Since the last blog summarising blog post, we've been beavering away at building the final prototype for our toy, oh, and we came up with a name for it too, Phonicubes... phonics, and cubes!
Jason has been working on building the sound board, which is an integrated Arduino and Waveshield on one board.
Steve designed and built the enclosure for the toy, which you can see to the right.
In the mean time I've been collecting everyone's work and source files and posted everything up on github for your perusal. I've also soldered together the prototype using the following schematic (although we used a duemilanove instead of a nano so we could use the protoshield we had lying around).
With all this soldered together and mounted inside the owl shaped enclosure, I thought it was time for a demo video:
Final parts list & costs
Protoshield (optional) £6
Arduino duemilanove £20
Custom arduino & waveshield £15
ID-2 RFID module £14
Acrylic for cubes (2x A4 sheets) £3
MDF board for the enclosure £1
Wire & misc bits £2
Total, approx £81
I'm pretty certain we can get these costs down, we can most likely merge the sound board and control board which would immediately drop £20 off. If we design a PCB for the whole thing we'll not need the protoshield either dropping another £6 off.
With more time we should also be able to design a much cheaper RFID solution, I did a lot of investigation into building our own RFID reader module, parts for that would be less than £5 easily. We could also use much lower strengh magnets instead of the neodymium ones in the prototype. This would drop the price by around another £5-10. That would bring the cost down to around half of what we spent on the prototype, around £40 at consumer prices. Not bad
Reproducability and Part Availability
We have one uncommon part in our design, the ID-2 RFID reader. This module is available from quite a few UK and European distributors, along with Sparkfun and a few others in the US. It would also be possible to drop in the ID-12 or ID-20 without any code changes. These parts have an integrated antenna, so they'd have to be positioned correctly.
For the case and the cubes, we laser cut our parts. This was because, thankfully, we have access to laser cutters which allow us to do some very rapid prototyping. However, there's not reason why you couldn't print the designs out on paper to use as a guide on a jigsaw to cut the pieces manually. You could even build the device out of cardboard using just a craft knife, some hot glue and a soldering kit.
Improvments and next steps
Currently the RFID card to word mapping is stored in program memory on the arduino, if you want to add a card/word combo then you have to re-flash the controller. We were planning on storing this information on the SD memory card in the wave shield, but alas we didn't have time to implement it.
Also, the resistor values we using in our potential divider circuit aren't giving us the values we were expecting on the analog input from the arduino. This means that some of the cubes have blank faces at the moment, and we were unable to add some of the words we were planning to include. Matt created a spreadsheet to calulate the resistor values, which seems to be correct. If anyone has any ideas please give us a shout.
Overall I think the project went really well, everyone had something to do and we all pulled together to create something that looks awesome and actually works!