[sdiy] Signal indicator board...

[Jay Schwichtenberg]

Hello,

Also, if you get a high spike of a couple of cycles you may not see it.
Using some one shots can keep the indicator going long enough to see it.

Jay S.

> -----Original Message-----
> From: owner-synth-diy at dropmix.xs4all.nl
> [mailto:owner-synth-diy at dropmix.xs4all.nl]On Behalf Of Grant Richter
> Sent: Friday, May 02, 2003 10:20 AM
> To: Tim Ressel; Synth-Diy
> Subject: Re: [sdiy] Signal indicator board...
>
>
> This may interest you...
>
> All the VCAs in the Wiard modules use an LM339 quad comparator
> chip to form
> a 4 section VU meter. Like an LM3916, but with only 4 sections.
> An LM339 can
> be found as cheap as $0.29 each (quant. 200) whereas an LM3916 runs around
> $2.00.
>
> Use a resistor divider like this:
>
> +15V 5.1K 6.8K 2.2K 680 330 Gnd
>
> This gives you (roughly) reference voltage levels of 10V, 3.3V,
> 1V and 0.33V
> which correspond (again very roughly) to levels of +20, +10, 0
> and -10 dBv.
>
> Ideally, this should be a bi-polar circuit with an absolute value
> circuit in
> front of it. So you indicate both positive and negative waveform peaks. If
> you make the simplifying assumption that audio waveforms are
> ALWAYS centered
> around 0 volts, you can ignore the negative peaks, and eliminate the 2
> additional op-amps needed for the absolute value circuit.
>
> The 10 volt level corresponds to 20 volts peak to peak and is a clipping
> warning. LED colors I used are Green, Green, Amber, Red for -10,
> 0, +10 and
> +20.
>
> Tie the 4 negative comparator inputs together and to a 100K to ground, use
> as an input (high impedance). Run the reference levels to the positive
> comparator inputs. Connect the LEDs with current limiting
> resistors between
> +15 and the comparator open collector outputs. 10 resistors, 4
> LEDs, 1 chip.
>
>
> > From: Tim Ressel <madhun2001 at yahoo.com>
> > Date: Fri, 2 May 2003 09:00:53 -0700 (PDT)
> > To: Synth-Diy <synth-diy at dropmix.xs4all.nl>
> > Subject: [sdiy] Signal indicator board...
> >
> > Yo,
> >
> > I've been thinking (dangerous, I know) and I think
> > what the world needs is a little board that takes in a
> > signal and has two LEDs to show signal present and
> > overload. This makes a handy visual indicator as well
> > as a swell panel filler. Real simple circuit, possibly
> > surface mount to keep sizes small. It could be
> > single-supply to keep wiring down.
> >
> > So like, what do ya think??
> >
> > --Tim
> >
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