Category Archives: Engineering

Opinions, thoughts, and experiences in engineering

Grounding

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The importance of grounding is becoming more and more apparent to me as I progress through my schooling and projects.  I’d like to write a tutorial on grounding for beginners to help tame entry into a complex set of rules, theory, and practices.  Sadly, I don’t have time to do write a proper tutorial, so I’m going to put some links/references to other sites that have helped me, directly or indirectly learn about grounding, for the time being.

The Tape Monster

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I am leading a Micromouse Team for IEEE UCSD, and in trying to hack something together that would drive in a straight line, I ended up making a contrivance with a lot of tape holding it together.  I named it the Tape Monster, because it didn’t really work, and it looked horrible, compared to what I usually produce.

Now, it turns out that there is a preexisting Tape Monster, from before I joined the Micromouse Team in 2008, so my ‘creation’ is technically the Tape Monster mkII.  Fair enough, I guess.  Anyways, the robot has 4 Sharp GP2D120X sensors, an Arduino board, motor driver shield and a pair of DC motors with encoder feedback on them.  I wanted to power the thing from the USB port, but the cable bias was unacceptable, so I added some batteries.

Here’s where things get interesting.  Without encoder feedback based speed control, the value of Vin (feeding the H-bridges that drive the motor) matters.  The reason is that the higher Vin is, the PWM duty cycle required to overcome the parasitics of the motor is reduced.  Do I have equations a sexy graph for this?  No,  I wanted my robot to drive straight, NOW.  I would like to relate them, but that will have to wait for a night when I’m not under a massive time crunch.

You can follow the progress of my robot and see some of the data that I am using to drive my engineering and design decisions at the IEEE UCSD Wiki.

Now back to the regularly scheduled homework assignment….

Frustration with Config Management Software

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At work, I’ve been entering cabling into Windchill, which is a PTC database tool for keeping track of BOMs, configurations, and other stuff.

The frustrating part with this system is that I can’t import cable runs sheets from Atlium, and apparently, it can’t import a BOM from a Pro-E (which is a PTC product) drawing or an Excel sheet.

I’m not sure if this is a problem with Windchill, or if it that no one at my company knows where documentation are for this feature is.

So far I’ve managed to find a few workarounds that are making the entire thing less painful, but still we have over 1000 cable runs to enter and we’re at about a minute per cable.  It’s better than about 3 minutes for one cable, but still annoying.

Upgrading from WordPress 2.9.2 to WordPress 3.0

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After the automatic upgrade failed, I tried to execute a manual update.  That failed and resulted in an “Error 500″ problem on the admin pages.  I spent a couple of hours trying to figure out what happened and how to fix it.  Basically, I was able to fix it by clearing out wp-config.php and rebuilding it from wp-config-sample.php.   I used “wp-admin/setup-config.php" to effect the rebuild after I renamed the broken config file.  I saved the old config file by renaming it wp-config-old.php with my FTP client (FileZilla).  I edited the config file on my laptop with Adobe Dreamweaver, but any text editor should do.

I wrote this post after the fix, and also serves to test my posting ability.

Edit: One thing I forgot to mention is that I also had to disable and delete the security scan plug-in I had.  I think it was called WP-SecurityScan.  If you don’t disable it, you will get the “Error 500″ problem again.  I am hosted on a 1and1 linux based package.