A variable resistor that is utilized in controlling current is known as a rheostat. This device helps in varying the resistance in an electrical circuit without any interruption. The construction of a rheostat is much like that of the potentiometers. Even when three terminals are present, it utilizes only 2 connections, like a potentiometer. One of the connection is made with the wiper and the other one is made to the resistive element. Unlike the potentiometers, rheostats can convey a noteworthy current. Thus they are generally manufactured as wire wound resistors. The resistive wire is twisted around a protecting ceramic core and the wiper slides over the windings.

Rheostats were most commonly utilized in power controlling devices, for example, to operate the speed of motors, to control the intensity of light (dimmer), in ovens and heaters. These days they are not utilized for this capacity any longer. The reason behind this is because of its low efficiency. Because of its characteristic of variable resistance they are generally used for calibration in a given electrical circuit. In these cases, they are balanced distinctly during creation or circuit tuning. In these cases generally, trimpots are utilized, wired as a rheostat.

Types of Rheostat

There are many types of Rheostat. Let’s look at them below:

• Rotary Rheostat – As the name suggests, the rotary rheostat comes with a rotary resistive path. These have found its utilization in power applications. This kind of rheostat has a shaft which is mounted by a wiper. The wiper is just a sliding contact for a rotary rheostat that can pivot over three-fourth of a circle.

• Linear Rheostat – This kind of rheostat comes with a linear resistive path. The path is glided by the sliding terminal. Here we have got 2 fixed terminal but only one of them is used. The other one is attached to the slider. These are generally utilized in laboratory applications. For the most part, a wire-wound resistive way along with a linear cylinder-shaped material is utilized.

• Preset Rheostat – Whenever rheostats are utilized in the printed circuit board, they are either utilized as preset rheostats or trimmers. Trimmers are a small rheostat generally used in circuits for calibration. Though there is an option of 2 terminal trimmers, in most of the cases 3 terminal potentiometer trimmer is utilized as a 2 terminal rheostat.

Applications of a Rheostat

One of the most important applications of the rheostat as discussed above is to operate the flow of current. All of its other application is derived from this current controlling capability of the rheostat. For example, the rheostats are used to limit the flow of current such that high current faults could be prevented. It is important to choose the size of the rheostat according to the current requirement. For instance, if you have got a high current circuit then you need to have a rheostat of larger size. These kinds are used in dimmer circuits, in heaters, ovens as well as speed control circuits in motors.

This was all we have regarding Rheostat. Hope you liked the article. Brands that manufacture them are Ohmite, Vishay, and TE Connectivity. Make sure to check them out using the links as provided.  

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As the name suggests, the metal film resistor is manufactured by keeping a slim layer of metal onto a ceramic former. Here the metallic film behaves in the same manner as the resistance wire. You can even control its thickness, length, and width such that it can be produced to a high tolerance.

The metal film resistor can be pre-aged. Not only this, but the metal protected to ensure it does not see any deterioration in its quality with time. Thus, the stability for the long term is good.

In the present time, these metal film resistors are a well-known choice for leaded axial resistors and because of this, they are utilized in large quantities.

Construction of Metal Film Resistor

The metal film resistor is made by vacuum which deposits a layer of metal on a highly purified ceramic cylinder rod. Often, the more the thickness of the metal film deposited, the more is the stability in the value of the resistor. Generally, the thickness of the film lies in the range of 50 to 250nm as the stability levels are directly proportional to the thickness of the material. A variety of techniques can be utilized for this, but the most popular one is sputtering. The metal that is used for depositing are generally Chromium, Nickel, NiCr, but other metals like platinum with gold, or tantalum nitride may also be taken into consideration for some highly specialized applications.

As soon as the film gets deposited, a metal end cap is pressed over it. This reaches the resistive film and has the leads joined.

The next phase in the manufacture is to bring the value of resistance to the desired figure. This is achieved generally with the help of lasers to trim a helix into the metal film. This decreases the width of the current-carrying track while keeping the thickness of the deposited material within an optimum range for providing stability for long term.

Laser trimming’s accuracy level means that the resistor can be made to an extremely close tolerance level. A tolerance of 0.5%, 0.25%, 0.1%, as we all 2% and 1% are present. The tolerance of 1 and 2 percent are available on a wide scale. This makes the electrical circuits to keep up decent repeatability starting with one unit then onto the next.

