MOTM

i am considering several panel meter possibilities and i could use some 
help. if i integrate, say a 10volt DC voltage meter into my MOTM system, 
what will happen if:
A. i plug an AC/audio signal of, say +/-5v, into it?
B. a CV/audio signal exceeds the 10 volts? i would guess that the meter 
will become pinned, but not harmed.

would i be better off with a VU meter for audio and a DC meter for CVs?
any help is appreciated!
thanks
mark

I'm no expert, but it seems to me that you could do mechanical damage by
pegging the meter, and perhaps electrical as well since you are exceeding
its rating.

Dave Bradley
Principal Software Engineer
Engineering Animation, Inc.
daveb@...

> From: mark scetta <n0nspaz@...>
>
>
> i am considering several panel meter possibilities and i could use some
> help. if i integrate, say a 10volt DC voltage meter into my MOTM system,
> what will happen if:
> A. i plug an AC/audio signal of, say +/-5v, into it?
> B. a CV/audio signal exceeds the 10 volts? i would guess that the meter
> will become pinned, but not harmed.
>
> would i be better off with a VU meter for audio and a DC meter for CVs?
> any help is appreciated!
> thanks
> mark
>
>

In a message dated 02/22/2000 11:39:52 AM, n0nspaz@... writes:

<< would i be better off with a VU meter for audio and a DC meter for CVs? >>

To my knowledge the VU meter still needs a buffer amp, while the voltmeter 
does not.  The Wiard controller uses a -15v - 0v - +15v DC meter which is a 
good idea.

Ivan

Here's another though if you don't mind using a buffer.  I saw a simple
little op-amp circuit in the electronic book I am reading right now that
outputs a positive voltage equal to the incoming voltage (negative or
positive).  So essential, it returns the "real" number.  I was thinking
that would be an idea way to read CV on normal a 0-15VDC meter.  The meter
would be protected from incorrect polarity.  A couple of LEDs (here we go
again) could be added to indicate whether the voltage was negative or
positive.

I hadn't though too much about how to look at AC.  But, as I think about
this circuit it would seem to provide a rectified version of any audio. 
Some deflection is going to occur, but obviously not a peak value.  Hmmm...
 something else to play with and learn.

Larry H

> From: ivancu@...
> 
> In a message dated 02/22/2000 11:39:52 AM, n0nspaz@... writes:
> 
> << would i be better off with a VU meter for audio and a DC meter for
CVs? >>
> 
> To my knowledge the VU meter still needs a buffer amp, while the
voltmeter 
> does not.  The Wiard controller uses a -15v - 0v - +15v DC meter which is
a 

> good idea.
> 
> Ivan

Selco distributes Sifam meters in the US. They have analog VU meters
that only need need a single resistor to function properly. You could
probably mult to one easily. Also there are the National Semiconductor
Lm3914/3915/3916 chips which are already configured to do Linear/Log and
VU ballistics. . You then hook them up to some 10 segment Leds and they
work great. If you need to buffer a simple opamp follower would do the
trick Much cheaper to do than a good VU meter. The Sifams do work very
well though. Charles.

ivancu@... wrote:

> From: ivancu@...
>
>
> In a message dated 02/22/2000 11:39:52 AM, n0nspaz@... writes:
>
> << would i be better off with a VU meter for audio and a DC meter for
> CVs? >>
>
> To my knowledge the VU meter still needs a buffer amp, while the
> voltmeter
> does not.  The Wiard controller uses a -15v - 0v - +15v DC meter which
> is a
> good idea.
>
> Ivan
> -----------------------------------------------------------------------
>
> -----------------------------------------------------------------------
>

In a message dated 2/22/2000 9:39:43 AM, n0nspaz@... writes:

>i am considering several panel meter possibilities and i could use some
>help. if i integrate, say a 10volt DC voltage meter into my MOTM system,
>what will happen if:
>A. i plug an AC/audio signal of, say +/-5v, into it?

I say 0V DC (is this a trick question?)

>B. a CV/audio signal exceeds the 10 volts? i would guess that the meter
>will become pinned, but not harmed.

BINK!!!! I would think that number of events (and length of time) would be 
what would damage the meter, but I imagine everyone with a VOM has had it on 
the wrong range at one time or another and.....BINK!!!! Try not to do it is 
the general rule. And how accurate do you need that meter anyway?

What I've been thinking of is liberating some old VUs from a cassette deck to 
use for preamps. Any ideas on how best to do this? Recalibrate the meters?

JB