[sdiy] Making an audio spectrum analyzer from an old Casio LCD TV

[Eric Brombaugh]

On 09/08/2011 08:42 PM, aankrom wrote:
> I have an old hand-held Casio LCD TV and I thout it would be cool to
> make an add-on for it that would allow it to function like a spectrum
> analyzer. I was going to start with some sort of heterodyne system for
> the fron't end, but getting the final output to NTSC video is the
> insurmountable hurtle. It can be monochrome so I don't have to mess with
> color. I've seen projects using microcontrollers that output VGA, but I
> like my little TV idea.
>
> If I'm not mistaken would the easiest way to do it be to have the TV on
> it's side?
>
> Anyone done anything like this?

There are a couple of ways to do something like this, but basically it 
boils down to handling it digitally or in analog hybrid. I think the OP 
is referring to the latter.

In the analog hybrid approach, you'd have a video line counter that 
controls a sweep oscillator tuning across some band of interest. At each 
video line you'd dwell, integrating the energy at that frequency and 
using the result to control the 'on' time of the video line. This would 
result in a spectrum analyzer with the vertical axis being frequency and 
the horizontal axis being magnitude/power. It's a fairly simple concept 
that could be done with a low-end MCU coupled with oscillators, 
integrators, etc.

The digital approach would use DSP (FFTs, windows, etc) and more 
conventional video generation systems to create a frequency display in 
any format. I've done something like this with a dsPIC and a low-res 
graphic LCD here:

http://members.cox.net/ebrombaugh1/synth/dsPIC_lcd/index.html

Probably not what the OP was talking about though...

Eric