It is also to be noted that the metal film resistor also keeps an optimum temperature co-efficient which lies in the range of 50 and 100ppm /K.

The final step in the manufacturing process of the metal film resistor is to add up the markings and the protective coating. Generally, this protective coating comprises a resin that is included in many layers that are separately heated on. And at the end, the marking rings are added to demonstrate the estimation of metal film resistor and the other applicable attributes.

This was all we have regarding metal film resistors. Hope you liked going through the article. Brands that manufacture them are Vishay, Yageo, and KOA Speer. Make sure to check them out using the links as provided.

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A trimmer in electronics is an adjustable miniature electrical component. It is intended to be set accurately when introduced in some gadget, and never observed or balanced by the gadget's user. Trimmers can be variable capacitors, variable resistors (potentiometers), or inductors. They are commonly used in accuracy hardware like A/V segments and may be balanced when the equipment is serviced. Trimpots are generally used to calibrate electrical equipment initially after manufacturing. Contrary to many other variable controls, these trimmers are clamped on the circuit boards, turned with a little screwdriver, and appraised for several fewer calibration over their lifetime. Trimmers, for example, trimmable capacitors and trimmable inductors are generally found in radio and superhet radio receivers, radio frequency, and intermediate frequency circuits. They are set in the correct position during the time of the alignment procedure of the receiver.

In electronics, Presets are those adjustable components to which the user has no access to. They are made to adjust during the time of the manufacture of that device or during the time of its maintenance/repair. Several passive electrical components can be used as presets, like inductors, resistors, and capacitors.

General Considerations

Trimmers can be found with different levels of precision and sizes. For instance, we have the multi-turn trim potentiometer which reaches its end value after several turns of screw adjustment. This helps in getting a very high accuracy level. Often they also use a leadscrew (linear track) or a worm-gear (rotary track).

Resistors

Resistor trimmers can be found generally in the form of a Potentiometer, often known as trimpot. There are three terminals present in a potentiometer, but it can be modified for a two-terminal resistor by attaching the wiper to any one of the other terminals. Trimpot was patented in 1952 by Marlan Bourns and till then it is a registered trademark of Bourns, Inc.

There are two types of preset resistors that are found in the circuits commonly.

• The first one is the skeleton potentiometer that has the working principle the same as a regular circular potentiometer. The only difference is that it is stripped of its shaft, enclosure, and fixings. The complete movement of this kind of potentiometer is less than a single turn.

• The second one is the multi-turn potentiometer which provides movement to the slider along the resistive track through a worm gear set up. In this potentiometer, the gearing is done in such a manner that multiple turns are required for an adjustment screw to position the slider the complete distance along the resistive track.

This was all we have regarding Trimmer Resistors through hole. We hope that you liked the article. Brands that manufacture them are Bourns, TT Electronics, and Vishay. Make sure to visit them using the links as provided.

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A potentiometer is defined as a 3 terminal resistor having a rotating or sliding contact that makes up the adjustable voltage divider. If you are using only the two terminals present in it (one end and the wiper), then it behaves like a variable resistor or rheostat.

Potentiometer, a measuring instrument, is a voltage divider which is used to measure the electric potential difference. This electric component has got its name as a potentiometer because it is an implementation of the same principle.

Potentiometers are used mainly in controlling electrical devices like in audio equipment for controlling the volume. Potentiometers that are controlled by a mechanism can be utilized as position transducers, like, as used in a joystick. Potentiometers are used very often to control significant power (greater than watt) directly since the dissipated power in the potentiometer is comparable to the power present in the controlled load.

Nomenclature for Potentiometers

There is a vast amount of electronic equipment present in the industry. For the simplification of the people, each of them comes with its code and nomenclature. Let's have a look at the nomenclature as described for a potentiometer.

• Trimmer pot or Trimpot – A trimmer potentiometer is a potentiometer that is generally meant to be calibrated once or infrequently for the electrical signal to get tuned finely.
• Thumbwheel pot or Thumb pot – A rotating potentiometer (small) which can be calibrated infrequently with the help of small thumbwheel.
• Slider pot or Slide Pot – This kind of potentiometer is adjusted with the help of a wiper by shifting it right or left (or even up and down - It depends on the way of its installation), generally with the help of thumb or a finger.

