The Many Methods to Reading Resistor Values

The Many Methods to Reading Resistor Values:

In working on the builds for Weekend Projects, we’ve been dealing a lot with resistors of different values (indicated by the color bands on the resistors themselves). Trying to figure out the values of these common components can be confusing to new electronics hobbyists, so I thought it would be helpful to share some tips and tools for identifying them.

It seems like at least once a year here on MAKE there’s a “How-To Read a Resistor” post. They’re all incredibly useful in their own ways. I, in fact, use no less than four ways to read them, depending on where I am in the world and whether I’m trying to decipher a resistor’s value, or know the value and want to find the color scheme. If you’re fortunate enough to have a Maker’s Notebook, on page 162 is the Resistor Color Codes matrix. You can cleverly hack your own notebook with markers or colored pens like this so that the grid is more colorful and easier to reference. I also keep a printed-out version of this same matrix on my workshop wall, so all I have to do is look up to figure out “violet = 7″ or whatever value/color I’m hunting down. When working with beginners, I’ve found the resistor matrix to be a bit frustrating. It’s time-consuming trying to add up values in your head, and if you can’t write something down for whatever reason, it’s easy to forget. Which is why one of my favorite tools for beginners is the resistor color wheel [PDF]. I also keep a version of this pinned to my wall which I can easily spin, so when I’m looking for a 47k resistor, I quickly and easily know I’m looking for Yellow, Violet, Orange for the first 3 bands. But like I said, I have four ways to read resistors up my sleeves! The fourth is this HTML5 resistor calculator, which is incredibly handy when I’m neither in my workshop nor have my notebook with me to reference. As the name implies it only works with HTML5-compatible browsers, but all you have to do is scroll the dials into place and voila, you’ve calculated your resistor value. (NOTE: these color wheels are useful for standard four-band ‘carbon film’ resistors.)

Work with enough of the same resistors and you’ll start to memorize the color sequence and its value, but in the meantime these are some great ways to get started.

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