Infrared proximity sensor report file.

1. CONTENTS
DECLARATION
CERTIFICATE
ACKNOWLWEDGEMENTS
1. INTRODUCTION 02
2. REVIEW
2.1 PCB 03
2.2 RESISTOR 03
2.3 IR LED 04
2.4 PHOTODIODE 05
2.5 PRESET 06
2.6 LM358 07
2.7 WORKING PRINCIPLE 08
2.8 IR CRICUIT SENSOR 09
2.9 CONCLUSION 10
3.0 REFRENCES 11
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2. 1. INTRODUCTION
Infrared technology addresses a wide variety of wireless applications. The main areas are sensing
and remote controls. In the electromagnetic spectrum, the infrared portion is divided into three
regions: near infrared region, mid infrared region and far infrared region.
The wavelengths of these regions and their applications are shown below.
• Near infrared region — 700 nm to 1400 nm — IR sensors, fiber optic
• Mid infrared region — 1400 nm to 3000 nm — Heat sensing
• Far infrared region — 3000 nm to 1 mm — Thermal imaging
The frequency range of infrared is higher than microwave and lesser than visible light.
For optical sensing and optical communication, photo optics technologies are used in the near
infrared region as the light is less complex than RF when implemented as a source of signal.
Optical wireless communication is done with IR data transmission for short range applications.
An infrared sensor emits and/or detects infrared radiation to sense its surroundings.
The working of any Infrared sensor is governed by three laws: Planck’s Radiation law, Stephen –
Boltzmann law and Wien’s Displacement law.
Planck’s law states that “every object emits radiation at a temperature not equal to 00K”. Stephen
– Boltzmann law states that “at all wavelengths, the total energy emitted by a black body is
proportional to the fourth power of the absolute temperature”. According to Wien’s Displacement
law, “the radiation curve of a black body for different temperatures will reach its peak at a
wavelength inversely proportional to the temperature”.
The basic concept of an Infrared Sensor which is used as Obstacle detector is to transmit an
infrared signal, this infrared signal bounces from the surface of an object and the signal is
received at the infrared receiver.
sed There are five basic elements used in a typical infrared detection system: an infrared source,
a transmission medium, optical component, infrared detectors or receivers and signal processing.
Infrared lasers and Infrared LED’s of specific wavelength can be used as infrared sources. The
three main types of media used for infrared transmission are vacuum, atmosphere and optical
fibers. Optical components are used to focus the infrared radiation or to limit the spectral
response. Optical lenses made of Quartz, Germanium and Silicon are u to focus the infrared
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3. radiation. Infrared receivers can be photodiodes, phototransistors etc. some important
specifications of infrared receivers are photosensitivity, detectivity and noise equivalent power.
Signal processing is done by amplifiers as the output of infrared detector is very small.
2.1 PCB Connection
A zero printed circuit board, or PCB, is used for Electronics and Communication support and
electrically connect electronic components using conductive pathways, tracks or signal traces
etched from copper sheets laminated onto a non-conductive substrate.
The PCB is printed circuit board having circuit made with cooper layer on the
plate there are various steps to design a PCB for that the basic thing required is circuit. So, the
circuits required for the system.
2.2 Resistor
A resistor is a passive two-terminal electrical component that implements electrical resistance as
a circuit element. The current through a resistor is in direct proportion to the voltage across the
resistor's terminals. Thus, the ratio of the voltage applied across a resistor's terminals to the
intensity of current through the circuit is called resistance.
V= IR
where I is the current through the conductor in units of amperes, V is the potential
difference measured across the conductor in units of volts, and R is the resistance of the
conductor in units of ohms. More specifically, Ohm's law states that the R in this relation is
constant, independent of the current.
38
Resistors are common elements of electrical networks and electronic circuits and are
ubiquitous in electronic equipment. Practical resistors can be made of various compounds and
films, as well as resistance wire (wire made of a high-resistivity alloy, such as nickel-chrome).
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4. Resistors are also implemented within integrated circuits, particularly analog devices, and can
also be integrated into hybrid and printed circuits.
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RESISTOR
2.3 IR LED
An IR LED, also known as IR transmitter, is a special purpose LED that transmits infrared rays
in the range of 760 nm wavelength. Such LEDs are usually made of gallium arsenide or
aluminum gallium arsenide. They, along with IR receivers, are commonly used as sensors.
!
IR LED
The appearance is same as a common LED. Since the human eye cannot see the
infrared radiations, it is not possible for a person to identify whether the IR LED is working or
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5. not, unlike a common LED. To overcome this problem, the camera on a cell phone can be used.
