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.