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Lesson3

v5	v6
18	18	The 10K resistor is called a pull-down resistor. It is used to keep the Arduino digital input in a known state when the switch is open. Without it, the digital input (which is very sensitive) could change its state due to electrical noise (e.g. from fluorescent lights). The 10K resistor keeps the input pin at the ground level maintaining a 'low' at the digital input until the button is pushed. When the button is pushed, the input pin is connected directly to +5v through the switch. Because the switch has extremely low resistance, the +5V overwhelms the weak pull-down resistor and the input pin will read high.
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20		It's important to understand pull-up and pull-down resistors as they are required in many circuits. They are such a common requirement that many modern microcontrollers (like the arduino) have them built in where they can be turned on and off under software control see [https://www.arduino.cc/en/Tutorial/InputPullupSerial here].
	20	It's important to understand pull-up and pull-down resistors as they are required in many circuits. This [https://www.youtube.com/watch?v=wxjerCHCEMg brief video tutorial] explains pull-up resistors. They are such a common requirement that many modern microcontrollers (like the arduino) have them built in where they can be turned on and off under software control see [https://www.arduino.cc/en/Tutorial/InputPullupSerial here].
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22	22	== Debouncing ==