CARBON COMPOSITION RESISTOR

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Carbon composition resistors (CCR) are fastened type resistors. They’re made out of fantastic carbon particles blended with a binder (for instance clay). After baking, it has a strong type. Though carbon composition resistors are broadly utilized in circuits, the vast majority of resistors are these days made by deposition of a steel or carbon movie over a ceramic provider.

CARBON COMPOSITION RESISTOR ADVANTAGES AND DISADVANTAGES

The large benefit of carbon composition resistors is their capability to face up to excessive vitality pulses. When present flows via the resistor, all the carbon composition physique conducts the vitality. The wire-wound resistor, for instance, has a a lot smaller quantity of the wire to conduct. carbon movie resistor So the thermal mass of the carbon composition resistor is far greater, leading to a better vitality functionality. Carbon resistors will be made with a better resistance than wirewound resistors, and are significantly cheaper. Nonetheless, the properties are much less good when it comes to temperature coefficient, noise, voltage dependence, and cargo.

carbon composition resistor wikipedia

Fifty years in the past, carbon composition resistors had been broadly utilized in client electronics. Due to the low stability of the resistance worth, any such resistor just isn’t appropriate for any trendy excessive precision utility. For instance, the resistance worth can change as much as 5% over a shelf life of 1 12 months. With heavy use the worth adjustments much more: as much as 15% for a 2000h take a look at at full ranking with 70°C. Soldering may cause a 2% change. The rationale for this instability is inherent to the design of the resistor. The carbon composition comprises supplies with completely different warmth enlargement properties.

CARBON COMPOSITION RESISTOR ADVANTAGES AND DISADVANTAGES

When conducting carbon particles and the nonconducting binder warmth up or calm down, stresses come up within the resistor physique. The mechanical contact between the conducting particles will change, and this results in a change in resistance worth. Additionally, noise properties should not good as a result of combination of various supplies. The noise stage will increase when present flows.

Resistors of 0.25W and 0.5W, have a most voltage of respectively 150V and 500V. Insulation resistance is poor with roughly 10^9 Ω (order of magnitude worse than different varieties). Another reason for the lower in using any such resistor is the high-temperature coefficient of round 1200 ppm/° C. The working temperature vary is between round -40 to 150 ° C. Nonetheless, the resistor derates above 70 ° C.

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CARBON COMPOSITION RESISTOR APPLICATIONS

Carbon composition resistors are appropriate to face up to excessive vitality pulses whereas having a comparatively small dimension. For that reason, the carbon composition resistor continues to be utilized in many purposes right this moment. Purposes embrace the safety of circuits (surge or discharge safety), present limiting, excessive voltage energy provides, excessive energy or strobe lighting, and welding.

steel movie resistor

An instance of an utility is a medical defibrillator. The delicate measurement gear connected to the affected person must be protected towards the excessive vitality pulses of round 30 Joule. Carbon composition resistors are utilized within the gear or the leads and have to face up to all pulse vitality.

CARBON COMPOSITION RESISTOR MANUFACTURING

The resistive materials for the carbon composition resistor is a mix of graphite, ceramic mud and resin. The combination is pressed into sticks below excessive stress and temperature. The connecting wires are centrally pressed in each ends of the resistor. Alternatively, steel caps are fitted on each rod ends, which type the attachment for the wire leads. After the baking course of an enormous resistance physique is created. Disadvantage of this course of is the problem to predetermine the resistance worth.

The resistor physique is porous and due to this fact a coating is required. Prior to now some resistors had been made with out coating. The resistance worth is established by various the size of the carbon composition physique, to create an sufficient path for present. To range the dissipation, resistors are made with completely different diameters to offer a big sufficient floor to dissipate warmth.

carbon composition resistor image

Commercially out there carbon composition resistors have dissipation values between 1/8W and 1/4W, whereas within the Eighties resistors had been out there as much as 5W. Though many suppliers switched to producing different varieties of resistor, some suppliers are specialised in carbon composition resistors.

Within the desk under {the electrical} resistivity is proven for the resistor materials.

MaterialsResistivity Ω / m
  
graphite4×10^-6 – 11×10^-6
amorphous carbon35×10^-6 – 50×10^-6

HISTORY OF THE CARBON COMPOSITION RESISTOR

The carbon composition resistor exists over hundred years. At first of the 20 th century, the resistors had been produced with out coating. The lead wires had been straight soldered onto the resistor physique.

wire wound resistor

The one out there resistor varieties till the Nineteen Sixties had been wirewound and carbon composition. Within the Nineteen Sixties and 70s, there was a shift in using carbon composition resistors to different varieties just like the carbon or steel movie resistor.

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