BitCake – Electronic Birthday Cake
Impress your friend with the ultimate geek’s Birthday Cake! A hand-made open source electronic cake with candles you can blow out!
- Features 9 LED candles that you can blow on, to make them flicker and go out, like you do with a real birthday cake! Each candle blinks with random period and phase that depends on the intensity of the air flow
- Piezo sensor and a special air trap to detect air flow with astounding sensitivity using resonance effect
- Atmel ATTiny44 microcontroller on board with 4 kilobytes of flash memory and 256 bytes RAM
- Open source hardware and firmware. Can be re-programmed with an ICSP programmer or Arduino board via Arduino IDE
- Size 42 x 42 x 18 mm, weight 26g
- Powered by a single AAAA/LR61 battery (included)
- 3.3V step-up converter on board
- Ultra low shutdown current (less than 1 ΅A in deep shutdown)
- Hand-soldered using lead-free solder
BitCake is an open source hardware product that you can reproduce at home by following this circuit diagram:
The heart of the device is Atmel ATTiny44 microcontroller. Its built-in differential ADC channel with 20x gain is connected to a piezo sensor. The rest nine general input-output pins are connected to nine separate LEDs circuits.
A step-up DC-to-DC power converter is used to increase output voltage to 3.3V at the expense of increased current provided by the battery. For that purpose, Holtek 7733 integrated circuit is used. Its SOT-23-5 package has additional Chip Enable (CE) input that turns off the converter into deep shutdown with ultra-low supply current.
For more detail: BitCake – Electronic Birthday Cake