# Resistor Color Code Tattoo

Our good friend Jimmie P Rogers— of LoL Shield fame, amongst many of us who love Arduino and LEDs —has a brand new tattoo of the resistor color code: Black, Brown, Red, Orange, Yellow, Green, Blue, Violet, Gray, White.  I’m pretty sure that Jimmy himself has known this color code since he was in diapers, but now he has an always-present chart that he can use as a visual aid while teaching electronics.  And at five inches across, it doubles as a ruler (albeit one that will grow less accurate with age).

So, that’s pretty neat.  But two things bring this above and beyond the “usual” coolness of a geek tattoo.  First, Jimmie designed it in Processing, and second, as an open source tattoo, you can download the source code on his web site.

And for those of us who may be a little less committed: Our own favorite mnemonic for the resistor color code is “Black Beetles Running On Your Garden Bring Very Good Weather.”

# Basics: Picking Resistors for LEDs

So… you just want to light up an LED. What resistor should you use?

Maybe you know the answer, or maybe everyone already assumes that you should know how to get to the answer.  And in any case, it’s a question that tends to generate more questions before you actually can get an answer: What kind of LED are you using? What power supply? Battery? Plug-in? Part of a larger circuit? Series? Parallel?

Playing with LEDs is supposed to be fun, and figuring out the answers to these questions is actually part of the fun.  There’s a simple formula that you use for figuring it out, Ohm’s Law. That formula is V = I × R, where V is the voltage, I is the current, and R is the resistance. But how do you know what numbers to plug into that formula to get out the right resistor value?

# Mystery components!

While picking out interesting vintage diodes at the electronics flea market, we came across a couple of components— possibly also diodes because of where we found them —of types that we have never seen before.  And we can’t resist a good mystery.

First, there’s this little two legged can, marked with 650, a black dot, and CO on one side. The other side (as you can see in the photo above this one), is marked T 1 and has black and red dots.

Secondly, a couple of things that look kind of like resistors:

They are very small, only about the size of 1/4 W resistors.  They are marked with a red capitol letter “P” and a set of four colored stripes. The “P” marking interrupts the three narrower bands in both cases.

Here’s a good look at the color bands: brown, violet, green, and then a broad yellow.  (We could be reading this wrong; is the broad stripe supposed to be read first?)

This one has brown, violet, green, and then broad violet.

So, what are they?  We don’t actually know, but if you do, or if you have a good guess, we’d love to hear it!

# Navel gazing: The first three months, and folks we admire.

Yes, it’s time for the state of the blog address. We took the EMSL blog online on June 21, 2006, three months ago. (It was about time that we started organizing our projects.)

So, happy quarter-birthday to us. Thus far we’ve put up some thirty projects. We’re actively working on about forty others right now.

If you haven’t bookmarked us, now is a fine time to do so. =)

Minor announcement I: We’ve just created a new group on flickr as a repository for our project photos.

Minor announcement II: We’ve also updated our CafePress shirt design:

Front: “Resistor”                      Rear: “Join the resistance.”

(Get one.)

Minor announcement III: Today we’re adding a new section of links to our web page, “Honorary Mad Scientists,” a short, specific, non-exhaustive list of creative people, sites, and/or blogs that we admire. We thought about calling the list “people like us,” but (1) it’s cocky of us to think that we can be as cool as these people and (2) maybe these folks don’t want us to suggest that they are anything like us. So, we’ll just call them Honorary Mad Scientists; read on for a partial list.
Continue reading Navel gazing: The first three months, and folks we admire.

# New EMSL shirt design: Join the resistance

New EMSL shirt design at our vanishingly-small CafePress store.

Get them while they’re– well, whenever you want. \$9-17.

(We don’t make money off of sales; we just want more people to join the resistance!)