The camera can show us the IR rays being emanated from the IR LED in a circuit.
2.4 Photodiode
A photodiode is a type of photo detector capable of converting light into either current
or voltage, depending upon the mode of operation. The common, traditional solar cell used to
generate electric solar power is a large area photodiode.
!
Photodiode
Photodiodes are similar to regular semiconductor diodes except that they may be either exposed
(to detect vacuum UV or X-rays) or packaged with a window or optical fiber connection to allow
light to reach the sensitive part of the device. Many diodes designed for use specifically as a
photodiode use a PIN junction rather than a p-n junction, to increase the speed of response. A
photodiode is designed to operate it.
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6. 2.5 PRESET
A preset is a three legged electronic component which can be made to offer varying resistance in
a circuit. The resistance is varied by adjusting the rotary control over it. The adjustment can be
done by using a small screw driver or a similar tool. The resistance does not vary linearly but
rather varies in exponential or logarithmic manner. Such variable resistors are commonly used
for adjusting sensitivity along with a sensor.
The variable resistance is obtained across the single terminal at front and one of the two other
terminals. The two legs at back offer fixed resistance which is divided by the front leg. So
whenever only the back terminals are used, a preset acts as a fixed resistor. Presets are specified
by their fixed value resistance.
PRESET
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7. 2.6 LM358
The LM358 is a low power dual operational amplifier integrated circuit originally introduced by
National Semiconductor.[1] It is used in detector circuits.
The abbreviation LM358 indicates an 8-pin integrated circuit, comprising two operational
amplifiers at low power. The LM358 is designed for general use as amplifiers, high-pass filters,
low band pass filters, and analog adders.
LM358 IC
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8. 2.7 Principle of Working
The principle of an IR sensor working as an Object Detection Sensor can be explained
using the following figure. An IR sensor consists of an IR LED and an IR Photodiode;
together they are called as Photo – Coupler or Opto – Coupler.
When the IR transmitter emits radiation, it reaches the object and some of the radiation
reflects back to the IR receiver. Based on the intensity of the reception by the IR
receiver, the output of the sensor is defined.
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9. 2.8 Obstacle Sensing Circuit or IR Sensor Circuit
A typical IR sensing circuit is shown below.
It consists of an IR LED, a photodiode, a potentiometer, an IC Operational amplifier and
an LED.
IR LED emits infrared light. The Photodiode detects the infrared light. An IC Op – Amp is
used as a voltage comparator. The potentiometer is used to calibrate the output of the
sensor according to the requirement.
When the light emitted by the IR LED is incident on the photodiode after hitting an
object, the resistance of the photodiode falls down from a huge value. One of the input
of the op – amp is at threshold value set by the potentiometer. The other input to the op-
amp is from the photodiode’s series resistor. When the incident radiation is more on the
photodiode, the voltage drop across the series resistor will be high. In the IC, both the
threshold voltage and the voltage across the series resistor are compared. If the voltage
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10. across the resistor series to photodiode is greater than that of the threshold voltage, the
output of the IC Op – Amp is high. As the output of the IC is connected to an LED, it
lightens up. The threshold voltage can be adjusted by adjusting the potentiometer
depending on the environmental conditions.
The positioning of the IR LED and the IR Receiver is an important factor. When the IR
LED is held directly in front of the IR receiver, this setup is called Direct Incidence. In
this case, almost the entire radiation from the IR LED will fall on the IR receiver. Hence
there is a line of sight communication between the infrared transmitter and the receiver.
If an object falls in this line, it obstructs the radiation from reaching the receiver either by
reflecting the radiation or absorbing the radiation.
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11. 2.9 CONCLUSION
There are five basic elements used in a typical infrared detection system: an infrared source, a
transmission medium, optical component, infrared detectors or receivers and signal processing.
Infrared lasers and Infrared LED’s of specific wavelength can be used as infrared sources. The
three main types of media used for infrared transmission are vacuum, atmosphere and optical
fibers. Optical components are used to focus the infrared radiation or to limit the spectral
response. Optical lenses made of Quartz, Germanium and Silicon are u to focus the infrared
radiation. Infrared receivers can be photodiodes, phototransistors etc. some important
specifications of infrared receivers are photosensitivity, detectivity and noise equivalent power.
Signal processing is done by amplifiers as the output of infrared detector is very small.
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12. 3.0 REFERENCES
1. http://www.semico.com
2. Heath, Steve (2003). Embedded systems design. EDN series for design engineers (2 ed.).
Newnes. pp. 11–12. ISBN 9780750655460
3. http://www.youtube.com
4. www.infineon.com/mcu
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