homemade electronic components and devicespdf

Cool Homemade Stuff etc.

This Page Started November 2007

Welcome to sparkbangbuzz.com.

This is a homepage of really fun scientific and technical projects that are easy to build and

informative.

If you have any comments or submissions, E-mail to me a message at [email protected]

Disclaimer

Anyone reading this web page should not assume that any given subject is safe or legal. The

purpose here is to give information only. I take no responsibility for what anyone may do with

the information given here. What you do with it is your own business and responsibility.

Building some of the projects, described here, can be dangerous, illegal or both; and require

that the builder or user be very conscientious and able to exercise a great deal of Caution and

Common Sense. A project described as "relatively safe" may not be completely safe. It may be

described as "relatively safe" only because it appears to be safer than making a batch of

Nitroglycerine. Never get cocky where safety is concerned.

POLITICAL CORRECTNESS!!! This page welcomes all varieties of race, gender or anyone

interested in its contents. If you are offended by anything that seems politically incorrect, don't

write to me. I do not care to be annoyed by fanatic whiners who expect every printed line to

pass correct political specifications.

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Homemade Memristor.

Homemade Memristor.

A homemade memristor was made from pieces of brass, copper or lead that had been

turned to a dark color from exposure to sulfur.

Homemade Copper Oxide Thermoelectric Generator Can Light An LED.

Homemade Copper Oxide Thermoelectric Generator.

Simple homemade copper oxide thermoelectric generator can be made from two pieces of

copper wire. A single junction can generate more than 300 millivolts when heated with a

flame. Sixteen of these in series can light an LED.

Thermocouple Made From Ordinary Copper And Steel Wire.

Copper And Steel Thermocouple.

A thermocouple made of ordinary copper and steel wire can generate enough current

through a coil to deflect a compass needle using just the heat from my fingers.

Fly and Levitate Objects With Static Electricity.

Static Electricity Flyers.

Light objects made from plastic grocery bag material can be flown and levitated above a

charged balloon or piece of styrofoam. A simple electrostatic glider can be made that flies

just like a walkalong glider.

Evaporograph.

Evaporograph.

This simple to make evaporograph will show images of cold objects when they make

contact with a sensitive membrane. The membrane can also be made to show images of

infrared heat.

Homemade Magnetic Amplifiers using common 12 Volt Transformers.

Homemade Magnetic Amplifiers using common 12 Volt Transformers.

This article is to de-mystify the esoteric magnetic Amplifier and show how one can be built

at home using common everyday 12 volt transformers.

Homemade Magnetic Audio Amplifier using toroids found in parts box.

Homemade Magnetic Audio Amplifier.

An audio amplifier can be built without using any tubes or transistors.

Homemade FET Transistor Made From Cadmium Sulfide Photoresistor.

FET Transistor Homemade From Cadmium Sulfide Photocell.

A common cadmium photoresistor (called photocell in the text) was made into a crude

insulated gate field effect transistor. Definite transistor action was observed after

improvising a gate on the photocell. Even though the voltage gain was small, a considerable

amount of power gain was produced.

Corona Oscillator And Corona Triode.

Corona Oscillator And Corona Triode.

A pin point near a flat positive high voltage plate forms an oscillator that produces pulses

roughly in the AM broadcast band frequency range. A control element near the pin point

can control the overall current and frequency. This makes a triode that exhibits gain.

Zinc Negative Resistance Oscillator.

Anyone can make an active semiconductor device at home by heating galvanized sheet

metal. With it, simple rf and audio oscillators can be built. Amplifiers can also be built.

With a carbon microphone or transformer connected, the rf oscillator can even transmit

audio to a nearby am radio. Really!! I'm not kidding. Zinc Negative Resistance Oscillator

Zinc Negative Resistance Crystal Oscillators and Zinc 80 Meter CW

Transmitter.

Zinc Negative Resistance Crystal Oscillators.

This is a continuation of my first article on zinc negative resistance oscillators made from

the simple homemade zinc negative resistance diode.

