Tinkering Loudspeakers

It has been quite a while here in this blog lately, but it does not mean that nothing is happening.

I am working on an interesting performance project with a singer and a sound recorder. This performance requires quite expensive equipment, so we need to get external support for financing before we can continue further. However, this project has made me study more deeply programming languages such as Processing, VVVV and Pure Data.

In the mean time I have continued in my other project where I will make "an audiobook" of my own. For this project I need to have loudspeakers that are as flat as possible. This has proven to be quite difficult task.

Passive speakers as such are not a good option, because Arduino (+ Mp3 player) will not be able to feed enough power to them. You can get some signal out, but the sound is so silent that it is practically useless. I tested several passive speakers with Arduino/MP3Trigger and the results were poor. Therefore I needed to have some kind of powered amplifier to get reasonable loud sound out of the system.

I could have tried to make a powered amplifier by myself, but it would not be flat enough for my purposes. Then I finally remembered that what I need was actually already  in my storage !! Cheap, ready-made speakers intended for MP3 players.

I had bought some HAMA loudspeakers couple of years ago. At that time, I was not satisfied them, because they were too bulky. Because I was not using them, I though it does not matter if I broke one down to see if there is something useful inside.

And there was everything what I needed: a very small and neat power amplifier and quite flat loudspeakers!! I just needed to remove one led (only indicating that the device was powered).  I also modified the circuit so that the device is always on if the external power is connected. I got what I wanted easily and much cheaper than if a have bought parts and build everything from scratch (HAMA loudspeakers costed about 10 €)

The lessons learned could be that tinkering your old useless gadgets might be more worthwhile that buying new stuff.


p.s. While looking for some help from internet, I found interesting link that showed how to make very flat loudspeaker from fabric. Although they are not very practical to my "audiobook" project, I will definitely try making my fabric speakers in the near future.

The most stupid Arduino mistakes I have made

Lets face it! There are stupid mistakes, and most of them are repeated time after time. At least I do it !

Luckily you will gradually learn to check the most common causes before panicing and causing more severe mistakes than the original one. Here are a list of the most common and "stupid" problems I have faced while working with Arduino.

ARDUINO

Actually I have been lucky and I have never broke any arduino board by causing short circuits  etc. I think the reason is that I am always using RED wire for the power and BLACK wire to the ground. And I never ever use these wires to connect data ports. 

I have also learned to CONNECT FIRST ALL GROUND WIRES before connecting anything else.  Possibility to have some kind of voltage peaks while connecting the circuit to the power source is diminished.

One weird error happened once with my robot - it started to move by itself when I put my hand near it!!

It took some time to figure out the reason. My robots have two arduino board that are connected together. The first arduino was controlling the motors and the second one was handling all the communications and data from sensors. Obviously the data signal that commanded first arduino to steer motors was floating. When I approached the robot, the state of that data signal changed due to my capacitive load I was introducing to the circuit.

The reason was naturally as simple as that these two aduino boards did not had a common ground. The correction was easy. I just connected all the ground signals to one common ground. Since this, I have remembered to check that my circuit will allways have only one common ground. The lesson was learned.

ARDUINO + MP3 PLAYER

1) You connection should  be OK, but the MP3 files are not playing

- Are you sure that you have correct memory card in the MP3 player?
- Are you sure that you have turned the loudspeaker on?
- If you use serial connection : are the RX and TX signals cross-connected?  the RX port of the arduino should be connected to the TX port  of the MP3 player, and vice versa.
- Have you renamed your files in PC having Windows operating system? Windows may add EXTRA suffix at the end of the file without showing it!! You may think that name of your file is for example TRAC0001.MP3 but actually it is TRAC0001.MP3.MP3. In this case the MP3 player will not recognize the file. I have learned to check the filenames by using MS-DOS/Windows promt before moving them to the memory card.

Robots don't cry?

My art piece: ROBOTS DO NOT CRY? is currently presented at juryed exhibition ARTISTS 2010 by Finnish Artist association. Exhibition has 93 artworks that were selected from 1841 proposed ones.

The exhibition is at Tampere, Finland. My work is at Galleria Nottbeck. The exhibition is open during 30.10.-5.12.

The artwork consist of three robot balls that are covered by woolknit. These robotballs present crying songs (laments) that describes different feelings from joy, frustration, and sorrow. The crying songs have been traditionally presented at funerals, weddings, and other social situations. While presenting the songs, they also move slowly.

More information about this work can be found from my web pages.

Playing music with Arduino + VMUSIC2

23.5.2009 I got first sound out of Mp3 player that was controlled by arduino. I used VMUSIC2 module, which can play mp3 files from USB memory stick.

I needed to update the firmware in order to make it working with all available commands (for example volume control).

VMUSIC2 module is not very well documentes so big thanks goes to Arduino forum for good hints (http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1187669098) and http://www.instructables.com/id/Getting-started-with-VMUSIC2

After updating the firmware, the VMUSIC2 started behaving like the manual described.

After reading the manual more carefully, I noticed that the MPEG3 chip was actually a product of VLSI solutions - A Finnish company located about 300 meters from my working place at the same campus.

Well now I certainly know where I will call if I am having problems with VMUSIC2 mp3 decoding :-)

See also following links for useful information: http://byungjun.pe.kr/xe/?document_srl=20431 and Vmusic-tips-and trics

Eventually, I did not use VMUSIC2 because all USB sticks I found were too big to fit properly to the robot chassis I was building. Instead I used MP3 Trigger with microSD card.