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AVR Programming Guides
We have some nice AVR code samples to share. Lots of AVR goodies like timers, interrupts, and pin I/O for the beginner. |
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Watts Tables
Use these tables to help you determine how much various items in your house cost you by the day, month, and year. |
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Saving Electricity
A list of a variety of ways to help you save money by learning how much it costs to run things. |
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Read Your Power Meter
By reading your power meter you can get a good idea of how much various electrical devices cost you. |
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Introduction to Resistors Page 2
Determining the Value of a Resistor
There are 2 common ways to determine the value of a resistor, and we will cover them both.
- Reading the color bands
- Using an ohmmeter
Reading the Color Bands
Most hobby resistors have color bands on them that help you to determine their resistance value. Reading the bands is like solving a puzzle. Some people enjoy it, some people hate it. You'll have to give it a try and see where you stand. Don't worry if you hate it, there are always other ways to figure out what resistance a particular component is.
Lets look at a close up of a resistors color bands.
Ignore the gold band for now. The meaning of a color depends on if it is in the first two bands, or if it is the third band. The first two bands are used as regular numbers, while the third band is used as a multiplier. Lets take a look at a table of what the colors mean.
| Color |
1st band |
2nd band |
3rd band (multiplier) |
| Black |
0 |
0 |
x1 |
| Brown |
1 |
1 |
x10 |
| Red |
2 |
2 |
x100 |
| Orange |
3 |
3 |
x1,000 |
| Yellow |
4 |
4 |
x10,000 |
| Green |
5 |
5 |
x100,000 |
| Blue |
6 |
6 |
x1,000,000 |
| Violet |
7 |
7 |
x10,000,000 |
| Gray |
8 |
8 |
x100,000,000 |
| White |
9 |
9 |
x1,000,000,000 |
Focus on the top 5 rows, they are the most important. For now you can ignore green, blue, violet, gray and white. After you get the hang of resistor color codes come back and review the second half of the table.
Examples of Resistor Values
Lets see some examples to understand how the table works.
Example 1
| Band 1 |
Band 2 |
Multiplier |
Value |
| Brown |
Black |
Red |
??? |
Example 1: Brown - Black - Red
Referring to the table, brown in band 1 = 1, and black in band 2 = 0. So far our value is 10. Finally, red in band 3 = x 100. So our final value is:
10 x 100 = 1,000 = 1k ohms or 1kΩ
Example 2
| Band 1 |
Band 2 |
Multiplier |
Value |
| Red |
Red |
Brown |
??? |
Example 2: Red - Red - Brown
Referring to the table, red in band 1 = 2, and red in band 2 = 2. So far our value is 22. Finally, brown in band 3 = x 10. So our final value is:
22 x 10 = 220 = 220 ohms or 220Ω
Example 3
| Band 1 |
Band 2 |
Multiplier |
Value |
| Orange |
Orange |
Orange |
??? |
Example 3: Orange - Orange - Orange
Referring to the table, orange in band 1 = 3, and orange in band 2 = 3. So far our value is 33. Finally, orange in band 3 = x 1000. So our final value is:
33 x 1000 = 33,000 = 33k ohms or 33kΩ
Common Resistor Values
It seems that some resistor values show up more often than others. It is very handy to be able to recognize these most common values without having to look them up. Here we will present you with a table of the common values. Notice that we have used some of the higher numbers here. Refer to this table if you need help figuring out a resistors value.
| Band 1 |
Band 2 |
Multiplier |
Value |
| Brown |
Black |
Brown |
100 ohms |
| Red |
Red |
Brown |
220 ohms |
| Yellow |
Violet |
Brown |
470 ohms |
| Brown |
Black |
Red |
1k ohms |
| Brown |
Red |
Red |
1.2k ohms |
| Red |
Red |
Red |
2.2k ohms |
| Yellow |
Violet |
Red |
4.7k ohms |
| Brown |
Black |
Orange |
10k ohms |
| Yellow |
Violet |
Orange |
47k ohms |
| Brown |
Black |
Yellow |
100k ohms |
| Brown |
Black |
Green |
1M ohms |
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