Electronic Design

Bob's Mailbox

Readers of this column may remember the letter from Mike McGinn that appeared in the Sept. 15, 1997 Mailbox. Mike had everything he needed to go trekking with Bob—except a working kidney. So, it is with a great deal of pleasure that we present his most-recent communication.—ED

Hi Bob:
Thanks for the inspiration. On October 20, while recovering from hernia surgery, I got the call I was waiting for. The installation took six hours (which, I understand, is better than NT) and the kidney worked as soon as it was hooked up. I was out of the hospital in 10 days.

I don't know if someone who has not gone through this can appreciate how much it changes your life. Little did I realize how depressed I had become on dialysis, but the fact that I used to go around thinking, "This is my life in hell," should have been a clue. Now my marriage is better, my life is better, and I can do more with my six year old son. It's a whole new life. I can probably even go hiking now, but my strength is not all back yet. It was truly a happy holiday season in my house. We have much to be grateful for.
via e-mail

Mike, we sure hope you can resume vigorous hiking soon. If you're permitted to do it, it's really good for your legs—and your head. Best wishes —RAP.

Dear Bob:
If one more note on prototyping won't kill you, read on...

1. Amusement: Jameco Electronics sells the "Wideband 100-MHz Prototype Board" (catalog 974, p. 84). It consists of the white plug-in-the-leads breadboard inside an aluminum box (7.4 by 5.1 by 1.5 in.) with four BNC connections on two of the ends. I bought one for $59.95 (don't worry—I don't actually use it!) and have it hanging in my office. I show it to the students who come through here and discuss under which conditions you can actually get away with using it. It is amazing how many do not realize how much stray capacitance is built into those white boards. And, I cannot count the number of times I have been told "No, that is a resistor, not an inductor," when the resistor is sticking up 1 in. off the board. (Actually, the quality of the proto-board in the Jameco box is pretty good when compared to the Radio Shack version, but 100 MHz??? I'll try to remember to send you the test results next month.)

2. Strange-behavior department: I spent nearly 13 years at Sandia National Laboratories before coming to Kansas State University. I run a department (chief engineer and "pointy-haired boss" rolled into one!) here that supports all of the research groups on campus with custom electronics, sensors, and data acquisition systems. I employ a small full-time staff and about eight EE students part-time. It is nearly the only exposure the students get to "practical" engineering issues.

To their credit, most of them eat it up and recognize the value in and need for this experience. However, I have observed an interesting phenomena here (and at Sandia). The first time a new hardware engineer has to actually build what they design, they go into overload, sometimes for as long as four weeks! Having to specify resistor type, tolerance, wattage, capacitor dielectric, cap. tolerance, cap. package, IC package, heat sink style, connector type (and plug vs. socket), and so on, for a large design overwhelms them.

I even saw a very talented engineer give up hardware and shift to software (surely software has equivalent "loose ends"?) because he couldn't get over it. Then they figure out some ground rules, make some guesses, talk to some old guy and realize that many of the components in a large design just aren't that hard to spec and they move on. Have you observed such behavior?

3. Regarding practical training for engineering students, I don't have an answer, but I sympathize with the engineering schools. A good engineer needs to understand the theory so that they can extend their knowledge to "non-cookbook" situations, but at the same time, they must get their hands dirty to see where the theory can be applied. Do I want to spend my life laying out printed circuit boards? No! Did I need to do it a few times so that I really understand the compromises, problems, and gotcha's? Sure did, and because I have a good foundation in theory, I am a better engineer. But most companies are putting a lot of pressure on engineering schools to produce engineers specifically trained for their current employment needs. I argue that this is just as bad as producing a theoretician.

4. My favorite prototyping materials are Vector 8007 and 4112-4 boards. They are about 4.5 by 6.5 in., have a ground plane on the top, and various pad patterns on the bottom. I use very short pieces of 24 ga. wire where I cannot use the component leads to interconnect and keep the wire close to the surface of the board. Add standard copper clad to make shields, boxes, etc. The Vector boards work great for through-hole technology, and I have used them (with care) up to about 150 MHz. If memory serves, they are about $35 each, from Newark and others (not cheap, but very nice to work with).
via e-mail

Surely there must be a good way to say "unless noted, all capacitors 0.01µF = ceramic disk type X5U; all resistors are 1% RN55D..." Keep it simple and standard. I have heard of cases where a white solderless board was used to make an experiment that ran up to 100 MHz. But it would be WRONG to count on it. There must be a better way, and you have defined one.—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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