Geekspace for Women

Posted by ubergeeke on August 21st, 2008 in blogpost

After a frightful amount of time on my workbench, the Amerikit AK510 Motion Detector Kit has been moved from the “to-do” pile to the “completed” pile.

The remaining parts of this build were to:

• finish soldering the remaining components to the board, including the speaker and the battery connector,
• install the board and speaker to the case,
• attach a 9V battery,
• finish the case assembly, and
• test for proper function.

The final steps of the assembly included some interesting challenges.

Missing parts. The schematic and parts list included a 1.8 M-ohm resistor which was not present. It wasn’t really worth it to special order the part, so I substituted a 1 M-ohm resistor in series with an 800 k-ohm resistor. More on that later.

The Hakko 703B soldering iron. I could not get the contact pads hot enough on the board. On a friend’s recommendation (thanks, Andrew!), I dropped the iron temperature from 750 F to 650 F, I was using no-lead solder, and I kept the tip tinned as well as I could, but I couldn’t find the balance. The result was some shoddy work in a few places - you might be able to see in the photo - though overall, I’m glad to have logged the time with the irons.

Long story short: component installation and final assembly went without a hitch. Bad news: it doesn’t work.

Define “not working”: when I flip the switch, the alarm sounds, and stays on. This is, I believe, called “failure”.

Now, this is actually a gift horse, so I’m not checking teeth. I made the mistake of saying last week that I needed to spend more time doing circuit troubleshooting, because I’m not yet confident in my ability to fix theoretical and practical problems. Well, guess what? Since I shot off my big mouth, I now get to do exactly that: troubleshoot my circuit.

That said, this project still gets promoted from “to-do” to “completed, but not working correctly”.

Lessons learned:

• I learned how to solder two resistors in series into a very small space. I’ll cover this in a later post this weekend.
• I need to spend *a lot* more time with my soldering irons, preferably with someone more experienced than I peeking over my shoulder. I don’t think my technique is completely wrong, but it lacks some finesse, and I’d like to improve that before I work on boards with smaller components.

What are your thoughts on this project? Have you built one of these kits, or something like it? What kinds of things did you learn in the process?