Here’s some details about the hardware setup for the woot-off lights. It’s exactly as I described in the first post – this just includes the schematic and goes a little more in depth.
Quick and Dirty Schematic for Woot-Off Light Control
Let’s take it from left to right. USB input to the Arduino to send serial data. The current from the USB port is not sufficient to start the motors (they require a bit of boost when turned on and consume less current during normal operation), therefore we use the DC input on the Arduino board to supplement the USB. Feed it somewhere between 7-10V (up to 12V should be fine). The Arduino contains a regulator to lower the Vin down to 5V.
The 5V is then connected to the V+ of the lights (red wire). The GND of the lights is connected to Pin 18 of the ULN2803 IC. The ULN2803 also has it’s own 5V/GND connections (the 5V connection is necessary in this application because of the inductance of the motors). When the ULN2803 receives a HIGH input on Pin 1 (coming from Pin 9 on Arduino), it connects Pin 18 to GND (note that this is the same for all pins on the IC except 9/10 – i.e., Pin 2 controls Pin 17, etc). Thus, the lights are now fully connected to both 5V and GND, the circuit is complete, and we have spinny lights.
Work continues on reading a Woot-Off Tracker from a C++ application – if anyone has tips or ideas, they’d be appreciated.
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