In the early 1920's Oleg Losev in Russia experimented with negative resistance oscillators

and circuits using zincite. One of the main problems was that usable zincite came from only

one place in the world - New Jersey.

My articles are about doing very similar experiments using heat treated galvanized sheet

metal. I believe Losev would have been very excited if he had been able to try heat treated

galvanized sheet metal as a substitute for zincite and it may very well have worked even

better.

"Easy Ten" A simple 80 Meter CW Transmitter Using A 2N3904.

A very simple 80 meter CW one transistor QRP transmitter made from a common npn

transistor, two resistors, two capacitors, a 3.5 - 4 mhz crystal and a 9v battery. I call this

transmitter "The Easy Ten" because it can be easily heard from a distance of over ten

miles.

This article includes some good basic philosophy on antennas.

"Easy Ten" A simple 80 meter CW Transmitter Using A 2N3904.

Flame Triode With Gain.

I have found a simple way to make a triode with gain using an alcohol flame. This flame

triode exhibits both power gain and voltage gain. By making a flame dual triode, I have

been able to make a free running multivibrator oscillator and code practice oscillator.

I also observed a very intriguing phenomenon of flame electrical conductivity; that

electrons from a cathode, placed inside of the flame, can flow to the anode even when the

anode appears to be placed well outside of the flame.

Flame Triode With Gain.

Homemade Cathode Ray Tubes.

Homemade Cathode Ray Tubes.

Homemade T.E.A. Lasers.

Homemade T.E.A. Lasers.

A simple and crude conversion of a lawnmower to run on propane. Runs Great!!. Propane

Powered Lawnmower.

Experiments with a borax or baking soda rectifier. borax rectifier.

A simple homemade wide range variable electrolytic capacitor using baking soda can vary

in capacitance in one continuous sweep over a 5000 to 1 range. This capacitor can vary the

frequency of a simple relaxation oscillator over a similar range. Even the zinc negative

resistance oscillator can be continuously swept over the entire audio range. Homemade

wide range variable electrolytic capacitor and oscillator.

Copper Oxide is really neat stuff. It is very easy to make a simple photocell capable of

deflecting a volt meter with a small flashlight or listening to audio from a sound modulated

light beam. Very Simple Homemade Photocell

It is easy to make a thermistor, thermoelectric generator or pressure sensor by heating a

piece of copper wire.Homemade Thermistor and Pressure Sensor

A drop of salt water on some aluminum can produce some very interesting electronic

sounds when amplified. Very interesting sounds from a drop of salt water on aluminum.

Do you get more thrust by blowing air out a tube than you would get in the negative

direction by sucking the same amount of air into the tube??? I did some experiments and

found out a pretty definitive answer. The answer may be surprising to many. Jet Negative

Thrust by Sucking???

I have always been fascinated with the old Arc transmitters of the early period of wireless

radio. Not to be confused with Spark Gap transmitters, the Arc transmitter was different

and was supposed to produce a continuous wave signal that could be sound modulated.

What follows is a description of a crude circuit that I built. Simple Arc Transmitter

The coherer was one of the first detectors of radio signals ever used 100 years ago. I tried

building one. Getting impressive results turns out to be much easier than I have always

thought. Simple Homemade Coherer

It is incredibly easy to make a homemade device that behaves similar to a tunnel diode.

Using it, a simple rf oscillator was made which could be coaxed into running at 12 mhz.

Homemade Tunnel Diode and RF Oscillator.

I made an active semiconductor device at home with Iron Pyrites. With it, a simple

continuous wave broadcast band oscillator (transmitter) was built. With a carbon

microphone connected, it could even transmit my voice to a nearby am radio. Iron Pyrites

Negative Resistance Oscillator

More ways to make a homemade negative resistance devices that are much superior to iron

pyrites in ease of use and consistancy. More Negative Resistance Materials.

A simple home made negative resistance audio code practice oscillator that also makes

experimenting with negative resistance materials fun and easy without having to use an

oscilloscope or curve tracer.Negative Resistance Code Practice Oscillator.

