Last Friday my little one brought back an empty Yakult bottle from the Kindergarten. The teacher said the kids should build something with it.
Since we once already did a similar build she was asking me to build a robot. Well, a robot would be nice but I decided to go more easy, doing a blinky LED combined with a LDR.
The three LEDs are connected to the three digital outputs of an Cheapduino and since they are supposed to blink in series one after another sharing a common 10k (to save power) current limiter resistor to the ground. A 51k resistor is going from VCC to A0 and the LDR is connected to GND and A0 as well. The system is powered by a 3.7V/180mAh LiPo. The code is quite simple.
I just took the example for "Read Analog Voltage" and modified it with the LED code. Not very sophisticated but working :-) A main switch is turning the blinky bottle on. Then the setup blinks three times the white onboard LED on Pin 13 to indicate that the system is ready. (remember, the Cheapduino with the Atmega8 needs a couple >8 to 10< seconds to initialize). When the LDR is getting to less light the red LEDs will blink ten times one after another. That's all :-)
The decoration was made by my little one as well the drawing on the bottle.