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?
Key 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.
Look around. Notice the smart “intelligent” systems? Be it the T.V, washing machines, video games, telephones, automobiles, aero planes, power systems, or any application having a LED or a LCD as a user interface, the control is likely to be in the hands of a micro controller!
Measure and control, that’s where the micro controller is at its best.
Micro controllers are here to stay. Going by the current trend, it is obvious that micro controllers will be playing bigger and bigger roles in the different activities of our lives.
These embedded chips are very small, but are designed to replace components much bigger and bulky In size. They process information very intelligently and efficiently. They sense the environment around them. The signals they gather are tuned into digital data that streams through tributaries of circuit lines at the speed of light. Inside the microprocessor collates and calculators. The software has middling intelligence. Then in a split second, the processed streams are shoved out.
What is the primary difference between a microprocessor and a micro controller?
Unlike the microprocessor, the micro controller can be considered to be a true “Computer on a chip”.
In addition to the various features like the ALU, PC, SP and registers found on a microprocessor, the micro controller also incorporates features like the ROM, RAM, Ports, timers, clock circuits, counters, reset functions etc.
While the microprocessor is more a general-purpose device, used for read, write and calculations on data, the micro controller, in addition to the above functions also controls the environment.
8051 micro controller
The 8051 developed and launched in the early 80`s, is one of the most popular micro controller in use today. It has a reasonably large amount of built in ROM and RAM. In addition it has the ability to access external memory.
The generic term `8×51` is used to define the device. The value of x defining the kind of ROM, i.e. x=0, indicates none, x=3, indicates mask ROM, x=7, indicates EPROM and x=9 indicates EEPROM or Flash.
A note on ROM
The early 8051, namely the 8031 was designed without any ROM. This device could run only with external memory connected to it. Subsequent developments lead to the development of the PROM or the programmable ROM. This type had the disadvantage of being highly unreliable.
The next in line, was the EPROM or Erasable Programmable ROM. These devices used ultraviolet light erasable memory cells. Thus a program could be loaded, tested and erased using ultra violet rays. A new program could then be loaded again.
An improved EPROM was the EEPROM or the electrically erasable PROM. This does not require ultra violet rays, and memory can be cleared using circuits within the chip itself.
Finally there is the FLASH, which is an improvement over the EEPROM. While the terms EEPROM and flash are sometimes used interchangeably, the difference lies in the fact that flash erases the complete memory at one stroke, and not act on the individual cells. This results in reducing the time for erasure.
Different microcontrollers in market.
- PIC One of the famous microcontrollers used in the industries. It is based on RISC Architecture which makes the microcontroller process faster than other microcontroller.
- INTEL These are the first to manufacture microcontrollers. These are not as sophisticated other microcontrollers but still the easiest one to learn.
- Atmel Atmel’s AVR microcontrollers are one of the most powerful in the embedded industry. This is the only microcontroller having 1kb of ram even the entry stage. But it is unfortunate that in India we are unable to find this kind of microcontroller.
The best thing done by Intel is to give the designs of the 8051 microcontroller to everyone. So it is not the fact that Intel is the only manufacture for the 8051 there more than 20 manufactures, with each of minimum 20 models. Literally there are hundreds of models of 8051 microcontroller available in market to choose. Some of the major manufactures of 8051 are
The Philips‘s 8051 derivatives has more number of features than in any microcontroller. The costs of the Philips microcontrollers are higher than the Atmel’s which makes us to choose Atmel more often than Philips
Dallas has made many revolutions in the semiconductor market. Dallas’s 8051 derivative is the fastest one in the market. It works 3 times as fast as a 8051 can process. But we are unable to get more in India.
These people were the one to master the flash devices. They are the cheapest microcontroller available in the market. Atmel’s even introduced a 20pin variant of 8051 named 2051. The Atmel’s 8051 derivatives can be got in India less than 70 rupees. There are lots of cheap programmers available in India for Atmel. So it is always good for students to stick with 8051 when you learn a new microcontroller.