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Old Feb 01, 2012, 01:00 PM
Slow Flyer
Bombay's Avatar
Richmond, TX
Joined Apr 2008
3,234 Posts
Question
Piezo buzzer help

Rookie/newbie question…

I dismantled a carbon-monoxide detector to salvage some of the parts for RC use. The detector ran on a 9v AC power supply and had a 9v battery back-up. I would like to use the alarm/buzzer for a rc project, but I have been unable to get it to activate.


I de-soldered it from the board. It has 3 pin-type connectors that are labeled G, F, and M…with the G being spaced slightly farther apart than the F and M. I have tried hooking up a 9v battery to the connectors in different arrangements, but have not been able to activate it.

Any ideas?


I found these schematics online (which I do not understand). The model of the buzzer is EFM-290ED

http://www.micromel-components.de/pi...0ed_290es_.htm
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Old Feb 01, 2012, 02:40 PM
Registered User
crazy4volvo's Avatar
Warsaw, Poland
Joined Mar 2009
49 Posts
This buzzer needs an external oscillator/amplifier circuit to operate. The schematic you found is an example of such circuit built with digital CMOS inverting buffers instead of audio amps. Pins G and M are the buzzer's "power" inputs. Pin F provides positive feedback signal which is amplified by CD4049 causing oscillations in similar way, as microphone connected to amp and loudspeaker. If you were able to dismantle a CO detector I'm pretty sure you can build such a simple circuit .

The buzzer alone acts like a capacitor, so you can only hear single click every time you change the polarity of the battery connected to G and M.
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Old Feb 07, 2012, 08:29 PM
Slow Flyer
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Richmond, TX
Joined Apr 2008
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Dziękuję !

Unfortunately, desoldering the parts from the board is about the extend of my electronics knowledge.

I'll keep it on hand if I decide to brush up on my electronics skills.

Thanks again
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Old Feb 09, 2012, 07:48 AM
Dave the Rave
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Joined Jun 2007
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Originally Posted by Bombay View Post
Dziękuję !
Gesundheit!
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Old Feb 09, 2012, 08:09 AM
Slow Flyer
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Richmond, TX
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Quote:
Originally Posted by dmccormick001 View Post
Gesundheit!
I'd recommend some heavy-duty antibiotics for that!
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