Zinc negative resistance RF amplifier for crystal sets and negative resistance regenerative

receivers. Zinc RF Amplifier

I have always wondered if a vacuum tube could operate with a degree of vacuum attainable

by amateur means. This is how I broke open a vacuum tube triode and operated it after

pumping it down with a vacuum pump. Home Evacuated Vacuum Tube

The next step - an actual homemade vacuum tube diode. Home Made Vacuum Diode

The next step - first attempt at making an actual homemade vacuum tube triode. Home

Made Vacuum Triode

Magnetic levitation using permanent magnets. No superconductors, no energy input for

stabilization and no spinning tops. Earnshaw - take a hike. Permenant Magnet Levitation.

Magnet Kicker keeps any magnet in motion to make simple motors or "perpetual motion"

toys. Magnet Kicker.

Can ordinary propane, such as that used for fuel, be used as a refrigerant? It sure can!!

Homebuilt Refrigeration System from hardware store parts.

The next step. Can an old refrigerator operate when charged with ordinary propane? Old

Refrigerator Charged With Propane.

Throw staples, tacks, screws etc. like a knife thrower and stick them in the target. Fun and

impressive hobby. How to throw staples, tacks, screws etc.

Almost everyone gets a kick from making a good sounding explosion, especially if it can be

done with very easy to get materials. Well here is a relatively safe way of doing it with

compressed air. Airbang

A "Dry Ice Bomb"??? Who Needs Dry Ice? Airbomb

Simple Static Electricity Generator. The Electrophorus is wimpy, the Wimshurst Machine

performs but is much more difficult to build. ThisSimple Static Electricity Generator. is

incredibly simple to make and fills in part of the huge performance gap that exists between

the Electrophorus and the Wimshurst Machine.

Send sound on a modulated LED light beam. Sound Modulated Light Beam.

Send sound on a modulated Laser Beam. Sound Modulated Laser.

Send sound on a Modulated Flashlight Beam. Sound Modulated Flashlight.

Broadcast a signal through your entire house with a magnetic field. Broadcast with

magnetism.

Thirty foot long steel wire makes far out music. Wiremusic.

Links

Videos of sparkbangbuzz.com projects and other web interesting web sites.

Links.

Homemade Memristor

By Nyle Steiner K7NS.

Aug 29 2011.

Curve traces from two homemade memristors.

Modified curve tracer is applying AC voltage. Horizontal axis represents voltage and the

vertical axis represents current. In both cases, the curve always passes through zero voltage

and current. This requirement must be met in order to be classified as a memristor.

Memristor test setup and schematic.

When S1 is closed the LED shows the status of the memristor. If the memristor is in the low

resistance (on) state the led will light. If the memristor is in the high resistance state (off)

the led will not light. S2 turns the memristor on. S3 turns the memristor off.

The 3 volt battery and 1k pot supply just enough voltage to light the led without effecting

the on off state of the memristor.

Nearly ten years ago I was hiking up a mountain road when I noticed a lot of small gravel

and the smell of sulfur. Some empty brass cartridges that were lying in the gravel had

turned to a dark black color.

I took some of the cartridges home to investigate the electrical properties of the dark black

corrosion. When the cartridge was contacted with a piece of aluminum and connected to

the curve tracer, the left pattern shown near the top of this page was observed.

I let several pieces of copper, brass and lead set in a container of sulfur for a considerable

length of time.

All of the above pieces, after removing from the sulfur, displayed similar memristor

characteristics.

I recorded this in my notebook as a curious memory phenomenon but did not think much

more about it until recently reading about the memristor and realizing how similar it is to

what I had been observing. I decided to do some additional experimenting and build the

test circuit (animated photo and schematic shown above) to demonstrate the memristor

action of the corroded pieces of metal.

I also tried putting a small pile of sulfur on a piece of sheet copper.

