PROS AND CONS REACTION TO OCTOBER 27
EDITORIAL ABOUT HYDROGEN FUEL CELLSDear Editor: All the excitement over hydrogen fuel cells is really neat, but think about this:
A terrorist wants to blow up a major building. He pulls his manure-laden pick-up truck over to the nearest fuel-cell pitstop and presto, he has upped his energy density by who knows how much.
In addition, although hydrogen is a "renewable" resource, just exactly how is it going to be renewed? Most systems rely on either chemical or catalytic separators, and the chemicals used are really toxic, or the catalysts age over time, and are rare besides. Electrolysis won't work, because it takes more energy to separate the hydrogen from water than the hydrogen returns. Therefore, some external source is required to supply the missing energy. And I haven't seen the equations that describe how this works.
Add in the issues with heat generation (which is a pollutant without chemicals), weight of the generators and tankage, and the issues of controlling the escape of hydrogen in closed spaces (think underground parking garages), and you have some real obstacles to overcome.
Worse, I haven't seen anyone addressing the developments required to simplify the production of hydrogen.
I'm not anti-technology or anti-advancement, but I would just like to know why the oil companies think this is a good idea. They don't stand to make anything off of a nearly free resource (as hydrogen is touted in some areas).
Les Howell
Staff Technologist
Teradyne Inc.
Dear Editor: I've been reading Electronic Design for many decades. With me, your magazine consistently rated between excellent and delightful. This is why it bothers me that, in your October 27 Editorial, you (and many others too) have fallen prey to the incessant drumbeat of false advertising.
Please bear with my somewhat pedantic explanation for my reasoning:
Hydrogen, in sharp contrast to natural gas, oil, wood, etc., is not a primary energy source. It only exists as a man-made product. Further, a hydrogen fuel cell is an energy storage device. And just like any other energy storage, such as a battery, it gives back but a fraction of the energy needed to manufacture it in the first place.
No doubt, the hydrogen fuel cell has excellent, special applications. The U.S. space program used 2 + O2 fuel cells throughout. It is also quite dangerous: Remember Apollo 13? I for one do not care to sit in my car over a 1000-psi hydrogen bottle. After an accident, for instance, the hydrogen burns with an invisible, extremely high-temperature flame. Nor do I care to let this thing be handled by an ordinary neighborhood mechanic.
I've read about hydrogen being cracked aboard a car, stationary generator, etc., from other fuel. Now this is a scam, if I ever saw one. The hydrocarbon fuel has to be cracked, because your run-of-the-mill fuel cell cannot handle carbon. Remember, liquid or gas fuels are generally hydrocarbons. Fully half of their energy derives from the carbon portion, and it gets thrown away! So, before hydrogen is used in the fuel cell:
| 100% | Original fuel |
| 45% | After cracking (5% to run the cracker) |
| 36% | After fuel cell (80% efficient) |
Good diesel engines regularly get there, and big power stations are in the mid-40% range. What's more, cracking pollutes. So where is the advantage?
Because of all these drawbacks, you might conclude, I am categorically against the hydrogen fuel cell. But let me emphatically state: I can hardly wait for a methanol-fueled laptop, cell phone, as well as all the sundry small appliances. In these applications, the efficiency does not matter as much as continuous operation. Undoubtedly, the methanol fuel cell would represent a notable advance over present-day batteries, just as today's lithium units have it all over yesterday's leaky zinc-carbon ones!
Finally, we must all understand that research is necessary and good, and nobody in his/her right mind refuses federal grants, when given.
Levente Letso
AT&T Bell Labs (retired)
GROUNDING MIXED-SIGNAL CIRCUITS PROPERLYDear Editor: A good article but perhaps a bit empirical on the antenna theory. For example, the author states:
"Radiation is, therefore, a function of the loop area outlined by the current path. It doesn't matter whether one or both of these conductors is a piece of wire, a pc-board trace, or a plane." This is not necessarily the case. A pc-board trace placed above a ground plane creates an antenna having twice the "current area" (length × current), as compared to the same trace driven against another trace. The radiation from the "ground plane" antenna is 6 dB higher, given the same antenna current. The radiation resistance is 4× for the ground plane case. This is due to the "image" antenna within the ground plane. For an electrically short trace, the vias are the real antenna.
Another generalization implies that the radiation is proportional to the loop area. It is not stated whether the resulting electric field or the resulting radiated energy is proportional to the loop area. Given a square, or a circular small loop antenna (<1/10 wavelength circumference), the radiated power is proportional to the area.
However, given a very rectangular loop antenna, such as a microstrip trace above a ground plane, the electric field will be proportional to the via height and not the horizontal trace length. This is due to radiation from the horizontal trace being largely canceled by the magnetic-field cancellation from the ground plane. The vias, being far apart, do not exhibit such high magnetic-field cancellation and radiate rather well as two very short dipoles.
It is also stated that proper termination can reduce EM radiation. EM radiation is due to the RF current flowing in the "antenna" portions of the circuit. As stated before, this can be mainly the vias. So, if termination reduces the RF current in the antenna portions, then it will reduce EM radiation. If it doesn't, then there is no reduction in EM radiation.
The article also mentions EM radiation from slot. EM radiation from long, narrow slots is largely from the short ends and can be reduced by making the slot very narrow.
