K.R.E Society’s Karnatak Arts, Science and Commerce College Bidar

K.R.E Society’s Karnatak Arts, Science and Commerce College Bidar
Dept of Electronics By M S Chelva UNT in partnership with TEA. Copyright ©. All rights reserved.

Using the Resistor Color Code
Resistance Using the Resistor Color Code Image source: Copyright © Texas Education Agency, All rights reserved.

Copyright © Texas Education Agency, 2013. All rights reserved.
What are Resistors? Resistors are important because they are control devices for electronics. Resistors can be physical devices. Resistance can also be a physical characteristic of a circuit or component. Resistors allow a circuit to deliver exactly the right amount of current, voltage, or power to a circuit or device (and no more). Copyright © Texas Education Agency, All rights reserved.

What is Resistance? Resistance is defined as the opposition to current flow. The primary purpose of a resistor is to control current. By control we mean limit or adjust A resistor is a linear device (unlike some other circuit components that are not linear) Like diodes and transistors Linear means that the voltage across a device is directly proportional to the resistance value. Doubling resistance doubles the voltage drop. The relationship between resistance and current is also linear, but it is an inverse relationship. Doubling the resistance value cuts the current in half. Copyright © Texas Education Agency, All rights reserved.

Fixed vs. Variable Fixed resistors are designed to have a nearly constant amount of resistance regardless of voltage, current, age, heat, or time. They have a stable value within a tolerance. The narrower the tolerance, the more expensive Variable resistors can change resistance value. They are adjustable. Examples: potentiometers and rheostats Copyright © Texas Education Agency, All rights reserved.

Symbols and Characteristics
Resistor schematic symbols are used to represent a variety of circuit components with resistance. The schematic symbol is a zigzag line. Real resistors look like a tube or a cylinder. A resistor is often called a load on a circuit. A fixed resistor has a zigzag line symbol. A variable resistor has an arrow through (or pointing toward) the zigzag line. Copyright © Texas Education Agency, All rights reserved.

More Resistor Characteristics
Another important characteristic is the power rating. A power rating is related to physical size. The resistance value has nothing to do with physical size. Resistance is often related to a concept like friction, but they are not exactly the same. Resistance is useful. Copyright © Texas Education Agency, All rights reserved.

Types of Resistors Fixed Symbol: Image source: These resistors are called carbon composition resistors, which are the most common type. They are made with a high resistance filler material like an epoxy that is mixed with a variable amount of carbon. The amount of carbon in the mixture determines the actual resistance value, with a higher concentration of carbon giving lower resistance. Increasing or decreasing the concentration of carbon in the mixture does not affect the size or shape of the resistor, so you cannot tell the resistor value from its size or shape. Copyright © Texas Education Agency, All rights reserved.

Measurement and Symbol
Resistance is measured in Ohms Symbol for resistance is (Greek symbol Omega) Copyright © Texas Education Agency, All rights reserved.

Resistor Color Code Chart
A typical resistor package is too small (and too cheap) to have its value stamped as a number on the outside of the package. Also, numbers would only be on one side of the resistor, so if it were placed with the number down, you could not read the value. So we need another way to indicate the resistance value. The way we determine value is called the resistance color code, which are color bands that circle around the outside of the resistor package. The color bands are easier to see and read than numbers. Source: Copyright © Texas Education Agency, All rights reserved.

Memory Aid (mnemonic) Black (0) Brown (1) Red (2) Orange (3) Yellow (4) Green (5) Note that primary colors are used in the color code. Blue (6) Violet (7) Grey (8) White (9) Copyright © Texas Education Agency, All rights reserved.

Memory Aid (mnemonic) Black (0) = Big Brown (1) = Boys Red (2) = Race Orange (3) = Our Yellow (4) = Young Green (5) = Girls Blue (6) = But Violet (7) = Violet Grey (8) = Generally White (9) = Wins Copyright © Texas Education Agency, All rights reserved.

Notice this gap between the 3rd and 4th color band.
Identifying the Bands Notice this gap between the 3rd and 4th color band. The gap is one of the main ways to identify the tolerance band. The fourth band is almost always gold, which is another way to identify it. But yellow or orange can look similar to gold, which makes it hard to tell what the value is sometimes. Copyright © Texas Education Agency, All rights reserved.

Identifying the Bands One band can also be closer to the end on one side. This is the first band. On small resistors, it may be hard to tell which band is closer to the end. Copyright © Texas Education Agency, All rights reserved.

Identifying the Bands Here is a picture showing the color bands starting closer to one end. Image source: In this picture there is no noticeable gap. When resistors can start with a color band close to the end, the gap is not important. Copyright © Texas Education Agency, All rights reserved.