After just a few hours, I removed the sulfur and noticed that it had formed a black colored

area on the copper. This black copper when in contact with a piece of aluminum produced

the curve trace shown on the right near the top of this page.

Sparkbangbuzz Home Page.

Copper Oxide Thermoelectric Generator Can

Light An LED


July 2011.

Just 16 copper oxide junctions can produce enough voltage

to light an LED.

Copper oxide, the kind that forms on pieces of copper when you heat them with a flame, is

very fascinating stuff. Besides being usable for other things such as making photo sensors,

thermistors, pressure sensors and diodes, it can also be used to make an impressive

homemade thermoelectric junction capable of producing hundreds of millivolts when

heated with a flame.

Making a simple copper oxide thermoelectric junction.

The copper oxide thermoelectric generator or junction is very easy to make. Just heat two

pieces of ordinary copper wire in a propane flame, to form a copper oxide layer, and then

place the two wires in contact with each other. That is all there is to it. An electrical

potential will be produced between the two wires when one wire is heated to a much hotter

temperature than the other.

The hottest wire will be negative and the cooler wire will be positive.

A single copper oxide junction can easily produce enough current to deflect the meter to

more than full scale when it is set to read 0 to 50 microamps or 0 to 100 millivolts.

With the meter set to read 0 to 500 millivolts the copper oxide junction can produce

readings in excess of 300 millivolts.

The switch near the meter is a reversing switch for convenience whenever I want to reverse

the connections to the meter.

Coper oxide thermopile made with 16 junctions in series.

This thermopile which consists of just 16 copper oxide junctions in series can produce

between two and three volts when heated in a flame. This thermopile is shown at the top of

this page, producing enough voltage to light an LED.

It would require more than 100 thermocouples made of special wire in series to light the

same LED. It would require roughly 1600 copper and steel thermocouples to light the same

LED.

The trade off is that the wire thermocouples can easily produce much more current than is

easy to do with the copper oxide junction. Typically the copper oxide junction can easily

produce hundreds of millivolts whereas a wire junction can easily produce hundreds of

milliamps.

The pictures above are pretty self explanatory. The wire pieces are made of 18 awg bare

copper wire and are 3 inches long from the hot tips to the hairpin ends. The L shaped

bends are 3/4 inch from the hot tips. The circular wood mount for all of the wire pieces is 6

inches in diameter and the cutout center section is 3 1/2 inches in diameter.

All of the copper wire pieces are mounted at intervals of 22 1/2 degrees to equally space

them around the circle.

Each L shaped wire is the cold positive side of a junction and each longer straight piece is

the hot negative side of a junction.

The thermoelectric junctions are formed by the copper oxide between each straight piece of

wire and the L shaped piece that rests on top of it.

Most articles, that describe copper oxide projects, usually discuss the subject of cupric

oxide (black) or cuprous oxide (red) and the task of separating them. From many

experiences in making thermoelectric generators and doing other copper oxide

experiments, I have found that it usually just doesn't matter. When a copper oxide device is

made professionally this of course is an important subject but for the purpose of home

experimentation, impressive results can usually be obtained without having to bother with

separating the black copper oxide from the red copper oxide.

When heating pieces of copper, it is typical to have a top layer of black oxide form with a

layer of red oxide underneath but, I have found that the black copper oxide layer may also

contain a significant amount of red copper oxide.

Pieces of black copper oxide will often fall off in flakes after heating a piece of copper. I

once ground up some of these black looking copper oxide flakes in a mortar and pestle and

the result was some reddish brown powder that looked a lot like red cuprous oxide. I have

also done other experiments that indicated the presence of red cuprous oxide in black

cupric oxide flakes.

What is happening?

I have spent my entire life reading whatever technical books and articles I could find and

can recall seeing only one book that tells how to make something like this and none that

explain how this device works. It would be safe to say however, that an explanation could

be found in the institutionalized literature. Not being presently affiliated with any

institutions, I do not have ready access to most of their literature which makes the cost of

reading it prohibitive. So, I will offer my own take on what is happening.

