Searching \ for '[PIC]: Spectrum analyser' in subject line. ()
Make payments with PayPal - it's fast, free and secure! Help us get a faster server
FAQ page: www.piclist.com/techref/microchip/devices.htm?key=pic
Search entire site for: 'Spectrum analyser'.

Exact match. Not showing close matches.
PICList Thread
'[PIC]: Spectrum analyser'
2002\05\14@174213 by Jamie Donald

picon face
Does anybody know how to implement an audio spectrum analyser, say for instance a 7 band bar graph display.
I'm not too sure on the process of taking an ac signal and taking an average level at several frequencies, is it possible?

Thanks in advance Jamie..

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.


2002\05\14@183655 by Thomas C. Sefranek

face picon face
Brouse for FFTs.

Jamie Donald wrote:

> Does anybody know how to implement an audio spectrum analyser, say for instance a 7 band bar graph display.
> I'm not too sure on the process of taking an ac signal and taking an average level at several frequencies, is it possible?
>
> Thanks in advance
> Jamie..
>
> --
> http://www.piclist.com hint: The PICList is archived three different
> ways.  See http://www.piclist.com/#archives for details.

--
 *
 |  __O    Thomas C. Sefranek   spam_OUTtcsTakeThisOuTspamcmcorp.com
 |_-\<,_   Amateur Radio Operator: WA1RHP
 (*)/ (*)  Bicycle mobile on 145.41, 448.625 MHz

hamradio.cmcorp.com/inventory/Inventory.html
http://www.harvardrepeater.org

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.


2002\05\15@025717 by Joe Farr

flavicon
face
Everyday Practical Electronics mag did a PIC based spectrum analyser
that outputs the results to a PC in their Feburary 2002 edition.
If you look on their web site http://www.epemag.co.uk you should find a pointer
to their ftp area where you can download the software which might give
you some ideas.
It was based on a PIC 16F877,a 32Kb SRAM and an external AtoD converter.
The supporting article talks a lot about FFT's





{Original Message removed}

2002\05\15@052623 by Jamie Donald

picon face
I did not realise that something like this could be so complicated and it
would possibly be easier to implement using analogue electronics but that
would not be as much fun to play with
Unless anybody knows of an easier to understand explanation of FFT's.

Cheers....

----- Original Message -----
From: "Joe Farr" <.....joe.farrKILLspamspam@spam@KCSL.UK.COM>
To: <PICLISTspamKILLspamMITVMA.MIT.EDU>
Sent: Wednesday, May 15, 2002 7:45 AM
Subject: Re: [PIC]: Spectrum analyser


Everyday Practical Electronics mag did a PIC based spectrum analyser
that outputs the results to a PC in their Feburary 2002 edition.
If you look on their web site http://www.epemag.co.uk you should find a pointer
to their ftp area where you can download the software which might give
you some ideas.
It was based on a PIC 16F877,a 32Kb SRAM and an external AtoD converter.
The supporting article talks a lot about FFT's





{Original Message removed}

2002\05\15@053040 by Dwayne Reid
flavicon
face
At 10:42 PM 5/14/02 +0100, Jamie Donald wrote:
>Does anybody know how to implement an audio spectrum analyser, say for
>instance a 7 band bar graph display.
>I'm not too sure on the process of taking an ac signal and taking an
>average level at several frequencies, is it possible?

I recall that Circuit Cellar Ink magazine published a very nice unit
designed by, I think, Robert LaCoste.  I'll have to check the spelling of
his name to make sure but you can head over to their web site
<http://www.circuitcellar.com> and search for the term "spectrum analyzer".

Hope this helps!

dwayne


Dwayne Reid   <.....dwaynerKILLspamspam.....planet.eon.net>
Trinity Electronics Systems Ltd    Edmonton, AB, CANADA
(780) 489-3199 voice          (780) 487-6397 fax

Celebrating 18 years of Engineering Innovation (1984 - 2002)
 .-.   .-.   .-.   .-.   .-.   .-.   .-.   .-.   .-.   .-
    `-'   `-'   `-'   `-'   `-'   `-'   `-'   `-'   `-'
Do NOT send unsolicited commercial email to this email address.
This message neither grants consent to receive unsolicited
commercial email nor is intended to solicit commercial email.

