Generally, street lights are switched on for whole night and during the day, they are switched off. But during the night time, street lights are not necessary if there is no traffic. Saving of this energy is very important factor these days as energy resources are getting reduced day by day.
Alternatives for natural resources are very less and our next generations may face lot of problems because of lack of these natural resources.
This article describes about the circuit that switches the street lights on detecting vehicle movement and remains off after fixed time.
Step 1: Principle Behind AVR Microcontroller Circuit
The proposed system consists of Atmega8 microcontroller, LDR, PIR sensor and RTC. This system controls the street lights using light dependent resistor and PIR sensor.
Street lights are switched on depending on the intensity of the Sun light on LDR. If the intensity of Sunlight on light dependent resistor is low, its resistance value is high. This value increases and becomes high when it is completely in dark. This resistance value decides when the street lights are required to switch ON. As the resistance value is maximum in the midnights, real time clock comes into the play. The controller checks peak time during which there is no traffic and switch OFF the lights. When there is any vehicle on the road, it is detected by the PIR sensor. Whenever PIR sensor is detected it just indicates the microcontroller to switch on the street lights. Then lights are switched on for 2 to 3 minutes and switched off automatically. Another way to this approach is, one can maintain minimum intensity without completely switching off the lights by using PWM and switch them on to maximum intensity whenever it detects the vehicle. But in this article the circuit is designed in such a way that lights are completely switched OFF and will be switched ON only when there is any vehicle.
Step 2: Circuit Diagram
Step 3: Circuit Components
- DS1307 ICP
- IR sensor
- LED array
Step 4: Circuit Design
The proposed circuit consists of ATmega8 microcontroller, PIR sensor, light dependent resistor and real time clock, Liquid Crystal Display.
Passive Infrared sensor, also called as PIR sensor is connected to the PD0 pin of the microcontroller. PIR sensor senses the motion of the objects. The PIR sensor internally will have an IR detector. Every object in the world radiates some IR rays. These are invisible to the human eye but electronic components can detect them. Different objects will emit IR rays of different wavelength. These rays were detected by the PIR sensor. PIR is initially high and is set to low automatically after sometime. Whenever it detects the motion of any object, it becomes low. LDR is connected to the ADC pin – ADC0 of the microcontroller as LDR will produce analog value which is converted to digital by the ADC. Light dependent resistors will have low resistance in light and high resistance in dark. The resistance of Light dependent resistor in dark is in range of ohms and in dark its resistance is in the range of mega ohms. When the light falls on LDR it resistance is reduced to a great extent. Real time clock IC used is DS1307, which is I2C compatible. Real time clock has 8 pins.1 and 2 pins are connected to the crystal oscillator.3rd pin is connected to a battery.6th pin of RTC is connected to PC5 pin of microcontroller.5th pin is connected to PC4 pin of microcontroller. I2C is inter integrated circuit. This is two wire interface protocol in which only two signals were used to transmit the data between two devices. LCD is used for displaying time. LCD interfacing in 4bit mode is shown in the circuit diagram. Time from RTC is read and displayed on the LCD.
Step 5: How to Operate This Circuit?
- Initially power the circuit.
- LCD displays the time read from RTC.
- Place the LDR in darkness. Now street light is switched ON.
- Now micro controller continuously checks the time. Street Light is switched on for fixed timings written in the code.
- After this time, they are switched of automatically.
- Place your hand in front of PIR sensor, this switches the street lights again, indicating that on the detection of any object street light is ON.
- After 2-3 seconds delay, lights are again switched of automatically.
Step 6: Principle Behind 8051 and IR Sensor Circuit
Here is the circuit that uses the 8051 and IR sensor sensors, to be able to replicate the same circuit in a different way.
