Figure $14$ A circuit made in MultiSim Live

b$.$ You are required to modify the circuit in Figure $14$ using MultiSim Live. Your circuit should switch on the lamp when the intensity of the light in the environment is less than $1000$ Lux and otherwise switch it off.

i$.$ What should be the polarity of output voltage of the op$-$amp to illuminate the lamp? To achieve this polarity which should be greater, $\backslash ($ V$+\backslash )$ or $\backslash ($ V$-\backslash )?$

Change the voltage $\backslash ($ V$\_\{1\}\backslash )$ from $1\mathrm{.}5$ V to $9$ V $.$ Enter a value for $\backslash ($ R$\_\{1\}\backslash )$ in the following table for an LDR resistance when the ambient light is a less than $1000$ Lux. Give resistor values $\backslash ($ R$\_\{2\},$ R$\_\{3\}\backslash )$ and $\backslash ($ R$\_\{4\}\backslash )$ for the Wheatstone bridge that will illuminate the lamp for your LDR value of $\backslash ($ R$\_\{1\}\backslash ).$ Enter your resistor values in the table below. Explain your choices.

ii$.$ Give a screenshot of your circuit with the lamp illuminated when the ambient light is just under $1000$ Lux. Give another screen shot with the lamp not illuminated when the ambient light is just over $1000$ Lux. The values of $\backslash ($ R$\_\{2\},$ R$\_\{3\}\backslash )$ and $\backslash ($ R$\_\{4\}\backslash )$ should be the same in both screen shots.

c$.$ A similar circuit is to be used by a robotic vehicle that has a device to measure and test the light intensity of streetlights. Your task is to design a circuit for this device. For this the lamp and switch in Figure $14$ are replaced by LEDs.

If the light intensity is less than $100$ Lux a red LED should be illuminated as a warning that the streetlight has failed the test, otherwise, a green LED should be illuminated to show that it has passed.

Assume you can use a $9$ V DC power supply to power the Wheatstone Bridge, standard resistors, a red and a green LED and an LDR with the characteristics provided in Figure $13.$

Assume that the LEDs normally operate at $25$ mA and have a maximum current of $30$ mA $.$

Assume also that the LEDs have a forward voltage of $1\mathrm{.}5$ V $.$ For this you need to modify the LED's characteristics in MultiSimLive. To do this, click on an LED to select it$,$ and click on the button at the top right of the MultiSimLive window. Then you should set the Emission Coefficient, N$,$ to $2.$ Do this for both LEDs. This panel also lets you set the colour of the LEDs. Do this for one LED to make it green $($the other is red by default$).$

i$.$ Using MultiSim Live, design a circuit to meet these specifications.

Give a screenshot of your circuit showing the red LED illuminated for light just below $100$ Lux. Give another screenshot of your circuit with the green LED illuminated for light measured just above $100$ Lux.

ii$.$ Give your resistor values, $\backslash ($ R$\_\{2\},$ R$\_\{3\}\backslash )$ and $\backslash ($ R$\_\{4\}\backslash ),$ and explain how you selected them.

iii. Explain how the LEDs were configured in your circuit.