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Magneto resistive random access technology (MRAM) for better memory storage

Technologists researching at the laboratories of the National University of Singapore in the department of Electrical and Computer Engineering have developed a new technology that will help in enhancing storing information in electronic systems in a better and more durable manner. Called Magneto Resistive Random Access Technology, this innovative method increases the storage space considerably and ensures that all fresh data will remain intact, even when there is a power failure. The team of researchers, led by Dr. Yang Hyunsoo, has filed for a provisional patent in the USA. They claim that the development will bring about a structure that will be of use to MRAM chips of the next generation.

This innovative method of storing information has a very wide field of application. All devices in the field of electronics such as Personal computers, laptops, mobile phones and all mobile devices will benefit from this unique technology. Data storage is required in various fields of activity such as in transportation, avionics, military, robotics, industrial motor controls, management of energy and power. Another major user is electronic equipment for health care.

According to Dr. Yang, the new technology will increase storage space, and enhance the memory. According to him, computers, laptops, etc., do not need booting up and there is no necessity for using the “Save” key regularly. Fresh data is not deleted even when there is a stoppage of power, unlike the current DRAMs in use. What is of greater significance is the memory will last for a minimum of 20 years and maybe for an even longer period. Compare this to the present method of storing information, which gives the user only about a year of stored data. One of the best uses is in the case of mobile phones. According to Dr. Yang, “we usually need to charge them daily. Using our new technology we may need to charge them on a weekly basis.” This will be a substantial cost-saver.

MRAM, the new technology, enables data to be retrieved even if the equipment concerned is not powered up. Additionally, MRAM consumes low power and has high bit density. The new technology is expected to bring about a sea of changes in computer architecture. Manufacturers will find it easier to use MRAM as flash memory can be dispensed with. That will also help in bringing down the cost substantially. The success of MRAM has induced major semiconductor manufacturers like Intel, IBM, Samsung and Toshiba to conduct further research.

Currently, MRAM uses technology based on current induced magnetization in a horizontal plane. It requires ultra-thin ferromagnetic structures, less than 1 nanometer, which are difficult to manufacture, has low reliability and the retention period is less than a year. The NUS team collaborating with Saudi Arabia’s King Abdullah University of Science and Technology has developed a multi-layer magnetic structure of 20-nanometer thickness. It effectively provides a film structure that helps in the storage of information and data for at least 20 years. The team is looking for collaboration with the industry.

What Is An Electronic Load And Where Do You Use It?

Power supply manufacturers need to test their products dynamically. Instead of using fixed-resistor banks of different sizes, electronic loads allow them to simulate easily and quickly various power states. Using an electronic load, large ranges of power sources such as converters, inverters, UPSs and electromechanical sources such as batteries and fuel cells may be tested. For varying loads, electronic loads are easier to use and provide a much higher throughput compared to fixed-resistors.

For example, a handheld device may have to be tested for sleep, power conservation and full power modes. These are easier to test using a single electronic load, but may require several combinations of fixed-resistors. Additionally, an electronic load may be programmed to represent closely a real environment for a power source. This may take the form of modulation to improve the performance of power supplies by providing a faster transient response as compared to a standard power supply.

An electronic load usually consists of a bank of power transistors, power MOSFETs or IGBTs mounted on a suitably sized heat sink, and cooled with fans. An electronic circuit governs the amount of current that the power devices can draw from the power supply on test. To protect the power devices from damage, electronic loads usually have a pre-settable power limit. The manufacturer usually provides a power curve for the safe operation of an electronic load. The user must be aware of the simultaneous maximum voltage and current that can be applied to the electronic load to ensure the electronic load is not overpowered.

It is important to select a suitable electronic load for the testing. For example, a power supply rated for 12V and 30A, may never be operated at 12V and 30A continuously. While testing, the operator may run it at 12V and 5A and then at 3V and 30A. That means an electronic load of 90-100W is sufficient to test the supply.

To improve the performance of a power supply, an electronic load may be used as a high-speed current modulator. In such cases, only a fraction of the power rating of the power supply is required. When the current is modulated to the highest level, the voltage across the load is likely to be very low. As the current is modulated off, the voltage rises to its maximum. Usually, if the modulation of the current is from zero to some maximum, the load power required is one-quarter of the operating voltage times the current rating with some margin added.

Electronic loads are very useful for dynamically testing power sources. In this form of testing, the current is quickly pulsed between two states, simulating a possible sleep mode and a full power mode of a device. This pulsing can be as fast as 20,000 times a second.