--
http://www.piclist.com#nomail Going offline? Don't AutoReply us!
email EraseMElistservspam_OUTspamTakeThisOuTmitvma.mit.edu with SET PICList DIGEST in the body


2002\05\15@092931 by Scott Dattalo

face
flavicon
face
On Wed, 15 May 2002, Jamie Donald wrote:

> I did not realise that something like this could be so complicated and it
> would possibly be easier to implement using analogue electronics but that
> would not be as much fun to play with
> Unless anybody knows of an easier to understand explanation of FFT's.

Think of an FFT as a whole bunch of narrow bandpass filters centered at
frequencies i*f i=0,1,2,3,4,... f=sampling frequency. A way to understand
how they're implemented is by looking at filter banks. The original poster
asked for 7 banks, so let's make it 8 for ease of computation.

Suppose the signal is sampled and split into two parts: a low frequency
portion and a high frequency portion. I.e. pass the signal through a low
pass filter and a high pass filter. Take these two signals and split them
again into low and high frequencies. This produces 4 new signals of low
low middle, high middle, and high frequencies. Repeat once more and you
get 8 frequencies. So in 3 "steps" the input signal was divided into 8
frequency bins.

This is *not* exactly how an FFT works, but it's conceptually similar. In
fact, it might be easier to implement this "algorithm" instead of an FFT.
One of the restrictions of an FFT is that the frequencies are equally
spaced. If you implement filter banks, then you can individually choose
the widths of the frequency bins.

--
http://www.piclist.com#nomail Going offline? Don't AutoReply us!
email listservspamspam_OUTmitvma.mit.edu with SET PICList DIGEST in the body


2002\05\15@170024 by T.C. Phelps

picon face
Hi,

> I did not realise that something like this could be
> so complicated and it would possibly be easier to
> implement using analogue electronics but that
> would not be as much fun to play with


I'm not an expert in analog electronics, but how about
this: Design a notch filter RLC or RC-Opamp circuit
(RC-OpAmp is probably preferable -- no clunky
hard-to-find inductors), and then depending on how
many bands you want in your analyzer, use that many
notch filters and select component values so that the
upper cutoff frequency of a lower frequency filter is
equal to the lower cutoff frequency of a higher
frequency filter. Pass the input to all of the filters
in parallel, and you'll get seven (for a 7 band
analyzer) output signals that correspond to your
bands. Pass each of these through an envelope
detector, then measure the voltage of each signal.
That voltage can then drive a bar graph LED (for
example). There's a few circuits on the internet
already designed that convert a voltage signal to a
bar graph signal, just check some of the circuit
archives kicking around and you'll probably find
something.

That's off the top of my head... I hope none of the
analog pros on the list are shaking their head at me;
Maybe one of them can comment on the feasibility of
this approach. :)

T.



__________________________________________________
Do You Yahoo!?
LAUNCH - Your Yahoo! Music Experience
http://launch.yahoo.com

--
http://www.piclist.com#nomail Going offline? Don't AutoReply us!
email @spam@listservKILLspamspammitvma.mit.edu with SET PICList DIGEST in the body


2002\05\16@055113 by Brandon Irwin

flavicon
face
I don't really know the context of this discussion, but

I believe the nice spectrum analyzers use heterodyne receiver...
Just have a local oscillator and mix it with the incoming signal to get an
IF at whatever freq you want, then just band pass the IF and detect the
amplitude (am radio with a sweeping LO)...I've never heard of it done with
many many filters, although it would be fun to watch someone *else* make it
that way...   :)

If you want some good info on Spectrum analyzers, I recommend
http://cp.literature.agilent.com/litweb/pdf/5965-7920E.pdf  (I think this
is the one, cant get acrobat to work)


Brandon Irwin

At 13:52 5/15/2002, you wrote:
{Quote hidden}

-------------------------------------
This message was written using the Dvorak keyboard layout.

--
http://www.piclist.com hint: To leave the PICList
KILLspampiclist-unsubscribe-requestKILLspamspammitvma.mit.edu


2002\05\16@083541 by Olin Lathrop

face picon face
>>
Does anybody know how to implement an audio spectrum analyser, say for
instance a 7 band bar graph display.
I'm not too sure on the process of taking an ac signal and taking an average
level at several frequencies, is it possible?
<<

Look up FFT (Fast Fourier Transform).


*****************************************************************
Embed Inc, embedded system specialists in Littleton Massachusetts
(978) 742-9014, http://www.embedinc.com

--
http://www.piclist.com hint: To leave the PICList
RemoveMEpiclist-unsubscribe-requestTakeThisOuTspammitvma.mit.edu


More... (looser matching)
- Last day of these posts
- In 2002 , 2003 only
- Today
- New search...