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'Audio Tachometer'
1998\10\27@160630 by Andy Kunz

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Anybody have any hints on designing an audio tachometer, or better yet, do
you know where I can buy one.  I need a 50Hz to 10KHz range.

Thanks.

Andy

==================================================================
Andy Kunz - Statistical Research, Inc. - Westfield, New Jersey USA
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1998\10\27@163530 by Stig Brautaset

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-----Original Message-----
From: Andy Kunz <spam_OUTmtdesignTakeThisOuTspamFAST.NET>


>Anybody have any hints on designing an audio tachometer, or better

I'm very curious what an audio tachometer is. I have never heard of such a
thing before, and I'm not very reluctant to think you are yanking my chain
here... :-)

==================================================
Stig Brautaset - .....sbrautasKILLspamspam@spam@c2i.net - ICQ: 11052183
student of electronics, homepage at http://home.c2i.net/sbrautas
==================================================

Drive carefully; 90% of the worlds population are due to accidents.

1998\10\27@175115 by kfisk

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Are you talking about a VU meter? In other words, a meter which displays the
relative audio power on a bar graph display? or a meter?  If you are, check
out Radio Shack. I can't say for certain they still carry these, but they
did at one time.

{Quote hidden}

1998\10\27@182925 by WIL REEDER

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Hi Andy;

There is a TONAL VOLTMETER project on the Poptronix website. This would
give you the basics for the output. Add a clipper and integrator to get a
linear voltage from the ign. pulses. Hope this helps.

Wil Reeder
Vancouver,Canada
teachtechspamKILLspambc.sympatico.ca

----------
> From: Andy Kunz <.....mtdesignKILLspamspam.....FAST.NET>
> To: EraseMEPICLISTspam_OUTspamTakeThisOuTMITVMA.MIT.EDU
> Subject: Audio Tachometer
> Date: Tuesday, October 27, 1998 1:03 PM
>
> Anybody have any hints on designing an audio tachometer, or better yet,
do
> you know where I can buy one.  I need a 50Hz to 10KHz range.
>
> Thanks.
>
> Andy
>
> ==================================================================
> Andy Kunz - Statistical Research, Inc. - Westfield, New Jersey USA
> ==================================================================

1998\10\28@003057 by Russell McMahon

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The frequency meter which is being discussed at present sounds like
an ideal solution to the electronic component - it should just
require a rescaling of the time base to get the range correct.


regards


       Russell McMahon

From: Andy Kunz <mtdesignspamspam_OUTFAST.NET>

>Anybody have any hints on designing an audio tachometer, or better
yet, do
>you know where I can buy one.  I need a 50Hz to 10KHz range.

1998\10\28@004809 by Mark Willis

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Might take a longer time per sample;  you might want to median filter
(with sanity checking) a few samples to get an even longer effective
timebase?

 Mark

Russell McMahon wrote:
{Quote hidden}

1998\10\28@082147 by Andy Kunz

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>There is a TONAL VOLTMETER project on the Poptronix website. This would
>give you the basics for the output. Add a clipper and integrator to get a
>linear voltage from the ign. pulses. Hope this helps.

I'm looking for a frequency measuring device (which directly correlates to
RPM) which uses a microphone as the input.  No chain yanking <G>

I need to get an idea of the RPM my boats motors are turning, without
putting something in the boat.

Andy


==================================================================
Andy Kunz - Statistical Research, Inc. - Westfield, New Jersey USA
==================================================================

1998\10\28@130407 by Tom Handley

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  Howdy Andy. I'm a little confused. In the Parallax list you mention:

     I'm looking at an 1/8" dia shaft with a 1.25" propeller on the end,
     rotating between 1K and 60K RPM.

  In this list you mention:

     I'm looking for a frequency measuring device (which directly
     correlates to RPM) which uses a microphone as the input. No chain
     yanking <G>

     I need to get an idea of the RPM my boats motors are turning, without
     putting something in the boat.

  Is this the same project? Are you looking for a commercial product? If
you really want to design this and need help, I can think of several ways
to do this cheaply, but you already know how to do this with your expertise
in this area. Anyway, let us know the details and I'm sure you will get a
lot of suggestions from the practical to the `Rube Goldberg' ;-)

  - Tom

At 08:19 AM 10/28/98 -0500, Andy Kunz wrote:
{Quote hidden}

1998\10\28@141652 by Andy Kunz

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>   Is this the same project? Are you looking for a commercial product? If

No, I'm looking for two things that are related to one another.