Another requirement that electronic loads are adept at is low voltage testing. Although most electronic loads will refuse to operate when the applied voltage is below 1V, there are some models, which perform comfortably down to 0.6V. This is a very useful feature when testing fuel cells where the operation at low voltages is crucial.

Home Protection with Raspberry Pi

Planning to go on a vacation, but afraid of who will look after your home for you? Worry not, for the mighty Raspberry Pi (RBPi) is here. Not only will RBPi look after your entire house, it will send you an email of what is happening in your home and let you see it on your mobile or on a PC. How cool is that?

Most alarm systems incorporate three primary sensors. The first is a temperature sensor to detect the rise in temperature in case of a fire. The second is an intrusion detection sensor to detect if an intruder has gained access to the insides of the house and third is a motion detection sensor. Apart from these primary sensors, you may add smoke detectors and cameras according to your necessity.

The software consists mainly of a database to store all the events with a time stamp, a dashboard to display the status of the sensors, configure them and to program the alarm system. The Raspberry Pi also acts as a web-server to send email alerts and to display the dashboard on a remote computer or Smartphone.

Depending on the size of the home, its vulnerability and the number of sensors being used, you could divide the area into a number of zones. This makes it easier to arm the sensors belonging to a specific zone. For example, a door and few windows of your home may be facing a busy street during the day and you may decide not to arm the sensors in this zone in the daytime. As night falls, the street gets deserted and you may want the sensors in that zone to be armed for the night.

Dividing the home into zones also has the advantage of knowing in which area or areas the alarm has been triggered. The camera for that zone can then be switched on to assess the situation visually.

Since RBPi runs on Linux, and Linux multitasks very well, the software runs in the background. The software is programmed to wake up RBPi about once every minute and check in on each of the armed sensors in all the zones. If there is no activity, it simply updates the logs for the database and the dashboard and goes back to sleep.

If a sensor trips, or generates an activity, Raspberry Pi records it in its logs, and sends you an email with the details. The dashboard then indicates the alarm condition in the zone where the alarm originated. You have a choice of turning off the alarm after checking it out.

You can login to the server from a remote PC using a username and a password. The web-browser will display the dashboard and a green button lets you know that the RBPi is running your home alarm software and is transmitting the information from the sensors. If the alarm system goes down for some reason, or there is a problem with the connectivity between the Raspberry Pi and your computer, this green button will turn red within a minute. You can now proceed to test, arm or disarm the sensors in each zone. For details of software and setup, refer here.

Sensing humidity using advanced technology

An approaching thunderstorm creates a very stuffy environment with oppressively heavy moisture in the air. The presence of water in the air is termed as humidity and this largely affects human comfort. The amount of water vapor influences many physical, chemical and biological processes. In industries, measuring and controlling humidity is critical since it can affect not only the health and safety of personnel, it can affect the business cost of the product as well.

Sleep apnea leads to repeated cessation of breathing during sleep. People, who suffer from sleep apnea, have to wear a mask to prevent nasal collapse. The mask is connected to a Positive Airway Pressure machine that sends pressurized air through the nasal passage of the patient, to prevent it from collapsing. It is important to monitor the humidity of the air the patient receives, keeping it at the appropriate level of comfort to allow the patient to sleep comfortably.

Traditionally, humidity or relative humidity was measured with the wet and dry bulb hygrometers. This method is neither accurate nor convenient in the industrial environment. With advancement in technology, solid-state devices are now available, which measure humidity with very high accuracy, repeatability and interchangeability. Solid-state humidity sensors are generally of two types, capacitive and resistive.

In resistive type humidity sensors, the resistance of the element changes responding to variations in humidity in the environment. The construction is in the form of two intermeshed printed combs, made of a thick film conductor of a precious metal such as gold or ruthenium oxide. The two combs form two electrodes, the space between them being filled with a polymeric film. This film has movable ions whose movement is governed by humidity. The film thus acts like a sensing film whose resistance changes with change in humidity.

The capacitive type of humidity sensor has an Alumina substrate on which the lower electrode is formed using either gold or platinum. A dielectric polymer layer such as thermoset polymer is then deposited on the lower electrode. This layer is sensitive to humidity. On top of this polymer layer, a top electrode is placed, and this is also made of gold or platinum. The top layer is porous and allows water vapor to pass through into the sensitive PVA layer. Moisture enters or leaves the sensing layer until the vapor content is in equilibrium with the environment. This sensor is therefore a type of capacitor whose capacitance changes with the change in humidity.

The arrangement of a hygroscopic dielectric material sandwiched between two pairs of electrodes, forms a capacitor whose value is governed by the dielectric constant of the hygroscopic material and the sensor geometry. At normal room temperatures, the value of the dielectric constant of water vapor is about 80, which is much larger than the constant of the sensor dielectric material. Therefore, as the sensor absorbs water vapor from the environment, it results in an increase in the capacitance of the sensor.

