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Noisy buzzer on PIC output

B

Bill

Jan 1, 1970
0
I am driving a piezo buzzer (RS 273-074 3-16v DC) from one of the outputs
of a PIC16F88. I am getting a very faint buzz from the buzzer even when the
PIC output is low (almost like I am picking up the clock oscillations).

I have tried .01uf caps both in parallel and series with the buzzer. I have
also tried .01uf on the power supply leads of the PIC. I have also tried
pulling the buzzer H and L with 10K resistors.

Any ideas how I can supress the noise.

Thanks
 
J

John Fields

Jan 1, 1970
0
I am driving a piezo buzzer (RS 273-074 3-16v DC) from one of the outputs
of a PIC16F88. I am getting a very faint buzz from the buzzer even when the
PIC output is low (almost like I am picking up the clock oscillations).

I have tried .01uf caps both in parallel and series with the buzzer. I have
also tried .01uf on the power supply leads of the PIC. I have also tried
pulling the buzzer H and L with 10K resistors.

Any ideas how I can supress the noise.
 
J

jasen

Jan 1, 1970
0
I am driving a piezo buzzer (RS 273-074 3-16v DC) from one of the outputs
of a PIC16F88. I am getting a very faint buzz from the buzzer even when the
PIC output is low (almost like I am picking up the clock oscillations).

I have tried .01uf caps both in parallel and series with the buzzer. I have
also tried .01uf on the power supply leads of the PIC. I have also tried
pulling the buzzer H and L with 10K resistors.

Any ideas how I can supress the noise.

try a pair of anti-parallel 1n914 diodes in series with the piezo.
a pull-down resistor on the pic output may help too.

Jasen
 
J

John Popelish

Jan 1, 1970
0
Bill said:
I am driving a piezo buzzer (RS 273-074 3-16v DC) from one of the outputs
of a PIC16F88. I am getting a very faint buzz from the buzzer even when the
PIC output is low (almost like I am picking up the clock oscillations).

I have tried .01uf caps both in parallel and series with the buzzer. I have
also tried .01uf on the power supply leads of the PIC. I have also tried
pulling the buzzer H and L with 10K resistors.

Any ideas how I can supress the noise.

What does the other side of the piezo connect to?
Is the supply for the PIC bypassed?
What else is running on that supply?
 
A

Anthony Fremont

Jan 1, 1970
0
John said:
What does the other side of the piezo connect to?

That's what I was wondering, hopefully not a car battery. :-O I assume he
only needs DC applied and not a pulse train. Given that, I'm thinking that
the other end is connected to a voltage slightly higher than the PIC Vcc or
lower than it's Vss allowing current to flow thru the protection diodes. If
so, it'll probably take care of itself when it burns out that diode. ;-)
Is the supply for the PIC bypassed?
What else is running on that supply?

I'm betting on your first question. JF's idea should work fine too, but I
think the OP should find out what the real problem is. It's most likely not
the PIC, unless the output port is somehow damaged.
 
J

Jack B. Pollack

Jan 1, 1970
0
I am driving a piezo buzzer (RS 273-074 3-16v DC) from one of the
outputs
try a pair of anti-parallel 1n914 diodes in series with the piezo.
a pull-down resistor on the pic output may help too.

Jasen

Thanks,

The diodes did the trick :)
 
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