A counter or a tachometer is an instrument that helps in measuring the speed of rotation of a disk or shaft, like that present in a motor. This device generally shows the RPM (Revolution Per Minute) on a calibrated analogue dial. The digital displays are getting much popular these days.

The word speedometer as well as tachometer have the same meaning i.e. a device used in measuring the speed. But by convention in the world of automobiles, one is used for representing the speed of the vehicle and the other one represents that of the engine.

The 1^st made tachometer depended on estimating the Centrifugal force. Its operation was similar to the Centrifugal governor. The person who invented this device was Dietrich Uhlhorn, a German Engineer, in 1817. From 1840, this device is utilized to calculate the engine’s speed.

Revolution counters or tachometers present in aircraft, cars and other automobiles show the rotation rate of the crankshaft of an engine. It has also got a marking that points to the range that is safe for the rotation speed. This helps the driver in choosing the right gear and throttle setting. Overheating and inadequate lubrication is the major consequence of their prolonged use at high speed.

In analogue tachometers, if the speed rises more than the safe operating speed then it is displayed by a zone of the gauge with a red mark. Thus, offering to ascend to the declaration of “redlining” an engine - firing it up to the most extreme safe point of confinement. The modern cars used these days also come with this red mark in their tachometer. However, they are of no use as their engines come with a limiter which automatically limits its speed to prevent the car from any damage. Diesel engines with conventional mechanical injector frameworks come with an integral speed limiter which stops the engine to speed up. Thus the tachometer used in them lacks redline.

The trucks and tractors come with a tachometer that has a green arc in them. This green arc lets the driver know the speed at which the engine is producing the maximum torque. Some tractors also come with a PTO (Power Take-Off). The tachometers in them help in letting the driver accustomed to the speed of the engine needed to rotate the PTO at the standardized rate. Tractors having more than one ‘road gear’ often have tachometers with multiple speed scale. The green arc is said above is also present in the tachometer of an aircraft to show the cruising speed range of their engine.

Traffic Engineering

From the above discussion, it is clear that tachometers help in estimating the volume (flow) and speed of the engine. A vehicle is fitted with a sensor and conducts "tact runs" that keep a record of the traffic information. The information gathered here is a complement to loop detector data. To get measurably huge outcomes needs a large number of runs. Nonetheless, due to the cost and spacing tach runs is a popular practice.

This was all we had about counters and tachometers. Brands that manufacture them are Panasonic, Omron, and Crouzet. Make sure to check them out through the links as provided.

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A varistor is an electrical device having an electrical resistance that differs with the potential applied to it. A varistor is popularly known as Voltage Dependent Resistor (VDR). It possesses a non-ohmic and non-linear Current-Voltage characteristic which is equivalent to a diode. Unlike the diode, it has a similar characteristic for the flow of both directions of current. Customarily, varistors were made by joining 2 rectifiers i.e. either the germanium-oxide or the copper-oxide rectifier in a configuration that is anti-parallel. The electrical resistance of the varistor is high at low voltage but as the voltage increases the resistance decreases. The varistors that are used presently are fundamentally dependent on sintered ceramic metal-oxide materials. On a microscopic scale, it shows directional behavior. This category is popularly known as MOV or Metal Oxide Varistor.

Varistor serves as a compensation and a control element in the electrical circuit either to defend against excess voltage or to offer optimal operating conditions. When utilized as defending devices, they shunt the current established by the exorbitant voltage away from touchy segments when activated.

Composition

As said earlier, the newest form of varistor that is used is the Metal Oxide Varistor. This kind of varistor is constituted by a ceramic mass of zinc oxide grains with metal oxides (like a small quantity of cobalt, bismuth, manganese oxides) placed in the middle of 2 metal plates, which comprise the device’s electrodes. A diode junction is formed between each grain and its neighbor.

When the electrodes are given a small potential difference then only a small amount of current flows through the diode junction which is a result of reverse leakage. On the other hand when a large voltage is applied on the electrodes a large amount of current flows, as the diode junction separates itself because of the combination of electron tunneling and thermionic emission. The consequence of the above-said behavior is a non-linear Current-Voltage characteristic where the MOV possesses a low resistance at high voltage and high resistance at low voltage.

