hack65.pdf

Don Lancaster’s

Hardware Hacker

Short haul telemetry

Max-min slope theory

SETI books & resources

Unique new optical link

Maximum power transfers

June, 1993

A s I might have mentioned a

your generator to look and act like a

current source .

For instance, a current source load

for a transistor amplifier can offer an

enormously high voltage gain. These

unusual apps sometimes justify the

low power and bad efficiency.

Do note what this maximum power

transfer curve is telling us: You can

deliver the most power to a load by

throwing half of the generated power

away in your source!

The max power transfer curve is

surprisingly broad. Double or halve

time or two before, I am the

sysop of Guru’s Lair and do

have bunches of reprints of

my Hardware Hacker , Ask the Guru ,

Blatant Opportunist , Resource Bin

and LaserWriter Corner columns.

We might start off with a pair of

back-to-the-basics fundamentals…

Maximum Power Transfer

Say you’re using an electrical or

electronic generator. Say further it

happens to provide a one ohm source

impedance and is outputting a one

volt signal. What is your "best" load

resistance?

As figure one shows us, there is no

"best" choice. Only compromises that

depend entirely on exactly what you

are trying to do.

If you make your load resistance

fairly high, you’ll get high efficiency

and good regulation. But you will be

unable to get the maximum possible

power from your generator . Your ac

power utility is an example where the

generator impedance is made as low

as possible to minimize all the source

and transmission losses.

If you make your load resistance

equal to your source resistance, you

should extract the maximum possible

power from your generator. But the

efficiency will be a mere fifty percent

and your regulation will be poor.

Video and rf transmission lines get

important areas where you want to

precisely match load to the source.

Besides delivering maximum power,

you’ll also minimize reflections and

standing waves. Other areas where

"make load = source" are important

are the older power audio amplifiers

driving speakers, car batteries when

cold cranking, and solar cells trying

to deliver as much power to the load

as possible.

You also have the choice of using a

very low load resistance. Which will

give you a horrible efficiency and a

terrible regulation. It also will only

deliver a tiny fraction of the possible

generator power. But there are a very

few lower level uses where you want

(A) Typical generator and normalized load. Varying load resistor R

changes the total delivered power…

(s ourc e)

(load)

(B) Maximum power transfer takes place whenever the source

resistance matches the load resistance…

1.0

100%

0.5

50%

LOAD RESISTANCE IN OHMS

Borrow these two rules from differential calculus…

d(uv) = vdu + udv

d(u n du) = nu n-1 du

The voltage across the load will be…

V L = R/(1 + R)

The load power E 2 /R will simplify to…

P L = R/(1 + R) 2

Take the derivative and set it equal to zero…

(1 + R) -2 - 2(1 + R) -3 = 0

And simplify to…

(1 + R) - 2 = 0

Which solves as R = 1.

Fig. 1 – THE MAXIMUM POWER TRANSFORM THEOREM tells us that you

deliver the most possible power to a load only when you purposely burn up

half of the generated power in your source. Here are some key details.

65.1

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.

Hardware Hacker

construct any economical high power

E-field machine.

As far as I know, there never has

been any E-field machine anywhere

ever produce commercial "nickel per

kilowatt-hour" ac power. I’ll give you

an Incredible Secret Money Machine

if you can prove me wrong on this.

And while any piezo generator is

obviously an E-field machine, it is

only a "fair to middlin" one at its very

best. Sigh…

Finding Maximums

and Minimums

There’s a number of fairly obvious

ways you could verify that maximum

power transfer curve of figure one.

Being lazy, I just told the incredibly

superb general purpose PostScript

computer language to plot it for me.

As we have seen before, PostScript is

now the ultimate hacker’s language.

Or, you could go into the lab and

use a wattmeter and a variable load

resistor. Which should give you the

same curve, again with its maximum

value matching your source.

Let’s try using some math instead.

There’s this ugly rumor going around

that electrical circuits will obey math

rules. And that you can predict what

they will do simply by looking at the

underlying math.

In the figure one circuit, we have a

voltage divider which attenuates our

one volt input by…

e out = R/(1 + R)

Your output power should be this

voltage squared divided by the load

resistance. Which simplifies to…

P out = R/(1 + R) 2

You or a computer can then plot

this curve for different values of R to

generate the max power curve.

