After looking around for solutions to build my project, I was fortunate enough to find the perfect circuit board which makes building this 10x easier - I don't have to code an arduino at all! (Hopefully)
Here's my wonderful shopping list:
As soon as my package arrived, I started testing the WAV Trigger. There's a bit of a learning curve, but it isn't very steep. There's an open source program that writes the init files which tells the WAV Trigger which ports do what and how - there are 16 available on the board but for now I'm only using 8 (a full tonic scale). This is all uploaded to a micro SD card along with all the WAV files. All I have to do is label them 001, 002, 003, etc and they're automatically assigned to their corresponding port.
Above is the very useful (but not very pretty) program to upload the INIT file onto my SD card. There's so much stuff you can do with this, and I'm definitely going to play around with it a lot!
I soldered a few header pins to test out different types of switches. I found that the roller switch (bottom) works the best for my prototype. Using this switch lets me be able to roll the car backwards and forwards on the track, while the others posed some mechanical difficulties with what I'm doing.
Some people suggested using sensors or reed switches, but after thinking about it, they might unnecessarily complicate the mechanics of the inner components. Sensors would probably need an Arduino to control the on/off levels and using reed switches in such close proximity would be difficult. I'm trying to keep this mechanical and I love the clicky feel to these microswitches.
On the left is the speaker, which works pretty well (Sparkfun doesn't have a very extensive speaker inventory). I was playing some noises when I set the speaker head face down over a roll of electric tape - the sound was so much better! I'm going to have to figure out a good resonator that doesn't take up too much space....
One problem I've faced is getting the WAV files to work - I'm not quite sure why, but only the sample WAV files that I downloaded on the product page produce sound when uploaded onto the SD card. Maybe it's because I've converted them to WAV files? Or that I'm using iOS when WAV files are for Windows? Not sure!!
Here's a little foamcore mockup I made just to play around with how small or big the car can be. Hopefully I can make the car as hand-sized as possible for the hands of the children. :)