IR sensor

sensors

sensor is a device which  is able to detects the  change  in the ambient condition.sensors used for an element which produces a signal relating  to the quantity being measure.
for example  … an electric resistance temperature element ,the quantity being measured  is temperature and sensor transform an input of the temperature into a change in resistance.the main purpose of the sensor is  events or change in  environment.
       in other words we can say that sensor is a part of measurement system that provide the response to the particular measurable  physical parameter.
there are different term which is known as transducer ……………
transducer 
 transducer is a device that convert the one form of energy into the another  form of energy.
for example in ultrasonic non traditional machining process magneto type of transducer change the electric energy signal into the vibrational  movement of the abrasive particles.
difference between sensor and transducer 
transducer and sensor are physical device that are used  in electrical, electronics,and many types of application.
 
1.transducers are used to convert the energy form one form to another form.while sensors measure energy level and convert it into electrical signal  that can be measure digitally.
2.transducer is a device that convert the primary form of energy(mechanical,thermal,chemical,optical)  into a corresponding signal  with a different energy form . but a sensor that measure a signal or also acquires  information from the real world.
there are several types of sensors used in  robot  to make the robot more advanced
1.IR  sensor
2. temperature sensor
3.pressure sensor
4.proximity sensor
6.Hall effect sensor
7.pneumatic sensor
8.piezoelectric sensor
9.liquid level sensor
10.liquid flow sensor
11.light sensor
12.optical sensor
13.tactile sensor
14.humidity sensor
 
the above given sensors are the most common sensors that are used in robotics 
now i will tried to give you whole about the sensors that are given  earlier.

1.IR  sensor

                         IR sensor is an electronic device.    the infra red radiation  which is the part of electromagnetic spectrum having a longer wavelength than the visible wavelength but smaller then the microwave.wavelength ranging between 0.75 to 1000 um.this type of sensor mainly used in tv remote control.these infra red is not visible to  human eyes. As we know that if the temperature of  any object which is expose to the surrounding is lower than the absolute temperature of the surrounding then it radiates some electromagnetic waves or thermal radiation . these waves basically in the form photon packets.these type of wave or spectrum can not be sense by human eyes but IR sensor can detect these radiation.in this way the emitter is IR LED and detector is IR photodiode which is sensitive to the IR spectrum (these IR spectrum emitted by IR LED).
                 when the IR light falls on the receiver (photodiode) the voltage and the resistance change in the proportion of the magnitude of the light.                          

images?q=tbn:ANd9GcRikx2QUvKGl9XJA4WbStpavcubpfowpsKBqkIW5Az1oP40pV07 IR sensor

working of the IR sensor circuit 
IR sensor  used in most of the electronic control systems like robot 
we can built many types of  small robotic circuit like line follower robot,obstacles detector robot etc.
here i am going to give you little bit knowledge about the circuit .
 
in above  given circuit  we are basically using two electronic component IR receiver and IR transmitter.
 IR transmitter   IR transmitter is nothing but a LED (light emitting diode).
IR transmitter emits the infra red light which is connected in the circuit in forward bias.to limit the current supply in the IR led branch we use the 100 ohm resistor.the IR light can not be visualize by human eyes. 
 IR receiver  it receives the infra red light which is coming from the transmitter.it is basically a photodiode.To regulate the IR receiver led we use a high value resistance(10k to 1M ohm) which is required for IR receiver  led.this is situated in reverse biased.
comparator used in basic circuit of the IR sensors
their is a comparator used .the main application of the compatator is to compare the two  voltage .it convert  two analog signal into a single digital output.here LM358  comparator is used. 

images?q=tbn:ANd9GcTjKftKcZ6_XxU0OS3yHW7C5fMA-_k9P3iqjds1KouvNOvoENyT IR sensor

images?q=tbn:ANd9GcTco639KQQPwupqCPbbbRpmSn7j8cAS08cEhtvw0ZTNg2TFoDbK IR sensor
A normal LED is used for  batter observation .

working of the circuit
                                          As the +5 vcc supply is applied to the circuit the current will flow through the the transmitter branch .to limit the current supply for performance  of the transmitter, a 100 ohm resistor is placed in the way of the transmitter . the IR transmitter emits the infra red light.these infra red light is received by the IR receiver or photodiode. the function of the photodiode is to convert the light into the current.photodiodes are made up of semiconductors.photodiode is the p-n juction diode.

when the photons having sufficient energy falls on the photodiode it creates a pair of electron and holes which results to flow of current . due to this reverse brake down of  the receiver will occur and current will shorted to the ground , voltage  between R2 and the IR receiver become about to zero.in vertical branch a variable resistance is attached . LM358 comparator is also attached to this circuit as follows.comapator compares the voltage at 2 and 3  pin (which are coming from the 2 and 3 vertical branch discuss earlier).
here the voltage at pin 2 is getting low assume to be zero and at pin 3 it is less than 5V. so op-amp give the 1 digital signal which indicates that the LED (which is provided at the last vertical  branch ) will not glow.because digital signal 1 means 5V so due to this the potential difference in last branch become zero and current will not flow and led will not glow.which indicate that the robot will stop in its earlier position.
in other way if the light does not falls on the receiver in then reverse brake down of the receiver does not occur and in that case if we measure the voltage across the pin 2 and ir receiver it has voltage less than 5 volt.so op-amp gives the 0 digital signal and led will glow.

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