Step 7: Circuit Diagram
Step 8: Components
- AT89C52 Microcontroller
- AT89C52 Programmer Board
- 11.0592 MHz Quartz Crystal
- 22pF Ceramic Capacitor
- 2 x 10K Resistor
- 10uF Electrolytic Capacitor
- Push Button
IR Transmitter and Receiver Section
- 8 x IR LED (IR Transmitters)
- 8 x 470R Resistor
- 8 x Photo Diode (IR Receivers)
- 8 x 3.3K Resistor
- 1K x 8 Resistor Pack
- 8 x 2N2222 NPN Transistors
- 8 x 100R Resistor
- 8 x White LEDs
Step 9: Principle of Operation
The principle behind the working of the project lies in the functioning of IR Sensor. We are going to use a Transmissive type IR Sensor in this project. In Transmissive IR Sensor, the IR transmitter and receiver are placed facing each other so that IR receiver always detects IR Rays emitted by the IR Transmitter. If there is an obstacle between the IR Transmitter and Receiver, the IR Rays are blocked by the obstacle and the IR Receiver stops detecting the IR Rays. This can be configured to turn ON or OFF the LEDs (or street lights) with the help of microcontroller.
Step 10: Circuit Design
The main components of the project are AT89C52 Microcontroller, IR Sensor (IR Transmitter and IR Receiver) and LEDs. The basic connections required for 8051 Microcontroller involve crystal, reset and External Access. In order to use the on-chip oscillator, the 8051 microcontroller requires an external clock. This is provided by a crystal oscillator. An 11.0592MHz quartz crystal is connected to XTAL1 and XTAL2 pins with two 22pF ceramic capacitors connected to it. The reset circuit of the microcontroller consists of a 10K resistor, 10uF capacitor and a push button. All the connections of the reset circuit are shown in the circuit diagram. External access Pin is used to access external memory when it is connected to ground. Anyway, we are not going to use any external memory here. So, connect this pin to Vcc via a 10K resistor. The next hard ware we are going to connect is the IR Receiver. We are going to connect the 8 IR receivers to port 0 pins of the microcontroller. In order to use the PORT0 as I/O port, we need to connect external pullup resistors to the port 0 pins. After that, connect the output of the IR receiver i.e. anode terminal of the photo diode to port 0 pins. Cathode terminals of the photo diodes are connected to supply. Also, a 3.3k Resistor is connected between the anode terminal and ground. The next part of the circuit is IR transmitter. IR transmitter is not a part of the microcontroller connections as the only job of the IR transmitter is to continuously emit infrared rays. Hence, connect the 8 IR transmitters with corresponding 8 current limiting resistors of 470 ohms with a power supply. Finally, we need to connect the LEDs. We need to connect the LED’s with the help of transistors to the PORT2 of the microcontroller. The base of the 8 2N2222 transistors is connected to the PORT 2 of the microcontroller while the emitters of the transistors are connected to ground. An LED along with a series current limiting resistor of 100 ohms is connected to the each of the collector terminal of the transistor.
Step 11: Working
The aim of this project is to design a street light control system using 8051 microcontroller, which automatically turns on or off the street lights by detecting the movement of vehicles. The working of the project is explained here.Below GIF demonstrates the working of the project.
The IR transmitter is placed directly in line of sight with IR receiver, so that the IR receiver continuously receives infrared rays. Once the IR receiver receives infrared rays, the microcontroller will detect Logic 1. If the infrared rays are blocked by some means, the microcontroller will detect logic 0.
So, the program for the microcontroller must be written in such a way that it will turn ON the LEDs, which means here the street lamp, when it detects Logic 0 and it will turn OFF the LEDs, when it detects Logic 1. Consider the two IR sensors i.e. IR Transmitter and IR Receiver are placed on the either side of the road. As per the circuit diagram, the IR receivers are connected to the PORT0 and the LEDs are connected to the PORT2 of the microcontroller. At the beginning, when there is no obstacle, the IR receiver continuously detects IR light transmitted by the IR Transmitter. When a car or any other vehicle blocks any of the IR sensor, the microcontroller will turn ON the immediate three LEDs. If the car blocks the first IR sensor, the first three LEDs are turned ON by the microcontroller. As the car moves forward and blocks the second IR sensor, the corresponding next three LEDs will be turned ON and the first LED of the previous set is turned OFF. The process continues this way for all the IR Sensors and LEDs.
Step 12: Applications
- The street light control circuit can be used in normal roads, highways, express ways etc.
- The project can also be used in parking areas of malls, hotels, industrial lighting, etc.
Step 13: Advantages
- If the lighting system implements all LED lights, the cost of the maintenance can be reduced as the life span and durability of LEDs is higher than Neon based lights which are normally used as street lights.
- As the lights are automatically turned ON or OFF, huge amount of energy can be saved.