of only two wires. Interacting with these devices is usually done with a microcontroller and an I2C library, but [Kevin] wanted to take that one step further. He’s bitbanging I2C devices by hand and getting a great education in the I2C protocol in the process.

Every I2C device is controlled by two connections to a microcontroller, a data line and a clock line. [Kevin] connected these lines to tact switches through a pair of transistors, allowing him to manually key in I2C commands one bit at a time.

[Kevin] is using a 24LC256 EEPROM for this demonstration, and by entering a control byte and two address bytes, he can enter a single byte of data by hand that will be saved for many, many years in this tiny chip.

Of course getting data into a chip is only half of the problem. By altering the control byte at the beginning of an I2C message by one bit, [Kevin] can also read data out of the chip.

This isn’t [Kevin]’s first experimentation in controlling chips solely with buttons. Earlier, we saw him play around with a 595 shift register using five push buttons. It’s a great way to intuit how these chips actually work, and would be an exceptional learning exercise for tinkerers young and old,

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Voice Controlled Home Automation Uses Raspberry Pi And LightwaveRF

August 11, 2013 by 32 Comments

It’s not quite artificial intelligence, but saying “Jeeves, lights!” will switch on the bulbs in the room. [Chipos81] built the voice-activated home automation around a Rapsberry Pi board with LightwaveRF devices switching lights and outlets.

The LightwaveRF system offers a WiFi link which provides Internet connectivity for all of those devices in your house. This makes it a snap for [Chipos81] to control them from the RPi. To provide speech recognition he’s using CMU Sphinx. It’s an open source speech recognition library developed by researchers at Carnegie Mellon University and released under a BSD license. It seems to do a great job in the video of quickly parsing several sets of commands.

“Jeeves” will even talk back to you to confirm a command. This is generated by Festival, a package developed by the University of Edinburgh.  This provides some entertainment in the last seconds of the video as we detect a distinct Scottish accent when it says “See you tomorrow”.

The GPIO pins provide a bit of feedback, using three colored LEDs to let you know what is going on with the system. There’s even an IR LED used to add voice control to your Television.

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Defeating Reddit’s CAPTCHA

August 11, 2013 by 14 Comments

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Here’s something we’re sure SEO specialists, PR reps, and other marketeers already know: how to write a script to game reddit.

The course of upvotes and downvotes controls which submission makes it to the front page of reddit. These submissions are voted on by users, and new accounts must log in and complete a CAPTCHA to vote. [Ian] discovered that reddit’s CAPTCHA is not really state-of-the-art, and figured out how to get a bot to solve it

The method exploits the 8-bit nature of the distorted grid in the CAPTCHA. Because this grid isn’t pure black or pure white, it’s at a lower intensity than the letters in the CAPTCHA. Putting the CAPTCHA through a threshold filter, deleting any blocks of pixels smaller than 20 pixels, and running it through a classifier (PDF there), a bot can guess what the letters of the CAPTCHA should be.

Out of the 489 CAPTCHAs [Ian] fed into his algorithm, only 28 – or 5.73% – were guessed correctly. However, because he knows which CAPTCHAs had failed segmentation, ignoring those can increase the success rate to 10%. Theoretically, by requesting new CAPTCHAs, [Ian] can get the accuracy of his CAPTCHA bot up to about 30%.

Combine this with a brilliant auto voting script that only requires someone to enter CAPTCHAs, and you’ve got the recipe for getting anything you want directly to the front page of reddit. Of course you could do the same with a few memes and pictures of cats, but you knew that already.