Street Light Which Glow on Vehicle Detection

Every day there is vast wastage of resources, like electricity and water.  One such example is of Street lights which are not turned off even during day time hence, acting a source of wastage of energy, as they glow even when sunrises, or the hours when no one is present on the street. One such alternative which can be adopted is to switch ‘ON’ the street lights only when a vehicle is passing by.

We can utilize the concepts of IR waves which are emitted by body and the controlling actions of micro controller.

The PIR sensor (Passive Infrared) detects the waves coming from a vehicle and triggers the microcontroller to switch on the bulb. The bulb autonomously switches off, after a certain time period defined in the controller programming.

                                                 

Figure 1.1: The proteus simulation of the project.

We used 8051 microcontroller.

• For ease to test the programming of controller according to application we have used LED and resistance (470 ohms) has been used instead for Bulb and Relay for ease.  
• Push button is used for negative edge triggering, just like PIR sensor will do along with inverter.

These connections have been separately explained in the next sub topics.

PIR sensor module and its relevance in the circuit:

                                                          

Figure 1.2: (a)PIR Sensor Module (b)PIR schematic diagram

The PIR module consists of

a. Fresnel Lens

b. PIR Sensor

c. Comparator

The PIR sensor itself is a passive device and it generates the voltage by infrared radiation emitted by surroundings. Fresnel lens expands the field of vision of a PIR sensor by converges infrared radiation to a single point. The voltage generated by three terminal PIR sensor is compared to predefined V_ref   which can be adjusted by on-board potentiometer. The output of the PIR module is a logic ‘HIGH’ when it detects IR radiation.

However, microcontroller requires negative edge (1-0-1) to trigger the interrupt. Hence, we use transistor as an inverter as shown in the figure 1.2.

R_b=R_c=4.7K.

Driving relay using transistor BC548

figure 1.3:Relay using transistor BC548

In order to drive AC load through micro controller we require a relay and a transistor. We have used 5 V mechanical relay which consists of 5 contacts. The five contacts of a relay are coil terminals, NO (Normally Open) and NC (Normally Close). The load’s neutral and 230V AC supply neutral is made common. The NO terminal of relay is connected to the live wire of AC supply and Common terminal is joined to live wire of the load.

When the input terminals of relay receives 70-80 mA current the inductive coil energizes. However the micro controller pin cannot provide with such large amount of current. We therefore use BC548, npn transistor which helps in driving the relay, and the configuration is shown in above Figure 3.

The collector is connected to relay, and a diode is placed in parallel to coil. The diode is used to avoid inductive kickback which can damage the micro controller pin.

Once coil energizes, the contact moves from NC to NO connecting load to source. But after certain delay time, the controller stops the current. The coil enervates, and the contact shifts back to NC.

This is the flowchart for programming the microcontroller, we used 8051 any other controller can be used. But for application it is best suited, as it is cheaper in compared to other controllers. We used the interrupts, we can use polling method. But polling method and interrupts have their own differences.

This is the flowchart for programming the microcontroller, we used 8051 any other controller can be used. But for application it is best suited, as it is cheaper in compared to other controllers. We used the interrupts, we can use polling method. But polling method and interrupts have their own differences.

Figure 1.4: This is the real-time circuit we made to test the feasibility of the solution we thought for the given application.

We have the proteus simulation of our working project.

The code will be available to blog followers upon request.:)