Well, It's floobydust time again. So here's another collection of various odds and ends that I've been gathering.
• Several people were quite quizzical: In my column on Ball-on-Beam Balancing (Fig. 1) in the Nov. 20,1995 Special Analog Issue, I mentioned that I had written about PID controllers in the June 29,1994 issue, WRONG DATE! The PID Stuff was in the June 26,1995 Analog Special Issue. Sorry. If you need a copy, holler.
• Meanwhile, I optimized my Balloon-Beam Balancer (BOBB) for better settling than I had last November at WESCON. I improved the settling time from about 10 seconds to approximately 4 seconds. That is MUCH faster and smoother than the Fuzzy Logic Version. And with only a slight percentage of overshoot. Actually, I have tweaked it up to show settling time down near 3.2 seconds—BUT, if any noise ever gets into the system, it starts flipping the ball into the air!
And the ball does not always come down on the beam! In other words, it's getting pretty shaky. But when set up for 4 seconds, it's fine, and very well behaved. In the meantime. I'll be working on further improvements.
I sent a videotape of my good WESCON BOBB Demonstrator's performance to Dr. Li, but he claims he has not looked at. He says he is not interested in sending me a copy of HIS videotape of HIS Ball-on- Beam Balancer, even though he has sent copies to many other people. What a sore loser!! But maybe he is just ashamed. Co-author Dr. William Marcy, the Dean of the Computer Science Dept, at Texas Tech University, is unresponsive, too.
Dr. Li still claims Fuzzy Logic has advantages when you have a badly nonlinear system—such as a Ballon-Beam Balancer. He claimed his system was superior because it still worked OK when he stacked some paper clips on his beam. I set a pair of pliers that weighed as much as 300 paper clips on my beam, and it still worked fine. So I'm supposed to be impressed by Fuzzy Logic?
• Back in the March 4,1993 issue, I wrote about trying to engineer a better scheme to charge the batteries for my camcorder with a hand- crank generator or similar scheme. I recently found some information about a refillable chemical battery that just uses magnesium cathodes in a salt water solution. This version weighs 4.6 lb. complete, dry. Then when you add 8 oz. of salt and 48 oz. of water, it can put out as much as 0.4 A at 10 V. You can get about 80 Ah on one charge, which costs barely $12 for the anodes. This is about two times better than 6 sets of 8 alkaline D cells (which provide about the same power), both in COST and in WEIGHT. So if you want a reasonable number of watts, and you don't mind 4 extra pounds in your canoe, this is a good solution for about $139. Call Ashford Associates in Boca Raton, Fla., at (407) 368-5966, and leave your address. The "battery" is able to put out full power in about 30 seconds after you pour in the salt water.
But if you stop drawing power, it is recommended to remove the salt water from the electrodes, within a couple hours. Don't leave the salt water in there indefinitely, and don't throw it away—^just save it until you need power again. When you have used up the electrodes, and you have to add 1 lb. of new magnesium electrodes, and also 1/2 lb. of new salt in new water, the residue (salty, magnesiumy, water) is non-toxic.
• I thought about buying one of those batteries, but decided it was too heavy, and I don't need that much juice. Instead, I invested $90 in a 17-V, 0.25-A solar array, Solarex Model S- MSX5 from Backwoods Solar Electric, Sandpoint, Idaho. Call (208) 263- 4290 for a catalog. This weighs about 1.2 lb. and I can tie it on top of my pack. I should be able to charge my batteries full, easily, and I can thus survive a day or two of clouds. We shall see. It's no heavier than my old hand- crank, and I couldn't record much more than 20 minutes a day of video, with that.
• Back in the October 25,1994 issue, I griped that I often got a 150-yard offset between my known position and my GPS receiver's computed position. When this happened consistently in my OWN FRONT YARD, I got suspicious. After several fruitless inquiries, a sailor tipped me off: Bob, are you using the wrong DATUM?" I checked. I was using the wrong datum. When I switched to the North American Datum 1927 (NAD27, commonly specified on most USGS maps), the error cut in half. Ahem.... (What's the old saying about the ''sudden cessation of stupidity??")
