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Re: Can a piezo buzzer generate damaging voltages?

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On 10/12/2017 6:32 AM, petrus bitbyter wrote:
> 
> 
> "John Speth"  schreef in bericht news:ormah5$4ue$1@gioia.aioe.org...
> 
> On 10/11/2017 4:10 PM, Chris wrote:
>> On 10/10/17 00:15, John Speth wrote:
>>> My team is being asked to find out why a circuit is failing for no
>>> obvious reason. The circuit has a piezo buzzer (CEP2242 from CUI, Inc).
>>> The buzzer is driven by a MCU driven FET that completes a circuit like
>>> this: high side power 3.3V -> buzzer -> FET -> ground (BSS123LT1 FET on
>>> the low side).
>>>
>>> Does anybody have any experience with the possibility of a piezo buzzer
>>> generating damaging voltage spikes when dropped? We have no protection
>>> diodes on this part of the circuit.
>>>
>>> At this stage, we have no information of exactly what's failing. We do
>>> have evidence that some failed units have been dropped. I'm following
>>> through on a hypothetical failure path which we need to either consider
>>> further or discard.
>>>
>>> Thanks - JJS
>>>
>>
>> Piezo buzzers are capacitive, so do you have a load resistor across
>> the piezo ?, otherwise no current will flow other than for the first
>> pulse, which charges up the capacitance. A load resistor might fix
>> the spike problem, though clamp diodes to ground and to the +3.3
>> volt rail, to limit excursions, would be a better solution...
>>
>> Regards,
>>
>> Chris
> 
> |capacitance).  I suppose the buzzer has a built-in load resistor
> |because the circuit doesn't have a discrete load.  The data sheet
> |doesn't say one way or the other.  I'll need to look into that.
> |
> |JJS
> 
> According to the datasheet this buzzer is DC powered and it has a 
> driving circuit build in. The voltage range is 3-16 V and it will draw 
> 7mA max. Next to impossible to damage other components unless it is 
> defective itself or used in a very wrong circuit design.

Yep, you've exposed my ignorance :)  I totally missed that datasheet 
info.  While it doesn't eliminate the possibility of buzzer induced 
damage, I think it greatly reduces the possibility.

JJS

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Thread

Can a piezo buzzer generate damaging voltages? John Speth <johnspeth@yahoo.com> - 2017-10-09 17:15 -0700
  Re: Can a piezo buzzer generate damaging voltages? Clifford Heath <no.spam@please.net> - 2017-10-10 13:55 +1100
  Re: Can a piezo buzzer generate damaging voltages? o pere o <me@somewhere.net> - 2017-10-11 11:08 +0200
    Re: Can a piezo buzzer generate damaging voltages? Clifford Heath <no.spam@please.net> - 2017-10-11 22:37 +1100
      Re: Can a piezo buzzer generate damaging voltages? o pere o <me@somewhere.net> - 2017-10-16 09:56 +0200
  Re: Can a piezo buzzer generate damaging voltages? Chris <xxx.syseng.yyy@gfsys.co.uk> - 2017-10-11 23:10 +0000
    Re: Can a piezo buzzer generate damaging voltages? John Speth <johnspeth@yahoo.com> - 2017-10-11 16:46 -0700
      Re: Can a piezo buzzer generate damaging voltages? "petrus bitbyter" <petrus.bitbyter@hotmail.com> - 2017-10-12 15:32 +0200
        Re: Can a piezo buzzer generate damaging voltages? Chris <xxx.syseng.yyy@gfsys.co.uk> - 2017-10-12 14:31 +0000
        Re: Can a piezo buzzer generate damaging voltages? John Speth <johnspeth@yahoo.com> - 2017-10-12 13:48 -0700
          Re: Can a piezo buzzer generate damaging voltages? Jan Coombs <jenfhaomndgfwutc@murmic.plus.com> - 2017-10-15 18:12 +0100

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