By the way, this stunt of using one

volt generators with one ohm source

impedances is called normalization .

If you can ever analyze something

using easy numbers instead of hard

ones, it will usually pay to do so.

Anything that can be scaled can also

be normalized. Much more on this in

my Active Filter Cookbook .

But there is a much better way to

find your maximum power transfer

point. There is a math process called

max-min theory that easily lets you

find maximum or minimum points for

At a local MAXIMUM , the slope (or the

first derivative) will be ZERO and the

rate-of-change of slope (or the second

derivative) will be NEGATIVE …

At a local MINIMUM , the slope (or the

first derivative) will be ZERO and the

rate-of-change of slope (or the second

derivative) will now be POSITIVE …

At an INFLECTION POINT , the slope

(or the first derivative) will be ZERO

and the rate-of-change of slope (or the

second derivative) will also be ZERO …

Fig. 2 – MAX-MIN THEORY is a branch of differential calculus that lets you

quickly and easily find a maximum or a minimum of any reasonable curve.

your load and your power that gets

delivered only drops by about twelve

percent or so. Thus, an exact match

sometimes isn’t all that important for

maximum power transfer. A precise

match just might be needed for other

reasons, though. Such as to eliminate

standing waves and reflections.

If you are going to mismatch, it

usually pays to do so on the high side.

This way your overall efficiency will

be better, even if the delivered power

drops a tad.

Let’s look at several examples of

how a bad source-to-load mismatch

can severely do you in. In figure two,

let’s take a piezo striker and see what

we can get out of it. Let’s assume the

striker has a source impedance of ten

megohms and outputs a peak of 1600

volts. We will also disable the spark

gap to prevent breakdown.

Into an open circuit, we get zero

power. For maximum possible power,

we’ll use a ten meg load, matching

source to load. Half the voltage will

appear across the load, and our power

will end up as 640 milliwatts. Per the

usual P = E 2 / R rule.

Which is over half a watt, so we

should be able to light a lamp with it,

right? Wrong. As 2-B shows us, a

flashlight bulb offers a resistance of

about ten ohms. With a ten ohm load

and a ten meg source, you can only

deliver 256 nano watts!

Your efficiency is essentially zero .

Ergo, no light.

Can you do better? Substituting a

neon lamp for a flashlight bulb would

help bunches. Instead, you can place

a transformer with a 1000:1 turns

ratio between the striker and the bulb,

as shown in 2-C . A 1000:1 turns ratio

gives you a 1,000,000:1 impedance

ratio. Your bulb now "looks" like a

ten meg load to the source. And you

should get nearly the full maximum

power flashing the lamp.

Remember, of course, that all piezo

devices are ac only generators.

Most small impedance mismatches

between source and load are not that

big a deal. But bad ones (especially

with high value sources driving low

value loads) will severely do you in.

Several columns back, we found

several good reasons why any piezo

power production hacks were likely

to end up a bad scene. Some of you

helpline callers pointed out there is

an even more fundamental gotcha.

Most power generators are either

E-field machines or H-field machines .

An H-field machine uses a changing

magnetic field to induce current into

a conductor . An E-field machine will

use a changing electric field to induce

a voltage across an insulator .

All E-field machines are inherently

high impedance devices. The power

density of all known E-field machines

is extremely low . E-field machines

tend to force you to the inefficient

extreme left of the maximum power

transfer curve of figure one. Precisely

where you don’t wanna be.

The curent state of the art in both

materials science and high vacuum

techniques simply will not allow us to

65.2

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.

June, 1993

new from

DON LANCASTER

ACTIVE FILTER COOKBOOK

The sixteenth (! ) printing of Don’s bible on analog

op-amp lowpass, bandpass, and highpass active

filters. De-mystified instant designs. $28.50

With an OPEN CIRCUIT , 1600 volts is

routed to an infinite resistor. The total

delivered load power is ZERO .

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With an MATCHED LOAD , 800 volts is

delivered to a 10 meg resistor. Total

delivered power is a fairly respectable

640 MILLIWATTS .

CMOS AND TTL COOKBOOKS

Millions of copies in print worldwide. THE two

books for digital integrated circuit fundamentals.

About as hands-on as you can get. $28.50 each.

