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Buzzer Help

Rajinder

Jan 30, 2016
542
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Jan 30, 2016
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Hi,
I have attached a copy of the voltge seen on a piezo buzzer. I need to ckamp this to 3V3 and then detect the edges of the waverform at 1.17 secs, feed this into a microcontroller and measure the time between pulses.

I was thinking of clamping the wavefor which is 30V by using a suitable resistor and zener diode at 3V3 or around that figure. This will remove the negative going part of the waveform. Then feed this into a differentiator to detect the positive edges and feet into a microcontroller I/O pin.

If the piezo was say operating at 20mA (for example), to calculate the series resistor with the zener is it simply a case of 30-3v3/20mA. Then ensuring power requirements can be satisfied i.e. wattage of resistor.

would this be then suitable to connect to the differentiator circuit? or would i need some further signal cleaning after the differentiator stage?

any help would be appreciated.

Best regards,
raj
 

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Arouse1973

Adam
Dec 18, 2013
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It must be the water draining away some of the magnetic field :)
 

Alec_t

Jul 7, 2015
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is it simply a case of 30-3v3/20mA.
Not unless you want 20mA flowing through the zener. The buzzer current is irrelevant. Make R=(30-3.3)/Izener. A zener current of just a few mA should be enough.
 

Rajinder

Jan 30, 2016
542
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Jan 30, 2016
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Thanks. If I put 5mA through the sender, that should be ok? Would there be a problem with the differentiator part of the circuit, just to detect edges or is there a better way to achieve this?
Best regards,
Raj
 

Alec_t

Jul 7, 2015
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Personally I'd use a CMOS Schmitt trigger, instead of a differentiator, to get sharp pulse edges.
 
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