Resistor value calculator in HTML5

A resistor is a two-terminal electronic component which implements electrical resistance as a circuit element. When a voltage V is applied across the terminals of a resistor, a current I will flow through the resistor in direct proportion to that voltage. The reciprocal of the constant of proportionality is known as the resistance R, since, with a given voltage V, a larger value of R further "resists" the flow of current I as given by Ohm's law.


Most axial resistors use a pattern of colored stripes to indicate resistance. Surface-mount resistors are marked numerically, if they are big enough to permit marking; more-recent small sizes are impractical to mark. Cases are usually tan, brown, blue, or green, though other colors are occasionally found such as dark red or dark gray.
Early 20th century resistors, essentially uninsulated, were dipped in paint to cover their entire body for color coding. A second color of paint was applied to one end of the element, and a color dot (or band) in the middle provided the third digit. The rule was "body, tip, dot", providing two significant digits for value and the decimal multiplier, in that sequence. Default tolerance was ±20%. Closer-tolerance resistors had silver (±10%) or gold-colored (±5%) paint on the other end.


Four-band identification is the most commonly used color-coding scheme on resistors. It consists of four colored bands that are painted around the body of the resistor. The first two bands encode the first two significant digits of the resistance value, the third is a power-of-ten multiplier or number-of-zeroes, and the fourth is the tolerance accuracy, or acceptable error, of the value. The first three bands are equally spaced along the resistor; the spacing to the fourth band is wider. Sometimes a fifth band identifies the thermal coefficient, but this must be distinguished from the true 5-color system, with 3 significant digits.
For example, green-blue-yellow-red is 56×10⁴ Ω = 560 kΩ ± 2%. An easier description can be as followed: the first band, green, has a value of 5 and the second band, blue, has a value of 6, and is counted as 56. The third band, yellow, has a value of 10⁴, which adds four 0's to the end, creating 560,000 Ω at ±2% tolerance accuracy. 560,000 Ω changes to 560 kΩ ±2% (as a kilo- is 10³).

To try out EaselJS (a javascript library for working with the html5 canvas element) and inspired by Resistor Colour Wheel I wrote a small experiment, that can help finding the value of resistors: HTML5 Resistor calculator.

ALERT! This experiment won't work at all in Internet Explorer. You need Chrome, Firefox, Safari or any other browser supporting HTML5.

Aventail Connect VPN on Mac OS X

Here's a tip that can save you some trouble. If you use SonicWall Aventail Connect to make VPN connections on Mac OS X, you'll run into the same problem I did eventually. If you system crashes while using the Aventail it won't start again unless you cleanup some files.

The files are located in:


/Users/<YOUR USER>/Library/Application Support/Aventail/run


with the names: SEM.pid and SEM.sock.


Just remove both and Aventail will start and connect normally.

Linux / Mac OS X cleaning music library

If you love to listen to music, you'll probably have a huge MP3 library. Imagine that you gathered a lot of MP3 and you never bothered to keep the library clean until it was too late, and now you've a massive amount of folders and mp3 files all together with trash ( .txt, .url, .nfo, etc etc ... ) and you decided it was the time to clean it up.

You could do it the hard way, using OS X "Spotlight", finding and removing the stuff you don't want or you can do it the smart way with the beauty of command line shell.

Here's a simple and very useful command that will remove all unwanted files keeping only the ones you want. Just fire up the command shell to the folder which is the base of your library and run the following command:


find . ! \( -iname '*.mp3' -o -iname '*.wma' -o -iname '*.m4a' -o -iname '*.cue' -o -iname '*.wav' \) -type f -exec rm {} \;

You can add another set of file extensions to ignore by appending -o -iname '*.newExtension' inside the parentheses.