Question

5. (15 points) Pulse width modulation (PWM) from pin 10 of an Arduino Uno (the kind you used in lab) is used to control the brightness of an LED. The 5 V PWM output is connected through a 262 Î© resistor to the LED and from the other end of the LED to ground. You can dim the LED almost continuously with commands like: AnalogWrite(10,255); // Power the LED at maximum brightness AnalogWrite(10,0); // Turn the LED off completely. In the following, assume that the diode drop for the LED is 1.8 V (typical for a red LED). (a) The LED is flickering at 490 Hz, which becomes noticeable when your eyes scan quickly past the LED. Explain why the flicker is happening. Draw a time series of the voltage and label the period. (b) To eliminate the flicker, your lab partner puts a low pass filter (with fe well below 490 Hz) between the Arduino and the 262 Î© resistor. What is the lowest value of x for which AnalogWrite(10,x) will light the LED? (c) Suggest an alternate way to make the flickering less noticeable (a qualitative answer is sufficient) as we did in lab.

          5. (15 points) Pulse width modulation (PWM) from pin 10 of an Arduino Uno (the kind you used in lab) is used to control the brightness of an LED. The 5 V PWM output is connected through a 262 Î© resistor to the LED and from the other end of the LED to ground. You can dim the LED almost continuously with commands like:

AnalogWrite(10,255); // Power the LED at maximum brightness
AnalogWrite(10,0); // Turn the LED off completely.

In the following, assume that the diode drop for the LED is 1.8 V (typical for a red LED).

(a) The LED is flickering at 490 Hz, which becomes noticeable when your eyes scan quickly past the LED. Explain why the flicker is happening. Draw a time series of the voltage and label the period.

(b) To eliminate the flicker, your lab partner puts a low pass filter (with fe well below 490 Hz) between the Arduino and the 262 Î© resistor. What is the lowest value of x for which AnalogWrite(10,x) will light the LED?

(c) Suggest an alternate way to make the flickering less noticeable (a qualitative answer is sufficient) as we did in lab.

5 15 points pulse width modulation pwm from pin 10 of an arduino uno the kind you used in lab is used to control the brightness of an led the 5 v pwm output is connected through a 262 resist 96997

Added by Matthew O.

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