Electronic Design

What's All This Floobydust Stuff, Anyhow? (1993)

As we mentioned in this column a year ago, "floobydust" is a recently-coined term for "miscellaneous" or "pot-pourri," a regular jumble of ideas. Am I wrong??

  • Back on March 4 (ELECTRONIC DESIGN, p. 108) I wrote that the Electronics Flea Market at Foothill College in Los Altos, Calif., runs on the second Saturday of every month from April through October. Unfortunately, the last Electronics Flea Market of the season is September. Hope I didn't mislead you too badly. (I wished there was one in October, but I guess the guys who run it have a right to take a break.)
  • Also in March, on the same page, I indicated that you could buy a plastic raincoat for your camcorder for only $150. NOT a great buy. Last month, I was wandering through Fry's, a very good electronics store in Sunnyvale, Calif.,1 and I found a raincoat for small camcorders that I could afford—$14.95—for model V-0794, by Ambico. Rather than an expensive optically flat glass front, it just has an open hood. I've used an umbrella while shooting with my camcorder in light rain, and this should work at least as well. It will be a lot lighter and more compact. If your camcorder is less compact than 10 inches long, contact the manufacturer 2 for advice on what model will fit your machine.
  • I'd like to be able to tell you about a simple circuit for recharging your alkaline flashlight batteries. A reader in New Zealand clipped it out of a British electronics magazine3. It proposed that a forward pulse of charging current followed by a negative pulse would be compatible with the alkaline's chemistry and work sufficiently, as opposed to a dc recharging current, which works badly. I'd like to be able to recommend this circuit, but when I built it and checked it out, it ran badly. So far, I haven't been able to make it work adequately. If I can make it work, I'll let you know.
  • I placed an order for a "Supercharger" that's supposed to be able to recharge ordinary alkaline flashlight cells. They said it would take 8 weeks, and that is true. I ordered it in August and it's now the end of November, and I'm still waiting. If I can get it to work, I'll let you know, and how well. It may be an improved variation of the circuit in the previous paragraph. About $59.
  • I also bought a Ray-O-Vac "Renewal" recharger ($30) for charging up the Ray-O-Vac "Renewal" alkaline batteries4. Allegedly, these can be recharged 25 times. However, each time you recharge the battery, the capacity shrinks a little more. Even though you recharge the battery 25 times, you only get as much energy as 8 new batteries. Still, if you use a lot of Alkaline batteries, this could pay for itself fairly quickly. Even as cell capacity decreases, the cell still holds 3X or 2X or 1X as much as a good NiCd battery, which costs more but can be recycled more than 100 times. So the Ray-O-Vac Renewal system can definitely save you some money compared to throwing away flashlight batteries. It may also have advantages if NiCds aren't suitable. However, I've tried several times to get basic technical information from Ray-O-Vac, and they have yet to respond.
  • As I mentioned earlier, I think I can recharge my camcorder's NiCds on long hiking trips with a special high-efficiency switch-mode regulator that uses Alkaline D-cells as the main energy source. Alkalines hold 3X more energy (per ounce) than just carrying more NiCds. However, we've been too busy to build this switcher, so that will have to wait a little more. Sigh. Meanwhile, on my summer back-packing trips, I just carried my old hand-crank gear-motor, and it continued to work well.
  • A friend tipped me off to the advantages of zinc-air batteries.5 These can put out 2X more energy per ounce than alkaline D cells, which in turn can put out 5X more energy than lead-acid cells, or 3X more than NiCds. So you could use 1 pound of zinc-air cells to recharge 1 pound of NiCds six times! That sounds like the way to go, except that if you try to draw too much current from the zinc-air cells, they go to pot. If you really want to get the full energy from a zinc-air cell, you have to spread that energy transfer very carefully out over 200 hours. In other words, they're not ideal for a fast recharge. Also, they're not cheap—maybe cheaper than lithiums, but cost per watt-hour is higher than alkaline D-cells; and availability is quite poor, special order and all that.
  • Several people asked, "Why do you have to double-clutch a VW?" I had to reply, you do not have to, but it is fun, it sounds and feels right, and keeps you in practice. One reader said that, when starting up in traffic, he doesn't just shift from neutral into first, but from neutral to second to first. In a car without synchromesh on first gear, this saves on wear and tear. I confirm that I also usually do that, just to share the wear on all of the synchronizers—even though I don't have to. Also, I have a habit, after I shift into fourth gear, to reach down and check my handbrake to make sure it is off. About 99% of the time it is off. Just a precaution.
  • April is coming, and we shall have a fine kettle of hoaxes in the April 1 issue. Meanwhile, those of you who are thoughtful about audio equipment will be pleased to learn of The Audio Critic magazine6. It debunks various myths and ridiculous claims about super-high-end audio equipment, when claims are made that obviously can't be proven but rather must be accepted on faith. If you could use an occasional sanity check, their magazine (quarterly) is a good investment. Their "Hip Boots" column is priceless.
  • I got dozens of checklists from readers, hiking checklists and lists for business trips, with lots of interesting ideas. I sent out dozens of my basic lists, too. On my back-packing checklist, I have amended it to reject any shirts with less than 27 inches from the top of the shoulder to the bottom of the side seam. Shirts shorter than that tend to not stay tucked in, and are uncomfortable.
  • A friend up in Oregon suggested that if you want to get a floating scope with low capacitance to ground, the Fluke Model 97 is quite compact.7 It has less than 8 pF, much less than most scopes. This low capacitance can help improve rejection of ground noises.... In the old days, if you really wanted to get the best isolation of a circuit, you did not use a Teflon spacer. Instead, you hung your circuit from a silk thread. I once measured some silk thread. I figured out that a 3-inch piece of silk thread has a resistance of about 3 × 1015 ohms in dry weather, and a capacitance about 0.02 pF more than the air itself. Not bad. The Fluke 97 weighs only four pounds, and needs only about eight strands of silk thread....
  • Doctor Science has a brand new book out, just in time for Christmas: Dr. Science's Book of Shocking Domestic Revelations—marvelous lunacy and advice on home repairs and construction.... Very reasonable at $17.50 (includes shipping).8 To order, call 1-800-989-DUCK. If you want to order on CD-ROM, hold your breath and count by ones to 6 × 1023. It should be ready by then.
  • In the field of battery charging and alternative energy, I recommend Home Power—The Hands-on Journal of Home-Made Power.9 This is good reading for people who are interested in cost-effective systems, not the fancy battery-power systems that only a marijuana-grower can afford. Practical insights. Low smarm content. Examples of good engineering using recycled, home-engineered parts for thoughtful cost-effective systems. It's well-written and doesn't insult your intelligence.
  • I have heard that Whirlpool's $30-million prize-winning high-efficiency refrigerator is supposed to use Fuzzy Logic. One report claimed that it uses F.L. "to make the compressor more efficient." But another guy said baloney—it just uses F.L. to reschedule the Defrost cycle so it won't waste energy doing a Defrost if no Defrost is needed. Does anybody know what the truth is?
  • Most F.L. controllers that we see have one input for (x) and one input for (dx/dt). The Fuzzy guys thus have two knobs. I usually run my controller with one input for x, one for dx/dt, and one for x.dt. So I have three paths, commonly known as Proportional, Integral, Derivative (usually called PID), and thus I have 3 knobs. The Fuzzy guys pretend they don't need any Integral term-they can make just as good a controller for a linear system with 2 knobs as I can with 3—but they're wrong. The Shadow Knows!! More later...

