Electronic Design

Bob's Mailbox

Dear Bob:
I've been following the technique of breadboarding with copper clad. I have used the Moto-tool approach to cut between the traces, but I think I have an easier way. I noticed that merely scoring the copper with a knife and a straight edge is enough to allow it to be pulled away from the board. So, I soldered two utility knife blades together so that they would both cut at the same time. Now, when installed in the utility handle, they make two neat, parallel cuts 20 mils apart that can be pulled away easily with an X-ACTO knife. Thinking that 20 mils might be small for my purposes, I tried grinding off the cutting edge of another blade to use as a spacer. Now the three-blade sandwich makes a 40-mil line.
JIM PHILLIPS
via e-mail

Hey, Jim, I'll have to try that. I am not sure it's much faster than just using a hacksaw to cut a line. But it sure will make L-shaped cuts better than a hacksaw can!—RAP

Dear Bob:
I, too, have seen the ice-water and pizza diet floating around the net, and tried to debunk it. Interestingly, I came on the same thing a long time ago (mid-1950s) when I was a kid. You see, I like soft drinks with "lots" of ice, and my mother complained about the number of calories they contained. I calculated about how much energy it took to raise the water to body temperature (including the latent heat of melting). And, yes, I did understand the difference between calories and kilocalories, even then, at about 10. It really did make a difference of about one-third in the number of calories—if you fix drinks the way I do. I don't know if my mother ever bought the calculation, though.

By the way, there is another reason why manhole covers are round besides keeping them from falling into the hole. You can move them by rolling, which is harder, though not impossible, with triangular covers.
BRUCE WALKER
via e-mail

In many places, rolling a manhole cover may not be a big deal, but in other cases, it's a distinctly neat feature. Thanks for pointing this out.—RAP

Dear Bob:
This is in regard to your International Travel column in the March 9, issue. I recently returned from four months in Turkey. I didn't trust the tap water, but realized bottled water would be very expensive. I took along iodine tablets for emergencies, but for regular drinking water I used a camper's micropore filter, and filtered the tap water in my apartment. It was a lot cheaper than bottled water.

I was going as a visiting professor, and knew I'd also be giving some seminars. Taking along all my overhead slides would have been a horrible burden. Instead, I saved my slides as PowerPoint files on a ZIP drive. Once there, I was able to print them out on transparencies. On one occasion, I had to give a briefing to the Turkish Department of Defense. One of my colleagues translated my slides into Turkish, and in effect, we gave two briefings in parallel. We showed both sets of slides at the same time. I would say a few words in English, and my colleague would then repeat what I said in Turkish. It worked out fairly well, but not as well as speaking directly to the audience.
JOE MARTINO
via e-mail

You are correct that the water filter is a wise third option. I should have mentioned that. AHA! You've run the double-foil presentation and it seemed to work! I'm glad to hear that.—RAP

All for now. / Comments invited!
RAP / Robert A. Pease / Engineer
[email protected] team.nsc.com—or:

Mail Stop D2597A
National Semiconductor
P.O. Box 58090
Santa Clara, CA 95052-8090

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