Automatic Street Light Controller Circuit Using Relay and LDR
Have you ever considered how Automatic Street Light turn on at night and switch off automatically in the morning? Is there somebody who comes to turn these lights on and off? There are numerous ways to switch on the street lights, however the circuit below illustrates an Automatic Street Light Controller Circuit that automates the process by using LDR and Relay.
The circuit used here is a simple light/dark actuated switch with a relay at its output that just turns on/off a street light and can also be expanded to operate any electrical appliance in a home.
- Circuit Diagram of Automatic Street Light Controller Switch Circuit
- Components used in this Circuit
- Components Description
- Testing of LDR
- Factors for Selecting an appropriate Relay
- Automatic Street Light Controller Circuit Simulation Video (Old Circuit)
- Working of Automatic Street Light Controller Switch Circuit
- Automatic Street Light Controller Project Output Video
Many individuals are afraid of darkness, so we’ve detailed a simple circuit that will automatically switch on a street light made up of LEDs or a bulb paired with a relay to help them in such situations. It is well illuminated enough to observe the objects in the immediate vicinity.
This circuit is simple to set up and operate, and it runs on batteries. Because there are only a few components in the circuit, it consumes relatively little power.
The entire circuit is based on the IC LM358, which is a voltage comparator that is configured as an operational amplifier. The essential component for sensin is the LDR (Light Dependent Resistor), whose resistance is proportional to the amount of light falling on it.
Circuit Diagram of Automatic Street Light Controller Switch Circuit
Components used in this Circuit
- IC LM358 – 1
- Resistor 10KΩ – 1
- Potentiometer 10KΩ – 1
- 5V Relay Module – 1
- Small LED Strip
- 9V Battery
- LDR – 1
- Connecting Wires
It is an Operational Amplifier IC. It is available ib 8-pin DIP Package and can be used in several configurations like Amplifier, oscillator, comparator etc.
LDR is a device whose sensitivity depends upon the intensity of light falling on it. When the strength of the light falling on LDR increases the LDR resistance decreases, while if the strength of the light falls on LDR is decreased, its resistance increased.
In the time of darkness or when there is no light, the resistance of LDR is in the range of mega ohms, while in the presence of light or in brightness in decrease by few hundred ohms.
Testing of LDR
efore mounting any component in the circuit it is a good practice to check whether a component works properly or not so that you can avoid consumption of time in troubleshooting. For testing LDR set the range of multimeter in resistance measurement.
Measure the resistance of LDR in the light or brightness and the resistance must be low. Now, cover the LDR properly so that no light falls on it and once again measure the resistance. It must be high. If you got the satisfactory result, then your LDR is good.
It is a two-terminal passive component that is used to control current flow in a circuit. The voltage that appears across a resistor is directly proportional to the current that runs through it.
There are two types of resistors:
I Fixed Resistor — a resistor with a fixed resistance value.
ii) Variable Resistor – A variable resistor is one whose resistance value can be adjusted. For example, if we have a 5K resistor, the resistance value will vary from 0 to 5 k.
The value of resistance can be estimated using a multimeter or by looking at the colour code on the resistor.
It offers isolation between the controller and the device since, as we all know, devices can operate on both AC and DC, but they receive signals from a microcontroller that operates on DC, therefore a relay is required to bridge the gap. When you need to regulate a significant amount of current or voltage with a tiny electrical signal, the relay comes in handy.
Factors for Selecting an appropriate Relay
- The voltage and current required to strengthen the coil.
- The maximum voltage which we will acquire in the output.
- Amount of the armature.
- Amount of contacts for the armature.
- Number of electrical associates (N/O and N/C).
Automatic Street Light Controller Circuit Simulation Video (Old Circuit)
Working of Automatic Street Light Controller Switch Circuit
The circuit’s operation is simple to comprehend. We used the IC LM358, which is essentially an operational amplifier, in this design. These IC’s pins 2 and 3 are used to compare voltages and give us a high or low output based on the voltages at the input pins.
The LDR and the 10K Resistor in this circuit produce a potential divider pair that is utilised to provide a changeable voltage at the non-inverting input (that is Pin 3). With the help of a 10K potentiometer, the second potential divider is formed around the inverting input (Pin 2), which will receive half of the supply voltage.
As we know the property of LDR that during the day time, its resistance is low, the voltage at the non-inverting input (i.e. pin 3) is higher than the voltage at the inverting input (pin 2). Hence, the output at the pin 1 is high. As a result, the relay is OFF and the LED (or the bulb) will not glow.
But in dimness or at night time, we know that resistance of LDR is high. Hence, the voltage at non-inverting input pin 3 of the IC LM358 decreases than the inverting input pin 2. As a result, the output pin 1 moves to low state, which further makes the relay to activate and the LED or bulb associated to it will glow.