Resistors in Electronics

The resistors size is dependent on the need. They are available in sizes ranging from 0.01 Ohms to 10 Megaohms. However, there is a lot of flexibility in sizes that are commercially available. The external sealing material is equipped with color coded bands that designate the rating when viewed in a specific sequence. There are four band, five band, and six band color coded options. Each color band represents a numerical value, a resistance multiplier (in Ohms), and a percentage tolerance.

Current shunt resistors are not designed to be used at their full capacity continuously. “Continuously” is defined as being more than 2 minutes of use. Doing so could overheat and damage the resistors which would give inaccurate measurements. If a shunt resistor becomes too hot for too long will be permanently damaged. Most shunt resistors have a “derating factor” of 66%. This means that you would not operate the 100Amp shunt resistor in our example at more than 66 Amps.

Pulse resustors are specifically used in a circuit to literally "withstand" the excess load and heating that accompanies a transient energy event. Hence, they are typically known as Power Withstanding Resistors (PWRs). Fusing with flameproof protection, under specific fault conditions, can also be designed into the resistor performance where necessary. The types of resistor technologies available are wirewound, metal film, metal oxide, and surface mount. Telecommunications, computers, consumer electronics, and office equipment are just a few of the applications in which a pulse resistor may be used.

So whether designer, troubleshooter, or electronics hobbyist, having a basic understanding of how a resistor is used in the design of electronic and electrical equipment, can only serve to meet the objectives of the application and bring about a greater appreciation for electronic technology.

Resistors and Electronics

Resistors are manufactured from wire coated with resistive materials and then sealed with an insulator. The type and corresponding properties of the resistive materials used determine its overall strength. There are different types of resistors, but the most common types are the carbon, metal film, which includes metal oxide and thick film, and wirewound resistors. Selection of one type of resistor over another other depends on the application, cost, and technical specifications of the resistor itself.

The resistors size is dependent on the need. They are available in sizes ranging from 0.01 Ohms to 10 Megaohms. However, there is a lot of flexibility in sizes that are commercially available. The external sealing material is equipped with color coded bands that designate the rating when viewed in a specific sequence. There are four band, five band, and six band color coded options. Each color band represents a numerical value, a resistance multiplier (in Ohms), and a percentage tolerance.

Let’s say you have a 100 Amp current shunt resistor used to measure the current flowing in or out the the battery bank of a renewable energy system, such as solar or wind turbine. You can connect a standard multimeter (0-100mV) to the shunt resistor’s leads to monitor how much current the batteries output or how much current is being used to charge the batteries.

So whether designer, troubleshooter, or electronics hobbyist, having a basic understanding of how a resistors are used in the design of electronic and electrical equipment, can only serve to meet the objectives of the application and bring about a greater appreciation for electronic technology.

Information about Resistors

The resistors size is dependent on the need. They are available in sizes ranging from 0.01 Ohms to 10 Megaohms. However, there is a lot of flexibility in sizes that are commercially available. The external sealing material is equipped with color coded bands that designate the rating when viewed in a specific sequence. There are four band, five band, and six band color coded options. Each color band represents a numerical value, a resistance multiplier (in Ohms), and a percentage tolerance.

Current shunt resistors are not designed to be used at their full capacity continuously. “Continuously” is defined as being more than 2 minutes of use. Doing so could overheat and damage the resistors which would give inaccurate measurements. If a shunt resistor becomes too hot for too long will be permanently damaged. Most shunt resistors have a “derating factor” of 66%. This means that you would not operate the 100Amp shunt resistor in our example at more than 66 Amps.  Current shunt resistors can be used in a wide variety of applications including automotive, marine and renewable energy systems.

Pulse resustors are specifically used in a circuit to literally "withstand" the excess load and heating that accompanies a transient energy event. Hence, they are typically known as Power Withstanding Resistors (PWRs). Fusing with flameproof protection, under specific fault conditions, can also be designed into the resistor performance where necessary. The types of resistor technologies available are wirewound, metal film, metal oxide, and surface mount. Telecommunications, computers, consumer electronics, and office equipment are just a few of the applications in which a pulse resistor may be used.

So whether designer, troubleshooter, or electronics hobbyist, having a basic understanding of how a resistor is used in the design of electronic and electrical equipment, can only serve to meet the objectives of the application and bring about a greater appreciation for electronic technology.

Resistors Are Cool

Electronic engineers and manufacturers are realizing the increasing importance for "designing in" an adequate margin of safety to protect against high energy, short term current surges or voltage spikes. Likewise, protection also needs to be considered in the final circuit design where there exists a potential for more frequent, but less intense power surges.  Resistors are an important part of any electronic system.

One thing to look at is tolerance to actual resistance specification of resistors. If the manufacturer states a 5% tolerance to the ohm spec, it really needs to be at or below that number. Another thing to check is how much voltage it can handle. This should be listed in the spec sheet for each particular resistor. Depending on whether the design is for a high-power application like a power supply or something much lower, like a calculator, one needs to watch for that. Lead sizing should fit the design. For example, one should not buy a through-hole type when a surface mount design is preferable during the engineering phase. Also, temperature specifications should be looked at to ensure thermal breakdown does not become a problem during peak performance of the resistor. It needs to be able to handle rapid fluctuation in temperatures, as various devices can change temperature quickly in real world applications.

A resistor is a passive current limiting device. Current limiting in that they are used to slow or limit the amount of electrical current traveling through them just like a cyclist experiences when attempting to peddle full speed after encountering an increasingly strong headwind. In controlling the flow of current, the electrical potential (voltage) can also be managed. They are passive since no external power or other source is required for them to function properly.