Ir Trans and Receiver

7/28/2019 Ir Trans and Receiver

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Infrared transmitter

Features 880 nm

Nine standard packages in hermetic and low-cost epoxy

End- and side-radiating packages

Graded Output

High efficiency GaAIAs, 880 nm LPE process delivers twice the power of

Conventional GaAs 940 nm emitters

Infrared (IR) radiation is electromagnetic radiation whose wavelength is longer than

that ofvisible light (400-700 nm), but shorter than that of terahertz radiation (100

m - 1 mm) and microwaves (~30,000 m). Infrared radiation spans roughly three

orders of magnitude (750 nm and 100 m).

Direct sunlight has a luminous efficacy of about 93 lumens per watt of radiant flux,

which includes infrared (47% share of the spectrum), visible (46%), and ultra-

violet (only 6%) light. Bright sunlight provides luminance of approximately 100,000

candela per square meter at the Earth's surface.

Overview

Infrared imaging is used extensively for both military and civilian purposes. Military

applications include target acquisition, surveillance, night vision, homing and

tracking. Non-military uses include thermal efficiency analysis, remote temperature

sensing, short-ranged wireless communication, spectroscopy, and weather

forecasting.. Infrared astronomy uses sensor-equipped telescopes to penetrate

dusty regions of space, such as molecular clouds; detect cool objects such as

planets, and to view highly red-shifted objects from the early days of the universe.

At the atomic level, infrared energy elicits vibration modes in a molecule through a

change in the dipole moment, making it a useful frequency range for study of these

energy states for molecules of the proper symmetry. Infrared spectroscopy
http://en.wikipedia.org/wiki/Electromagnetic_radiationhttp://en.wikipedia.org/wiki/Wavelengthhttp://en.wikipedia.org/wiki/Visible_lighthttp://en.wikipedia.org/wiki/Terahertz_radiationhttp://en.wikipedia.org/wiki/Microwaveshttp://en.wikipedia.org/wiki/Order_of_magnitudehttp://en.wikipedia.org/wiki/Lumen_(unit)http://en.wikipedia.org/wiki/Spectrumhttp://en.wikipedia.org/wiki/Visible_lighthttp://en.wikipedia.org/wiki/Ultra-violethttp://en.wikipedia.org/wiki/Ultra-violethttp://en.wikipedia.org/wiki/Luminancehttp://en.wikipedia.org/wiki/Candelahttp://en.wikipedia.org/wiki/Target_acquisitionhttp://en.wikipedia.org/wiki/Night_visionhttp://en.wikipedia.org/w/index.php?title=Thermal_efficiency_analysis&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Remote_temperature_sensing&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Remote_temperature_sensing&action=edit&redlink=1http://en.wikipedia.org/wiki/Wireless_communicationhttp://en.wikipedia.org/wiki/Spectroscopyhttp://en.wikipedia.org/wiki/Weather_forecastinghttp://en.wikipedia.org/wiki/Weather_forecastinghttp://en.wikipedia.org/wiki/Infrared_astronomyhttp://en.wikipedia.org/wiki/Telescopeshttp://en.wikipedia.org/wiki/Molecular_cloudhttp://en.wikipedia.org/wiki/Planethttp://en.wikipedia.org/wiki/Redshifthttp://en.wikipedia.org/wiki/Universehttp://en.wikipedia.org/wiki/Atomhttp://en.wikipedia.org/wiki/Vibrationhttp://en.wikipedia.org/wiki/Moleculehttp://en.wikipedia.org/wiki/Dipole_momenthttp://en.wikipedia.org/wiki/Infrared_spectroscopyhttp://en.wikipedia.org/wiki/Wavelengthhttp://en.wikipedia.org/wiki/Visible_lighthttp://en.wikipedia.org/wiki/Terahertz_radiationhttp://en.wikipedia.org/wiki/Microwaveshttp://en.wikipedia.org/wiki/Order_of_magnitudehttp://en.wikipedia.org/wiki/Lumen_(unit)http://en.wikipedia.org/wiki/Spectrumhttp://en.wikipedia.org/wiki/Visible_lighthttp://en.wikipedia.org/wiki/Ultra-violethttp://en.wikipedia.org/wiki/Ultra-violethttp://en.wikipedia.org/wiki/Luminancehttp://en.wikipedia.org/wiki/Candelahttp://en.wikipedia.org/wiki/Target_acquisitionhttp://en.wikipedia.org/wiki/Night_visionhttp://en.wikipedia.org/w/index.php?title=Thermal_efficiency_analysis&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Remote_temperature_sensing&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Remote_temperature_sensing&action=edit&redlink=1http://en.wikipedia.org/wiki/Wireless_communicationhttp://en.wikipedia.org/wiki/Spectroscopyhttp://en.wikipedia.org/wiki/Weather_forecastinghttp://en.wikipedia.org/wiki/Weather_forecastinghttp://en.wikipedia.org/wiki/Infrared_astronomyhttp://en.wikipedia.org/wiki/Telescopeshttp://en.wikipedia.org/wiki/Molecular_cloudhttp://en.wikipedia.org/wiki/Planethttp://en.wikipedia.org/wiki/Redshifthttp://en.wikipedia.org/wiki/Universehttp://en.wikipedia.org/wiki/Atomhttp://en.wikipedia.org/wiki/Vibrationhttp://en.wikipedia.org/wiki/Moleculehttp://en.wikipedia.org/wiki/Dipole_momenthttp://en.wikipedia.org/wiki/Infrared_spectroscopyhttp://en.wikipedia.org/wiki/Electromagnetic_radiation


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examines absorption and transmission of photons in the infrared energy range,

based on their frequency and intensity.