Voltage Rating

MOVs are categorized by the range of voltage that they can endure without damage. The other parameter is the varistor’s breakdown voltage, maximum current, energy rating in joules, response time and operating voltage.

The rating of energy is regularly characterized utilizing institutionalized transients like 10/1000 microseconds or 8/20 microseconds. Here 10 microseconds are the front time of the transient and 1000 microseconds is the time of half value.

Capacitance

The range of capacitance for varistors which are consumer-sized i.e. 7 to 20mm in diameter is from 100pF to 2,500pF. Varistors that are used in micro electric protection have low capacitance like around 1pF. You can get this kind in cellular phone. These varistors having low capacitance cannot withstand the flow of a large amount of current as the PCB mount size is compact.

Response time

The response time of the MOV isn't institutionalized.

Hope you liked the article on Varistors. Brands that make them are Littelfuse, EPCOS, Panasonic. You can refer to them using the links as provided. Thank you for reading.

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TRIAC stands for Triode for Alternating Current. It is a genericized trademark for an electrical device that has 3 terminals and when triggered conducts electrical current in both directions. Its conventional name is bilateral triode thyristor or bidirectional triode thyristor. A thyristor is comparable to a relay where a small voltage induced current can control a lot bigger current and voltage.

Thyristors can be said to be the superset of TRIACs. TRIACs are also relatable to SCRs (Silicon Controlled Rectifiers). TRIACs and SCRs can be distinguished in one characteristic feature i.e. the first one is bidirectional, the flow of current is in both the direction but the later one allows the flow of current in only one direction. Generally, the TRIACs get initiated by the consequence of a positive or a negative potential to the gate but the SCR needs only a positive potential. Once activated, SCRs and TRIACs keep on conducting, regardless of whether the current in the gate ceases, until the principle current dips under a specific level called the holding current.

The GTOs or Gate Turn-Off Thyristors are the same as TRIACs but when the signal in the gate ceases, it provides much more control by turning OFF.

The bidirectional feature of this equipment makes it a good switch for AC or Alternating Current. A trigger, when applied in the main circuit at AC's controlled phase angle, permits control of the average current streaming into a load. This feature is popularly used for managing the speed of dimming lamps, electric heaters, and universal motor.

Factors that affect the working of TRIAC

TRIACS, unlike SCRs, needs appropriate enhancement for its legitimate working. There are some inherent drawbacks like TRIACs Backlash effect, Rate effect, etc. Thus designing it requires proper case.

• Backlash Effect

This effect is one of the most acute Control Hysteresis that grows in the speed control or the lamp control circuits with the help of a Potentiometer for controlling the Gate current. The glowing brightness of the lamp gets a minimum when the potentiometer's resistance increases to the maximum. The lamp never gets ON when the pot is turned back until and unless the resistance of the pot drops to its lowest value. The main reason behind this is the discharging of the TRIAC's capacitor. The triggering pulse is provided to the gate by a Diac. Triac releases through the Diac, generating the Backlash effect.

• Rate Effect

The Rate effect generally takes place due to high inrush current when overwhelming inductive loads switch on and also because of a momentary variation in frequency, voltage or current in the mains.

• Effect of RFI

RFI or the Radio Frequency Interference seriously influences the working of Triacs. Depending on the resistance and the supply voltage of the load, the load current is seen to sharply increase from 0 to a high value whenever the TRIAC switches on the load. This forms pulses of RFI.

This was all regarding TRIACs. Brands that manufacture it are Littelfuse, STMicroelectronics, and NXP. We hope that you liked the article. If you want to refer to the brands then just follow the links as given.

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A thermal cutoff is a safety device for electrical equipment. It ceases the flow of current in a device when heated to a specific temperature. These devices can be reset either automatically or even manually.

Thermal fuse

Thermal fuse is a cutoff that utilizes a fusible link (applicable for only one time). The thermal fuse is not like the thermal switch that gets reset automatically whenever there are temperature drops. On the contrary, it's like an electrical fuse – a one-time-use device that cannot reset itself and needs to be replaced when it is triggered. Thermal fuse is generally used in those situations where overheating is a rare occurrence.

