Friday, November 18, 2011

Audio Tutorial: Add Sound To Your Cake

Hey gang!  You remember on Tuesday when I mentioned that we had Tow Mater talking on the cake we did for Kaben's birthday?  Well, I asked Chaddy to put together a little tutorial on just how he did it (it was in fact all his idea).  I'm sure every toy is made and put together differently; but this was our first experience with it and it really wasn't too hard!  So I'll let Chaddy finish this from here on!  Enjoy!

As we were designing the cake for Kaben and the Tow Mater element was discussed, we went out shopping for a model to use for sculpting.  Lucikly, Cars is still a big thing and our local Target had plenty of toys to  choose from, including one that said a few phrases each time you pushed a button on his hood.  I thought it would be really cool to add it to the cake design.

I put a lot of time into deciding exactly how it would get implemented, but my first problem was whether or not I could get the module out without breaking it.  This is how I did it.

Tools / Items that came in very helpful during this project:
  • Talking Toy (duh!)
  • Small Screwdriver Set
  • Electrical Tape
  • Hot Glue Gun
  • Exacto Knife
  • Small Hobby Hacksaw

Click on any image in this tutorial to see a larger version
OK, now that we have our toy, how do we get into it?  Well, if we want to get to the bottom of things, flip this little guy over and see what's on the bottom.

OK, there's some screws here so that's a good place to start!  I started by opening the middle screw first as I figured that housed the batteries.

Yep!  There's the batteries!!  Now I'm no electrician by any stretch of the imagination, so I'm going to leave this alone for now and remove the screws in the front and back.

With those 2 screws removed, the bottom opens right up.  The little wheels were on a small metal axle and lifted right out.  I saw lots of electronic stuff there inside, and that's what we want!

To my surprise, none of the pieces were really secured at all.  A little gentle tugging and the every came right out!

With everything out, we can set the top of the toy to the side.  From now on, I will refer to the elements of the toy with the letters above:

  • A - Battery / Power
  • B - Voice Module Chip
  • C - Switch
  • D - Speaker
  • E - LED light (we didn't use this as an element in the cake)
OK, so I had everything out... did it still work?  I pressed and button, and it did work, but the sound was very faint.  Had I broken the speaker while removing it?  I looked at it and it appeared to be in tact.  I placed it against the plastic case of my screwdriver kit and hit the button again.  This time it was much louder and it sounded just right.  The speaker needs something to vibrate against which makes it the speaker.  I guess it  works like the talking greeting cards.

I wanted to try and salvage the toy (we still needed it as a model), so at this point I used a small hobby hacksaw to cut out the battery pack (the red/black striped areas) and I was actually able to get the toy completely back together, and I'm not really the mechanical type.

Since I know the speaker needs something plastic or paper to vibrate on, I decide that placing the whole rigging in the underside of the cake drum.  It was at this point that I found that the battery pack I tried so hard to keep together was way too big to fit in the quarter inch space that the cake drum would allow.  I took the batteries out (3 small pill type batteries) and wrapped them together in electrical tape, making sure the positive and negative ends were still exposed.  I then cut the battery pack down until it was just the 2 contact ends with the lead wires on them.  I placed them on the proper ends of the batteries and used a little more electrical tape to hold them in place.  I then pushed the button and made sure I still had sound - yep!  (Sorry I didn't get a picture of that part).

Then I looked at the amount of wire I had between each component and started making small cuts on the underside of my cake drum.  It's just corrugated cardboard on the inside, so you can make a little cut and peel out a layer with your finger.  I did this for each of the components.  The unused LED light?  I just stuck it inside the hole I made for the Voice module (B & E).  I also made a shallow cut between all the boxes so I could run the wires.  If you can make your holes just the right size, everything will fit nice and snug.  If you have some wiggle room, just use a little hot glue to secure things down.

For the switch, I decided that it would look best if it was on the side of the cake board (see "C" above).  I cut a small notch out of the side and it fit in there perfectly.  A little dollop of hot glue held it in place.  At this point I taped a piece of cardboard over the rest of the components, except the speaker.  We later covered the cake board in foil to hide the switch, but you could have just as easily covered it with ribbon, just make sure to keep the speaker opened and the button revealed.

Here's a video of the finished project, with sound!!

We later learned that once the cake was on the board that the sound did get a little muffled again.  Luckily, we were able to have Jenniffer's brother make a couple of support legs to keep the board off of the stand at the last minute.  I would like to experiment again and find better placement for the speaker that would be less prone to the muffling problems.  I also learned that it wasn't nearly as hard as we had it made up in our minds.

I know this post was long and rather text heavy, but I appreciate you sticking around and reading through it.  If I missed anything or you have questions, please leave a comment and I will answer you (if I can)!!


  1. Fantastic post!! I tweeted it, everyone must know! Thanks so much for sharing this! x

  2. Thank you for sharing! So interesting!


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