Both the resistive type and capacitive type of humidity sensors are available in the form of small surface mount SMD packages, and pre-calibrated to simplify, speedup manufacturing and reduce the cost for Original Equipment Manufacturers.

How do photovoltaic cells work?

Your calculator probably has a darkish colored panel just above the display. The panel is made up of solar cells that power up your calculator if there is enough light. You may also have seen some solar panels, which people use for charging up their cell phones. Earlier, these solar cells or photovoltaic cells were exclusively used to power the electrical systems of satellites. However, they are now commonly used in less exotic ways as well.

How do photovoltaic cells convert light to electricity? For this, you must understand the way these cells are constructed. A photovoltaic cell has two silicon plates bonded together. Pure silicon is an insulating material and is unable to conduct electricity. This is because of the atomic structure of silicon, which has place for eight electrons in the outermost shell of its atoms. However, there are only four electrons present.

Therefore, when silicon atoms come together, they share their electrons. Each atom shares one electron with its neighbor and they become a pair. That means at any time, four atoms surround each silicon atom, bringing up its catch of electrons to eight on the outer shell. Since all the electrons are now bound up, there is none left free to move about and carry electric charge.

To make the silicon plates able to carry electric charge, one of the two plates must have some free electrons and the other plate must have some holes or lack of electrons. This is done by the process of doping. While making the plates, one of them is given a few phosphorus atoms as impurities. Since phosphorus has five atoms in the outermost shell of its atom, when combining with the silicon atoms, one of its electrons remains unpaired. This makes the silicon plate with the phosphorus impurity have excess electrons and this is called the n-type silicon.

Likewise, the other plate is doped with boron, which has only three electrons in the outermost shell of its atoms. This leaves the combination of silicon and boron atoms with a deficit of electrons and this is called the p-type silicon. This is like a hole, which will readily grab a wandering electron to fill up its vacant space.

Light is essentially a barrage of energetic particles called photons. Photons impart their energy to the surface where they land, which is why you feel warm when you stand in sunlight. If light or photons are allowed to fall on the n-type silicon plate that has extra electrons, they receive the excess energy from the photons. The extra energy allows them to dislodge themselves from their original positions and wander off until they come to the other plate with the holes, where they are eagerly absorbed.

However, the n-type silicon plate that supplied the electrons now has a deficiency of electrons that it must fill up. For electrons to flow, the circuit must be externally completed. This is usually done by connecting a load to the solar cell through external wires. The plate makes up its deficiency of electrons by borrowing them from the connecting wire. In essence, photons drive the electrons through the entire circuit, and that makes the current flow through the solar cell and the load connected to it.

As soon as light falling on the solar cell is removed, the running electrons lose their drive, and the flow of current stops. Although the output from each cell is usually very tiny, by combining them in series and parallel, an impressive amount of power can be generated.

Transistors: What Is The Difference Between BJT, FET And MOSFET?

BJTs, FETs and MOSFETs are all active semiconductor devices, also known as transistors. BJT is the acronym for Bipolar Junction Transistor, FET stands for Field Effect Transistor and MOSFET is Metal Oxide Semiconductor Field Effect Transistor. All three have several subtypes, and unlike passive semiconductor devices such as diodes, active semiconductor devices allow a greater degree of control over their functioning.

Depending on their subtypes, operating frequency, current, voltage and power ratings, all the three types of transistors come in a large variety of packages, and all of them are susceptible to ESD or Electro Static Discharge. That means when you handle these devices, you must take adequate precaution against static charges destroying them.

he basic construction of a BJT is two PN junctions producing three terminals. Depending on the type of junctions, the BJT can be a PNP type or an NPN type. The three terminals are identified as the Emitter or E, the Base or B and the Collector or C. BJTs usually function as current controlling switches. The three terminals can be connected in three types of connections within an electronic circuit – Common Base configuration, Common Emitter configuration and Common Collector configurations. All the three connections have their own functions, merits and demerits. The BJT is Bipolar because the transistor operates with both types of charge carriers, Holes and Electrons.

The FET construction does not have a PN junction in its main current carrying path, which can be made from an N-type or a P-type semiconductor material with high resistivity. A PN junction is formed on the main current carrying path, also called the channel, and this can be made of either a P-type or an N-type material. The three leads of a FET are the Source (S), Drain (D) and Gate (G), with Source and Drain forming the ends of the channel and the Gate controlling the channel conductivity. Unlike the BJT, the FET is a unipolar device since it functions with the conduction of electrons alone for the N-channel type or on holes alone for a P-channel type.