One component is a little meltable pellet that holds down a spring. The spring gets released when the pellet melts completely. As a consequence of this, the circuit breaks up. The NEC Sefuse SF series, Tamura LE series, Hosho Elmwood D series and Microtemp G4A series may manufacture the alloy pellets containing silver, copper, and beryllium to melt at a precise temperature.

Thermal fuses have found its use in heating electrical appliances like hairdryers and coffeemakers. It serves as a safety equipment to cease the flow of current to the device in case of any malfunction that would result in the temperature to ascend to risky levels, potentially lighting a fire. Thermal fuses react only in case of excessive temperature and not during the flow of excess current. This is one of the main differences of the device with a normal electrical fuse. 

Thermal Switch

A thermal switch popularly known as a Thermal Cutout (TCO) or thermal reset is an electrical equipment that opens with a "plink" sound at a higher temperature and closes itself automatically when there is a drop in temperature. The thermal switch is a bimetallic strip that is often encased in a cylindrical glass bulb to shield it from short circuits or dust particles. Another basic configuration utilizes a bimetallic shallow dome-shaped top which "clicks" to an inside out inverted cap when warmed, for example, the "Klixon" brand of thermal cutouts.

The thermal switch can be reused. Thus it is used in temporary places that are user-correctable. Thermal switches are used as thermostats in some cooling and heating system. It is also used in power supplies in case of any malfunction (overload). Another category of thermal switch is the Positive Temperature Coefficient thermistor (PTC). These kinds of thermistors have a “switch” temperature. At this temperature, the resistance rises rapidly and limits the current in the circuit. It is used in motor overheat protection.

Thermal switch is also used in some luminaire, particularly with downlight, where unnecessary heating is well on the way to happen. This might sometime result in "cycling". It is the process where the lights turn on and off after every few minutes. Glimmering radiant Christmas lights take advantage of this impact.

This was all we have about Thermal Cutoffs. Brands that manufacture this equipment are TE Connectivity, Littelfuse and Bourns. Make sure to refer them using the links as provided. Hope you liked the article and Thank you for reading.

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A resettable fuse is a PPTC (Polymeric Positive Temperature Coefficient) device that is a piece of passive electronic equipment utilized in defending against overcurrent faults in electrical circuits. It is also popularly known as polyswitch or a multifuse or a polyfuse. In certain situations, it is noted that this device is much similar to PTC thermistors but instead of charge carrier effects, they are operated on mechanical changes in semiconductors. A PPTC device consists of a voltage rating and a current rating. This electronic device was invented by Gerald Pearson in 1939 at Bell Labs. It was described in US patent #2,258,958.

A PPTC device is manufactured using a crystalline organic polymer matrix which is non-conductive in nature. To make it conductive it is added up with black carbon particle. Several conductive chains of carbons are formed between the crystals when it is cooled. Now as it is good at conducting electricity, the current will pass easily. Passage of a large amount of current through the device will make it heated up. The polymer will expand due to the heating up of the device. As a result, the polymer will change to the amorphous state from its crystalline form. Now as the heat is causing the expansion in the polymer, the carbon particles will start to get separated and the conductive pathways will start to break. As a consequence of this, the device will heat at a much faster rate, expand more and the resistance will be increased. Due to this increase in the resistance the circuital current will decrease. The device still consists of a small amount of current (leakage current) flowing through it which is enough to keep the temperature at a level such that the equipment is at a high resistance state. The range of leakage current is from a few hundred mA at lower voltages to less than a hundred mA at rated voltage. It can be said that latching functionality is one of the characteristic features of the device. 

As soon as the power is removed from the device, the heating caused by the leakage current will cease and the resettable fuse (PPTC) will start to cool down. With the cooling of the device, the original crystalline structure is regained and it gets back to its low resistance state that can hold current. The cooling process of the device generally takes a couple of seconds. 

Resettable fuses are most commonly used in computer power supplies (generally of PC 97 standard), nuclear applications as well as aerospace applications. This device is also used in protecting audio loudspeakers (tweeters). A circuit designed with a PPTC device connected in parallel to the light bulb or a resistor helps in limiting the current through the tweeter to a safer limit. Thus the tweeter will not get damaged if the amplifier is conveying more power that is endurable by it.

