Kids ride-on beetle: custom sound board (Adafruit Audio FX)

So, this is a project that I 99% completed last year. I finished the final 1% today when I removed one part that I'd added on a temporary basis and replaced it with something more permanent.

First - the car. It's a 12v (2 x 6v) ride-on car that we got for my boy last spring. Here's some advertising blurb:

You'll see that the car comes with sound effects (a starting-engine sound and a horn) and the facility to plug in an ipod or other mp3 player so as to play one's music through the car's speaker. My boy doesn't have an mp3 player but was extremely pleased with the engine/horn sounds until, after about a week of ownership, they stopped working. As it happens, the volume for the horns (or mp3 player, if plugged in) is controlled by the knob on the dashboard. The knob operates a potentiometer which is attached to a small board which is programmed with the sounds and operates the led lighting. I've highlighted the knob on this library picture. The display next to the knob shows the battery voltage:

Now, we could have sent the car back to the seller at this point however that would have meant denying my boy his new toy. It would also have meant taking the whole thing apart and shipping the lot back to the seller. I decided that I would fix it myself and to hell with the warranty.

My first attempt at fixing the sound simply involved replacing the volume pot:

 This made no difference and my attention turned to the sound/lights board. To be fair, I couldn't really make head nor tail of it. However, I could see that it was horribly soldered and so I set about looking for a replacement. In the end, I settled on the Adafruit Audio FX Sound Board. I chose this because it comes with a built in 2x2W amplifier (the car's speaker is 7w and actually sounds pretty good). The soundboard will play WAV or OGG files and can hold 16MB of data. Data is added via the on-board micro-usb port. More to the point, the board can cope with 11 triggers which meant that I could add more buttons and sounds :). Here's a link to the official site and the picture below is the blurb and board I bought:

Once the board arrived I needed some more gear. This was mainly switches and wire. I also added an led to mount in the car's dash so that it was possible to see when the board was switched on (the board actually has it's own led but its surface mounted and cannot be seen if, like in this project, the board is to be mounted out of site). I also bought a key and barrel so that my boy could pretend he had an ignition key. Finally, since the car runs at 12v and the board runs at 5.5v max, I bought a battery holder for 3 AA batteries. I would use this to power the board and keep it separate from the car's own wiring. I got everything from CPC:

One balmy Saturday evening I set to work. First, some more holes in the dashboard for the extra switches. I also retained the car's original switches. The first picture below shows the standard dashboard. I removed the volume pot and the jack for the mp3 player. I also cut everything that looked like it was connected to the audio side of things on the car's sound/lights board. I then drilled holes for the five extra buttons, and modified two existing holes for the key and new led:

I then set about making the loom for everything:

Unfortunately I didn't take many pictures of that but the basic premise is that the new key switches the power from the battery pack. This illuminates the new led and powers-up the board. We then have a total of seven switches controlling sound. The switches are basic on/off type. The way the board responds to the switches is determined by the names given to each sound file. So, some switches play one sound in full when pressed. Others play a sound on a loop until pressed again. And one only plays a sound as long as the switch is actually pressed. Clever stuff. Here's a bad picture of the finished article:

And here's a vid of all the buttons doing their stuff. I downloaded the sounds off the internet. I was particularly pleased with the engine start sound which really does seem to be a VW Beetle setting off!

So, that was last spring. Since then, we've been through about four sets of batteries. That's not so bad, but since I didn't want my boy to fiddle with the batteries, I'd mounted the holder behind the dash. This meant removing the dash each time the batteries went flat. This was always a pain in the ass which brings me to the final 1% of the project: removing the separate batteries and wiring the sound board into the car's power using mini step-down transformer:

You can get these all over the place but I ordered mine from FastTech because I happened to be ordering a load of ecig stuff at the time and FastTech were only charging £1.30 rather than £15 or so from a UK seller. Today I cut the transformer into the power circuit for the car's LEDs. The circuit runs at 12-14v and I set the transformer to step-down to 3.9v. The board will work with a supply as low as 3v but the volume is a bit lower at that rate:

Everything is now back together and working well. Hopefully I'll never need to take that dashboard off again...

The video above is from last summer.

More soon, no doubt....

D