Identifying the Bands Here is a resistor showing the gap between bands. Image source: A resistor manufacturer will typically use one method or the other, but not both. Also, notice that the fourth band is silver. In this picture it is hard to see which band is closer to the end, but the gap is easy to see. Copyright © Texas Education Agency, All rights reserved.

Reading the Resistor Value From the Color Bands
These three bands identify the resistor value. The gap is one of the main ways to identify the tolerance band. The fourth band is almost always gold, which is another way to identify it. But yellow or orange can look similar to gold, which makes it hard to tell what the value is sometimes. If you misidentify which is the first band, you are reading values backward and can end up with drastically wrong expected values. Copyright © Texas Education Agency, All rights reserved.

Reading the Resistor Value From the Color Bands
The 4th band indicates the tolerance range. The tolerance is the amount that the actual value of the resistance can change or differ from the indicated or expected resistance value. Copyright © Texas Education Agency, All rights reserved.

Third Band: is the multiplier equals a single zero
Example Third Band: is the multiplier equals a single zero Copyright © Texas Education Agency, All rights reserved.

This is the tolerance band.
Example Fourth Band: Gold This is the tolerance band. Copyright © Texas Education Agency, All rights reserved.

Gold equals a tolerance of five percent.
Example Gold equals a tolerance of five percent. Silver has a tolerance of 10 percent. No fourth band indicates a tolerance of 20 percent, but these resistors are rare. With improved manufacturing standards since about 1980, it is easy to make resistors with a good tolerance cheaply. Resistors with poor tolerance have not been popular since ancient history (meaning since cell phones were primarily used as phones). Copyright © Texas Education Agency, All rights reserved.

So this resistor has a value of 470 Ω with five percent tolerance.
Example So this resistor has a value of 470 Ω with five percent tolerance. Tolerance is a plus or minus value; you add and subtract the percent tolerance value from the 470 ohms. Add and subtract 23.5 ohms from 470. Copyright © Texas Education Agency, All rights reserved.

This resistor should have a measured value between
Example This resistor should have a measured value between 446.5 Ω and Ω. This can be confusing because yellow kind of looks like gold, and in a real resistor, it would be easy to read values from the wrong direction. Copyright © Texas Education Agency, All rights reserved.

Determine the value of the following resistor. Equals 1000 Ω, plus or minus 5 percent Five percent is 50 Ω, so 1000 plus or minus 50 is a range of 950 Ω to 1050 Ω. Copyright © Texas Education Agency, All rights reserved.

Determine the value of the following resistor. Note this resistor is reversed, which is common because resistors can be randomly oriented on a circuit board. Read from right to left. Green, Blue, Orange, Gold Equals ohms, 5 percent tolerance Notice that orange does kind of look like gold. Copyright © Texas Education Agency, All rights reserved.

More practice: Determine the value of these actual resistors. Left most resistor: gold as a multiplier is times .1 (point one, or one tenth), so the value is 2.2 ohms. From left, the values are 2.2 Ω, 1k Ω (1000 Ω), 560 Ω, 1k Ω, 2.2 kΩ, 27 Ω, and 1k Ω again. For even more practice, go back to the first slide and try to read those resistor values. Copyright © Texas Education Agency, All rights reserved.

Resistor Tolerance Resistor tolerance is a range of resistance values where the resistor is still OK. Resistor values have a range because they can change with age, current, or temperature. The range is plus or minus from the indicated value. Often, the resistance value does not have to be exact. Use the indicated value of the resistor to determine tolerance. Copyright © Texas Education Agency, All rights reserved.

Resistor Tolerance Use the indicated value of the resistor to determine tolerance. Multiply the indicated value times the tolerance. Example: 5 percent of 1000 is .05 X 1000 = 50 Add and subtract the tolerance from the indicated value. Example: 1000 – 50 = 950, = 1050 The acceptable range of resistance is Ω to 1050 Ω. Copyright © Texas Education Agency, All rights reserved.

Resistor Measurement Read resistor value from color code. Measure the resistor value with a multimeter. Compare indicated value to measured value. Copyright © Texas Education Agency, All rights reserved.

Check it Out To measure resistance value: Plug the red (positive) lead into the V (Voltage/Resistance) connection hole. Plug the black (negative) lead into the COM (Common) connection hole. Turn the measurement range dial into the resistance settings area. Copyright © Texas Education Agency, All rights reserved.

Check it Out Set the range setting to a level higher than the resistance of the resistor you will be measuring. Touch the red lead to one end of the resistor and the black lead to the other end. The readout will display the resistance value according to the scale you set. Copyright © Texas Education Agency, All rights reserved.

