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Topic: * MP3 Shield * - Rogue Robotics rMP3 (Read 44 times) previous topic - next topic

Vertigo

#145
Jan 05, 2011, 03:20 pm Last Edit: Jan 05, 2011, 03:22 pm by Vertigo Reason: 1
Thanks Mowcius for your reply.

The project is simply a talking robot. I got 3 cards because we should use two robots in the future (+1 spare ::) ).

You got my idea exactly : rMP3 deserves a simple manual, tutorial or web page for arduino users, explaining "only" essential points such as
- what the board is for and can do (file formats, etc ...)
- input : what arduino pins are used and how to reroute pins if needed
- output : what speakers can be used (still working on this obviously)
- content of the rmp3 lib, and how basic functions work ...

Not saying the rMP3 is poorly documented at all, but the waveshield pages for example are more friendly, at least to my level of knowledge http://www.ladyada.net/make/waveshield/index.html

If I go back to the speaker issue, Mowcius, I'm using two 50mm 0.5W 8ohm speakers in series. As I wrote above the sound is pretty low, lower than a normally speaking person (that's a standard ;) ). Here's what I checked and tested :
- rMP3 : set volume to 0 (max)
- rMP3 : boost bass
- file : normalized to 100% (I tested other music mp3s, too)
- speakers : connect only 1 speaker, hence 8 ohm instead of 16. I was affraid to burn the card. Did not burn, but the sound was not louder.

Am I missing something ? what do you mean by "This depends completely on the speakers" ?

I measured the rmp3 output on my scope, it ranges between +/- 0.8V, is it supposed to be so ?



mowcius

#146
Jan 05, 2011, 04:35 pm Last Edit: Jan 05, 2011, 08:40 pm by mowcius Reason: 1
Quote
Am I missing something ? what do you mean by "This depends completely on the speakers" ?

What housing are the speakers in? Try taking a speaker out of it's speaker housing and see how much quieter it sounds.

Like anything, you can get good and bad speakers, better ones will be louder for the same impedance.

I will try to do some work on a simple guide to the rMP3 for arduino - if I can understand it - most other people should be able.  ;)

Mowcius

bhagman

Hey Vertigo,

I totally agree with you about having a tutorial or such for Arduino/Wiring etc.

I'd be willing to work out something for anyone who wants to build up a tutorial/howto on our wiki.  And I'll definitely take you up on your offer to translate to French.  Just email me and we can get things worked out.

RE: speakers - the audio output on the rMP3 (i.e. from the VS1011) can only drive a 16 Ohm impedance load minimum.

Impedance is only half of the equation though.  All speakers have two ratings: Impedance and Watts.  To effectively use your speakers to produce the sound level for which they have been designed, you need to drive it with enough current to move their coils.

For example, an 8 Ohm speaker rated at 25 Watts will require 14 Volts (RMS - Root Mean Square - roughly means average) to produce maximum output swing on the speaker coil.

The VS1011 can only provide 2 Vpp (2 volts peak to peak maximum, and typically 1.6 Vpp - which is what you've measured).  It is designed to drive headphones or a line-input, and hence it will not be able to effectively drive the two larger 8 Ohm speakers in series.


We are designing a small amplifier board that one can use with the rMP3/uMP3 to drive small speaker loads. Follow us on Twitter and we will announce when it's ready.

In the meantime, you can use a cheap set of pc speakers - they are usually amplified and cost very little.

b

--
Wiring - Open Source Electronics Prototyping Platform
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jennyc

Hey,

I have recently got my rmp3, and was wondering how do I get the mp3 songs that are playing on the rmp3, to act as an input to an Arduino module?

I would like to have the songs playing and controlled from my rmp3, and then analysed for frequency on my arduino module to activate different output pins for different frequency pitches?

Thanks

Jenny

mowcius


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