This was all we had about Resettable fuses. Brands that make them are TE Connectivity, Littelfuse and Bourns. Make sure to follow them by the links as provided. Thank you for reading up the blog.

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Unlike the CRT (Cathode Ray Tube), the LCDs (Liquid Crystal Display) are not able to produce light of its own. Thus it uses a backlight that provides illumination to it. Backlight provides illumination to the LCD from the back and side of the display panel. Backlight is generally used in small displays such as smartphones, LCD televisions, computer displays, wristwatches, etc.

For color screens, the LED backlighting comes under 2 categories. The first one is the RGB LED backlights and the second one is the white LED backlights.

• RGB LED backlights – The RGB LEDs are made up of red, blue and green LED which can be made to generate several color temperatures of white. RGB LED backlights are generally found in high display devices like HP EliteBook and HP DreamColor LP2480zx monitor. It has also found its use in Dell’s Studio series laptops. RGB LEDs are enabled to provide color gamut to screens. The 3 LED backlights can form a color spectrum that intently coordinates the color filters in the LCD pixels themselves. Using this technique, the filter passband is narrowed, as a result of which a narrow band of spectrum is allowed by each color component through the LCD. As there is a blockage of less amount of light, the efficiency of light is increased. In addition to that, the actual green, blue and red points can be displaced farther out such that more vivid colors can be formed by the display.

• White LED backlights – White LEDs are used frequently in the manufacture of desktop and notebook screens. A white LED is actually a blue LED with yellow phosphor to bring about the discharge of white light.

The LED backlights face several challenges as well. With the increase in the age of an LED, it's very hard to attain uniformity. As 3 different light sources are used i.e. red, green and blue, it means that with aging LED the white point of the display can get displaced at varied rates.  At higher temperature white LEDs faces blue shifts (from 3141K to 3222K for 10 degree Celsius to 80 degree Celsius). Power efficiency may also be kept as a point to note for LEDs.

To defend against the above-discussed challenges in white and RGB LED backlights, NDF Special Light Products has developed an LED technology known as 'advanced remote phosphor'. It uses blue pump LEDs in addition to a sheet having the printing of phosphorous luminescent materials. These are used in those LED applications that require a long life like Air Traffic Control displays, Cockpit display and medical displays.  The principle for this technology is similar to Quantum dots.

With time it is seen that notebook computer is using LED backlights at an immense rate. Since 2005 Sony is taking the help of LED backlights for its VAIO notebook. Asus, Apple, and Dell also made their own LED backlight notebooks by 2007. Today all screens of Apple use LED backlight, be it computer, laptops, etc.

Hope you liked the article on LED backlights. Brands that manufacture them are ELECTRONIC ASSEMBLY, Lumex and Newhaven Display. Make sure to follow them by the links as provided.

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Based on the IEEE 802.11 family of standards, Wi-Fi belongs to the family of wireless technologies used for networking. It is most commonly used in Internet access as well as in local area networking of devices. Devices that utilize Wi-Fi are laptops, desktops, digital cameras, drones, smart TVs, tablets, smartphones, digital audio players, etc.

Wi-Fi utilizes several parts which come under the IEEE 802 protocol family. It is intended to flawlessly interwork with its wired kin, Ethernet. Devices that are compatible can get connected with one other using a wireless access point. Not only this, but they can easily connect with other wired devices as well as with the Internet. There are different versions of Wi-Fi available as declared by IEEE 802.11 protocol standards. They are categorized on the basis of radio bands, also the Max. Ranges, and speeds that might be accomplished. Generally, Wi-Fi uses 5 gigahertz (60mm) SHF ISM and 2.4 gigahertz (120mm) UHF radio bands. These bands are further divided into several channels. A network can share these channels but at any point in time, only 1 transmitter can transmit locally on a particular channel.