The input impedance at the gate of an FET is very high, unlike the BJT, which comparatively has much lower impedance. Additionally, the conductivity of the channel depends on the voltage applied to the Gate, essentially making it a voltage-controlled device, unlike the BJT, which is current-controlled. The voltage applied to the Gate controls the width of the channel, allowing the FET to carry current between the Drain and Source pins. The Gate voltage that cuts off the current flow between Drain and Source is called the pinch off voltage and is an important parameter.

The MOSFET is a special type of FET whose Gate is insulated from the main current carrying channel. It is also called the IGFET or the Insulated Gate Field Effect Transistor. A very thin layer of silicon dioxide or similar separates the Gate electrode and this can be thought of as a capacitor. The insulation makes the input impedance of the MOSFET even higher than that of a FET. The working of the MOSFET is very similar to the FET.

You can read more about transistors in depth here.

Automate Your Home HVAC System from the Internet Using the Raspberry Pi

The HVAC devices in your home, typically the air-conditioner, thermostats, heating and ventilation, use one or more remote handheld devices working on Infrared (IR) technology. As the HVAC devices are from different manufacturers, you will most likely own a multitude of remote devices, making it difficult to handle and set each of them independently.

However, with the Raspberry Pi or RBPi, a small board called the IR Remote Shield and a wireless interface, you can control all the HVAC devices and that too from the Internet. Imagine setting up the environment in your home just as you are leaving office, so that you have a cozy atmosphere to relax at home.

There are two steps in this project. The first step involves teaching the Raspberry Pi and IR Remote Shield combination the codes that the remote handheld devices utilize to control the various functions of each of the HVAC devices. The second step is to connect the RBPi to the Internet through any one of the wireless interfaces such as Wi-Fi, 3G, GPRS, Bluetooth, and ZigBee or 802.15.4. These interfaces are available from Cooking Hacks, and you can choose one.

After you connect your RBPi to the Internet and feed in the IR codes used by your HVAC components, you can use a webserver, a laptop or even your Smartphone to control all your home HVAC appliances from anywhere in the world. But, a few words about Infrared technology first.

Started in 1993, IrDA or Infrared Data Association is the technology popularly used for controlling devices such as air-conditioners, TVs, radios, audio systems and many others. It is based on light rays in the infrared spectrum and invisible to the human eye. Using infrared transmitters and receivers, communication between two devices can be established in direct line of vision. The infra-red transmitters use special types of Light Emitting Diodes and the receiver uses a photocell sensitive only to the infra-red light.

Infra-red communication or control uses serial data transfer by emitting pulses of light, which is coded in binary, a language micro-processors are capable of deciphering. Therefore, for deciphering the binary code protocol that the remote is sending, you must hold the remote in front of the receiver on the IR Remote Shield mounted on your Raspberry Pi.

To decode and copy an IR code, press the “Receive” button on the IR Remote Shield. This will allow RBPi to capture the code the remote button is sending. In the software, you will have to tag each code with its individual function, for example, a certain code may be for raising the temperature and another for lowering it.

Once all codes from all the remotes are in the RBPi, it is a simple matter to map the codes and their functions on a web application. As the RBPi is connected to the Internet, any browser on the Internet can call up the web application, and the specific settings for the HVAC units altered. This allows the software program running on the RBPi to send the altered binary code to the specific HVAC unit via its IR link and change its status.

Digital Isolators vs Optocouplers

Industrial equipment may need to operate in a region of strong electromagnetic fields. There can be a sudden surge in the voltage applied to the equipment, which may be hazardous to the user and the gear. It is crucial that you incorporate a reliable isolation system to take of these issues.

Until very recently, the optocoupler was the only practical choice in providing safety isolation for manufacturers of medical and industrial isolated systems. The arrival of digital isolator has however, changed the situation greatly.

Digital isolators offer several advantages over optocouplers. They are more reliable, cheaper and have greater power efficiency compared to the optocouplers.

It is important that you understand the three vital aspects of an isolation system. These are the insulation material, the structure and the method of transfer of data.

Insulation Material

Typical insulation materials are silicon dioxide wafers and thin film of polymers. Optocouplers use polymer films. Digital isolators make use of a particular form of polymer called polyimide. This material serves to increase the efficiency of isolation systems.

Silicon Dioxide is not a very suitable material as an isolator. While you may increase the thickness of polyimide to increase the insulation, you cannot adopt the same method for silicon dioxide. Wafers thicker than 15 micrometers may crack during processing.