1)  I want an audio-input tach.  I need to hear what speed the motor is
turning at in my boats while they're on the water.  I know I'll probably
see harmonics and secondary tones, but Scott Dattalo can probably help with
filtering those out.

2)  I need a stroboscope for balancing the props (and driveshafts) at rpm.
The strobe is something I've never played with, but with the LED's
mentioned I think I got some good ideas.  The strobe may be activated
either by a pot to set frequency or by synching to the rotating prop with
an IR sensor to watch the blades go past.

>to do this cheaply, but you already know how to do this with your expertise

The audio part of the tach is the hard part for me.  I'm too digital.

The LEDs were good pointers - now I have something to play with.

Thanks.

Andy

==================================================================
Andy Kunz - Statistical Research, Inc. - Westfield, New Jersey USA
==================================================================

1998\10\28@164857 by Scott Dattalo

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Andy Kunz wrote:
>
> 1)  I want an audio-input tach.  I need to hear what speed the motor is
> turning at in my boats while they're on the water.  I know I'll probably
> see harmonics and secondary tones, but Scott Dattalo can probably help with
> filtering those out.

Since my hearing falls off 40dB between 2kHz and 3kHz this should be no
problem :).

If you're refering to some of the (digital) filtering I've done before
(and have mentioned on this list), you may keep in mind that these are
very narrow band pass. Chip was mentioning a more useful digital filter
a few days ago. Perhaps he can enlighten us with more details?

Scott

1998\10\28@193323 by Russell McMahon

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Seriously (but probably not usefully :-)) an instrument tuning aid
may help - sold for guitars etc with mic input and display. A
standard frequency meter with a mic and preamp is probably more
normal though.

   Russell.


From: Andy Kunz <KILLspammtdesignKILLspamspamFAST.NET>
>I'm looking for a frequency measuring device (which directly
correlates to
>RPM) which uses a microphone as the input.  No chain yanking <G>
>
>I need to get an idea of the RPM my boats motors are turning,
without
>putting something in the boat.

1998\10\28@205021 by Barry Hines

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>1)  I want an audio-input tach.  I need to hear what speed the motor is
>turning at in my boats while they're on the water.  I know I'll probably
>see harmonics and secondary tones, but Scott Dattalo can probably help with
>filtering those out.
>


Thinking about this makes me wonder if the "Doppler Effect" would screw up
your results??  You know, like when a passing train blows it's whistle and
the frequency of the whistle goes down as the train gets further away and
vice versa.  If the distance between your microphone and the sound source
never changed, this probably wouldn't happen.

Wouldn't it be more accurate and easy to make a tachometer for the boat that
would send it's results to you via RF???

Just some thoughts   :o)

Barry

1998\10\29@132130 by Peter L. Peres

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On Wed, 28 Oct 1998, Andy Kunz wrote:

> 1)  I want an audio-input tach.  I need to hear what speed the motor is
> turning at in my boats while they're on the water.  I know I'll probably
> see harmonics and secondary tones, but Scott Dattalo can probably help with
> filtering those out.

Nip one of your blades at the tip with a tiny watchmaker's saw (nip both
for balance), then try to enlist some help from someone with a hydrophone
to determine where your 'whistle' is and then build something that filters
this for you. You'd need a hydrophone but with those rpms and the nips
your boat will 'shine' out loud ;) Instead of someone with a hydrophone,
you can determine the thing by using your own bathtub, an underwater
microphone and an audio specan that goes up to 500 kHz or so (PC based ?)
imho. The frequency you will be looking for will likely be the highest
displayed in the Fourier plot for this setup.

Peter

1998\10\30@004919 by Andy Kunz

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>Thinking about this makes me wonder if the "Doppler Effect" would screw up
>your results??  You know, like when a passing train blows it's whistle and

Averaging will take care of it.  Already considered that.

>Wouldn't it be more accurate and easy to make a tachometer for the boat that
>would send it's results to you via RF???

Well, actually, my data logger just stores it onboard.  I need something
cheaper for average users.

Andy


==================================================================
Andy Kunz - Statistical Research, Inc. - Westfield, New Jersey USA
==================================================================

1998\10\30@020234 by Mark Willis

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Andy Kunz wrote:
>
> >Thinking about this makes me wonder if the "Doppler Effect" would screw up
> >your results??  You know, like when a passing train blows it's whistle and
>
> Averaging will take care of it.  Already considered that.

 Just have people sample when the boat's running more or less
tangential to them (i.e. not speeding towards or away from them)?

 Mark, RemoveMEmwillisTakeThisOuTspamnwlink.com

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