Dave Cuthbert
Dear Editor: This may be nitpicking, but the story on skin effect isn't quite correct. The formula given applies to a round conductor. Replacing Pi × diameter with 2 × (w + h) isn't the same thing. It isn't that high frequencies like to flow on the surface, they just hate the center of the conductor. In a flat conductor, the currents crowd to the edges and leave the center of the trace with very little current flow. To optimize current flow at high frequencies, round conductors are best and big conductors are better. This presumes litz wire is not suitable.
Bill Siebert
My advice to any EE just starting out is this: Never be an employee for any company other than an engineering services firm, preferably one's own. Such engineering companies sell only services, not airplanes, transistors, or cell phones.
While this may not be possible at the outset, you must always consider any position you take as an employee at the typical E/E products company as only a temporary position, and one that will probably vanish without warning tomorrow, normally the day after you close on a house. Every EE needs to work in engineering services because in such a situation, one is never tied to a specific project and so is not as likely to be declared surplus (or too old) and let go when a given project is over.
Corporate E/E engineering employees are no different from corporate lawyers and doctors—they are always looked at askance.
In regard to the matter of age: The first time I was let go with this excuse I was actually still quite young—just one-third through my engineering career! I found a new job in a few days (in a new town) and so was not able to share in the $4 million age-discrimination suit won by some of my fellow ex-employees.
As far as I'm concerned, that "one-third" measure of my career is still counting down. For even at age 71, I must and can keep working in the field.
Allen N. Wollscheidt
Dear Editor: As a transsexual woman who is a senior software engineer for a major corporation, I am proud that a scientist and pioneer of Lynn Conway's stature is a visible role model for other women like us and a shining public example of transsexual womanhood. For far too long, people like us have been regarded merely as sexworkers and punchlines, and Professor Conway's tireless efforts to help turn this image around have helped immeasurably.
Christine Beatty
Dear Editor: Thanks so much for this profile on Lynn Conway. I do believe she is the best at what she does, and she is very compassionate towards everyone at http://www.lynnconway.com. To have a very beautiful woman like Lynn is so important to all inventive people, most especially women, who can be inventive and smart in this world, too. All we need is the go-ahead from the male world for us to show them. We are here to be noticed by the educational, inventive world.
Kristi Ann Jorgensen
For instance, if you want to learn about CPLDs (complex programmable logic devices), both Xilinx and Altera have free tools. Plus, there are low-cost development boards. If you want to learn about writing C for embedded systems, you can get the free version of the HiTech C compiler, the free MPLAB software, and build an inexpensive programmer. If you want to learn about PHP embedded language and databases for Web sites, put Linux on a clunker PC, and get MySQL, Apache, and PHP.
In addition, newsgroups can be a valuable resource for learning. You can often get a quick answer to some fairly complex questions. Also, if you pick textbooks that are considered "classics" or "standards" on a topic, you will probably have a pretty easy time finding the problem/solutions on the Internet.
Brian Riordan
There are certainly some high-tech bathroom gadgets that may be worth the investment. Most of the electronics in public restrooms seems to be aimed at saving money, and the environment, by only supplying lighting, flushing, washing, and hand-drying when needed. This also helps provide a germ-free environment by eliminating commonly touched surfaces.
One would have to assume this is worth the cost of replacing the existing valve or switch with, for the most part, what seems to be battery-operated infrared sensors. Perhaps the maintenance costs of the electronically operated valves (including periodic battery replacement) is on par with, or even less than, manually initiated devices, but I have to assume it is mostly utility costs that drive such decisions.
However, it seems that active infrared is not enough—at the very least, it can't see through a standard home toilet tank, and it only works at very short ranges. So Kohler has been working on an ultra-wideband (UWB) radar sensor for detecting the presence of people to control bathroom ventilation on fluid valves!
Marc Ressler
Sensors and Electronic Devices Directorate
Army Research Laboratory
Dear Editor: Actually, your Editorial reminded me of a prediction I made a long time ago. I was taking a course in college about intelligent robots and computers. I was talking with the instructor and just offhand I said that there was one area where robots, computers, and electronics would never be applied—going to the bathroom.
How wrong I was! I'm reminded of that prediction just about every time I use a public restroom with the infrared-sensing flushing and faucet mechanisms.
Robert E. Fields
Materials Science and Technology Division, Electronic and Electrochemical Materials and Devices
Los Alamos National Laboratory
Dear Editor: The company I work for has been in the toilet electronics business for some time. The items you listed are really just "toys" meant to generate comments. Our emphasis is on the no-touch concept, which includes automatic toilet and urinal flushers, automatic soap dispensers, and automatic faucets. Paper towels have been shown to be the best in removing residual bacteria, and there has been little incentive to automate this aspect.
The addition of high-tech electronics to the bathroom can benefit health and well being. Taking this concept into hospitals and restaurants has obvious benefits to the consumer/patient/staff.
Interestingly, research shows only half as many men wash their hands as women.
George Jost
Dear Editor: Very interesting column. However, it has been published several times that when a commode is flushed, bacteria can travel five feet. So why doesn't the lid close prior to the flushing? Even if these new bathroom electronics were affordable, I would not buy them!
Verna Vocke
Dear Editor: Electronics is not just in gadgets or industrial controls but crossing all limits, depending on one's imagination. The article describes one more good application.
Rajiv Pujar
All letters, e-mails, and online comments are subject to editing for content and length.