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'[OT] self-oscillating magnetic buzzer'
1999\07\23@152254 by Eisermann, Phil [Ridg/CO]

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       I have a self-driven magnetic buzzer that i'm using in a
non-intended fashion. Instead of having the buzzer fully on, I
pulse it at approximately 60Hz, using a PIC, of course (This had
to be done as the buzzer draws just a little more current than the
capacitor-powered supply can provide). Does anyone know the
long-term affects of this on the buzzer life?

       The mfg. rep told me that it would be ok to do so.
However, the buzzer had a lead-time of 12 weeks, so the
board house substituted a "direct replacement" buzzer with
(nearly) the same characteristics. Now, i'm starting to see
more failures than make me comfortable.

       Alternately, does anyone know of a 5Vdc buzzer that
draws under 10mA? Either self-driven (10mA) or one that needs
to be driven (which could draw more instantaneous current, but
the average still needs to be 10mA or less).

Thanks for any help.

-Phil

1999\07\23@160808 by Bob Drzyzgula

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On Fri, Jul 23, 1999 at 03:20:59PM -0400, Eisermann, Phil [Ridg/CO] wrote:
>
>         Alternately, does anyone know of a 5Vdc buzzer that
> draws under 10mA? Either self-driven (10mA) or one that needs
> to be driven (which could draw more instantaneous current, but
> the average still needs to be 10mA or less).

A few of the Mallory Sonalert devices are rated within
that spec. Don't know your size, mounting or sound pressure
requirements, but e.g. the SC307N is a panel mount device
that will generate 80 dbA at two feet, on 3V with a 3mA
load. At 7V, it is rated for 90 dbA for a cost of 8mA.

No experience with it, I just happen to have one of their
brochures laying around. Check http://www.nacc-mallory.com.

--Bob

--
============================================================
Bob Drzyzgula                             It's not a problem
spam_OUTbobTakeThisOuTspamdrzyzgula.org                until something bad happens
============================================================

1999\07\23@190815 by paulb

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Eisermann, Phil [Ridg/CO] wrote:

> Does anyone know the long-term affects of this on the buzzer life?

 No, but ... if the device is self-oscillating ("negative-resistance
oscillator") and has no moving parts beyond the reed, why would it fail?

> the board house substituted a "direct replacement" buzzer with
> (nearly) the same characteristics.  Now, i'm starting to see
> more failures than make me comfortable.

 Can you define "failures"?  Failure to work under your conditions?
Failure to work at original specification?  Won't work as built?  Fails
later?
--
 Cheers,
       Paul B.

1999\07\23@212527 by Reginald Neale

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 Phil asked:

>        I have a self-driven magnetic buzzer that i'm using in a
>non-intended fashion. Instead of having the buzzer fully on, I
>pulse it at approximately 60Hz, using a PIC, of course (This had

 (much snipped)

 The main advantage of magnetic buzzers as opposed to the strictly
 piezo ones is the higher spectral content at low frequencies.
 In some environments they are easier to hear.

 But if you don't need the low frequency content, the active
 (self-driven) piezo types have equal db output at MUCH
 lower operating current.

 Reg Neale

1999\07\24@083339 by Eisermann, Phil [Ridg/CO]

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> -----Original Message-----
> From: Paul B. Webster VK2BZC [SMTP:.....paulbKILLspamspam@spam@midcoast.com.au]
> Sent: Friday, July 23, 1999 7:07 PM
> To:   PICLISTspamKILLspamMITVMA.MIT.EDU
> Subject:      Re: [OT] self-oscillating magnetic buzzer
>
> Eisermann, Phil [Ridg/CO] wrote:
>
> > Does anyone know the long-term affects of this on the buzzer life?
>
>   No, but ... if the device is self-oscillating ("negative-resistance
> oscillator") and has no moving parts beyond the reed, why would it fail?
>
Well, I wondered about the same thing :) according to the rep, it
was "designed for a dc signal"  and "shouldn't be driven by an ac
signal" That doesn't tell anyone much, of course. I haven't been
able to contact any technical personnel yet. Hopefully they
will get back to me soon.

> > the board house substituted a "direct replacement" buzzer with
> > (nearly) the same characteristics.  Now, i'm starting to see
> > more failures than make me comfortable.
>
>   Can you define "failures"?  Failure to work under your conditions?
> Failure to work at original specification?  Won't work as built?  Fails
> later?
>
Sorry, i wasn't very clear on this.  It works as designed for while. I'm
running a test this morning to see just how long that is. After some
time, the sound pressure drops to a point where it is just barely audible.


Thanks for everyone's responses so far.

-Phil

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