With a BADLY MISMATCHED LOAD ,

1.6 millivolts is delivered to a 10 Ohm

incandescent lamp. The total delivered

power is a useless 256 NANOWATTS .

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With a MATCHED LOAD , nearly 640

MILLIWATTS can be delivered to the

incandescent lamp by using a 1000:1

turns ratio matching transformer.

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sent to an 0 Ohm resistor. The total

delivered power will be ZERO .

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Fig. 3 – GROSSLY MISMATCHING your source and load impedances can

severely reduce your total available delivered power. Here are examples that

try to use a piezo striker as a power generator.

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Technical Insider Secrets

FREE

any reasonable curve. Figure three

shows you the key secret.

Any reasonable curve will also

have a slope . A slope is simply the

"steepness" or the "rise over run" of

any tiny portion of the curve. One

crude way to find the slope of any

point on a curve is to take a point just

before and one just beyond and create

a tiny triangle out of it. The rise/run

(or tangent ) of the triangle will equal

the slope of your curve.

As figure three shows us, there are

only three possible cases where you

can get a zero slope on a curve. These

happen only at a local maximum , at a

local minimum or, more rarely, at an

inflection point . And that’s all there

is to max-min theory.

Just find the math expression for

the slope of your curve. Set it to zero

and solve it. All solutions will be a

max, a min, or an inflection point.

How can you tell which is which?

Often, it will be completely obvious.

If not, you’ll go one step further and

find the slope of the slope . If you are

at a local maximum (3A) , the rate of

change of slope will be negative . At a

minimum, (3B) , the rate of change of

slope will be positive . And if you are

now at an inflection point, the rate of

change of slope will be zero .

Your "correct" and "exact" way to

determine the slope for any curve is

known as finding the derivative and

this whole field is called differential

calculus . You could find a full set of

rules in any university level Calculus

101 text. A good listing also appears

in the Mathematical Tables from the

Handbook of Chemistry and Physics .

I’ve shown how you use max-min

theory to prove the maximum power

transfer theorem in figure one. Sure

enough, the maximum is exactly at a

load impedance which matches the

source. Taking most derivatives is

quite simple. For instance, a parabola

y = x 2 has a slope anywhere of 2x .

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and proven real-world alternatives. 28.50

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ventures. Stuff you can use right now. $24.50

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A complete collection of all Don’s Nuts & Volts

columns to date, including a new index and his

master names and numbers list. $24.50

FREE SAMPLES

Check Don’s Guru’s Lair at http://www.tinaja.com

for interactive catalogs and online samples of

Don’s unique products. Searchable reprints and

reference resouces, too. Tech help, hot links to

cool sites, consultants. email: don@tinaja.com

FREE US VOICE HELPLINE

VISA / MC

SYNERGETICS

B ox 809-EN

Thatcher, AZ 85552

( 520 ) 428-4073

65.3

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.

Hardware Hacker

Good old u n du and friends.

Advanced math can be neat stuff.

And very valuable, too.

SETI Resources

NASA has recently started a new

and very aggressive SETI (search for

extraterrestial intelligence) program.

In the first few hours of operation,

more frequencies have been observed

in more ways than have in the entire

history of all previous ET watching.

One prominent researcher in SETI

is Frank Drake. He is famous for the

"Drake Equation" which accurately

predicts the number of intelligent civ-

ilizations and unintelligent senators

that are likely to be lurking in the

universe at any given time. Frank has

recently authored a new and highly

readable book titled Is Anybody Out

There? and published by Delacorte .

So, I thought it might be a good

time to do a resource sidebar on SETI .

I’ve included several associations and

a listing of the better books.

Besides the three groups Frank

mentioned in his book, I’ve added the

Amateur Radio Astronomers who also

publish a Radio Observer newsletter.

But note that their main focus is on

radio astronomy fundamentals. And

that they do distance themselves from

ET watching and the UFO crowd.

For several reasons, I strongly feel

that the odds for an imminent SETI

contact are quite high. As openers,

our signal detection, processing, and

computing abilities have skyrocketed

in the last several years. And should

continue to do so.

Shortly after World War II, our sun

suddenly turned into a radio star.

Captain Video , Roller Derby , and

Kukla, Fran, & Ollie became our first

goodwill ambassadors to outer space.

These signals are now 45 light years

away from us, and have now swept

out nearly a third of a million cubic

light years of space.