Origins of the term

The name means below red (from the Latin infra, "below"), red being the color of

the longest wavelengths of visible light. IR light has a longer wavelength (a lower

frequency) than that of red light, hence below.

Different regions in the infrared

Objects generally emit infrared radiation across a spectrum of wavelengths, but

only a specific region of the spectrum is of interest because sensors are usually

designed only to collect radiation within a specific bandwidth. As a result, the

infrared band is often subdivided into smaller sections.

An infrared emitter is an LED made from gallium arsenide,

which emits near-infrared energy at about 880nm. The infrared phototransistor acts

as a transistor with the base voltage determined by the amount of light hitting the

transistor. Hence it acts as a variable current source. Greater amount of IR light

cause greater currents to flow through the collector-emitter leads. As shown in the

diagram below, the phototransistor is wired in a similar configuration to the voltage

divider. The variable current traveling through the resistor causes a voltage drop in

the pull-up resistor. This voltage is measured as the output of the device
http://en.wikipedia.org/wiki/Photonhttp://en.wikipedia.org/wiki/Frequencyhttp://en.wikipedia.org/wiki/Photonhttp://en.wikipedia.org/wiki/Frequency


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Photo IR reflectance sensors contain a matched infrared

transmitter and infrared receiver pair. These devices work by measuring the

amount of light that is reflected into the receiver. Because the receiver also

responds to ambient light, the device works best when well shielded from ambient

light, and when the distance between the sensor and the reflective surface is

small(less than 5mm). IR reflectance sensors are often used to detect white and

black surfaces. White surfaces generally reflect well, while black surfaces reflect

poorly.


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How Infrared Trans Rex detectors work ?

Schematic Diagram for a Single Pair of Infrared Transmitter and Receiver


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Theory of Sensor Circuit


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= a/(a+R1) - b/(b+R1)

Description of operation of a typical circuit


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If the emitter and detector (aka phototransistor) are not blocked, then the output

on pin 2 of the 74LS14 will be high (apx. 5 Volts). When they are blocked, then the

output will be low (apx. 0 Volts). The 74LS14 is a Schmitt triggered hex inverter.

A Schmitt trigger is a signal conditioner. It ensures that above a threshold value,we will always get "clean" HIGH and LOW signals. Not Blocked Case: Pin 2 High

Current from Vcc flows through the detector. The current continues to flow through

the base of Q2. Current from Vcc also flows through R2, and Q2's Drain and Emitter

to ground. As a result of this current path, there will be no current flowing through

Q1's base. The signal at U1's pin 1 will be low, and so pin 2 will be high. Blocked

Case: Pin 2 Low Current "stops" at the detector. Q2's base is not turned on. The

current is re-routed passing through R2 and into the base of Q1. This allows current

to flow from Q1's detector and exiting out Q1's emitter. Pin 1 is thus high and pin 2

will be low. To detect a line to be followed, we are using two or more number of

poto-reflectors. Its output current that proportional to reflection rate of the floor is

converted to voltage with a resister and tested it if the line is detected or not.

However the threshold voltage cannot be fixed to any level because optical current


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by ambient light is added to the output current. Most photo-detecting modules are

using moderated light to avoid interference by the ambient light. The detected

signal is filtered with a band pass filter and disused signals are filtered out.

Therefore only the moderated signal from the light emitter can be detected.

Of course the detector must not be saturated by ambient light, this is effective

when the detector is working in linear region.


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The line position is compared to the center

value to be tracked; the position error is processed with

Proportional/Integral/Defense filters to generate steering command. The line

following robot tracks the line in PID control that the most popular algorithm for

servo control. The proportional term is the common process in the servo system. It

is only a gain amplifier without time dependent process. The differential term is

applied in order to improve the response to disturbance, and it also compensate

phase lag at the controlled object. The D term will be required in most case to

stabilize tracking motion. The I term that boosts DC gain is applied in order to

remove left offset error, however, it often decrease servo stability due to its phase

lag. When any line sensing error has occurred for a time due to getting out of line

or end of line, the motors are stopped and the microcontroller enters sleep state of

zero power consumption. Typical Examples of infrared Transmitter and Receiver

installation


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IR Receiver

Features

Tight production distribution.

Steel lead frames for improved reliability in solder mounting.

Good optical-to-mechanical alignment.

Plastic package is infrared transparent black to attenuate visible light.

Can be used with QECXXX LED, Black plastic body allows easy recognition

from LED.

Phototransistors also consist of a photodiode with internal gain. A phototransistor is

in essence nothing more than a bipolar transistor that is encased in a transparent

case so that light can reach the base-collector junction. The electrons that are

generated by photons in the base-collector junction are injected into the base, and

this photodiode current is amplified by the transistor's current gain. Note that while

phototransistors have a higher responsively for light they are not able to detect low

levels of light any better than photodiodes. Phototransistors also have slower

response times. A simple model of a phototransistor, would be a forward based LED(emitterbase) and a reverse based photodiode (basecollector) sharing an anode

(base) in a single package such that 99% (F%) of the light emitted by the led is

absorbed by the photodiode. Each electron-hole recombination in the LED produces

one photon and each photon absorbed by the photodiode produces one electron-

hole pair.


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IR Receiver needs to be in line of sight with the transmitter to efficiently transform

light impulses into digital values. The light emitted from the IR LED is modulated

with a lens into a compact beam and then turned an and of concerning the

message.

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Ir Trans and Receiver