Speaker control circuit

Hi,

I want to make circuit for interfacing speaker with microcontroller using audio amplifier. i have few queries regarding controlling the speaker. Kindly help me to clarify.

1) To vary the tone, can i change the input frequency to speaker ?
2) To vary the volume, can i change the input current or voltage to speaker ? Suggest me any application circuit or concept(no pot adjustment).
3) My input is battery supply(DC), Can i apply peak to peak square wave to speaker for its operation?
4) As per IEC60601-1-8, how to generate harmonics with fundamental signal to control the speaker? Suggest me any circuit or concept.
5) How to select amplifier for controlling 4ohm or 8ohm speaker ? and
6) How to calculate maximum input voltage for speaker ?

Thanks...

I suspect that you want an alarm that produces a beeeep sound.
1) The tone is the way the harmonics are arranged (a smooth sinewave with no harmonics or a harsh squarewave with many harmonics). I think that you want to change the frequency (pitch) of the tone, not the harmonics.

2) The volume output of an amplifier is controlled by the voltage of the signal at it input. You could also feed a fixed input level and vary the voltage gain of the amplifier.

3) I think your input is a signal, not a battery. The battery is the power supply, not the input signal.
An amplifier that has an input signal that is too high has clipping and produces squarewaves that sound harsh.

4) I do not know why you want to add harmonics to the fundamental frequency of the input signal.

5) An audio amplifier has a rated output power and a rated power supply voltage and current. For your tone, you probably do not care about the amount of distortion and noise (hiss and hum).

6) Test different levels and measure and select one that is loud enough.

1) Yes

2) If you use a class D part (you may be able to find a Class AB as well) for
amp there are parts that can manage volume over I2C link to micro. TI has parts
as do many other vendors....

3) Yes on square wave, you just have to meet P specs on the speaker.

4) Any detail on what harmonics you want. Of course square wave is rich in harmonics.

5) Generally you start with power spec, then look at architecture, Class D or AB or.., then
control ability (like power down/sleep modes, volume control, filtering), then distortion,
Z......

6) Speaker specs will determine I and V for speaker.

Just as FYI there are micros that can do Class D as well as general tasks, here is a basic
Class D approach with filtering, one chip (still needs external power fets) -




Regards, Dana.