Within this humongous volume are

several hundred "probable" candidate

star systems. Our own signals are

easily detectable at this range with

our present state of the electronic art.

In another 45 years, eight times more

volume will be swept out with eight

times more candidate star systems

now watching Your Hit Parade .

At a further signal strength drop of

less than six decibels!

SETI RESOURCES

Associations:

Amateur Radio Astronomers

247 North Linden Street

Massapequa NY 11758

(516) 798-8459

Pacific Astronomical Society

390 Ashton Avenue

San Francisco, Califronia 94112

(415) 337-1100

Planetary Society

65 North Catalina Avenue

Pasadena California 91106

(818) 793-5100

SETI Institute

2035 Landings Drive

Mountain View California 94043

(415) 961-6633

Publications:

Edward Ashpole, Search for Extraterrestrial Intelligence, Blandford, 1989.

Issac Asimov, Asimov’s Biogaphical Encyclopedia, Doubleday,1972.

John Billingham, Life in the Universe, MIT Press 1981.

Howard Blum, Out There, Simon & Schuster 1990.

Ben Bova, First Contact, New American Library 1990.

Ronald Bracewell, The Galactic Club, Stanford Alumni, 1974.

A.G. Cameron, Interstellar Communications, W. Benjamin, 1963.

Nathan Cohen, Gravity Lens, John Wiley, 1988.

Frank Drake Intelligent Life in Space, MacMillian 1962.

Frank Drake, Is Anyone Out There? Delacorte Press, 1992.

Robert Forward, Dragon Egg, Ballantine 1980.

Donald Goldsmith, Quest for Extraterrestrial Life, University Science, 1980.

Donald Goldsmith, Search for Extraterrestrial Life, Benjamin, 1980.

James Gunn, The Listeners, New York: Charles Scribners Sons, 1972.

J.S. Hey, The Evolution of Radio Astronomy, Neal Watson, 1973

John Lilly, Man and Dolphin, Doubleday 1961.

Thomas McDonough, Search for Extraterrestrial Intelligence, John Wiley, 1987.

Greg Mamikunian, Current Aspects of Exobiology, JPL, 1965.

Philip Morrison, Search for Extraterrestrial Intelligence, NASA, 1977.

Bernard Oliver, Project Cyclops Report CR-114445, NASA, 1973.

Dennis Overbye, Lonely Hearts of the Cosmos, Harper-Collins, 1991.

Michael Papagiannis, Strategies for the Search for Life, Reidel 1980.

Cyril Ponnamperuma, Interstellar Communications, Houghton Mifflin, 1974.

Robert Rood, Are We Alone?, Charles Scribners, 1981.

Carl Sagan, Contact, Simon & Schuster,1985.

Carl Sagan, Communications with Extraterrestrial Intelligence, MIT Press, 1973

Carl Sagan, Murmurs of Earth, Random House, 1978.

Iosif Shklovsky, Five Billion Vodka Bottles to the Moon, W. Norton 1991

Iosif Shklovsky, Intelligent Life in the Universe, Holden-Day, 1966.

Walter Sullivan, Search for Intelligent Life on Other Worlds, McGraw-Hill, 1964.

David Swift, SETI Pioneers, University of Arizona Press, 1990.

Frank White, The SETI Factor, Walker, 1990.

Recommended range:

1 to 36 inches

+5v

Data

input

Data

output

RY5AT01

RY5AR01

Fig. 4 – NEW SHARP OPTO CHIPS offer all sorts of new possibilities for

wireless communication, safety isolation, and short haul telemetry. The 500

kHz pulse modulation ignores ambient light and TV/VCR remotes.

65.4

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.

June, 1993

We are now in transition between

calling hundreds of candidate star

systems to annoying thousands more.

On the other hand, I personally feel

that looking for obviously modulated

narrow SETI signals in the expected

"water hole" frequency band might

not be the swiftest way to go. If Earth

is an even remotely typical example,

all the unintentional radiated signals

swamp those intentional ones by at

least a zillion to one.

And we have recently discovered

spread spectrum communications. If

you really want to punch any signal

through very high noise over great

distances, spread spectrum seems a

very good way to go. The chances are

that you could step up to multiple

dimensions of spectrum spreading.

Using, say, frequency, time, and

some sort of a trellis modulation type

of overlay.

