Question

Problem 10 Use the following circuit to answer the next four questions. Recall that the resistor enclosed in a circle with two arrows is a photoresistor/photocell. The photoresistor will be used to control the circuit's behavior. If the room is dark, the red LED will illuminate. In moderate light, the yellow LED will illuminate. In bright light, the green LED will illuminate. The reading from the photoresistor at pin AO is assigned to the integer variable, "photo_value. ☆ ☆ Red Yellow 3 1000 ☆ Green 1001 Š 1000 Pin 3 Pin 2 GND Pin AO Pin 4 +5V Arduino Uno 220 22 Refer to the circuit in Problem 10. The first decision structure we draft is shown below. Treat the comments as actual statements that would run as described. void loop() { //read value on photoresistor if (photo_value < 75) { //turn on red LED //wait one second else if (photo_value >= 75 && photo_value < 150) { //turn on yellow LED //wait one second else { //turn on green LED //wait one second //set pins 2,3,4 to LOW What is the effect of deleting the first else on the output? Two LEDs will illuminate No LEDs will illuminate All three LEDs will illuminate No effect Two LEDs could illuminate Refer to the circuit in Problem 10. We could revise the following decision structure by doing something with the blue delays. Treat the comments as actual statements that would run as described. void loop() { //read value on photoresistor if (photo_value < 75) { //turn on red LED 1/wait one second else if (photo_value >= 75 && photo_value < 150) { //turn on yellow LED 1/wait one second else { //turn on green LED //wait one second //set pins 2,3,4 to LOW Delete the blue delays and choose a position in the loop to place a single delay that yields the same circuit output. Select all that apply. We cannot replace the three delays with a single delay Before setting all the pins low Before reading the photoresistor value After reading the photoresistor value After setting all the pins low Refer to the circuit in Problem 10. What is the output of the circuit if a value of 80 is read from the photoresistor? Treat the comments as actual statements that would run as described. void loop() { //read value on photoresistor if (photo_value < 75) { //turn on red LED //wait one second if (photo_value >= 75 && photo_value < 150) { //turn on yellow LED //wait one second if (photo_value >= 150) { //turn on green LED //wait one second //set pins 2,3,4 to LOW Both the red and yellow LEDs will illuminate No LED will illuminate The green LED will illuminate The yellow LED will illuminate The red LED will illuminate Refer to the circuit in Problem 10. Write a function called 'holdphotovalue' that performs the actions in blue by filling in the blanks of the provided code: "The function takes the current reading from the photoresistor as the input. The function will return a new reading for the photoresistor if the photoresistor value changes more than 10 units after checking it again 500 ms later. If the difference is not bigger than or equal to 10 units, it will return the input reading." holdphotovaluel delay(500); int new_reading = analogRead( int difference = abs -new_reading); return photo_value; return

Answer 1

1-->

2 LEDS could illuminate because let us consider photovalue to be 200, in that case only green LED will blink

If photovalue is 50, then red and green will get illuminated

So only 2 LEDS can be illuminated.

2-->

Before setting all the pins low

This happens so because everytime the loop is run, we encounter either of the conditional statements, and so we will surely get a delay. So putting delay after reading the photovalue or before setting the pins to low will make our program work. But the problem with setting the delay after reading the photovalue is that it will wait for 1 second and the required LED will illuminate for infinite time. So what we want is to first illuminate the LED, wait for 1 second and then switch it off.
So the idea is to put the delay before switching of all the pins.

3-->

No LED will illuminate

When we read value 80, first if will not get executed because 75 is not greater than 80 and so we get into the else if condition, which says that 80 is not greater than 150, hence it will also not execute

So no LED will illuminate

4-->

int holdPhotoValue(int photo_value){

delay(500);

int new_reading = analogRead(A0);

int difference = abs(photo_value - new_reading);

if(difference<10){

return photo_value;

}

else

{

return new_reading;

}

}

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