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

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A Ldr Photocell Is Connected Into The Wheatstone Bridge Circuit As Shown In Figure Q 3 To Produce A Light Sensitive Swit 1 (52.87 KiB) Viewed 20 times

A LDR photocell is connected into the Wheatstone Bridge circuit as shown in Figure Q.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 Vp applied to the non-inverting pin. In this circuit, the relay turns “ON” when the voltage at point C 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) (C) Determine the minimum or maximum value of LDR resistance for the relay to turn 'ON'? (3 marks) +12V A w LDR DR Out w RE 10kΩ op amp 741 Relay Vo TR А RS w 1kΩ 2N2222 Vc VR: w R4 10k 2 B R: 4700 w Ov Figure Q.3