Henry Poon's Blog

While looking at some stuff on stepper motors for my courses, I came across a really nice resource on stepper motors.  The article outlines some of the rationale for choosing a stepper motor, the physics behind them, with practical examples of how they are used, and what motor parameters to look at when choosing one.  It also covers some information about closed-loop control of a stepper motor system.  It is quite a good read as a quick guide to how stepper motors work.  I found these notes to be very informative, and probably more informative than my class notes (although it doesn’t have as much math as in mine).

Link: http://www.societyofrobots.com/member_tutorials/node/120

I always wondered why Adobe Acrobat would always give me this “bad parameter” message, every time I scanned something.  Seeing that I never scanned a lot of stuff, I never bothered fixing it.  But now since I am scanning my friend’s notes for the classes that I missed, this issue has become way too annoying.

Apparently, the problem was that Adobe Acrobat didn’t have a default scanner set.  I would think the program would have known to use my default scanner device (really just my all-in-one printer), but it never set it.  To enable the scanner:

1. Click the “Create” button and click “Configure Presets”
2. Under the dropdown for the scanning device, choose your scanner
3. Scan away!

This method worked for me seeing that my scanner was already configured except for this little bit here.  If the correct scanner doesn’t show up the list, then it probably wasn’t properly configured to begin with.  In that case, it will take a bit of extra work for scanning to completely work.

That dreaded message appears every time I open a PDF.  It has bothered me for the longest time, and I’ve finally taken the time to get rid of it.  Before, every time I opened a PDF, Adobe Reader would process each page before it would let me scroll around.  It was very annoying.  Anyway, here is the solution:

UPDATE 12/08/10: One of the comments (thanks to Jørgen) provided an even better solution for getting rid of this annoying process.  It involves removing the plugins from Adobe Reader completely.

…Program Files…AdobeReader 9.0Readerplug_ins
there are 3 files you should delete (or maybe just rar them so you still got them in case something goes wrong)
Accessibility.api, MakeAccessible.api, ReadOutLoud.api
(if that gives troubles, just delete the files with the same name and .xxx where xxx stands for a certain language too)

OR – if you’re afraid Adobe won’t work or you’ll need the files later – rename the extension to .api_

Below is the original solution that I had.  It changes the settings so that the program will process each page as you read.  It’s not as good as the previous solution that completely disables it though.

1. Go to Adobe Reader’s Preferences (Edit > Preferences)
2. Go to the Reading tab
3. In Screen Reader Options, choose Only read the currently visible pages

Doing this pretty much tells Adobe to do the reading as you scroll through the pages.  Although this can still be annoying, but it’s way better waiting through that screen for larger PDF’s.

After fiddling with using the Serial Monitor on the Arduino IDE for serial communication inputs, I thought it was very useful to set up my own program to achieve the serial communication so that I didn’t have to rely on the Serial Monitor for it.  I came across a serial communication API called JavaComm (more info in the link below).  Only its 2.0 version will run on Windows, but there is a 3.0 version that is available for Linux users.  The article discusses how to use the library to achieve serial communication, and has a lot of example code to follow.  The PDF in the other link below has information on how to use the JavaComm API, and the information there is presented a little better than Wiki pages, since Wiki pages seem to be loaded with technical information that beginners (like me), can’t really follow too well.

Link: http://en.wikibooks.org/wiki/Serial_Programming/Serial_Java

Link: http://java.sun.com/developer/Books/javaprogramming/cookbook/11.pdf

This article (link at the bottom) is very useful for beginners that want to use XBee’s for wireless radio communication.  It discusses the basics of using XBee’s, such as using the computer to configure various options within the XBee such as the baud rate, network ID, etc.  It discusses two methods of setting the options in the XBee.  One method is through a program called X-CTU (GUI) and another method is using a CLI.  The important options in the XBee are discussed and explained so that everyone knows what they should be set to.

The configuration that I used was that I had my computer connected to an XBee USB Explorer via USB.  On the other end was an Arduino Duemilanove powered by six 1.2 V NiMH batteries, and this microcontroller powered the XBee using its 5 V pin.  I compiled and downloaded the program at the bottom of the article to my Arduino and I tested it using the Serial Monitor that comes with the Arduino IDE.

Even though the test program is simple, it shows that a wireless link can be made between the computer and the microcontroller, meaning that the microcontroller can process computer input to do even more crazy things.

Link: http://forums.trossenrobotics.com/tutorials/how-to-diy-128/xbee-basics-3259/