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# Automatic control of street light using LDR

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Many of the people have a phobia of darkness, so to assist them in such situation, we have explained a simple circuit. It will automatically turn on street light in the way of LEDs or bulb coupled with relay. Working this circuit is very much easy and also the power consumed by the circuit is very low because of the very few components used in the circuit.

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### Automatic control of street light using LDR

1. 1. Automatic Street LightAutomatic Street Light control using LDRcontrol using LDR
2. 2. Compiled by : Changela Savan IU124106008 Kavathiya Mit IU124106020 Loharikar Devang IU124106023 Zala Ajay IU124106062 Guided by:-
3. 3. Contents  Planning of Project  Introduction  Circuit Diagram  Hardware Requirement  Description of Hardware  Working  Simulation  Bread-board Mounting  PCB Mounting  Conclusion
4. 4. Week1 Week2 Week3 Week4 Week5 Week6 Week7 Week8 Week9 Week10 Week11 Selectionoftopic ProjectResearch Abstact Presentation HardwarePurchasing BreadboardMounting Simulation PCBMounting ProjectReport Submission PlanningofProject
5. 5. Introduction Many of the people have a phobia of darkness, so to assist them in such situation, we have explained a simple circuit. It will automatically turn on street light in the way of LEDs or bulb coupled with relay. Working this circuit is very much easy and also the power consumed by the circuit is very low because of the very few components used in the circuit.
6. 6. Circuit diagram
7. 7. Components:  IC CA3140 – 1  Resistor R1 (10 K) – 1  Resistor R2 (3300 E) – 1  Resistor R3 (1 K) – 1  Variable Resistor VR1 (10 K) – 1  Capacitor C1 (10uF) – 1  LDR – 1  Transistor T1 (BC548) – 1  Relay-1  LED-1
8. 8. Description of Hardware : (1) LDR: Sensitivity depends on intensity of light. Resistance of LDR decrease with increase in intensity of light and vice-versa.
9. 9. (2) Resistor: It is a passive component having two terminals that are used to manage the current flow in the circuit. A current that flows via a resistor is directly proportional to the voltage that appeared into resistor. Two types: (1) Fixed value resistor (2) Variable resistor
10. 10. (3)IC CA3140 :
11. 11. IC  The CA 3140 is an operational amplifier can works on supply voltage 4V to 36V & very low input current from 10pA to 1mA.  Here, The CA3140 works as a comparator and gives fast response &high speed.
12. 12. (4) Relays  Relays is an electrically operated switch.  Current flowing through the coil of the relay creates a magnetic field which attracts a lever & changes the switch contacts.  It has 3-pin,4-pin,5-pin etc…but we have used 5-pin in our circuit diagram.
13. 13.  Relay offers easy way for LED to indicate a voltage is present at Relay coil.  As no input state, the COM is connected To NC & when operating V is applied to relay coil Gets energized &COM Is now with NO.
14. 14. (5) BC548 Transistor :  It is a general purpose silicon, NPN, bipolar junction transistor. It is used for amplification & switching purpose.  Here, for switching purpose it is biased so that it remains on if there is signal at its base , other- wise it is completely off.
15. 15. Working of Automatic Street Light Controller Switch Circuit:  The working of circuit is very much easy to understand. In this circuit, we used IC CA3140 which is basically an operational amplifier. Pins 2 and 3 of these IC are used to compare the voltage and give us the output in return i.e. it works as a potential divider in its inverting and non-inverting inputs (pins 2 and 3).
16. 16. Cont.  In this LDR and VR1 form one potential divider which is used to provide a variable voltage at the inverting input (that is 2) and the second potential divider is built around non-inverting input (pin 3) with the help of R1 and R2 which will grant half of the supply voltage to non inverting pin.
17. 17. Cont.  As we know property of LDR that during the time of day resistance is low therefore voltage at the inverting input ( IE pin 2) is higher than the voltage at the non-inverting input (pin3) hence the output at the pin6 is low so the transistor goes into the cutoff state which means LED or bulb will not glow.
18. 18. Cont.  But in dimness or in night we know that resistance of LDR is high hence voltage at inverting input pin 2 of the IC CA3140 decreases than the non inverting input pin 3 as a result output pin 6 moves to high state which make transistor to conduct and the LED or bulb associated to it start simmering.
19. 19. Simulation (using Proteus): 3 2 74 6 1 58 U1 CA3140 R1 10k R2 330 RV1 10K R3 1k Q1 BC548 C1 10u GND RL1 RTE24005F VCC RelaySupply D1 LED-GREEN GND 12 LDR1 TORCH_LDR