Digital Potentiometer

A digital potentiometer, generally known as digipot, is an electronic equipment that copies all the functionality of analog potentiometers. Just like the analog potentiometer, the resistance present between the 2 terminals can be adjusted through digital input signals.

There are 2 main functional types of digital potentiometers.

• Non-Volatile – It uses a strong mechanism like that present in EEPROM or flash memory to retain their set position.
• Volatile – It loses its set position as soon as the power is removed from them. It is generally designed to initialize at the base position.

The use of digipot is much complex than that of a simple analog potentiometer. Not only that, but there are many noticeable limitations as well. Still, they are broadly utilized, regularly for factory calibration and adjustment of hardware, particularly where the constraints of mechanical potentiometers are dangerous.

Membrane Potentiometers

A membrane potentiometer is a potentiometer that takes the help of a conductive membrane that is distorted by a sliding element to contact a resistor voltage divider. Linearity lies between 0.5 percent to 5 percent as per the designs, materials, and processes used while manufacturing. The repeat accuracy generally lies in the range of 0.1mm to 1.0mm with an infinite resolution theoretically.

This was all we have regarding Potentiometers. Brands that manufacture them are Bourns, Honeywell, and Vishay. Make sure to go through them using the links as provided.

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A tantalum electrolytic capacitor is one of the passive components of an electronic circuit. It comprises of a pellet of permeable metals of tantalum (anode) which is covered all around by an insulating oxide layer forming the dielectric. It is covered solid or even liquid electrolytes (cathode). The tantalum capacitor has a very thin and comparatively high permittivity dielectric layer and because of this, it is much better than other capacitors in having high Capacitance/Volume as well as lower weight.

Tantalum is known to be a conflict mineral. The Tantalum Electrolytic Capacitors are found to be more costly than the Aluminum Electrolytic Capacitors.

Tantalum capacitors are intrinsically polarized segments. If the reverse voltage is applied then the capacitors may get destroyed. Bipolar or Non-polar Tantalum Capacitors can be made by adequately interfacing two capacitors which are polarized in series, with the anode having an orientation in the opposite direction.

Basic Construction of Solid Tantalum Electrolytic Capacitors

A Tantalum Capacitor is basically a chip capacitor which consists of tantalum powder pressed and compacted into a pellet and forms the anode of the capacitors. The oxide layer of tantalum pentoxide forms the dielectric and the cathode is a solid manganese dioxide electrolyte.

Types of Tantalum Capacitors

The Tantalum Electrolytic Capacitors are made up in 3 different styles:

• Axial Leaded Tantalum Capacitors – This kind of capacitor is generally used in medical, space and military applications.
• Tantalum “pearls” single-ended style (resin-dipped) used for PCB mounting.
• Tantalum Chip Capacitors – It has an SMD style and is used for surface mounting. Eighty percent of all Tantalum Capacitors are SMDs.

Chip Capacitors

As said above, more than eighty percent of Tantalum Electrolytic Capacitors are made in SMD style as Tantalum Chip Capacitors. The end faces consist of contact surfaces, furthermore, is fabricated in various sizes. One can identify different sizes using case code letters. For some of them which have been fabricated for a long time, the measurements and case coding overall makes are still to a great extent equivalent. But due to the new features of Tantalum Electrolytic Capacitors, like the “face down” technique to decrease inductance and the multi-anode technique to decrease the ESR has resulted in a much broader range of chip sizes and case codes. These takeoffs from EIA benchmarks mean gadgets from various producers are never again constantly uniform.

Wet Tantalum Capacitors

One of the main characteristics of the modern days Wet (non-solid) Tantalum Electrolytic Capacitor is the energy density they have as compared to the Wet Aluminum Electrolytic Capacitors and Solid Tantalum Capacitors. The self-healing property in them enables the formation of dielectric thickness with a much lower safety margin. In addition to that, Wet Tantalum Capacitors can be operated at an excess voltage from 100 V to 630 V. Apart from that it has the lowest leakage current and a relatively low ESR than all other electrolytic capacitors.

Hope you liked the article on Tantalum Capacitors. Brands that manufacture these types of capacitors are Kemet, Vishay, and AVX. Make sure to check them out using the links as provided.

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