Join Peggy Fisher for an in-depth discussion in this video Reading resistors, part of Up and Running with Arduino.
- Now I'd like to show you how to read your resistors. A resistor resists the flow of electricity. The flow is called the current. each resistor is labeled to help us determine how strongly it resists the current flow. The resistance value is called the om, represented with the Greek letter, omega. Resistors come with many different resistance values, such as a 220Ω, a 560Ω, 1K, 10K, et cetera. All the resistors are color-coded.
These colors are used to calculate the amount of resistance. Here is a picture of a resistor. Each color on the resistor is called a band. To read the value of your resistor, you must read and translate all the color bands on the resistor. It might be easier to start from the right to get the tolerance value and the multiplier first. Note the tolerance values are usually gold or silver in color. In the example on the right, there are four bands of color, plus the tolerance. Let's read this resistor.
The color of the tolerance band, the far right, is gold, indicating a 5% tolerance. This means that the actual value is accurate to within 5% of what the color-coding says. This tolerance usually isn't a problem in projects for the Arduino, but it is definitely good to know this information for future projects that have more specific requirements. Next we have our multiplier band. In this case it's red, red has a value of 100. The digit bands are brown, brown, black.
So this translates to 1, 1, 0. To put it all together, you get 1, 1, 0, times 100. Which equals 11,000Ω, or an 11kΩ resistor. After a little practice of reading these codes, you'll become pretty quick at figuring out the values. But if you need a little help, there are plenty of great resistor code calculators available online. Keep in mind that not all resistors will have the same number of colored bands, so always read from right to left, starting with the tolerance, then the multiplier, then the digits.
Some of the common resistors that we'll use while we're working with our Arduino, include the 220Ω resistor, the 1kΩ resistor, and the 4.7kΩ resistor. Before we leave our discussion on resistors, I wanna talk about pull-up versus pull-down. These are two terms that you will often see when working with electronics. A pull-up resistor is a resistor connected between a signal conductor and a positive power supply. The pull-up resistor is used to ensure that the signal will be a valid, logical level, if any external devices are disconnected.
A pull-up resistor pulls the voltage of the signal it is connected to, towards its voltage source level. A pull-down resistor, on the other hand, works in the same way, but it's connected to ground. It holds the logic signal low when no other active device is connected. There's a great description with images in the Arduino playground, for pull-up and pull-down resistors.
If you're new to do-it-yourself computing, start by learning how to get your Mac or Windows computer communicating with Arduino and reviewing the basics of electronic components and circuits. Then tour the most basic Arduino model, the Uno, and learn to write your first program. Peggy also reviews the five other major Arduino offerings: the Leonardo, the Yun, the Esplora, the Robot, and, for wearable tech, the LilyPad. Along the way, Peggy shows how to put your knowledge to work in several sample projects, including a Morse code translator and a light-driven music instrument.
- Installing Arduino software on Mac and Windows
- Understanding circuit diagrams
- Using a solderless breadboard
- Writing your first project for the Arduino Uno
- Programming the Arduino Leonardo
- Connecting wirelessly to the Arduino Yun
- Displaying and moving with the Arduino Esplora
- Driving with the Arduino Robot
- Sensing and adjusting light
- Creating wearable tech with Arduino LilyPad
- Troubleshooting techniques