Showing posts from January, 2008

Develop with Arduino

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I'm visiting a school in northern Finland next week. This is the presentation I'm giving. It's intended for first year students so you'll find it very basic, and you'll miss the fun of some demos. By putting it here I have a backup plan if I lose my pendrive :-)

Using eBay's Best Offer feature

I'm still dealing with a non-responsive eBay seller after I've got burned by a non-working 8GB compact flash. I've seen that many people do not like to talk about this type of failures that happen on eBay from time to time. I'm still trying to get my money back from PayPal so maybe not everything is lost.

But now I wanted to buy some cheap control chips for bipolar stepper motors. Nothing fancy with micro stepping or digital current control, just a simple chip that can also be used for other purposes too. I saw this video and I learned about the L293. It is an old chip that several manufacturers mark as deprecated.

Instead of going to a local shop I went online to eBay and I saw several sellers have it available. I tend to favor European sellers if the price is right as I do not particularly enjoy periods longer than two months for delivery (something I've experienced first hand from Hong Kong lately). One of the sellers had a price that seemed ok, but they also did …

On-line math calculation

I know several nice Math software packages, mostly for Windows (Derive, Mathematica, MathCAD, Matlab ...). My university has licenses for some of them but I am not always on campus, using Windows, when I need some help. There are some free math programs too (Scilab, Octave, Maxima, Axiom ...).

What it is not always known is that there is an interesting set of on-line calculators and solvers that sometimes can help you get the job done without installing anything. Quite interesting when you are not even using your own computer.

For easy calculations and units conversion Google calculator is a neat tool. How do you use it? Just type your calculation on Google search box (i.e. "5/sin(32)" or "25 celsius in farenheit" ). Really worthwhile to convert between American and European fuel economy units!

But maybe you already have a calculator so this Google feature while nice does more or less the same. You may need to do something more advanced like online matrix calculation.…

Troubling iMac

A few months ago I bought a shiny 20" iMac. While the initial impression was good, I was not happy after the trouble I had installing Leopard and certain incompatibilities it brought.

Just when it seemed things were settling down I've got the system just dying on me after opening a large (120MB) PDF file. The screen turned black and then the system rebooted spontaneously. Another computer was on at the same time and it did not experience any problem, so I do not think that was because of a power spike.

Today, when I started the system there was a multilingual message in a centered dark square telling me to press the power button for several seconds to shutdown the system (neither the keyboard or the mouse worked). I have never seen that image before (but I failed to take a photo), it contained the message in Japanse too. It happens to be an OS X kernel panic.

When I powered on the system again I heard the welcome sound and next two beeps and then three beeps that repeated over …

Other Hacks

While searching the net for possible uses of old hard drive voice coil actuators I've came across this video. A video is worth even more than a thousand words so I'll let it talk.