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Off Go The Lights!

Tom Thoen

Figure 1.  My first PCB

Figure 1.  My first PCB Figure 2.  What the room looked like after plugging in the board

Off Go The Lights! After designing boards for over 20 years, it was difficult to think of a specific story that stood out – there are always the “minor” issues of accidently leaving off the silkscreen, component overlaps, or through holes 3 mils too small…but then I remembered the very first PCB I ever designed…it was a project that literally left me in the dark. Before even knowing what “circuit analysis” meant, before practically any understanding of theory or equations, I loved to play with electronics. At the age of twelve I cut my teeth on such great hardware as my brother’s “65 in 1” kit from Radio Shack, P-box projects, Heathkit kits (when I could afford them), and circuits from the great project books by Forrest Mimms. Popular Electronics and Elementary Electronics fueled my interest for learning more. However, I had never even thought of designing my own PCB until I bought a kit from the local Radio Shack. My first design was simple. It was a single, curving trace – far more artistic than practical. The single trace was made with a very large Markie in a magical snake-like pattern. As I recall it looked something like this (please see Figure 1).

Trying to look back, I had no idea what the function would be – I just wanted to make a PCB! After carefully prepping the board, I started to etch it. As I recall, the instructions stated that the board would be fully etched within ½ hour. As we all know, without some heat and agitation, the etching process usually takes longer, especially with a home-brew board (and LOTS of copper to remove!), but with my inexperienced eye, I thought it was all done when the areas around the traces were black. Again, please recall that a) I had no formal training in electronics and 2) had never etched a board before. So, I had a final board. But how to test it??

In my young pre-teenage mind I thought “well, it’s a circuit, why not hook it up to something that produces electricity?” So, I promptly grabbed an old power cord from a broken lamp, along with a wire stripper, and proceeded to carefully tin both the neutral and hot leads from the 120V power cord. Next, I carefully soldered them to the two pads on the bottom of my new PCB. For some reason, either due to the inherent guilt of trying to use acid in the house without permission, or the fact that I was going to plug something into an outlet when I knew I shouldn’t (or maybe even premonition??)

I declined to inform my parents of my (wrong)doings. If I were writing an instruction manual for operating my circuit, it may have looked something like this: 1. Carefully lay the PCB down on the floor of the room. Make sure it is resting on a soft cushion of thick, moderately flammable carpet. 2. Unplug your clock radio to make room for the new plug. 3. Make sure your parents are down the hall so they have no idea what you are doing. 4. Plug in your device and see what happens!! The moment had arrived! I was going to test my first PCB. In went the plug, out went the lights, amidst a shower of sparks.

Since this was in the evening, of course all the lights went out in the house. My father yelled, “What’s going on?” (please see figure 2). Quickly I unplugged the board – it was smoking and putting out a terrible smell – a considerable amount of insulation had melted off the power cord. Amazingly I avoided getting into too much trouble…at least as well as I can remember. Looking back of course the absurdity of what I was doing has brought some good laughs from friends in industry. Fortunately I now have the privilege of teaching PCB design at Cal Poly Pomona, one of the California State Universities – the PCB’s my students design using Eagle are so superior to the boards I made in High School and even College. However, when my students are disappointed that sometimes their projects don’t “do what is expected” I can tell them the story of my first project – and how much better their projects are compared to my first one.

- Shared December 4, 2012