Spectrum Analyzer Users Custom Characters On An HD44780 Display

September 8, 2011 by Mike Szczys 8 Comments

[Camilo] built a spectrum analyzer to use with his audio system (translate). The hardware is quite simple, using an op-amp, microcontroller and LCD display. He chose an LMV324M low-voltage op-amp which connects to the incoming audio signal and feeds its output to the microcontroller’s ADC. In this case, he chose a Freescale microcontroller from the HCS08 family which is running at 20 MHz. This gives the project enough speed to properly analyze the incoming audio. He mentions that he’s following the guidelines set forth in the Nyquist-Shannon sampling theorem and using the Fast Fourier Transform when processing the samples.

This isn’t the first time we’ve seen a character LCD used as a display for a frequency analyzer. This other ATmega8-based rendition supported several different screen layouts. These displays have enough RAM to store eight custom characters. Each character is 5×8 pixels, lending eight levels to each character for a total of 16 for each column seen above. We love the simplicity of the hardware in the project but we wouldn’t mind seeing an additional potentiometer to fine-tune how the data is displayed on the screen to take advantage of its full range. See the project in action in the clip after the break.

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PIC-based Voice Recorder

September 3, 2011 by Mike Szczys 34 Comments

[Vinod] just finished building a voice recorder and it turned out even better than he thought it would. The video after the break shows him recording what is surely one of your favorite songs from his cellphone and then playing it back. The audio quality does sound quite good for a project with very few components.

A PIC 16F877A makes up the majority of the build. Its ADC is used to capture the incoming line from an amplified microphone input (you’ll find that amp schematic half way through his post). He’s storing the data on an MMC card, which was a bit of a hack since the PIC has limited RAM to manage that overhead. The stored data is in a raw format, as the card is not accessed using a file system. This makes it easy to record at a high bit rate, leading to better audio quality. Playback consists of connecting a speaker via a low-pass filter and amplifier circuit to the hardware PWM output on the PIC.

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Speaker-mounted WAV Player For Street Performances

August 29, 2011 by Mike Szczys 21 Comments

This naked speaker is the basis for [MaoMakMaa’s] newest project called the Wavedrone. He plans on using the autonomous and cable-less device during street performances. You can hear the effect of some stretched jazz cords being played on it in the video clip after the break. The sound is kind of an ethereal background noise that observers might not immediately realize is there.

You can see the 9V battery which serves as the power source clinging to the frame of the speaker. A 7805 linear regulator tames that battery and feeds the two IC’s on the circuit board seen to the right. The ATtiny85 is reading music from an SD card and playing it back in mono (obviously) with the help of an LM386 audio amplifier chip. The trimpots that go into the high pass and low pass filters in between the microcontroller and amplifier allow for a bit of sound manipulation, but we’re more impressed with the quality of the sound this is getting when properly trimmed.

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Cellphone Controlled Retro-radio Stores And Plays Your Digital Library

August 24, 2011 by Mike Szczys 6 Comments

[Autuin] was worried about having desirable electronics stolen while on the road with his band. He didn’t want to take a laptop along on tour, but he didn’t want to be without his music either. To solve this problem, he built a music player inside of a cheap-looking radio. His write-up covers two different portable MP3 solutions, but it’s the second rendition that catches our attention.

After hollowing out the old radio he filled the void with an Asus WL-HDD 2.5. That hardware is meant to be an easy way to add network storage; it houses a laptop hard drive and has WiFi and Ethernet connectivity. But it also has one USB port, and can be hacked to add a second. [Autuin] did just that, using the two USB connections to add a Bluetooth dongle and a USB sound card. Music is synced with the hard drive via some cat-5 cable that’s hidden in the battery compartment of the vintage box. The NAS runs Linux, and the audio playback software is controlled though a Mobile Java application running on a somewhat broken cellphone. That’s an idea that might find its way into our next project.

Hacking A2DP Support Into An Old Car Stereo

August 22, 2011 by Mike Nathan 21 Comments

a2dp_tape_deck_retrofit

[Roofus] had an older car, and unfortunately his stereo’s cassette player just wasn’t doing it for him. He always wanted to simply get into his car, pull out his cell phone, and have his music ready to play without any fuss. After messing around with all sorts of different tape adapters, he got fed up and decided to rig up an A2DP (Stereo Bluetooth Audio) adapter on his own.

He pulled the head unit out and started looking around to see how he could wire an adapter in. He figured the best course of action would be to remove the tape deck, and fool the stereo into thinking that a tape had been inserted. After spending some time tracing wires and studying how his old tape adapters worked, [Roofus] had an A2DP connection wired in and was ready to rock out.

Greeted with nothing but silence, he turned to his favorite hacking site (Hackaday, naturally) for assistance. Some friendly forum-goers helped him identify a ground loop issue, and he set off to his nearest RadioShack for a pair of isolation transformers that would fix his problem.

Once he knocked out the ground loop issues, his adapter worked like a charm. He put everything back together, and aside from a tiny switch he installed to toggle between audio sources, you would never know it was there.

This GLaDOS Potato Is A Lie

August 21, 2011 by Mike Szczys 24 Comments

Why settle for virtual reality when you can make the digital world into reality? [Josh] wanted to have a GLaDOS potato accompany him through life when not playing Portal 2. He set to work to see what kind of replica prop he could come up with. Judging from the image above, and demo video after the break, he nailed it right in the spud.

There’s no worrying about rot. The potato and a few parts were molded from Sculpey and baked in the oven. Since the fake spud is hollow in the center it’s easy to hide the bits that make it talk. An old MP3 player was loaded with quotes from the game, and plays them back via an LM386 audio amplifier circuit and a speaker hidden below the electronic eye. The eye is lit by five yellow LEDs which are also tied into the amplifier to make them blink and fade with the intensity of the audio signal.

A paint job and the nails and wire really make the build look just right. Now [Josh] needs to host a geek-themed Halloween party so he can really show this off.

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A Quick And Dirty VU Meter For Your Next Party

August 21, 2011 by Mike Szczys 12 Comments

If you want an easy project to spice up your next party, chances are you already have parts on hand to throw together [Mikerbot’s] quick and dirty VU-meter lights. The circuit he designed uses the audio input to trigger the base of a PNP transistor, toggling power through a string of LEDs. He’s using four lights for each of the stereo output signals, making them pulse with the music as seen in the video after the break. The circuit is built on a breadboard, and housed in a picture frame with a less-than-impressive diffuser (we think that’s always the hardest part… check out the Heavy Frost used in this project if you want something that works really well).

There are some VU meter chips out there that will really augment this concept. But one improvement might be to throw in an amplifier chip like the LM386 and a couple of potentiometers so that you can dial-in the sensitivity.

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