Hi,
Im using a Piezo Audio Indicator model KPE-276A
http://www.datasheetarchive.com/pdf-datasheets/Datasheets-12/DSA-228130.pdf (not using the KPE-276 because this one is louder..)

It is part of a Circuit which can get 12-24V and since it can tolerate up to 20V i put a resistor 500 oham in serial to it.

simple schematic (w/o the relay and holding circuit):
Vcc-------Resistor-------Speaker-------GND

The Speaker works but sometimes it makes a very low sound as if choking.
when i connect it directly to Vcc 12-20V it works perfect allways.

Is there a problem connecting a resistor to Piezoelctric device ?
Do i need a different resistor or maybe put diode instead .... ?

Thanks in advance.

 

Hello,

Perhaps you could use a 4.7 Volts zenerdiode in series.

Greetings,
Bertus

 

Thanks, I did run it with Zener and it worked fine, but so did the Resistor in the begining (i found the problem few monthes after the card started to work...)
I want to understand why the Resistor is causing Problems.

Thanks again.

 

It is supposed to be driven from a low impedance supply.
Its voltage varies wildly when it is fed through a resistor. The resistor reduces the voltage only for part of the cycles.