|Feb 01, 2012, 02:00 PM|
Piezo buzzer help
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.
I found these schematics online (which I do not understand). The model of the buzzer is EFM-290ED
|Feb 01, 2012, 03:40 PM|
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.
|Feb 07, 2012, 09:29 PM|
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.
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