Q.3 A LDR photocell is connected into the Wheatstone Bridge circuit as shown in Figure 2.3 to produce a light sensitive

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Q 3 A Ldr Photocell Is Connected Into The Wheatstone Bridge Circuit As Shown In Figure 2 3 To Produce A Light Sensitive 1 (64.24 KiB) Viewed 18 times

Q.3 A LDR photocell is connected into the Wheatstone Bridge circuit as shown in Figure 2.3 to produce a light sensitive switch that activates when the light level being sensed goes above or below the pre-set value determined by potentiometer VR, which set at 22k12. The op-amp is connected as a voltage comparator with the reference voltage Vo applied to the non-inverting pin. In this circuit, the relay turns "ON" when the voltage at point is less than the voltage at point D. (a) What is the value of LDR resistance when the bridge is in balance condition? (3 marks) (b) What is the value of point voltage Vc and Vp at the balance condition? (4 marks) Determine the minimum or maximum value of LDR resistance for the relay to turn "ON"? (3 marks) +12V A w LDR DR Out RS 10k w op-amp 741 Relay TR D Vo RS A Vc 2N2222 1kg VR: RA 10k RS 4709 W W B Ov Figure Q.3