# Total newbie question:

Discussion in 'Electronic Basics' started by Blarg, May 26, 2004.

1. ### BlargGuest

How do I get a piezo-electric buzzer to make an audible sound? I've heard
that I need an IC circuit to
'drive' the buzzer, but I can't seem to find out what an IC driver circuit
consists of.

I'm trying to make a super compact circuit that will make a sound at low
(1.5-3.5v DC) voltage.

2. ### SoerenGuest

Hi,

The term "buzzer" is normally used for those which contains the driver
and only needs a supply voltage. They can be found with working voltages
down to 1.5V.

If a driver is needed, you only have a raw piezo disk, which must be
driven by an oscillator - preferably one with a transformer coupled
output, if you want it to be loud when run from a low voltage.

--
Regards,
Soeren

* If it puzzles you dear... Reverse engineer *
New forum: <URL:http://www.elektronikteknolog.dk/cgi-bin/SPEED/>

3. ### ZwoxGuest

How do I get a piezo-electric buzzer to make an audible sound? I've heard
With a piezo buzzer you should only need to connect the buzzer to a DC
source to hear an audible tone. Try connecting your buzzer to a single AA
battery and find out. It's different if what you have is a piezo-electric
transducer, in which case you will indeed need an oscillator.

Zwox

4. ### CFoley1064Guest

Subject: Total newbie question:
Hi, Blarg. The smallest piezo beepers don't have drivers built in. They're
just piezoelectric disks, to which you have to apply an AC voltage at the
appropriate frequency to get them to beep. The piezo elements will output a
voltage if they're flexed, and will flex if you apply a voltage. Since sound
requires a "back-and-forth" flexing, you need an AC voltage.

I'd suggest getting a beeper with the drivers built-in. That'll probably be
the smallest solution, even though their package will be somewhat larger.
However, if you've got a few gates of a 74HC14 to spare, this will work down to
3VDC or so (view in fixed font or M\$ Notepad):

Piezo Element Driver
___
.--|___|--.
Control | 33K |
Signal | | .-.
___ | |\ | || || /|
o-|<-|___|-o -| >O---o-------|| ||-----O< |--.
3.3K | |/ | || || \| |
1N914 --- | || || |
---.1uF | '-' |
| | |
| '-----------------------'
===
GND

The first schmitt triggered inverter acts like an oscillator, and the second
inverts that output to drive the other side of the piezo element. It won't
work very well for larger elements, because they have larger capacitance, which
strains the HC14 output FETs and leads to reliability problems. You're driving
a capacitance here. It will work fairly well, however, for *small* piezo
elements. Note that when one side of the element has 3V across it, the other
side has 0V. When the oscillator changes states, the voltages are reversed.
Voilla, AC. The control signal input swamps out the oscillator feedback when
it's low, and lets it oscillate when it's high. If you don't need control,
just omit the 3.3K resistor and the diode, and it will beep when you power it
up.

You might have to tweak the R value a little to get the desired frequency, but
this will get you started, anyway.

Good luck
Chris

5. ### Robert C MonsenGuest

I like CFoley's solution. You can also drive it with a 555, which
might give you slightly better control and predictability for the
frequency. There are circuits all over the internet for this, so just
go look around. A 555 at radio shack is about a buck.

Regards,
Bob Monsen

6. ### BlargGuest

Thanks to all. Cfoley, your solution seems elegant, but is way over my
head. I also must ask, what is a 555? Some type of
oscillator circuit?
My circuit needn't be controlled beyond on and off. A continuous tone is
fine.
Here's the tricky part: The whole thing, including battery, must weigh
under 2 grams.

Again, thanks to all who responded!

7. ### SoerenGuest

Hi,

Then your best bet is an astable multivibrator made from a couple of SMD
transistors, driven from the tiniest button cell, but getting below 2 grams
will be tricky still.

With the piezos terminals driven from the collectors, you should be able to
get a (not very loud) sound.

--
Regards,
Soeren

* If it puzzles you dear... Reverse engineer *
New forum: <URL:http://www.ElektronikTeknolog.dk/cgi-bin/SPEED/>

8. ### Rich GriseGuest

For the absolute minimum, see if you can get a 3-lead transducer -
the 3rd lead is a feedback lead, so it, one transistor, and two
resistors make an oscillator. I don't know exactly what the
element is technically called, but someone here probably does.

Good Luck!
Rich

9. ### CFoley1064Guest

Subject: Re: Total newbie question:
Hi, Rich. Paradoxically, these 3-lead devices are called "self-drive" beepers.
You need a transistor and a couple of resistors to get gain for the feedback
to create self-sustaining oscillations. Here's an example:

http://www.murata.com/catalog/p37/es0041.pdf

Good luck
Chris

10. ### Robert C MonsenGuest

A 555 is a timer IC, which also makes a pretty good oscillator, given
a couple of resistors and a capacitor. You can use it to create the
"A/C" waveform you'll need to drive your little piezo thingy. I have a
'get up and move' circuit that makes me get up and push a button
across the room every 20 minutes (So I'll stretch my back, I have back
problems.) It uses a 555 to drive a piezo thingy, and a timing
cap/resistor to delay the buzzer from going on for 20 minutes using
the reset pin on the 555.

FYI, I suspect you won't be able to get a battery that is as light as
2 grams. I'd rethink the specs. Take a look at the battery specs on
www.duracell.com for some clues about battery size.

I'll send you a schematic for the nag circuit if you want.

Regards,
Bob Monsen

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