Continuing on the subject of Fuzzy Logic, I must recommend a newsletter10 from one of the few promoters of F.L. who is a real engineer, not just an ivory-tower theoretician. The guy, Dave Brubaker, is thoughtful about solving real problems with F.L. I have learned more positive, useful information about F.L. from Dave's newsletter than from everybody else put together. NOT just platitudes. Ask him for a couple samples of his newsletter, and information on how to order it for $24 per year.

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

References:

  1. Fry's Electronics, 1177 Kern Ave., just off Lawrence Expressway, about 1/3 mile south of U.S. 101, Sunnyvale, Calif. Great assortment of electronic merchandise, from fuses and resistors and ICs up to fancy TV and electronic systems. Also stores in Palo Alto and Fremont. Inquire at 408-733-1770, 415-496-6000, or 510-770-3797.
  2. Ambico Inc., 50 Maple St., Norwood, N.J. 07648; phone: 1-800-621-1106.
  3. "Better use of dry batteries," Rod Cooper, Practical Electronics, July 1986.
  4. Ray-O-Vac "Renewal" rechargeable alkaline battery system. Charger costs only $30, nicely built, a real bargain. Special "Renewal" alkaline cells cost 2X more than ordinary alkaline cells; only the Renewal cells can be recharged in the recharger. Available in good department stores or electronics stores. I bought mine in Target.
  5. Eveready DA412P zinc-air battery can put out 4.8 V × 6.5 A-hr. That's about as much energy as 4 alkaline C-cells or 2 D-cells, but it weighs only 3.7 ounces, or a factor of 2.7 less. It costs $12 or a factor of 4.5 more than the alkaline cells. You can get this energy only if you draw less than 40 mA for longer than 160 hours. Minimum order is 75 pieces. Zinc-air is great for hearing aids—and for astronauts.
  6. The Audio Critic magazine: published quarterly, $24 per year, by: Critic Publications Inc., 1380 Masi Rd., Quakertown, PA 18951.
  7. Fluke Corp. Model 97, handheld meter and 50-MHz oscilloscope, 4 lb., $1950. Phone: 1-800-44-FLUKE.
  8. Dr. Science's Book of Shocking Domestic Revelations, ISBN 0-688-11444-X. $17.50 includes shipping. To order, call 1-800-989-DUCK.
  9. Home Power, published bi-monthly for $15 per year, by Home Power, P.O. Box 520, Ashland, OR 97520.
  10. David Brubaker, The Huntington Group, 883 Santa Cruz Ave., Suite 27, Menlo Park, CA 94025-4669.
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