LED Dance Pad

Posted on Feb 4, 2014

Using LEDs as light sensors. A DDR pad. We designed our pad to have no moving parts. Instead, we chose to measure light reflectance off the user`s feet to determine if one of the arrows was being stepped on or not. Since a design with no moving parts offers little to no tactile feedback, we wanted to make sure the pad offered some other form of feedback, so the user would know when they

LED Dance Pad
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had successfully stepped on the arrow. The design consists of one master controller and four slave controllers. Each slave controls a set of 15 LEDs. Thirteen LEDs are placed around the border of the arrow and flash in rhythm with the music. The remaining two LEDs are used as an illumination and sensing pair - the LED pointing straight up acts as a permanent flashlight, and the LED at an angle serves to sense reflection of the previous LED off the foot of the player. Readings are taken with the technique described in the MERL paper, summarized here. We place the interior sensing LED in reverse bias mode to allow the LED to charge up a capacitance in the LED junction itself. When a reading is to be taken, we set the cathode to input mode, disable the internal pull-up resistor, and time how long it takes the capacitance to discharge. Greater light input results in a shorter discharge time. As light from the illumination LED reflects off the foot of the player, the time the LED takes to discharge through the microcontroller decreases. By comparing this time to a threshold, the slaves determine if the arrow is pressed, and will raise or lower a line to the master accordingly. The master runs the main DDR pad controller program. It determines when the arrow LEDs should be on by and receives constant readings from the slaves. The master passes the readings from the slaves on to the Xbox 360 controller. The master can receive...

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