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Design - Dimming and User Input
Dimming
Since I have decided to display how high the amplitude of the audio is with LEDs, it would be convient to the user if the device could dim the LEDs when the ambient light is low. This "kind gesture" also has the added benefit of saving some power because the LEDs are not activated all the time. For the device to sense the current ambient light level, a simple component called a photo resistor will be used.
A photo resistor is a piece of semi-conductor that becomes more conductive when light, that is shining on it, increases in intensity. As such, this type of device can be used as a sort of light controlled resistor that can be integrated into a voltage divider. The output of this voltage divider can then be fed into the analog to digital converter of the micro-controller where the resulting digital information can be used to control the light intensity of the LEDs of the display.
Voltage Divider
Touch Sensor
While working on this project, I came to the idea that it would be advantageous to the user if an allowance were made to be able to change how the LEDs reacted to the amplitude of the incoming audio signal. A touch sensor, such as the QT110 from QProx, would work very well in fulfilling the required user interface to implement such a function.
The implementation of this circuit was derived directly from its datasheet. The only major change to this circuit was the suppression of the "heartbeat" indicator because the output of this chip will be connected to one of the input pins of the micro-controller that is set to sense the change in logic on that particular pin. This suppression is achieved by placing a capacitor of arbitrary value between the output pin of the QT110 and ground.
Touch Sensor Circuit
