>-----Original Message-----
>From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] 
>Sent: 06 October 2006 13:39
>To: Microcontroller discussion list - Public.
>Subject: Re: [EE] audio frequency sine oscillator help needed
>
>
>slippyr4 wrote:
>> I need to design a circuit such that a signal from a PIC 
>will cause a 
>> beep signal. My definition of a beep signal is aproximately 1KHz, 
>> close to a sine wave, and in the region of 75ms long. I need the 
>> output signal to be audio "line level" - which although 
>poorly defined 
>> seems generally to be regarded at 1V peak to peak, AC, driven by a 
>> lowish impedance. The audio signal I generate needs to connect to a 
>> line in jack on a tape recorder. The whole circuit runs in a 
>car - so 
>> it's a noisy environment. I'm not looking for Hi-Fi quality 
>audio, but 
>> it does need to be reasonable.
>
>Drive the attached circuit from a 0-5V PIC pin.  Use a 500uS 
>periodic interrupt to toggle all the pins you want producing 
>the 1KHz tone.  Set all the pins that are supposed to be quiet 
>to high impedence.  I think the tone purity will be good 
>enough.  I haven't figured out the exact resulting amplitude, 
>but I think it will be within acceptable range of a audio line input.
>

A quick simulation suggests approximately 1.6 volts pk-pk with the output unloaded, assuming 5v pk-pk input.

Regards

Mike

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