Music Box

The idea behind this circuit was to model the detection of the fluorescence emitted by the bacteria: if we apply an intense source of light directly to the light-to-frequency converter (which is the same than the one used in the prototype), it models a great intensity of green fluorescence (and thus supposedly a large concentration of Arsenic in the sample). If no light is applied, the light-to-frequency converter only senses ambiant light which models the situation when the concentration of Arsenic is so low in the sample that not much fluorescence is emitted by the bacteria.

The basic components of this circuit are the light-to-frequency converter (TSL235), a piezo speaker (to produce sound) and the arduino manage the input and output of the components. We also added a RGB LED to keep visual information, two potentiometers to modulate the sound produced by the piezo (one for the volume and one for the speed) and two buttons to be able to choose two different musics.

Note:

The LFT sends a squared frequency signal to the arduino. The file Counter.cpp counts the number of time the signal goes from 0 to 1 and it is this number of counts we compare to a threshold to determine if the light intensity (imaginary arsenic concentration) is acceptable or not. Our prototype shows here a limit because the threshold has to be adapted to the light intensity of the environment where the device is being used.

Here is the scheme of the circuit:

Fritzing scheme of the Music box

Fritzing scheme of the Music box


The arduino code ca be found here: https://github.com/biodesign-coco/Sonification/tree/Music-Box (don't forget to add the MusicPlayer library)

In order to finalize our prototype and our project, we decided to solder the components of the Music box on a printed circuit.

The EPFL has a small laboratory where you can design your own circuit. To have access to this laboratory, we had to follow an introductory course which was given by Manuel Leitos.

We then designed our printed circuit board using the EAGLE (Easily Applicable Graphical Layout Editor) software, which has a freeware version available. To learn how to use this software, we found a tutorial on Sparkfun. We added two different libraries on EAGLE in order to find our specific components. Both libraries are on github, the first one is Adafruit, and the second one is Sparkfun.

Components of the circuit: 1 arduino uno, 2 potentiometers, 2 push buttons, 1 RGB LED, 1 piezo speaker, 5 resistors.

The design of the a printed circuit on EAGLE happens in two steps :

First we created a schematic (once we found all the components, we connected them on the Schematic following the fritzing scheme) :

Schematic_MusicBox

Figure of the Schematic of the Music Box

Then we designed a board from the schematic. The board  is not created automatically: you have to dispose the components yourself so that no line crosses each other, because this will lead to a short circuit. We also had to be carefull on which side of the plate the components would be solder and therefore do the routes on the right side. That took us quite some time to achieve. Especially we had to design on Eagle the potentiometers because we couldn’t find the specific type that we had. We also modified the spots of the RGB led because they were too close from each other.

Board_MusicBox

Figure of the board of the Music Box

Once the design of the circuit was done, we printed both sides on two plastic films and we aligned them in order to have each on one side of the copper plate. The printing has to be done quite precisely because every mistake made by the printer is found afterwards on the PCB. This is also why we used two films for each side : the printer makes small random holes in the black area of our circuit (only seen with the microscope naturally) so if we add another film the random holes won’t be at the same place thus the result will be more precise. However in order to achieve this precision the two films had to be perfectly aligned with each other.

printing of the eagle board on plastic film

Printing of the eagle board on plastic film

Then, we went to the laboratory and followed a specific procedure:

  1. Wash the copper plate with water and alcohol to remove fats. We had to scrub the plate quite hard because the fat makes bad conduction so we want to remove all of it.
  2. Dry the plate in the oven at 80°C.
  3. Cover the plate with photoresist with this machine. The plate goes down in the tank and is removed automatically.
  4. Then put the plate in the oven at 80°C for the photoresist to dry (8 minutes)
  5. At this step we actually print the circuit on the plate: put the plastic films and the plate in the UV machine and the photoresist will go away only in the areas not covered by ink
  6. When we reveal the plate afterwards (with developer), the circuit is already distinguishable on the plate
  7. The plate is then put in the etching machine to eat away the remaining copper that is not covered by the circuit
  8. The final step is the stripping: the remaining photoresist is stripped away with alcohol, leaving only copper

IMG_6136

We printed it twice in case something went wrong. After that, we checked with the microscope that the printing was correct, we drilled the holes and we cut the circuit to have the following final result:

drilling the holes and cutting the plate

Drilling the holes and cutting the plate

Finally, the last step was to solder the components on the PCB but we didn’t finish that yet.

IMG_6150

 

 

 

 

 

 

 

 

 

 

 

Final current version of the Music Box

 

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