Non Volatile Random Access Memory (NVRAM)

NVRAM stands for Non Volatile Random Access Memory. It is a type of random access memory which does not lose its information when power is switched off. Now a days most commonly form of random memory access used SRAM or DRAM both require continual power in order to maintain their data. The NVRAM is a small 24 pin DIP (Dual Inline Package) integrated circuit chip and is thus able to obtain the power needed to keep it running from the CMOS battery installed in your motherboard. NVRAM is therefore a type of non-volatile memory that offers random access. There are two types of NVRAM.

One type of NVRAM is EEPROM that is Electrically Erasable Programmable Read-Only Memory circuit chips which maintain its information when power is switched off. In this case, NVRAM is composed of a combination of SRAM and EEPROM chips incorporated into a single semi-conductor die.

Another type of NVRAM is SRAM that is made non-volatile by connecting it to a constant power source such as a battery. Since SRAM requires continual power supply in order to save its contents, an NVRAM that is made from an SRAM will need to use an available power supply to make sure it continues working.

Advantages of NVRAM :-

1.NVRAM's serve applications that require high-speed write/read operations with non-volatile memories such as parallel processing controllers for antilock braking systems and LANs..
2.NVRAM chips work as SRAM.
3.NVRAM chips does not require much power and backup can be guaranteed for up to ten years.
4.The performance of NVRAMs is superior in comparison to other NVM products

Disadvantages of NVRAM :-

1.If the CMOS chip is not making proper contact with the motherboard's contacts. At this situation NVRAM would not be successful.
2.If the battery embedded in the NVRAM chip fails, then this means that your system clock will stop running and important system configuration information may not be maintained.

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Application of Photo Sensors in Smoke Detectors

Smoke sensor

There are two main types of smoke detectors: ionization detectors and photoelectric detectors. A smoke alarm uses one or both methods, sometimes plus a heat detector, to warn of a fire. The devices may be powered by a 9-volt battery, lithium battery, or 120-volt house wiring. Here let us discuss about photo

Photoelectric Detectors

In one type of photoelectric device, smoke can block a light beam. In this case, the reduction in light reaching a photocell sets off the alarm. In the most common type of photoelectric unit, however, light is scattered by smoke particles onto a photocell, initiating an alarm. In this type of detector there is a T-shaped chamber with a light-emitting diode (LED) that shoots a beam of light across the horizontal bar of the T. A photocell, positioned at the bottom of the vertical base of the T, generates a current when it is exposed to light. Under smoke-free conditions, the light beam crosses the top of the T in an uninterrupted straight line, not striking the photocell positioned at a right angle below the beam. When smoke is present, the light is scattered by smoke particles, and some of the light is directed down the vertical part of the T to strike the photocell. When sufficient light hits the cell, the current triggers the alarm.


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Hall Effect Sensor

Hall Effect Sensor is a transducer which varies the output voltage according to change in magnetic field.

Electricity carried through a conductor will produce a magnetic field that varies with current, and a Hall sensor can be used to measure the current without interrupting the circuit. Typically, the sensor is integrated with a wound core or permanent magnet that surrounds the conductor to be measured. One very important feature of the Hall effect is that it differentiates between positive charges moving in one direction and negative charges moving in the opposite.

How Hall Effect Sensor Works: -

Hall Sensor usually have three pins and below is the related diagram in fig1.

The Hall Effect refers to the potential difference (Hall voltage) on opposite sides of a thin sheet of conducting or semiconducting material through which an electric current is flowing, created by a magnetic field applied perpendicular to the Hall element. Here we have an amplifier in the cicuitry, it amplifies the signal carried by the Hall Element because the Hall effect sensor produce a very low signal.

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