RoHS and its Importance

RoHS stands for “restriction of hazardous substance“. The term was coined by European Union (EU) in the year 1998 after it noticed alarmingly large quantities of hazardous waste being dumped into landfill sites. The volumes of these wastes were likely to increase 3-5 times faster than the average municipal waste. This indicated a very fast growing source of environmental contamination. RoHs is often referred to as the “lead-free” legislation, but it restricts the use of the following six substances:

1. Lead (Pb):- LEAD is mostly used and thus requiring the most attention. This is also the case for the entire electronics industry. Any cable sold with the RoHS qualification should be manufactured as such: Lead - Significant use in terminal finish for connectors/components, PWB board finish and solder for
   PWB assembly; use as UV/heat stabilizer in PVC cable jackets.
2. Mercury (Hg):- Not used.
3. Cadmium (Cd):- Very limited use as colorant for plastic materials.
4. Hexavalent Chromium (Cr⁶⁺):- Limited use as corrosion protection for retention hardware (e.g. screws, washers); limited use as conversion coating for metallic housings.
5. Polybrominated biphenyls (PBB):- Very limited use as flame retardant in plastic materials.
6. Polybrominated Diphenyl Ether (PBDE):- Very limited use as flame retardant in plastic materials.

Maximum allowed concentration values are:-

1. Up to 0.1 per cent by weight (1000 PPM) in standardized materials for lead, mercury, hexavalent chromium, PBBs and PBDEs.
2. Up to 0.1 per cent by weight (1000 PPM) in standardized materials for cadmium.

Note that not all electronic equipment fall within the scope of these regulations. For example, batteries are considered to be an ‘old area’ product and not currently covered by the regulations. Similarly, electronic equipment intended to product national security, or with a military purpose, is exempted.

To deal with this problem, the member states of the EU decided to create the waste electrical and electronics equipment (WEEE) directive, whose purpose is to:-

• Improve manufacturers’ designs, to reduce the creation of waste.
• Make manufacturers responsible for certain phases of waste management.
• Create systems to improve treatment, refuse and recycling of WEEE.
• Promote separate collections of electronic waste.

In 1998, a draft proposal called EEE (Environmental of electrical & Electronics Equipment) was also introduced along the same lines. Now, as the implementation of this policy becomes imminent, this policy is generally referred to as the RoHS directive.

As the restricted materials are hazardous to the environment and dangerous in terms of occupational exposure during manufacturing and recycling, the EU countries adhere to the RoHS. All the applicable products in the EU market after July 1, 2006 must be RoHS compliant. Therefore any business that sells applicable electronics products, sub-assemblies or components directly to EU countries, or sells to resellers, distributors or integrators that, in turn, sell products to EU countries, is impacted if it utilizes any of the restricted materials.

Read: http://www.torex-usa.com/rohs/

Blu-ray Disc

Blu-ray Disc (also known as Blu-ray or BD) is an optical disc storage media format. It is mainly used in high-definition video and data storage. Blu-ray Disc has the same physical dimensions as a standard DVD or CD.

A single-Layer Blu-ray has storage capacity of 25GB, while a dual-layer BD can store up to 50GB of data. As the name suggests, a blue-violet laser is used to write data on a Blu-ray disk, unlike the traditional method wherein red laser employed to store data on DVDs.

A Blu-ray disk can hold 9-hour high definition video and standard-definition (SD) video that can run 23 hours, on a 50GB disk. The BD-ROM movies will require a rate of MBPS for data transfer, so the expected speed is 2x (72 Mbps). There is also a scope for having much higher speed because of the larger numerical aperture (NA) adopted by the BD. It implies that a Blu-ray disk will need less recording power and lower disk rotation speed vis-à-vis conventional DVDs and HD DVDs. The sole limiting factor for blu-ray is the capacity of the hardware.

The storage capacity of Blu-ray disk (BDs) is five times that of conventional DVDs. BDs supports NPEG-2, MPEG-4 AVC and SMPTE VC-1 formats (codecs).

Blu-ray Disc uses a "blue" (technically violet) laser operating at a wavelength of 405 nm to read and write data. Conventional DVDs and CDs use red and near infrared lasers at 650 nm and 780 nm respectively.