Perhaps a "multi-level marketing

scheme" in which the unswift could

pick up that something was coming

down, the fairly bright could receive

useful info, and the superintelligent

could grab the full set of plans. This

surely would beat sending out prime

numbers forever.

The signals may be there but we

just might not be smart enough to

recognize them just yet. Perhaps the

fundamental question to ask is "What

spreading and modulation scheme

would give us the most bang for the

buck?" And then start looking for

something similar heading our way.

Let’s have your thoughts on this.

New Opto Chips

Infrared data communications has

recently become much simpler thanks

to a pair of Sharp circuits. Figure one

shows details.

These devices look like a transistor

with a built-in lens. Their RY5AT01

transmitter outputs a burst of 500 kHz

modulated infrared square waves if

fed a logic one. And outputs nothing

with a logic zero. This is a form of

modulation that’s called Amplitude

Shift Keying .

The RY5AR01 receiver accepts an

infrared signal and converts it back

into digital logic levels. An internal

digital filter rejects most interfering

signals or noise.

The modulation scheme largely

ignores ambient light. Signals from

NAMES AND NUMBERS

Cerac Inc

Box 1178

Milwaukee, WI 53201

(414) 289-9800

Delacorte Press

666 Fifth Avenue

New York, NY 10103

(212) 765-6500

GEnie

401 N Washington Street

Rockville, MD 20850

(800) 638-9636

Gerber Scientific

83 Gerber Road

South Windsor, CT 06074

(203) 644-1551

NASA

Langley Research Center

Hampton, VA 23665

(804) 865-3281

NEC

401 Ellis Street

Mountain View, CA 94039

(800) 632-3531

Radio Observer

7605 Deland Avenue

Ft Pierce, FL 34951

(407) 464-2118

RF Design

6300 S Syracuse Way, S650

Englewood, CO 80111

(303) 220-0600

Sharp

5700 NW Pacific Rim Blvd.

Camas, WA 98607

(206) 834-2500

Signetics/Philips

811 E Arques Avenue

Sunnyvale, CA 94088

(800) 227-1817

Synergetics

Box 809

Thatcher, AZ 85552

(602) 428-4073

Wired

544 Second Street

San Francisco, CA 94107

(415) 904-0664

most interfering TV or VCR remotes

are also strongly rejected. Data rates

up to 19,200 baud are supported. The

beamwidth is a somewhat narrow ten

degrees, and the recommended range

is 1 to 36 inches.

Obvious hacker uses include safety

isolation, data comm, handicapped

aides, virtual reality, robotics, and for

wireless mice.

Because of the narrow beamwidth,

the two devices must point directly at

each other at all times. While there is

good rejection to ambient light and

many random IR signals, there is no

selective coding. Which means that

you will have to strictly isolate each

optical linkup from any potentially

interfering neighbors. This turns into

an especially sticky problem in full

duplex (two-way) data comm.

Sadly, Sharp’s $10 intro price for

these is in the "What are they on, and

where can we get some of it?" range.

These will be superb products when

they drop to sixty cents each.

Short Haul Telemetry

There are all sorts of emerging new

uses for shorter range wireless data

communication. I’d like to apply the

generic term short haul telemetry for

any newer method that tries to send

information a few inches or a few feet

without any wires.

We’ve seen one possible need in a

previous column and in my ongoing

Hardware Hacker BOD reprints.

An Isopod is a tennis-ball shaped

beastie that you glomp onto an ac

power wire. The isopod automatically

measures and transmits the current to

a nearby receiver. This can greatly

simplify home energy management.

No rewiring, no electricians, and no

code hassles need be involved.

Another new need is for a wireless

pulse rate sensor for use on a bicycle

computer. And there are thousands

more. How about an "optical mouse"

that senses where you are looking ? Or

new ways to get data onto or off of a

rotating shaft or moving vehicle. Or

ground-loop-free alternatives to data

communications?

But why don’t you tell me instead?

For this month’s contest, either (A)

show me a use for the RY5AT01 and

the RY5AR01 , or else (B) dream up a

brand new application for short haul

telemetry.

There will be dozens of the usual

Incredible Secret Money Machine II

book prizes awarded, along with an

all-expense paid (FOB Thatcher, AZ)

tinaja quest going to the best of all.

65.5

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.

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