So I have this Turtle Keychain, when u press it, two LED's light up and it does this cute chirping noise.
I was wondering how would that be possible using a simple circuit. Im guessing its a piezzo buzzer and a simple oscilator.
Trying prototyping something quickly and with a 555-timer simple oscilator i get a continuous "BRRRrrrrrrr" sound (1khz or something) wich isnt cute or fun at all.
Question is, how would i be able to tune the sounds to something enjoyable, instead of a continuous annoying sound.
Lets keep it as simple as possible since the goal is to make custom keychains =)
I would google for a datasheet that contains application notes / examples. There you will most probably find a description how to tune it. Anyway 555 is common most probably wikipedia will describe this.
First, you need a piezo speaker/transducer, not a 'buzzer" or anything with a built-in sound generator... If you hook-up a piezo speaker to DC, you shouldn't get a tone.
The proper "chirp" might have several characteristics... It could be a swept or varying frequency, it could be more then one frequency at a time, and it could be amplitude modulated or amplitude "gated"
It might be best if you generate some tones on your computer first, to see what you can do with simple tones. If you don't already have an audio editor, [u]Audacity[/u] is FREE. It can very-easily generate tones, and from there you can experiment with quickly fading the volume up & down and you can mix two or more tones, etc. It actually has a "chirp" generator effect built-in. (I haven't tried it.) The default chirp settings generate a tone that sweeps from 440Hz to 1320Hz over a duration of 30mS.
You should be able to drive the piezo directly off your soundcard, but your regular PC speakers (or headphones) are fine for experimentation.
Trying prototyping something quickly and with a 555-timer simple oscilator i get a continuous "BRRRrrrrrrr" sound (1khz or something) wich isnt cute or fun at all.
When you say "BRRRrrrrrrr", I get the impression of something less than 1kHz. But with Audacity, you can easily generate tones of different frequencies to see what 1kHz sounds like. (Most piezo transducers are going to have trouble with 1khz signals... They do better at higher frequencies.)
P.S.
Note that the 555 (and most digital circuits) generates square and rectangle waves, which are more "harsh" sounding than sine waves. So, if you want to simulate the sound of a 555 with an audio editor, you'll need to generate square waves.