The Wire Up

Listen while you read: Franz Ferdinand - Lucid Dreams

The Resistor color code: a thing of genius, but how to memorize it? Not sure how the resistor code was dreamed up or how old it is but I'm sure ever since its creation there have been thousands of ways of memorizing it. Despite the vast amount, an engineer need only memorize one to thrive in the electronic world. If you don't already have one memorized I would highly recommend this popular saying that I was taught my first year of college. The saying will help you memorize the order of each of the colors in the code and therefore help you remember the value of each of the colors on a resistor band.

The saying: Bad Beer Rots Our Young Guts, But Vodka Goes Well.

The colors: Black, Brown, Red, Orange, Yellow, Green, Blue, Violet, Green, White.

The values: 0,1,2,3,4,5,6,7,8,9

Now, this color code is just for the first 2 to 3 bands which again, correspond to the 1st, 2nd and 3rd digits of the value in ohms. The 3rd and sometimes 4th band is the multiplier of the previous digits. So if the multiplier were to be orange simply add three zeros to the value: Red, Yellow, Blue, Orange would equal 246,000 ohms or 246 kohms.

The final band stands for the tolerance of the resistor. The tolerance is the percentage error that the measured resistance must lie between. So, if you have a gold banded resistor the tolerance is 5%. This means for a 1 kohm rated resistor the real resistance lies somewhere between 950 ohms and 1.5 kohms. The graphic below should help explain for those having trouble. There is even a 6th band which tells you temperature coefficient, the resistance of a resistor can change with temperature and sometimes the temperature coefficient is labeled on components that operate within a very small tolerance in extreme conditions.

Next post, I'll explain the coding for ceramic capacitors. No, I don't have nice little saying for that one, I just have it printed out and posted to my tool box. Make sure to leave a comment below and share your method for memorizing the color code. Stay Wired Up!

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Listen while you read: The Black Keys - The Wicked Messager


The kit I'm posting this week is a 3 stage FM transmitter you can use to spy on...umm rather, monitor auspicious noises. Its called a 3 stage transmitter because it separates the 2 amplification and oscillation stages into separt parts of the circuit. The first stage, isolates the microphone from the base voltage of a simple BJT transistor. The second, oscillation stage, generates a RF carrier wave. In FM, frequency modulation, transmission the input signal from the microphone is transposed on to a carrier signal. The carrier signal is what you tune your radio to listen to. Look at the picture below to see the difference between FM and AM modulation.

With AM, an increase in amplitude of the input signal results in an increase of amplitude for the final composite wave. Just the opposite is true for FM, an increase in amplitude of the input signal results in an increase of frequency for the final composite wave.

Our final and third stage is another amplification stage. This time it is with a special RF transistor along with a RF choke and a capacitor in parallel to reduce harmonics.

I put this project together back a few years ago and it was probably what inspired me to get into RF electronics. You can learn a lot by doing a project like this one, really how much you learn it is up to you. Since building this transmitter I have built two more sophisticated transmitters that both transmit in stereo. This one however, is a fairly quick build and should only take you a few hours. The range is pretty descent if I remember correctly, within a legal range inside the US obviously. Good luck with the project as always if you have questions you can email me at kurf@thewireup.com.

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Listen while you read: Department of Eagles - No One Does It Like You

MATLAB is an expensive and sometimes slow running calculation tool that can be hard to access when your shifting around on multiple computers. After searching for an alternative, I have come across an online calculator called Rascal. Rascal, created by Sebastian Ritterbusch, is an advanced scientific calculator that can mimic some of the functions of MATLAB. It is by no means a replacement but if your looking for something quick and can be loaded simply by visiting a webpage then Rascal is defiantly worth a look. You can download Rascal or use a full online version from here or try it right below. If you use the form below you will be redirected to the Rascal site.

Listen while you read: Empire of the Sun - Walking On a Dream

You may have noticed the new search bars down at the bottom of the page. From my web page you can search any three major semiconductor manufactures for parts and samples. Its simple just enter the part number in the correct search bar and hit enter. You will then be taken directly to the manufactures website where you will find the data sheet and other ordering information. Have fun and there will be more tools added to the site in the future so keep wired up!

To those of you using internet explorer, I suggests you change your browser, you may have noticed that some of the features on the website do night work including the last post which had some odd spacing after the pictures. I recommend switching browsers to either Firefox or another open source browser like Chrome. They are far safer and will even speed up your browser and obviously render pages correctly. If you have any suggestions on how I can fix the problems in explorer I would be happy to use your advice.

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Listen while you read: The Kills - The Tape Song

Finally, I have pictures of my project for you all. Progress is slow and I actually have had a slight set back. Something became corrupted in my PSoC code. The compiler thinks that the API has errors in it. I did something but have no idea how to fix it, the block schematic has not changed. Sorry to those who have no idea what I'm talking about, I doubt you really care to know either. I will spare you the technical content and try not to be overbearing for the simple hobbist. Blah. Anyway, enjoy the pictures.

Technorati Tags: Electronic Projects PCB Circuit Board Students Electrical Engineering

Listen while you read: Modest Mouse - March Into the Sea

Today I received an email that details a well learned lesson from an EET student from Purdue. Learning for the mistakes of your peers is a good idea but not buffering or protecting your outputs power traces is a very bad one. To often the thought of saving time or cost out weighs the thought of prevention planning. I myself have learned the hard way that patient planning always is faster then throwing something together and expecting things not to go "haywire". I think Murphy was an electrical engineer. (No, but close an aerospace engineer.)

Good morning, Professor-

Experience and planning. When designing any circuit, whether simple or complex, it's always a good idea to add circuit protection. However, I do not hear a lot about protecting vital elements of one's design within my colleagues' projects. Just last semester I saw a senior melt a battery because of a short in his circuit, which made me think, that could have been me. Unfortunately, for the student's in this generation, they have little patience when dealing with proper planning or just simply overlook the small stuff like buffering inputs to help alleviate loading or protecting against releasing the magic smoke from within.

While testing my motor controller, I made a simple mistake in soldering a short from power to ground. As soon as I connected my power supply to my circuit, I heard a hissing sound and then nothing. No output, no input, just plain nothing. Upon inspection of the circuit, I found the soldering mistake, but it was too late. Alas, but what do I see, that only a single trace was damaged. Well actually, the trace was broken at one point. The copper was tarnished all the way up to my first diode. Without that diode, my circuit would have been cooked. Good thing I learned from someone's stumbles prior to this and added substantial circuit protection. Now I am just repairing a single trace, rather than replacing expensive components. My only hope is that my fellow comrades have the insight to not overlook the small, simple details that could save them time and money when developing their projects.

Best regards,

ECET Student