In this project we will control Room light intensity using microcontroller. We will use infrared transmitter and receiver for this purpose. Infrared sensor available in the market we will use. In this circuit as we will get the signal from the sensors. As the number of persons entering in the room will increase intensity. We will 89c051 microcontroller for this purpose. We will program microcontroller with assembly language i.e. the programming will be in assembly language. In this project we will sense the signal from infrared sensor then according to increasing no of persons in the room microcontroller will increase the intensity of the room. This project will help in controlling many applications like in machinery to control machine with increasing strength of material.
We will use two set of ir sensors . one will count the no of persons increasing other will decrease the no of count decreasing.
We will use 12Mhz crystal to provide Clock to microcontroller.
There will IC 7805 as a voltage regulator. And two 1000µf and 470µf as a filtering capacitors.
How to control sensors
What is a voltage divider?
You are going to find out but don’t be in too much of a hurry. Work through the Chapter and allow the explanation to develop.
The diagram below shows a light dependent resistor, or LDR, together with its circuit symbol:
The light-sensitive part of the LDR is a wavy track of cadmium sulphide. Light energy triggers the release of extra charge carriers in this material, so that its resistance falls as the level of illumination increases.
A light sensor uses an LDR as part of a voltage divider.
The essential circuit of a voltage divider, also called a potential divider, is:
What happens if one of the resistors in the voltage divider is replaced by an LDR? In the circuit below, Rtop is a 10 resistor, and an LDR is used as Rbottom :
Suppose the LDR has a resistance of 500 , 0.5 , in bright light, and 200 in the shade (these values are reasonable).
When the LDR is in the light, Vout will be:
In the shade, Vout will be:
In other words, this circuit gives a LOW voltage when the LDR is in the light, and a HIGH voltage when the LDR is in the shade. The voltage divider circuit gives an output voltage which changes with illumination.
A sensor subsystem which functions like this could be thought of as a ‘dark sensor‘ and could be used to control lighting circuits which are switched on automatically in the evening.
Perhaps this does not seem terribly exciting, but almost every sensor circuit you can think of uses a voltage divider. There’s just no other way to make sensor subsystems work.
Here is the voltage divider built with the LDR in place of Rtop :
A temperature-sensitive resistor is called a thermistor. There are several different types:
The resistance of most common types of thermistor decreases as the temperature rises. They are called negative temperature coefficient, or ntc, thermistors. Note the -t° next to the circuit symbol. A typical ntc thermistor is made using semiconductor metal oxide materials. (Semiconductors have resistance properties midway between those of conductors and insulators.) As the temperature rises, more charge carriers become available and the resistance falls.
Although less often used, it is possible to manufacture positive temperature coefficient, or ptc, thermistors. These are made of different materials and show an increase in resistance with temperature.
How could you make a sensor circuit for use in a fire alarm? You want a circuit which will deliver a HIGH voltage when hot conditions are detected. You need a voltage divider with the ntc thermistor in the Rtop position:
How could you make a sensor circuit to detect temperatures less than 4°C to warn motorists that there may be ice on the road? You want a circuit which will give a HIGH voltage in cold conditions. You need a voltage divider with the thermistor in place of Rbottom :
This last application raises an important question: How do you know what value of Vout you are going to get at 4°C? ey point: The biggest change in Vout from a voltage divider is obtained when Rtop and Rbottom are equal in value
IC base 40 pin
7805 voltage regulator
diode in 4001
cap 10 µf 15v
ir tx rxer
copper clad board
· To control room light intensity acc. To manpower
· To controlling parking light intensity acct. to no of cars
· To change the motor speed according to increasing material in a machine.