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Arriving in Seattle

Just getting into Seattle for the Gnomedex conference.  Should have just enough time to check in and head over the registration party. More later.

Just noticed I’m wearing my Nerdery Overnight Website Challenge t-shirt. Really, I didn’t plan it that way.

I spent over a full day working with 12 other teammates to create a new website for the non-profit organization, DesignWise Medical. In 24 hours we put together a site that, in my experience as a Web developer, could easily have taken weeks, if not months, to produce. Pending approval of some of the content, the site will be live within a week.

The Challenge is a yearly event organized by Nerdery Interactive Labs. The goal is to match teams of developers and designers with non-profits eager to revamp, or start, their Web presence.

Our team, Full Court Press, was made up of 10 developers and designers, and 3 members from Designwise Medical. None of us had worked together previously, though many of us knew each other from the WordPress user group to which many us belong, or from other user groups.

Throughout the following 24 plus hours, with little to no sleep, we worked together, each chipping in where we could to help others on our team. Arguments were few, and unless I was just not paying attention, never heated.

We shared a cramped area defined by our square of four tables. A rat’s nest of cables and power cords in the center of the tables threatened to ensnare anyone who entered. As the hours wore on, and cans of Red Bull piled up, we went through waves of enthusiasm, slap-happiness, and flagging energy. The countdown clock, projected on two giant screens, constantly reminded us of the coming deadline of 9:00 AM.

Some took cat naps in the sleeping room, or sought rejuvenation from the oxygen bar. Hours ticked by in what seemed like minutes. Lunch, dinner, dinner 2.0 (at midnight), and finally, breakfast, blurred together in a parade of sandwiches, chicken wings, burritos, pizza, and bagels. Caffeinated beverages flowed all day and night.

There were moments of goofiness – the kind that often crop up during such times. Impromptu guitar sessions, a human pyramid, whoops and hollers when a Web page actually rendered without crashing.

When we were done,we all had a great sense of pride in what we had accomplished. I am so grateful for the chance to work with such a talented group of people. Thanks also to the organizers and sponsors of this event. Hope to see you all at next year’s Challenge.

Then, I remembered an old RC toy car my son had. The controller unit was simple, with just one button. Pushing the button made the car go forward. Releasing it made it go backwards while turning. On the receiver (car) side, the controller signal caused a voltage to toggle between -1.5 volts and +1.5 volts. With a little testing, I found a point that toggled between 0 and +3 Volts. This was just enough to provide drive an LED. A magnetic reed switch from Axman Surplus worked perfectly for the door sensor. This switch is in the off mode when the magnet and reed unit are near each other (door closed). When the door opens, the magnet will be pulled away and complete the circuit. The transmitter and switch are hooked up to a PIC16F684 chip. The reed switch is connected to pin 4, which is configured as a digital input. When the reed switch is open (door closed), the signal on pin 2 goes high. This turns on an NPN2222 transistor, which in turn causes the transmitter to send a signal. The receiving unit goes to +3 volts on the output when there is no signal, and drops to 0 volts when there is a signal. In other words, when the door is down, the LED indicator is off. This may seem overly complicated, but it has one advantage. If the garage-side (transmitting) unit fails, the light will come on. Although this may be a false positive for the door being up, it indicates that something is wrong on the transmitting side (power failure, loose wire?).

Circuitry from RC car repurposed as a garage door alarm

My wife and I are interested in making safety clothing for night bicycle riding and thought this might be useful. We ordered a five foot section of 3mm wide cable from here. Once I had the cable in hand, I attached a bright red LED to each end with shrink tubing.

End connections

A quick test shows that two LEDs provides a fairly even glow along the entire length of the tube. Each LED was rated to deliver 18,000 millicandelas of light.

Two LEDs powered up

This looks like it could be used on a bicycle helmet to provide a flashing illumination. More to come as we experiment.

Original bottom view

I had been experimenting with a simple circuit called a Joule Thief.  This circuit boosts a DC voltage to a higher voltage.  It’s is easy to make with easy to obtain parts.  The Web is full of plans for these devices.  The advantage for this project, is that such a circuit can drive a bright white LED from a single 1.5 Volt battery.  I figured that I could easily fit the circuitry and a single AAA battery into the battery compartment of the book light.  This would save batteries and provide a more even light across the page of a book.

Joule Thief

I replaced the incandescent bulb with a bright white LED that I encased in aquarium sealant inside of a short length of clear plastic tubing.  This helped to diffuse the light along the approximately two inches of tubing that the LED was attached to.  Here’s the final assembly and it’s use.

Ready to use

Modified lamp in use

wolfstone.halloweenhost.com

Breadboarding this was fairly easy and took just a few minutes.  I keep a lot of components around with breadboard wire already soldered, so that makes prototyping a lot faster.

Before I attached the motor, I verified that the circuit was performing as needed.  With the oscilloscope set to show 5 ms per division I could measure the minimum pulse width of 1.15 ms and a maximum width of 2.75 ms.

This seemed good enough to try, so I plugged in the motor.  The black wire is ground, the red (or orange) wire is positive, and the white wire is the signal (pin 3 on the 555).    I had nearly the full 100 degree rotation in the motor as I turned to potentiometer shaft back and forth from minimum to maximum.

Just for fun, I substituted a flex sensor for the potentiometer.  Not quite the same amount of rotation, but, I didn’t bother changing any other component values.

Servo Motor with Flex Sensor from Patrick Lewis on Vimeo.

The man answering the question is Jean-Louis Gassee, one-time Apple executive, probably best known for BeOS.

The correct answer, BTW, was “The Obfuscated C Contest.”

Accessing the DB server worked on the local machine, but, this was the message I received when attempting to access the it on a remote host.

“ERROR 2003 (HY000): Can’t connect to MySQL server on. . .”

I eliminated some other things as potential causes right away. My permissions for the user and host were set properly. The MySQL server was not started with the “skip-networking” option set, and the server was not restricting TCP access to localhost.

Narrowing this down to a firewall issue was pretty straightforward. First, I stopped the firewall.

/sbin/service iptables stop

Then I tried again to access the DB server remotely and succeeded. When I restarted the firewall, the problem returned.

Searching on the net, I came across this recommendation in many places. Basically, a command to add an entry to open port 3306.

iptables -A INPUT -i eth0 -p tcp -m tcp –dport 3306 -j ACCEPT

I entered this but it still didn’t help. Then, I began to look at the iptables configuration with this command.

ipatables-save

This just writes the iptables entries to STDOUT. What I noticed was that the entry for port 3306 was preceded another line. Here is how the two lines appeared.

-A INPUT -j REJECT –reject-with icmp-host-prohibited
-A INPUT -i eth0 -p tcp -m tcp –dport 3306 -j ACCEPT

I sent the result of the ‘iptables-save’ to a file and then edited this file and switched the order of the two lines above. Then I restarted the firewall.

/sbin/services iptables restart

This worked and my databases have been accessible since.