[sdiy] [OT] Mini-DSP or TI Mini-DSP for metal detector audio

[Barry Klein]

I suspect it is the kind of thing that you have to play around with various
parameters to find what is of most value.  The warble is sort of desired for
this type detector as it indicates your minimum threshold and that the unit
is working.  Any target will increase the loudness or frequency variation.
There is a Threshold setting as well as Volume and Tone.  So what may be of
most value is a processor that accentuates pitch change (by perhaps
different sound altogether) and loudness change by an expander.  Other
things of value may be some sort of target identifier that recognizes the
change in characteristics and gives a unique sound for each type of target.
Hair pins and nails for example have a quick double blip.  Iron targets
often sound different slightly from lead or gold.  
The warbling sound is often annoying to detectorists and those around them.
The goal of many tinkerers is to somehow reduce it to a steady tone by
designing out circuit noise and shielding out EMI.

Barry


-----Original Message-----
From: synth-diy-bounces at dropmix.xs4all.nl
[mailto:synth-diy-bounces at dropmix.xs4all.nl] On Behalf Of Gordon JC Pearc e
Sent: Sunday, May 06, 2012 03:24
To: synth-diy at dropmix.xs4all.nl
Subject: Re: [sdiy] [OT] Mini-DSP or TI Mini-DSP for metal detector audio

On 02/05/12 21:17, Barry Klein wrote:

> These detectors typically have a constant audio output tone that is a
little warbly but gets louder and/or varies in frequency if a target is
detected.
> There was a product called Superfix that may have had a DSP inside to
allow silence until a target is detected.  It was complicated to use though
and very very expensive.

If the tone is more-or-less constant and changes pitch on detecting a 
target, couldn't you just notch out its "idle" state?

-- 
Gordonjcp MM0YEQ
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