For World Maker Faire 2013, I made a heartbeat-activated boombox.
There are three medical-grade (meaning: expensive and accurate!) pulse oximeters which people can use to control three separate drum sounds, a snare, maracas, and a Djembe. An pulse oximeter sensor has a fantastic user interface, you simply put your finger into the clamp and the oximeter starts to read both pulse (units: beats per minute) and blood oxygen saturation (units: percentage).
Most people intuitively know how to use the pulse oximeter sensor, no explanations necessary.
The boombox itself is made by SONY. I designed a board that interfaces with the hacked pulse oximeter. The pulse ox has a beeper on it which I removed and then tapped into the beep output. The beeper beeps with the user’s heartbeat so this works great.
The pulse ox interface board controls three separate sound cards which contain the drum sound and three individual LED-reel circuits. I use sound cards from Electronics 123 as they are USB programmable and have pretty good sound quality. I removed the push button on-off switch and used a transistor to drive the sound card. The interface board is basically an Arduino, as I used the part of the Arduino that has the Atmel 328 and changed the power supply a bit to allow for increased power draw.
I used the AVRISP mkII programmer to work with the Arduino’s IDE over ICSP. I’m horribly out of practice with writing software so using the Arduino’s IDE was super easy.
I also put an LED driver on my board- it’s over-engineered, using a Mosfet that allows for 2 Amps, when the LEDs draw less than 1/2 an Amp!
Here’s the schematic HB Boombox2
I had this as a walk-around project (rather than being at a booth), so I used batteries to power the project. My biggest mistake was using Li-Ion batteries with JST connectors. The Li-Ion batteries ran out of charge after about 4 hours. The connectors fell off easily and were difficult to solder back on. I WILL NEVER USE JST CONNECTORS AGAIN!
I spent a ridiculous amount of Maker Faire time in the Radio Shack booth! Radio Shack was awesome though, they had a table in the back with a soldering iron and a never-ending stream of kids who played with the powered parts of the boombox. I’d be soldering one pulse-ox and two kids would be playing with the other two. The other thing was that people don’t like being around charging Li-Ion batteries. People kept asking me if the charger was safe and if it had built in protection. I assumed that it did, but I didn’t know for sure, so that made me really uncomfortable, just walking away while my batts were charging.
The sound luckily was powered by 6 D-size batteries that came in the boombox and it was nice and loud!
Best moment at Maker Faire was seeing my 9 year niece, Kaylee. She and two other young girls played the boombox for an annoyingly long time, but she turned to me and said incredulously “You made this?”.