The blue-violet laser's shorter wavelength makes it possible to store more information on a 12 cm CD/DVD sized disc. The minimum "spot size" on which a laser can be focused is limited by diffraction, and depends on the wavelength of the light and the numerical aperture of the lens used to focus it. By decreasing the wavelength, increasing the numerical aperture from 0.60 to 0.85 and making the cover layer thinner to avoid unwanted optical effects, the laser beam can be focused to a smaller spot. This allows more information to be stored in the same area. For Blu-ray Disc, the spot size is 580 nm In addition to the optical improvements; Blu-ray Discs feature improvements in data encoding that further increase the capacity.

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Signal Processing Process

• Signal processing is the analysis, interpretation, and manipulation of signals. Signals of interest include sound, images, and biological signals such as ECG, radar signals, and many others. Processing of such signals includes filtering, storage and reconstruction, separation of information from noise (for example, aircraft identification by radar), compression (for example, image compression), and feature extraction (for example, speech-to-text conversion).
  In communication systems, signal processing only occurs at OSI layer 1, the physical layer (modulation, equalization, multiplexing, radio transmission, etc) in the seven layer OSI model, as well as at OSI layer 6, the presentation layer (source coding, including analog-to-digital conversion and data compression).
  
  
  Signals are electrical representations of time-varying or spatial-varying physical quantities, either analog or digital, and may come from various sources. In the context of signal processing, arbitrary binary data streams are not considered as signals, but only digital signals that are representations of analog physical quantities.
  
  For analog signals, signal processing may involve the amplification and filtering of audio signals for audio equipment or the modulation and demodulation of signals for telecommunications. For digital signals, signal processing may involve digital filtering and compression of digital signals.
  
  Analog signal processing — for signals that have not been digitized, as in classical radio, telephone, radar, and television systems
  Discrete-time signal processing – for signals that are defined only at discrete points in time, and as such are quantized in time, but not magnitude. This theoretical discipline establishes the mathematical basis for digital signal processing, the technology of processing signals that are quantized in time and magnitude.
  
  Digital signal processing — for signals that have been digitized. Processing is done by general-purpose computers or by digital circuits such as ASICs, FPGAs, or specialized digital signal processors (DSP chips).
  
  Statistical signal processing — analyzing and extracting information from signals based on their statistical properties
  
  Audio signal processing — for electrical signals representing sound, such as speech or music
  
  Speech signal processing — for processing and interpreting spoken words
  
  Image processing — in digital cameras, computers, and various imaging systems
  
  Video processing — for interpreting moving pictures
  
  Array processing — for processing signals from arrays of sensors

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Battery Charging Technology

For rechargeable batteries, great care is required in the design of charging circuits and especially the Fast charging circuits. These circuits are dependent on the battery chemistry. On the other hand slow charging circuits – charging time more than 12 hours – are simpler than fast charging circuits.

Fast charging circuits have in-built means to terminate the charge because, overcharging the batteries may cause reduced battery life and sometimes even destroy the battery. Overcharging the battery may also lead to over-heating and emission of dangerous corrosive gases.

Below is a figure which shows the specifications of various types Rechargeable batteries:
Li-ion batteries are better than NiCd and NiMH in regard of self discharge.
The discharge rate is defined as the Max. allowable load or discharge current and is expressed in units of C-Rate.
The no. of charge and discharge cycles is the avg. no. of times a battery can be discharged and then re-charged and is measure of battery’s service life.
Memory in case of NiCd batteries usually disappears if the cell is almost fully discharged before recharging. However it is very rare that NiCd battery are discharged to that level before re-charging.

Below is the Battery Charging generalized circuit:
The battery is charged to full with a constant current supply. Voltage across the current sense resistor is used to maintain constant current supply. Control circuits and microprocessor is used to monitor voltage. Temperature sensors are used to monitor battery temperature and ambient temperature.

The above type of circuit is used for Fast charging applications.

Most difficult thing is to determine correctly that when to terminate the charging, since overcharging can damage the battery.

The charge may be terminated by monitoring battery voltage, voltage change vs. time, temperature change, temperature change vs. time, min. current at full voltage, charge time and various combinations of these depending upon the battery type.

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