I’m not sure how to connect everything [Uno to mp3/resistor to uno/speakers to everything]
It’s probably the most simple of processes but I’ve never done this before.
Well I’ve never used this particular MP3 module (it isn’t in the Arduino shield form factor, not a problem but connecting everything would have been a bit easier). However, after a cursory look at it you’ll want to wire up the “-” lead on each speaker (you mention “speakers” so I assume you have at least two) to the “A_GND” pin on the MP3 module. Then you’ll wire up the “+” lead on the speaker you want to be the right side speaker to the “R” pin, and similarly the on the speaker you want to be the left side the “+” lead will be connected to “L”.
As far as how to exactly interface it with the Arduino, it looks like you can use either serial commands or a 6 bit parallel I/O. I would look at the documentation to decide which you want to use. If you use serial you would use the TX (transmitter) and RX (reciever) pins on the Arduino, but wire them up to the opposites on the respective boards (so transmitter of one board goes to the reciever on the other, and vice versa). The other method would be to wire up six Arduino I/O pins to the IO1 thru IO6, and send numbers representing each command by a combination of 1s and 0s on the six wires. In either case the commands will be in hexidecimal (or HEX) so that’s why they appear in the documentation using both numbers and letters.
The conductive rubber will have to be cut into however many pieces you will need for your final number of audio tracks. However, you might want to experiment a bit with it still in one piece. In any case, you will need to connect wire (not necessarily with solder, but it can help ensure a consistent electrical connection) to each alligator pin and have them at opposite ends of a strip of rubber. That of course means that you will need a pair of alligator clips for each segment used by the final device, but these should be easy enough to get either online or at a local hardware or hobby store. Since this application is really only concerned with if a string is pulled and you don’t really care to know exactly how hard, you can use either analog or digital inputs on the Arduino.
Analog would allow you to measure the change in resistance and therefore calculate a force. If you want to use this method, refer to the thermistor tutorial. This is because even though they are measuring different things, they are resistive sensors and both normally need a voltage divider when used as an analog input. In your case, for an analog input you will need to determine a threshold value that will determine when the audio track is played. In effect this value will determine how much the rubber has to be stretched to be considered “pulled”. Have your sketch check each input pin if the threshold has been reached or exceeded and then play the appropriate audio track.
You could also use a digital input pin. The easiest way is to still use a voltage divider similar to the analog example. Yet, in this case the voltage divider will be set so when the rubber is in a relaxed state the voltage will between 3.5 VDC and 5 VDC. Voltages above ~3 VDC on Arduino digital input pins are treated as HIGH. Because the resistance increases when the rubber is stretched, it will eventually increase the voltage drop when stretched and cause the pin to read as LOW. So you still have a threshold, but it is one determined by your hardware, not software. Then your sketch would need to detect if an input pin has changed from HIGH to LOW, and thus play the associated audio track.