INFRARED SENSOR

Infrared (IR) sensors are used in night vision cameras and goggles to detect heat emitted by objects. Since ambient light is absent, radiations emitted by the object are picked up by the sensors and used to form an image of the object. These devices can detect the presence of an intruder and are very important in guarding sensitive infrastructure. They are also used for non-contact temperature measurement.

How it works:
Red color has the longest wavelength and infrared means the wavelengths below this visible red. The IR detecting unit uses a silicon photodiode as the light-detecting source to convert the infrared radiation into an electric current. Since an object like a human body has different temperature zones, the electric current that is produced will also vary and can be used to form a map of temperatures or varying infrared colors from dark red to blue.

Selection:
The following factors are useful in selection:

• Responsivity - the responsivity at different frequency range measured in mV


• Sensitivity is a very crucial factor in infrared sensors and it should be very high and efficient.


• Field of view - the circular range in which the unit can sense radiation


• Stability


• Type of electrode


• Response time is the time taken by the sensor to detect, sense the object and send response.

Applications:

• IR sensors are used to build cameras or radiation detecting units, night vision goggles, and security and monitoring equipment.

• IR sensors find usage in process industries where the temperature can be between –30 deg C to 3000 deg C. Some of the process industries are paper, glass, metals, plastics, cement, chemical, food, petrochemical, textiles, etc.


• They also help firefighters to see smoke and save lives. PDAs and other computers and digital cameras use infrared technology to send and receive data.


• They are also used in motion detection and other equipment.

Author: Ashutosh Saini (Component Engr.)

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Brief about ISDN Line Interface

Integrated services digital network (ISDN) is a type of telephone circuit that allows digital signals of data and voice to be sent using the standard telephone wire. It gives better reproduction of signals and speed of transmission. ISDN line interfaces allow routers and multi-channel port boards to be connected to the ISDN system or the central office. A set of protocols and codecs are defined that allow the encoding of digital voice and data so that they are understood by analog systems.

Types of ISDN line interfaces:

• Basic rate interface (BRI): These are used in TV and radio broadcasting centers and use the MPEG codec. They use up to two 64 kbps channels.
• Primary rate interface (PRI): These are used for PBX connections. They can have up to 23 channels.
• There are two types of channels: B (bearer) type used for data and information transmission and D (delta) channel used for signaling.

Selection parameters for ISDN line interfaces:

• Send/receive separation: To reduce leakage of signals from send and receive paths, extra circuits are attached so that signals from the send path do not mix with those from the receive path.
• Acoustic coupling reduction: In studios, when the speakers use a microphone, an acoustic path is formed between the sent and received paths. By using functions like reducing the dynamic gain and adaptive cancellation, this issue is reduced.
• DAC conversion: 16bit digital to analog converters are used for connecting the analog equipment to the digital.
• Sampling rate conversion: The studio and the ISDN equipment operate at different frequencies. A suitable step-up and down process is needed to get them both in sync.
• Auto gain control: This is used for both the send and receives signals to smooth out the variations and takes care of different types of phone instruments.
• Dynamic equalization: This feature balances the frequencies of different makes of equipment. The processor of three band dynamic equalization is used.
• Caller ducking: the host to ‘kill’ unwanted conversation from other callers.
• Caller ID verification: Allows caller ID information to be transmitted.

Other parameters to be considered are: memory per channel, voltage/current, tempratures, etc.

Applications:

ISDN line interfaces are used to transmit voice and data in studios, PBX, TELCO, radio broadcasting stations, conferencing between remote speakers, etc.

Author: Deepak Raina (Component Engr.)

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Advancement In Visible LEDs Technology

IRC Advance Film Division which is TT Electronics Company has developed company’s Anotherm Aluminum Substrate material which offers superior thermal management for use with LED technology.

IRC’s patented Anotherm substrate provides display system design engineers a lighter, cooler and less expensive method of mounting multiple visible LEDs.

IRC’s Advance Film Division recently developed this economical anodized aluminum substrate material with superior thermal conductivity to address the problem of heat dissipation in direct mounted LEDs and LED arrays.

The Thermally conductive aluminum alloy enables design engineers to mount Visible LEDs and other components directly to it, eliminating the need for attached heat sinks, mounting hardware and associated assembly costs.

Economical solderable thick film conductors can be screen-printed directly to the Anotherm substrate to connect surface mount packaged components. The rugged Anotherm technology can operate in extreme temperatures – up to 400 degrees centigrade.

Author: Sanjay Chawla

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