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Author Topic: PWM / Sound / Wireless (walkie-talkie)  (Read 1758 times)
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I have an idea about sending sound (through PWM) with this schema from 1 Arduino to another Arduino:

Arduino -> walkie talkie tx --------- air ------- Walkie talkie rx -> Arduino.

After reading http://www.arduino.cc/en/Tutorial/PlayMelody, I think it is possible. What I actually want is sending data, not sound, from 1 room to another room. I know for most walkie-talkies (frs/gmrs) this is not allowed, but since the Walkie-talkies I will be using are really toys, I don't see much of a problem.

The first Arduino is offering sound (data through PWM) to the first Walkie talkie microphone. The 2nd Walkie-talkie receives sound and offers the sound to a 2nd Arduino, 2nd Arduino reads it through Analogread() and converts it back to data.

Any ideas if this is doable?

Thanks,

JD
« Last Edit: May 23, 2008, 09:02:56 am by jds » Logged

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I've never done that, but it  might be possible. Some hypothetical bottlenecks:
1:  distortion from slow response of the amps causes ramp on Low->Hi and Hi->Low transitions so the recieving analogIn may somewhat lag behind.
2: noise. Very cheap toy walkie-talkies hiss, spit and krackle. You may need to shunt some high frequencies to ground with a capacitor.
3:Unintentional voltage bias: could/should we prevent output from the recieving walkie-t.. below 0 volts , maybe with a diode to ground? Disadvantage is we add more lag in the signal.

I guess you can make some schmitt trigger from the alalog value, have a threshold value to gate out the noise floor, and have the rest interpreted as being a full 5volt High signal.

Edit: I think you can send from a digital out pin, as you're only sending data. No need to send from a PWM pin, but to recieve on an analog pin has the advantage of tweaking out signal artifacts.
Also, you could eliminate errors from the speaker and microphone by directly attaching the Walkie-t's  amp output  into arduino.  
You can still have the cool "look at this!" factor  by faking it and detaching the microphone  ;D .

 I hope you can pull this off, it would be loads cheaper than bluetooth....
« Last Edit: May 29, 2008, 07:06:17 pm by electri-fire » Logged

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