more volume

RickM

I'm using freqout to the pizo.
I want more volume, how do i do this
thanx
rick

Steve Joblin

You will want to use an LM386 (http://www.national.com/ds/LM/LM386.pdf) amplifier chip... page 5 shows simple circuits that requires just a few ressitors and capacitors.

RickM

thanx
it appears the LM386 draws 4ma, can i use power from the basic stamp2 or do i need external power source
rick

Steve Joblin

Here is a great link I just found... http://braincambre500.freeservers.com/LM386 Audio Amp.htm

I would power the amplifier directly from the your power source.

Beau Schwabe

RickM,

This link might help... http://forums.parallax.com/showthread.php?p=464410· I'm not sure that a LM386 in a typical speaker configuration is adequate for driving a piezo.· In other words remove the series capacitor on the output of the LM386 if you decide to go that route.



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Beau Schwabe

IC Layout Engineer
Parallax, Inc.

RickM

Thanx All
I will try the LM3386 w/ a speaker......
Now... what if I want to play a .wav file?

Phil Pilgrim (PhiPi)

Here's a simple circuit that will provide a higher peak-to-peak voltage to the piezo:



The two op amp halves are connected as comparators, which compare the filtered input voltage from the Stamp to Vdd/2 (2.5V). (The reason for using an op amp instead of a comparator is that it has both high-side and low-side drive. Most comparators have open collector outputs.) The piezo is driven differentially. On my BOE, with Vin = 12V, I was getting a 20V P-P drive on the piezo speaker.

Since the output is a square wave, you won't get faithful reproduction of sine waves or dual-tone FREQOUTs. For that you'd have to add feedback to the op amps and treat them as linear amplifiers instead of comparators.

-Phil

roboman01

If you want more volume, then just get a piezo with a higher dB rating.