Another spec analyzer project

Discussion in 'Embedded Systems and Microcontrollers' started by sicesp, Jun 3, 2012.

  1. sicesp

    Thread Starter New Member

    Jun 3, 2012
    Looking for ideas to help plan a spec analyzer project.

    This project idea came to me when I purchased one of these light-up t-shirts which display a sound-responsive "graphic equalizer" on an LED (or EL) pad mounted on front of the shirt.

    These shirts, it turns out, do not really display an eight-band analysis as suggested by the light display, but rather just light the columns together in response to overall sound volume (in effect, a "one-band" spectrum analyzer). Clearly, this keeps down the cost and size of the controller box.

    However, the geek in me was bothered by this short cut. I would like a real multi-band analyzer light up shirt!

    One issue is that I am pretty sure I cannot use the existing light pad since the lights are wired as a print in the wrong way. I think it would be difficult to manipulate those connections since they are "printed" into the pad.

    So, did some searching and found an arduino shield made by which takes the input stereo audio, and ouputs a DC level on the output: seven bands multiplexed. Sounds promising. The Arduino is used to drive this board and also to read the output and drive the LEDs.

    The company also sells LEDs with imbedded controllers on a flexible strip for control via the Arduino. Again, sounds promising. These can be cut to size and fixed onto clothing.

    There are just several questions I have before I feel confident enough to start laying out my coin. (I don't have the infinite tinker time that I did when I was younger.) Any input will be much appreciated.

    (1) Would a 9V battery be adequate (and not to much either) to drive both the shield and the LEDs? (these shirts typically use anywhere from 2 to 3 AAAs but then it uses EL light, not typical LEDs; the original project at is designed for a 5V supply)

    (2) Safest way to merge the two stereo channels? since i'm only interested in mono for this application. Maybe to connect the channels at the audio input and then read only one channel on the digital output side?

    Thinking to use the ArduinoPro mini board for space conservation.

    Thanks in advance :)

    Sure would be great to find a source for custom EL pads and alter the design to handle that...
    Last edited: Jun 3, 2012
  2. MrChips


    Oct 2, 2009
    (1) A 9V battery may be convenient but wouldn't last very long. Capacity is about 500mAh. I would go with a 2 rechargeable NiMH cells, three to five times the capacity and rechargeable.

    (2) To convert stereo into mono, get two 100Ω resistors. Connect one resistor to each stereo channel and join the two resistors together. Where they meet, connect this to your mono input.
  3. sicesp

    Thread Starter New Member

    Jun 3, 2012
    Thanks! ........