• I've waited over a year, and still no one has told me of anybody selling an ordinary 1/4-in. electric drill. (I don't count battery-powered drills or professional models costing $120.) Sounds like a conspiracy to me....
• If you really want a sweatshirt that reads, "TEAM EFFORT is a lot of people doing what I say"—call The Paragon at (800) 343-3095. Or, from overseas, call (401) 596-3000. The cost is about $33. Sorry, t-shirts are not available with this pattern.
• Just in case anybody out there prefers old cars to new cars, be aware of efforts by bureaucrats, politicians, industrialists, and environmentalists to get us to trade in our ^‘old’’ cars. Despite the denials, we are very suspicious of the wording and interpretation of new laws that will force ^^old, polluting cars^^ off the road, and to eventually confiscate them. This is not the same as voluntary trading-in of old polluting cars, and it is not related to the use of old cars that do not pollute. FURTHERMORE, an “old caF’ may be as new as 4 years of age. I don’t know ANYBODY who wants the value of their new car to go to zero, in 4 years, because of some stupid bureaucracy, unless it’s the guy trying to sell you another new car.... We’ll keep an eye on this—especially the laws in New Jersey, where various test cases may be moving ahead.
• A couple of people pointed out that while typing is notorious for causing wrist strain and carpal tunnel syndrome, using a “mouse” can be just as bad. Personally, I hate all this double-clicking junk. My fingers do not like it. There are, however, other pointing and positioning schemes that are better than a mouse, and if you inquire, you may find one that gets along with you. Recently one reader observed that a wrist-cushion is a bad idea for carpal stress. But several people told me he’s wrong. So, you find out what is best for you. Get your doctor’s advice.
• As you read this, I’ll have just returned from a month in Nepal hiking with Peter Owens Treks near Dhorpatan and Dhaulagiri—but only up to 11,000 feet. If you want a good hike, an easy or moderate trek, call (510) 222-5307 or (800) 223-1813 and ask for a brochure. Would we keep going back to hike with Peter if we didn’t think his trips are grand, yet reasonably priced?
• A quick comment on a new book— What Engineers Know and How They Know It, by Walter G. Vincenti, Johns Hopkins University Press. It’s about $15, paperback; ISBN 0-8018-4588-2. I definitely recommend it to any engineer who has ever been interested in airplanes. Unfortunately, it is mostly about the history of airplanes and aeronautical engineering, not electrical engineering or electronics, or else I would recommend it to ALL of you guys. Did you ever wonder how the B-24 drew its superior performance from the Davis Wing, and why the Davis airfoil was never used after that? This book treats the multiple levels of awareness of knowledge and technology—the epistemology of engineering. Fun to read. Lots of interesting little stories.
• One more item: If you are getting jaded about all the hoopla and hype for “Continuous Quality Improvement,” and you’re skeptical of the spiraling Quality Bureaucracy, send a line to Q.C. Anonymous at ALGOR Entertainment, 5501 Pleasant Avenue S., Minneapolis, MN. 55419. They have a nice little newsletter they can send you about the foibles of TMQ (Totally Misguided Quality).
All for now. / Comments invited!
RAP / Robert A. Pease / Engineer Address: Mail Stop D2597A National Semiconductor P.O. Box 58090 Santa Clara, CA 95052-8090 BOB’S MAILBOX
Excellent column on ball-on-beam balancing. Replacing a 50 MHz/486 with a quad op amp...hmmm. Now, if you can just find a common-sense replacement for hogs-at-the-trough Microsoft Windows. Let’s put Bill Gates out of a job. It brightens my day to see a couple of geek Ph.D’s assaulted with reality and sober thinking. And, by the way, nice self portrait!
HANK WALLACE President
Atlantic Quality Design Inc, Fincastle, Va,
Gee, Hank, let's wait until the Fuzzy Logic guys have a replacement for Windows 95, and then I can replace THAT with a couple of op-amps. - RAP