Check it Out Record your actual measured resistance value for the resistor and the corresponding “color bands” on the resistor in the table in your Lab Journal. Set these resistors aside, they will be used later. Turn the measurement dial back to OFF when not in use to conserve the battery. Resistor Actual measurement Color bands 470 1.0K 1.5K 1.0M Copyright © Texas Education Agency, All rights reserved.

Make the Connection Use your multimeter to measure the resistance of your body from one hand to the other. Set the meter to 20M. Grab the tip of the red lead between two fingers in your right hand. Grab the tip of the black lead between two fingers in your left hand. Squeeze tightly, and note the resistance measurement on the readout. Record your measurement. What factors do you think cause the variations between the measurements of various people? Copyright © Texas Education Agency, All rights reserved.

Make the Connection Now lick the four fingers you used to get them wet and repeat the measurement. Record the new measurement. Does your body conduct electricity? How did licking your fingers affect the measurement? Compare your measurements with others. How do the measurements vary? What factors do you think cause the variations between the measurements of various people? Copyright © Texas Education Agency, All rights reserved.

Resistor Size vs. Value Notice that resistors come in many sizes. Resistance value is determined by the amount of carbon mixed in with filler in the carbon composition manufacturing process. Does resistor size have anything to do with resistor value? Copyright © Texas Education Agency, All rights reserved.

Resistor A resistor will drop (or use) some of the supplied voltage as current passes through it. This creates a voltage drop across the resistor. A resistor will have a voltage drop across it and current flowing through it. These two things multiplied together are the electrical definition of power. Copyright © Texas Education Agency, All rights reserved.

Resistor A resistor consumes power as it does its job of limiting current. A resistor is not designed to produce heat, but heat is produced when power is consumed. This is called self-heating. A resistor needs to be able to dissipate the heat it generates. Or it will burn up The heat generated can be expressed as a temperature rise per watt (or milliwatt) of power. Many resistor manufacturers are more concerned with the resistance change as a function of temperature than the point at which it burns up. Copyright © Texas Education Agency, All rights reserved.

Since a device loses heat through its surface, the larger the surface area, the more heat a device dissipates. Heat dissipation is related to device surface area. Larger devices have a larger surface area. A physically larger device is able to dissipate more heat and handle more power. Image source: Copyright © Texas Education Agency, All rights reserved.

Heat Dissipation Formula
Heat creates a temperature difference. At a large temperature, the device will burn up. For a given heat, a larger area results in a smaller temperature difference. This means a device with a larger surface area can consume more heat before it reaches a point where it burns up. Copyright © Texas Education Agency, All rights reserved.

Team Challenge Goal Analyze the relationship between voltage, current, and resistance in an electronic circuit. Materials List (per team) Calculator Multimeter and leads One 470W resistor One 1.0KW resistor One 1.5KW resistor One 1.0MW resistor Breadboard Breadboard wire pack (pre-trimmed wires for making connections on the breadboard) 6V battery pack (includes 4 – “AA” batteries) Copyright © Texas Education Agency, All rights reserved.

Team Challenge Connect battery to the ends of the “+” and “-” rows with the red wire going to the “+” and the black wire going to the “-”. Place the 470 resistor with one end in a hole in one column and the other end in a hole in another column. Connect a small wire from a hole in the “+” row into a hole corresponding to the column where one end of the resistor is connected. Connect a small wire from a hole in the “-” row into a hole corresponding to the column where the other end of the resistor is connected. Copyright © Texas Education Agency, All rights reserved.

Team Challenge The breadboard layout should resemble the image at right. To measure the voltage across the resistor, use the following setup and verify that the batteries are producing approximately 6.0V. Be sure to set the multimeter on the 20 setting in the DC Voltage setup area so that it will be able to measure 6.0V without over-ranging. Record the voltage measurement. Copyright © Texas Education Agency, All rights reserved.

Team Challenge Measure the current in the circuit. Insert the meter between the “+” row and the upper side of the resistor (remove the little wire that was connecting this side of the resistor to the “+” row). Copyright © Texas Education Agency, All rights reserved.

Team Challenge Verify that your current calculation was accurate. Be sure to set the multimeter on the 20m setting in the DC current setup area. Be sure that your red lead is connected to the “mA” connection of the meter instead of the “V” connection. Record your current measurement. Copyright © Texas Education Agency, All rights reserved.

K.R.E Society’s Karnatak Arts, Science and Commerce College Bidar

Similar presentations

Presentation on theme: "K.R.E Society’s Karnatak Arts, Science and Commerce College Bidar"— Presentation transcript:

Similar presentations

About project

Feedback

Log in

Auth with social network:

K.R.E Society’s Karnatak Arts, Science and Commerce College Bidar

Similar presentations

Presentation on theme: "K.R.E Society’s Karnatak Arts, Science and Commerce College Bidar"— Presentation transcript:

Similar presentations

About project

Feedback