Hacking An Old Radar Gun To Interface With A Laptop

November 1, 2012 by Mike Szczys 24 Comments

[Gregory Charvat] decided to see what he could do with this old Police radar gun. It is an X-band device that broadcasts continuous waves and measures the Doppler shift as they echo back. He cracked it open to see if he could interface the output with a computer.

After a little poking around he’s able to get it connected to a 12V feed from his bench supply, and to monitor the output with an oscilloscope. He established that it draws about 0.5A in current he built a companion board which uses AA batteries for power, and provides an audio output which can be plugged into his laptop’s audio-in jack. This technique makes reading the device as easy as recording some audio. From there a bit of simple signal processing lets him graph the incoming measurement.

In the video after the break you’ll see his inspection of the hardware. After making his alterations he takes it into the field, measuring several cars, a few birds, and himself jogging.

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AM Chiptunes Played By A Modified Antenna Analyzer

October 26, 2012 by Mike Szczys 5 Comments

Believe it or not, this VK5JST aerial analyzer kit is going to rickroll you. [Erich] wanted to see if he could use the device in a different way. His adventure led him to use it to feed different tones to an AM radio, producing the all too familiar [Rick Astley] offering.

There’s a fair bit of math that goes into getting the correct signals to generate a given pitch. But it basically boils down to patching into the hardware early in the RF generation. This way an audio signal can be rolled into the carrier frequency. Since this kit uses a PicAXE microcontroller with available source code it is rather easy to add audio input to tweak what the chip is putting out. But there is also some hardware tinkering to be done. Read more about that at the article linked above, and don’t forget to check out the bottom of that page to hear the final results.

LEDs Fade To The Music Using A Python Filter

October 25, 2012 by Mike Szczys 15 Comments

This little LED rig fades in time to music. The hardware itself is quite simple, some LEDs connected to the PWM pins of an Arduino. But the signal processing is happening on a computer using a Python script.

Many of the projects we see which pulse lights to music use the MSGEQ7 chip to perform hardware processing on the audio signal. But since [Zolmeister] is using a computer to play his tunes he took a different route. His Linux box uses PulseAudio to handle sound. This allows him to record from the audio playback which provides an internal source for the pyAudio package. His Python script saves snippets of the streaming audio to .wav files. I then normalizes the volume level and uses the amplitude to set a PWM value before deleting the sample and moving onto the next. These values are pushed to the Arduino at 115200 baud to achieve the results seen in the video after the break.

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Roll Your Own Parabolic Microphone

September 26, 2012 by Mike Szczys 28 Comments

Parabolic microphones are used to listen in from a distance. You see them on the sidelines of NFL football games, but they’re part of the standard issue in detective and spy novels. Now you can build your own parabolic microphone by following this example.

The one component that may be hard to find is the parabolic reflector. You cannot simply use a bowl or other curved object as the precise parabolic shape ensures that sound waves are reflected onto one finite focal point. For this build the reflector was obtained from an eBay seller. But the other parts are scavenged from easy to find sources. The microphone itself is an inexpensive element from Radioshack. It is mounted in the shell from a tweeter speaker, which helps to gather the sound if the element isn’t exactly aligned with the focal point. The setup also needs a preamplification system, which uses many components. Luckily there’s a schematic and other reference material linked in the write up.

You can also build a laser microphone which detects sound waves on a pane of glass.

[Thanks Anonymous]

Making Your Anime Papercraft Move To The Music

September 25, 2012 by Mike Szczys 15 Comments

This anime character is dancing to the music thanks to some animatronic tricks which [Scott Harden] put together. She dances perfectly, exhibiting different arm and head movements at just the right time. The secret to the synchronization is actually in the right channel of the audio being played.

The character in question is from an Internet meme called the Leekspin song. [Scott] reproduced it on some foam board, adding a servo to one arm to do the leek spinning, and another to move the head. These are both driven by an ATtiny44. All of the movements have been preprogrammed to go along with the audio track. But he needed a way to synchronize the beginning of each action set. The solution was to re-encode the audio with one track devoted to a set of sine wave pulses. The right audio channel feeds to the AVR chip via an LM741 opamp. Each sine wave triggers the AVR to execute the next dance move in the sequence. You can see the demo video for the project after the break.

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How To Build Your Own Dedicated Pandora Radio

September 20, 2012 by Mike Szczys 18 Comments

This mix of modern and retro acts as a standalone Pandora client. It’s certainly a radio upgrade, falling somewhere in between the passive listening of traditional broadcasts, and the complete control of music players that use playlists.

Inside the wooden case a BeagleBoard does most of the work. It’s running Ubuntu 12.04 on which pianobar, a command line interface package for Pandora is running. Those components alone would make a pretty nice listening experience, but since Pandora rolls different music into the mix it’s nice to be able to see what you’re listening to. The four-line LCD is wide enough to display plenty of information. It’s being controlled by a PIC24 microcontroller which also monitors the controls on the top. As you can see in the video after the break, the user interface offers almost everything you could want. It’s easy to switch stations, and you can still register your preferences on each track being played.

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Ugly Upgrade Keeps The Tunes Playing Longer

September 13, 2012 by Mike Szczys 25 Comments

[Sam] picked up a Sansa Clip audio player to listen to some tunes while working on projects. He liked the fact that he could run the Rockbox alternative firmware on the device, but thought the 15 hour battery life needed some improving. He swapped out the stock cell with a larger Lithium cell for a long life of 50-60 hours. It’s an upgrade fom 300 mAh to 1100 mAh, but as you can see, the size of the replacement made for some interesting case modification.

The battery swap required more than just taking one battery out and putting in the other. [Sam] is using a cellphone battery as the replacement and he didn’t want to have issues with the internal circuitry. He took the cell out of its plastic enclosure, removing the circuit board in the process. That PCB is the charging circuit, which he replaced with the one from the stock battery. After insulating the cell with a layer of Kapton tape he soldered it to the MP3 player and did his best to adhere all the parts to each other.

Sure, its ugly, but that makes it right at home on the work bench.