Design007 Magazine

PCBD-Aug2014

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56 The PCB Design Magazine • August 2014 waiting for Mike to show up. There was not much left to say or do until he got there. Out- side, a thunder storm raged, and we could hear the thunder even though we were in an inside room without windows. It was at this point that Bob, quite bored sit- ting around, said, "Did I ever tell you about the time I was struck by lightning twice in one af- ternoon?" I was stunned! I looked around the room, hoping that no one had been paying attention. But that was not the case at all; instead, every- one was looking at Bob like he had snakes com- ing out of his ears. I thought, Great! I bring this guy in, want- ing him to back up and explain some of the technology claims that he is making, and here he is telling a lame-brained, incredible story like this. And these guys are all here to prove him not only wrong, but certifiable to boot. To make matter worse, Mike had just walked into the room in time to hear Bob's claim. Without skipping a beat, Mike walked right up to Bob, held out his hand, and with a huge grin on his face said, "You have to be Bob Tarz- well. I've heard a lot about you." Bob smiled and shook his hand. And then Mike said, "Well, are you going to tell us how you were hit by lightning twice in one afternoon or what?" Now Bob had the full attention of everyone in the room. Meanwhile, I was trying to disap- pear under the table, pretending that I was not the guy who had brought him here. Completely unfazed, Bob told the story of how he had been struck by lightning twice in the same afternoon: It was at our house in Canada. We were just finishing lunch when a thunderstorm hit. Man, it was a big one, worse than the storm going on out- side now. I remembered that I had a car part in the back of the truck that I didn't want to get wet, so I ran out in the yard, got the part and took it to the garage. Just when I reached for the side door to the garage, I got hit by lighting. This was one of those all-metal buildings, so the lightning went right through it and into the doorknob and up my arm and knocked me down. When I woke up a few minutes later, all of the hair on my arm was gone. Since there was still lightning, I went into the garage to get out of the rain. When I got inside, a lightning bolt hit the electrical pole outside. The lightning traveled down the wires, into the garage along an extension cord on the garage floor, which I was standing on. Zap! I got hit again. The funny thing was that, except for a few scratches I must have gotten from fly - ing across the room, I was fine. Missing some hair, but OK. I looked tentatively over at Mike to see his reaction. I thought that he was going to signal me to follow him out into the hall and tell me to get my nut-case friend out of there. But in- stead, Mike laughed his ass off. Bob did his job, saved them a lot of money, and showed them how to make heavy copper boards. So, over the years, Bob and I have worked together on a number of projects: developing indestructible boards at Sierra Circuits and Tai- yo America, as well as focusing on printed elec- tronics. It has always been an adventure. I thought it might be fun to challenge Bob by writing a series of columns in which I ask Bob questions about technology and he an- swers them. We decided to present this to The PCB Design Magazine, because designers are always on the lookout for information about PCBs, from the very basics to bleeding-edge technology. Best of all, you, the readers, are in- vited to send Bob questions as well. Maybe we'll all learn something. So I contacted my friend, Editor Andy Shaughnessy, and here we are. For this first column (and it's a doozy), I asked Bob to talk about something that would shake up the industry. I wanted something re- ally earthshaking, and Bob delivered. Take it away, Bob! Bob Tarzwell: Under 270 volts, there is no self-arcing, no matter what the spacing! You don't believe me? Check it out. New information (at least for me, after 50 years in the business) shows that there is no dif- ference in spacing requirements for situations below 270 volts, because 270 volts will not self- arc regardless of spacing. Designer and engineer friends have all been laboring under the same belief as mine: As voltage increased from 5 volts on up, you had to add more spacing to prevent arcs. bob and me SPACING IS IRRELEVANT BELoW 270 VoLTS continues

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