There is a relatively high absorption rate by Wi-Fi’s wavebands and it is seen that it works very well in line-of-sight use. Obstructions like pillars, walls, home appliances, etc. immensely decrease the range, but at the same time in a crowded area, it helps in reducing interference among several networks. A hotspot (access point) offers an indoor range of about twenty meters (sixty-six feet) while the new ones brag to provide an outdoor range of one hundred and fifty meters ( four hundred and ninety feet). The coverage area of a hotspot can be as small as a solitary room having walls that block the radio signals, or as wide as several square kilometers with overlapping access points. Along with the time, the productivity and speed of Wi-Fi have expanded. Presently there are several versions of Wi-Fi that can reach the speed of 1Gbit per second and above when attached with compatible hardware at close range.

To get a system connected with a Wi-Fi network, a user should have the name of the network which is known as SSID (Service Set Identifier) and a password. There is a much higher chance for a Wi-Fi to get attacked than the network that is wired. The reason behind this is because anyone present within the range of a particular network with a wireless network interface controller can get access. Thus for the safety and security of a network, we have WPA or Wi-Fi Protected Access. The WPA includes technologies that are made to ensure data moving crosswise over Wi-Fi networks and incorporates solutions for the enterprise as well as personal networks. WPA utilizes the password verification technique to encode Wi-Fi packets to block hackers. With the advent of time, the security landscape has changed and the WPAs are getting stronger and smarter for protecting the data. 

Hope you liked this article on Wi-Fi. Brands that make them are Redpine, Microchip, and Digi International. Make sure to refer them using the links as provided. Thanks for reading.

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Programmable Logic IC Development tools are electrical components that are utilized to set up reconfigurable digital circuits. Before using them in any circuit is important that they are customized (reconfigured) by utilizing a specific program.

Let’s have a look on some variants of the above tools:-

• PLA – It stands for Programmable Logic Array. A PLA consists of a programmable AND gate array and a programmable OR gate array that are linked together to get complemented conditionally to generate an output. On the basis of IBM’s Read-Only Associative Memory (ROAM), the Texas Instruments made a mask-programmable IC in 1970. The device was named as TMS2000. It consisted of eighteen outputs and seventeen inputs with eight JK flip-flops for memory. Later this device was termed as Programmable Logic Array.

• PAL – It stands for Programmable Array Logic. This device consists of a series of transistor cells that are arranged as "fixed-OR, programmable-AND" plane to carry out a famous binary operation i.e. "sum of products" to generate an output. The PAL was introduced by the MMI in 1978. It was small, fast and cheap. It was available in 20 pins 300 mil DIP-packages. Later it was succeeded by AMD which introduced 24 pins 22V10 PAL with several new features.

• GALs – It stands for Generic Array Logic. It was an improved version of PAL which was introduced in 1985 by Lattice Semiconductor. The logical feature of the device was the same as the PAL but this one came with an additional feature of reprogramming. GALs are customized (programmed) utilizing a PAL programmer, or by utilizing the in-circuit programming method on supporting chips.

• CPLDs – It stands for Complex Programmable Logic Device. GALs and PALs are accessible just in little measures, proportionate to a couple of hundred logic gates. CPLDs and PLDs are taken help for larger logic circuits. The first method to program a CPLDs is by a PAL programmer. This method is not convenient for devices that have 100s of pins. The second process is by welding the gadget to its printed circuit board, at that point feed it with a Serial Data Stream from a PC. CPLD comes with a pre-built circuit that deciphers the stream of data and arranges the CPLD to play out its predetermined logical task.

• FPGAs – It stands for Field Programmable Gate Array. Early FPGAs were 82S105 sequencer and 82S100 array by Signetice. It was brought in the year 1970. 82S105 consisted of flip-flop functions while 82S100 was an array of AND terms. FPGAs are made up of a grid of logic gates furthermore, once put away, the information doesn't change, like that of an ordinary gate array. The term “field-programmable” in FPGA means the tool is programmed not by the manufacturer but by the customer. One of the main differences between a CPLDs and an FPGAs is that a CPLD generates logic functions using Sea OF Gate while an FPGA is based on LUTs (Look Up Tables). FPGAs are good for large scale machines while CPLDs are suitable for wide combinational logic applications.

So this was all about programmable Logic IC Development tools. Hope you liked the blog. Companies that manufacture programmable Logic IC Development tools are Lattice, Altera and Terasic Technologies. Make sure to refer them using the links as provided.

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