Automatic Garden Light Using LDR Sensor
An Automatic Garden Light using an LDR sensor, trimpot (potentiometer), LM358 operational amplifier, transistor, and LED is a more sophisticated version that incorporates an operational amplifier for improved signal conditioning. Here's a basic explanation of how this system works:
Components Needed:
- Light Dependent Resistor (LDR): Light-sensitive resistor that changes resistance based on ambient light conditions.
- Trimpot (Potentiometer): A variable resistor used for adjusting sensitivity or setting a threshold in the circuit.
- LM358 Operational Amplifier: Used for signal amplification and comparison.
- Transistor (NPN type): Amplifies the current from the operational amplifier to control the LED.
- LED (Light Emitting Diode): The output indicator or the actual garden light that will be controlled.
- Resistors and Capacitors: Used for setting up the necessary thresholds, for circuit stability, and for configuring the LM358.
- Power Supply: Provides power to the circuit.
Circuit Operation:
LDR and Trimpot Configuration:
Connect the LDR and resistort in a voltage divider configuration. The trimpot acts as a variable resistor to set the sensitivity of the LDR.
LM358 Operational Amplifier:
Connect the output of the voltage divider to one of the inputs (inverting(-) input) of the LM358 (Pin 2).
Connect a reference voltage (set by a potentiometer) to the other input (non-inverting (+) input ) Pin 3.
Signal Amplification and Comparison:
The amplified signal is compared by IC LM358, and when the voltage from the LDR and resistort in a voltage divider exceeds the reference voltage from Trimpot, the output of the LM358 changes.
Transistor Amplification:
The output of the LM358 is connected to the base of an NPN transistor. BD139
The transistor amplifies the current from the LM358.
LED Control:
The transistor's collector is connected to the negative side of the LED.
The LED's positive side is connected to the resistor for limited current dan otherside resistor connected to power supply.
The emitter of the transistor is connected to the ground.
Working Principle:
During the day or in well-lit conditions, the LM358 compares the LDR voltage with the reference voltage, and the output remains Low.
When it gets dark, the resistance of the LDR increases, causing the LM358 output to go high, and the transistor conducts, powering the LED.
Automatic Garden Light Using LDR Sensor
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