Structure

Digital isolators use either transformers or capacitors to transfer data across the isolation barrier. A transformer system has two coils placed side by side. Current flowing through a coil (called the primary coil) gives rise to a magnetic field in the space surrounding the coil. This induces a current to flow in the other coil (called the secondary coil).

A capacitor consists of two metal plates with the space between the plates filled with a non-conductor.

Optocouplers use light emitting diodes (LED) for data transmission.

Transfer of Data

The LED in an optocoupler turns on for logic high state and turns off for logic low state. The device consumes a significant amount of power when the LED is on. Digital isolators do away with this undesirable aspect. The sophisticated circuitry in the system encodes and decodes data at a rapid pace so that the transmission of data involves less power consumption.

A digital isolator using a transformer for data transmission transfers the data from the primary coil to the secondary coil during the pulses of current driving the transformer.

A digital isolator may use radio frequency signals as well, in a fashion similar to the way an optocoupler uses light from an LED. However, since a logic high state causes a continuous transmission of radio frequency signals, this method uses more power.

Digital isolators with capacitors have an advantage in that they consume lower currents for creating coupling electric fields for data transmission.

Ensuring the Correct Combination

It is important to use the right insulating material and the apt method for data transfer depending upon the application.

Since polymers provide more than adequate insulation, they are suitable in most applications. Polyimide insulation is particularly suitable for equipment used in healthcare and heavy industries.

Concerning data transfer, capacitor isolation is adequate for situations requiring just functional and not safety isolation. Isolation systems making use of transformers will serve the purpose of safety as well as functional isolation.

How to solder – an illustrated guide

Guide to learning to solderWe love when we come across electronics info and guides that others are sharing freely – and especially those that encourage others to share their knowledge and work.

For example…here is a fully illustrated guide to learning how to solder which was done by the fine folks at http://mightyohm.com. They’ve created a super guide with all the basics covered as well as some interesting tips and tricks that can make your soldering experience a little better. This would be a great staple for some basic electronics classes.

To see the full soldering guide, click on the image above.

Thank you to the creators of this comic book: Mitch Altman, Andie Nordgren and Jeff Keyzer. Great work!

Demystifying the A/D and D/A Converters

Analog and Digital Signals

Analog signals represent a physical parameter in the form of a continuous signal. In contrast, digital signals are discrete time signals formed by digital modulation. Most natural signals, like human voice and other sounds are analog in nature. Traditionally, communication systems were based on analog systems.

As demand for systems capable of carrying more information over longer distances kept soaring, the drawbacks of analog communication systems became increasingly evident. Efforts to improve the performance and throughput of systems saw the evolution of digital systems, which far surpasses the performance of analog systems, and offer features that were considered impossible earlier. Some major advantages of digital systems over analog are:

• Optical fibers can transmit digital signals and have virtually infinite information bearing capacity
• Combining multiple input signals over same channel is possible by multiplexing
• Digital signals can be encrypted and hence are more secure
• Better noise immunity leads to superior performance due to regeneration
• Much higher flexibility and ease of configuration

On the other hand, disadvantages include:

• Higher bandwidth required to transmit the same information
• Accurate synchronization required between transmitter and receiver for error free communication

Primary signals like human voice, natural sounds and pictures, etc., are all inherently analog. However, most signal processing and transmission systems are progressively becoming digital. Therefore, there is an obvious need for conversion of analog signals to digital. This facilitates processing and transmission, and reverse transition from digital to analog, since the digital signals will not be intelligible to human receivers or gadgets like a pen recorder. This need led to the evolution of Analog to Digital (A/D) Converters for encoding at the transmitting end and Digital to Analog (D/A) Converters at the receiving end for decoding.

Principle of Working of A/D and D/A Converters

An A/D converter senses the analog input signal at regular intervals and generates a corresponding binary bit stream as a combination of 0’s and 1’s. This data stream is then processed by the digital system until it is ready to be regenerated at the receiver’s location. The sampling rate has to be at least twice the highest frequency of the input signal so that the received signal is a near perfect replica of the input.

In contrast, a D/A Converter receives the bit stream and regenerates the signal by plotting the sampled values to obtain the input signal at the receiving end. The simplest way to achieve this is by using a variable resistor network, which converts each digital level into an equivalent binary weighted voltage (or current). However, if the recipient is a computer or other device capable of handling a digital signal directly, processing by D/A Converters is not necessary.

Two of the most important parameters of A/D and D/A Converters are Accuracy and Resolution. Accuracy reflects how closely the actual output signal resembles the theoretical output voltage. Resolution is the smallest increment in the input signal the system can sense and respond to. Higher resolution requires more bits and is more complicated and expensive, apart from being slower.