Copyright c 1997 by Don Lancaster and Synergetics (520) 428-4073 www.tinaja.com All commercial rights and all electronic media rights fully reserved. Reposting is expressly forbidden.63.6

Hardware Hacker

NAMES AND NUMBERS

Alpec55 Oak CourtDanville, CA 94526(510) 820-1763

Amusement BusinessBox 24970Nashville, TN 37202(615) 321-4250

Assoc Energy Engineers4025 Pleasantdale Rd, Ste 420Alanta, GA 30340(404) 447-5083

Carnivorous Plant NewsletterFullerton Arboretum, CSUFFullerton, CA 92634(714) 773-3579

Dialog3460 Hillview AvenuePalo Alto, CA 94304(415) 858-2700

Electric Power Research InstPO Box 10412Palo Alto, CA 94303(415) 855-2000

Elsworth Adhesives1610 North I-35, Ste 208Carrollton, TX 75006(214) 446-8000

Randy Fromm1944 Falmouth DriveEl Cajon, CA 92020(619) 593-6131

GEnie401 N Washington StreetRockville, MD 20850(800) 638-9636

Hoskins10776 Hall RoadHamburg, MI 48139(313) 231-1900

Integrated Circuit SystemsPO Box 968Valley Forge, PA 19482(215) 666-1900

Journal Acoustical Society335 E 45th StreetNew York, NY 10017(212) 661-9404

MCM Electronics650 Congress Park DriveCenterville, OH 45459(800) 543-4330

SynergeticsBox 809 Thatcher, AZ 85552(602) 428-4073

Teltone Corp22121 20th Avenue SEBothell, WA 98021(800) 426-3926

Unitrode7 Continental BlvdMerrimack, NH 03054(603) 424-2410

The bottom line: There are all sortsof incredible hardware hacking appswhich use piezoelectricity. Especiallywith all those new Kynar films. Butcommercial power generation doesnot seem to be one of them.

Piezo Resources

I’ve gathered some of places to gofor more piezo info into our resourcesidebar. Most of the sources shownbut not covered above are suppliersof materials and devices.

For this month’s contest, either (A)

tell me about a piezo trade journal,or (B) show me any new and hackerfriendly piezo ap that does not violatethe "no dc response" and "low temponly" rules. There will be all of myIncredible Secret Money Machine IIbook prizes, plus an all expense paidtinaja quest (FOB Thatcher, AZ) fortwo going to the very best of all.

As usual, send your entries directly

to me here at Synergetics and not toElectronics Now editorial.

More on EDM Machining

Warning: What follows can involvesevere shock and fire hazards. Do nottry this trick at home unless you knowexactly what you are getting into!

But this one seems far too cute toignore. Awesome, even.

I’ve had a lot of helpline requestsfor more details on the EDM electricdischarge machining we looked attwo columns back. It turns out a verycheap, stunningly elegant, and ultrasimple scheme for EDM machiningfirst appeared in the March 1968 issueof Popular Science and later on gotreworked in the January 1991 issue ofHome Shop Machinist. Their circuitappears in figure four.

All you have is a half wave dcpower supply powering a relaxationoscillator, with your insulated tool

ending up negative and the insulatedwork being positive. Any old threeamp, 400 volt power diode fromRadio Shack could get used as therectifier. Fresh and very high qualityelectrolytics are recommended. 200

volts minimum. Older or very cheapones could possibly explode in thiscircuit. A "bomb shelter" type of caseis recommended.

The light bulbs have much lowerresistances when they are cold thanhot. These sneakily act as dynamicregulators to limit the current shouldyour tool get stuck. This is elegantsimplicity at its best. The size of thesmaller lamp sets your cutting rate.

Both the tool and the workpiecemust get fully and totally insulatedfrom ground! If you want to groundyour workpiece (a darn good idea), alarge isolation transformer must beadded to your ac input.

While you might employ plain oldkerosine as a dielectric cutting fluid,it is highly flammable. Not remotelyas nasty as gasoline, but very much afire hazard just the same. I wouldinstead recommend using the "real"water based dielectric resins we sawback in the EDM survey. You’ll havethe best luck with a drill press or amill that has a slow controllable ratevertical power feed.

The most obvious use is to removebroken taps or stuck drills. Be sure toremember that a continuous flow ofdielectric fluid between the tool andwork must be maintained at all times.

A reminder that EDM Today is theleading trade journal here, and yourforemost place to check for ads onmachines, materials, and supplies.

New Tech Lit

From Teltone, their new DesignSolutions data book all about tonereceivers, call progress detector ics,and phone signalling devices. Alongwith a few good ap notes. FromUnitrode, the new Linear CircuitsHandbook. Mostly on drivers, powersupply circuits, and battery chargers.

Randy Fromm’s Big Blue Book ofReally Great Technical Informationtells you bunches about commercialvideo game repair. In a readable andwell organized format. Randy alsooffers videos on video monitors andon game repair and refurbishment.

He has lots of insider tricks that

Copyright c 1997 by Don Lancaster and Synergetics (520) 428-4073 www.tinaja.com All commercial rights and all electronic media rights fully reserved. Reposting is expressly forbidden.63.5

April, 1993

Fig. 4 – AN ULTRA-SIMPLE EDM LASHUP. The lamps act as dynamicregulators, with the smaller one setting your sparking rate Be certain to keepthe tool and workpiece insulated from ground at all times. A dielectric fluidmust be used. Kerosine is possible but not recommended.

110 vacpower

line

3 amp,400 volt

diode

40 wattlight bulb

200 wattlight bulb

both caps are200 µF, 200 v

To insulatedcutting tool

To insulatedcutting workpiece

WARNING: Extreme shock hazard!

+ +

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there ever was any piezo device todate which generated more recoveredelectrical power than was used in itsconstruction.

Many new piezo aps seem stuckunder a two watt limit. Recent fans,positioners, and stepper motors abovethis size have been non-competitivewith traditional solutions.

Commercial power recovery wouldrequire new devices hundreds or eventhousands of times larger than thetwo watt limit. Once again, wheneveryou push the envelope, something hasto got to give.

For piezo power generation, themechanical work input would have tobe oscillatory and usually has to beresonantly coupled. Ya gotta shakethe transducer, not simply push on it!Piezo devices also must be kept cool.If they get anywhere near their CuriePoint, all piezo effects stop.

Worse yet, the best efficiencies ofthe high power units are often fiftypercent or less. Leading to very badeconomics and internal heating.

Worst of all, most piezo elementsare inherently very high impedancedevices. Usually in the ten megohmrange. For maximum power transferout of any system, the impedances ofyour source and load must be madeequal. This means you’ll usually get ahigh voltage, higher frequency, high

impedance output from any piezodevice. Tens of kilovolts or higher forlarger devices. Efficiently convertingthis into recoverable power is not atrivial task.

Several of the ap notes drive homehow dramatically piezo output powerdrops when you try to drive too low aresistance load. From watts down tomilliwatts even.

It’s also not at all obvious to mehow you can efficiently and cheaplycombine the multiple outputs fromseveral piezo devices.

Finally, unless you are in an "Uh,compared to what?" situation in outerspace or on a desert island, the firstand foremost question in any powergeneration scheme is "What are theeconomics?" If the rate of the energyproduction cannot more than pay forthe time value of the money used inconstruction, then your conversionscheme is totally useless.

Infinite cost breakeven times aretrivially easy to pick up. All that hasto happen is that the interest on thetime value of the construction moneyexceed the value to date of all thegenerated power.

Viable alternatives to piezo powergeneration are covered in depth inElectric Power Research Institute orthe Association of Energy Engineerstech publications.