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Beep on Power On

Thu Feb 28, 2013 5:42 am

I would like to play an audible beep to indicate that my RASPI has power on. I would like to play this beep (or sound) as soon as power is applied.

Would you recommend using the GPIO pin for this? What hardware do you think I would need - I have very limited electronics skills, but can sought of manage a soldering iron.



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Re: Beep on Power On

Thu Feb 28, 2013 8:22 pm

You want this just when power gets turned on, or occasionally so you know the power is still on?

As soon as power gets turned on, the Pi will boot, so you could have it play a sound file at startup, although it would get through some of the boot sequence first. But you need some sort of speakers to play the sound. Not sure you need to use the GPI pins, unless you really want this to happen the very moment power is applied. Which OS did you install?
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Re: Beep on Power On

Thu Feb 28, 2013 11:35 pm

Thanks for your reply. I am using the Raspian Wheezy distro from the raspberry pi website.
Actually, I know how to play sounds through the speaker, what I am hoping for is a way for the Pi to "beep" as soon as power is supplied.
Any thoughts?

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Re: Beep on Power On

Thu Feb 28, 2013 11:54 pm

It can be done but I'm curious why you want the Pi to beep when it should be fairly obvious when its turned on??

You can do this using the GPIO 14 (TXD), just before it boots this pin is set low (0v) for a spit second and then goes high (3.3v) when its active.
An appropriate circuit would be needed to detect 0v to produce a buzzing sound and then turn off when 3.3v is detected.

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Re: Beep on Power On

Fri Mar 01, 2013 7:05 am

This could be done a number of ways with simple circuits conneted to the GPIO power pins. For example:

1. A capacitor that charges slowly from the 5v line, driving a transistor that runs another pair of transistors as an oscilator to produce the sound, stopping one the capacitor is charged.

2. A pair of 555 chips (or a 556). One in single-shot mode running for 1 second, triggering the other which drives a speaker at a set frequency.

3. (Less components, but more work). A simple PIC chip, programmed to produces a square wave on one pin for a second, then halt. (I would go with this, as I have a few spare chips around and have written code to do something along these lines, but a bit more sophisticated. It could be easily trimmed down to the code needed).

As the saying goes: "The world is the mollusc of your choice" ;-)

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