Charlie's RFID Teddy Bear

By David Harris
Category: Music, Arduino
Time Required: 1 day
Difficulty: Easy

This location-aware teddy bear reads RFID tags and plays different customizable sounds depending on where it is or what object it’s near — other toys, books, CDs, anything.

Charlie’s Bear helps children explore the world around them by producing sounds in reaction to other toys or objects nearby. It can play any sound files you upload to the memory card inside — for example, the voice of the bear, a noise that another toy might make, a theme song prompted by a toy from a TV show, or a reading of a favorite book.

I created the toy for my nephew Charlie, who was born with cerebral palsy. Charlie’s vision is poor, but he’s very tactile and auditory. This toy takes advantage of his excellent hearing and the joy he derives from music and sounds. And for all young children, this toy is an easy and safe way for them to pick their own music. Just bring a CD case (or other tagged item) near, and the bear plays it — no complicated CD player or computer.

At the heart of Charlie’s Bear, an Arduino microcontroller uses a radio frequency identification (RFID) reader to recognize nearby RFID tags, then uses an audio shield attachment to play corresponding audio files stored on an SD memory card. The SD card stores about a minute of audio content per megabyte, so a cheapo 4GB card will hold more than 60 hours.

Steps

Step #1: Assemble the electronics.

Solder the Wave Shield together, following the instructions at http://ladyada.net/make/waveshield. At the step where you screw the plastic volume dial onto the housing, just insert the screw without the plastic dial, and turn it to maximum volume level.
Cut and strip 4 wires about 6"–8" long, and solder them to the 4-pin connector, leaving the other ends bare. Mark the connector positions Vcc, Enable, SOut, and GND, to match the RFID reader’s serial header, and connect red and black wires to voltage and ground, respectively.
If your battery holder has wire leads, solder its red wire to the inner terminal of the barrel connector (power plug) and its black wire to the outer terminal. (If it has a 9V connector, solder the wires from a 9V battery snap.)
Screw the housing onto the plug and wrap the wires with electrical tape if needed to hold things firm. Solder the wires to the 9V battery clip and insulate with more tape.
The length of the wires isn’t critical, but leave enough room to place the RFID sensor in the bear’s chest and have the wires come out the back to reach the rest of the electronics.

Conclusion

Connecting Sounds With Objects

Combining object sensing with sound is more powerful than you might think. The most obvious application is just for the bear to make appropriate noises in response to other toys. But what about interacting with other objects, besides toys? An ID tag stuck inside the cover of a book can trigger the bear to read it. A tag in a CD case can trigger the bear to play the corresponding music, without a small child’s having to fuss with smudge- and scratch-prone CDs or age-inappropriate computers.

If you have a child who just won’t listen to you, maybe they’ll listen to their friend the bear. Record some tags in “bear voice” saying that it’s time to go to sleep or time to brush our teeth. And don’t forget to give the parents a keychain RFID tag that has no sound associated with it. This very handy tag will instantly make the bear go silent! These are some of the Charlie’s Bear sound applications I’ve used successfully with the kids in my life, and I’m sure you can come up with many more.

Mod Charlie’s Bear!

The software for Charlie’s bear is fairly straightforward and easy to modify. For example, the existing code interrupts the current sound playing when a new tag is brought into range, but you can change its behavior so that it plays the current sound file until the end before starting the new one.

There are a few obvious physical modi-fications you might like to try. The bear has no power switch, so to turn it off you need to unplug the battery pack. Instead, you could add a switch inside a paw or combination of paws.

Alternatively, you might like to add some kind of motion-sensitive switch and modify the code so it uses less power when idle. With software power management, turning off the RFID antenna will save the most power. Then the batteries will last long enough that you might never need to switch your bear off.

Or maybe the bear would like to dance along with the sounds it makes? Consider adding a vibration motor or stepper motors that the Arduino can trigger along with the sound files. Perhaps you can modify the code so that some tags play sound and others cause vibration or movement.

Let us know how you use Charlie’s Bear!

Resources

Charlie’s Bear software — CharlieBear.pde from http://makeprojects.com/v/28
RFID tag identifier — RFIDread.pde from http://makeprojects.com/v/28
Arduino IDE — http://arduino.cc
Audacity — http://audacity.sourceforge.net

This project first appeared in MAKE Volume 28, page 106.

3 Responses to Charlie’s RFID Teddy Bear

Goli Mohammadi on April 13th, 2012 at 5:48 pm said:

Awesome, Charles! Thanks so much for the feedback!

Reply ↓
keith on October 18th, 2012 at 2:06 am said:

Try turning down the baud rate in the Serial Monitor to 2400 and it should turn into English.

Reply ↓
Charles Bullock on December 19th, 2012 at 8:45 pm said:

For starters, I’ve added an on/off switch, just wired up a simple pushbutton. Right now it’s at the base of the lion’s neck (my wife found a great lion), but it’ll be moved to a paw or the tail soon.

Next step I have in mind is to modify a sound-to-light converter (I found a good cheap one [http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_147571_-1|here at Jameco]). Put the microphone inside near the speaker, use multiple different colored LEDs instead of just the included red ones, run the LEDs to the nose or ears, and then your animal will light up different colors as it talks or sings, and the brightness will be dependent on the volume.

Reply ↓