A thermocouple is generally thought of as being a junction between two dissimilar metals

but it might be better to say that it is a junction between two dissimilar conductors.

Touching the two oxidized wires together forms a junction of copper oxide to copper oxide.

This is not where the action is. The copper oxide on both wires should be thought of as one

solid conductor between the two copper wires - a very short one at that. This can now be

seen as the classic two thermocouples back to back circuit. We have a copper - copper

oxide junction on the hot wire and an opposing copper oxide - copper junction on the cold

wire. With this in mind it is now easy to view this device as being a normal thermocouple

circuit.

It is easy to wonder how this device could work at all because of the copper oxide, that is

between the two wires, being almost an insulator. Copper oxide however, also acts like a

thermistor with a very high negative temperature coefficient. Even the "cold" wire still gets

hot enough that the resistance of the copper oxide drops relatively to a very low value -

enabling current to flow.

I must give credit to an older book "Simple Scientific Experiments" by Aurel de Ratti as

being the one and only book I have ever seen that makes the reader aware of this copper

oxide thermoelectric generator. This book also contains other fascinating stuff. It is

reprinted and sold by Lindsay Publications Inc.

Thermocouples Made From Ordinary

Copper and Steel Wire


June 2011.

Two copper and steel thermocouples.

A piece of ordinary copper wire and a piece of ordinary steel wire were soldered together

at the ends to make two thermocouples back to back in a loop . Thermocouple wire was not

used in these experiments. I wanted to see what could be done with ordinary copper and

steel wire.

According to the second law of thermocouples, the solder used in the thermocouple

junctions has little or no effect as long as the thermocouple temperatures are kept below

the melting point of the solder.

Copper and steel is not a commonly used combination for making thermocouples and for

good reason. At a given temperature, the copper and steel thermocouple will be producing

a few tenths of a millivolt while a more conventional thermocouple might be producing 20

millivolts. Accordingly, I have experienced difficulty in finding voltage versus temperature

data for copper and steel thermocouples.

In spite of the very low voltages produced with a copper and steel thermocouple, it is

possible to generate impressive amounts of current if the circuit resistance is kept very low.

A standard D'Arsonval milliameter has far too much resistance to use at voltages around

one millivolt.

A DC clamp on milliameter adds no resistance to the circuit and can accurately indicate

how much current is being generated with a simple copper and steel thermocouple.

Five milliamps will flow through this loop just by applying the heat from my fingers to one

junction. With a flame held under one junction momentarily, we can easily observe 80 ma.

20 ma can be produced by touching a piece of ice to the opposite junction.

Thermocouple loop made into a coil can deflect a compass

needle.

DC current probe meters are certainly not found

everywhere but a compass can be used to indicate current

flow by making the thermocouple loop into a coil. This coil

uses 5 feet of copper wire but the use of 12 gauge keeps the

resistance low enough for observable current to flow.

The compass needle is most easily deflected when it is

perpendicular to the coil axis as shown in the above picture.

A piece of tissue paper was placed over the mirror in the

compass case to eliminate lighting glare while taking the

photographs.

A flame held under one junction will cause an easily

observable deflection of the compass needle.

When a flame is held under the opposite junction, the

compass needle will deflect in the opposite direction.

The magnetic field of the earth pulls on the compass needle

like a spring and makes it somewhat difficult to deflect. I can

get much more deflection of the compass needle after

carefully placing one or two magnets in the vicinity of the

compass to cancel some of the earth's magnetic pull.

With the magnets in place to counteract the earth's magnetic

field, I can get a very noticeable needle deflection just by

applying heat from my fingers to one thermocouple junction.

If a good compass is not available, the same results can be

obtained by hanging a magnet inside the coil from a string.

In the picture above, the string is suspended from a

photography tripod. On the left is a magnet carefully placed

to counteract the pull of the earth's magnetic field.

I noticed a peculiarity in the copper and steel thermocouple

while applying heat to a single junction connected to a

voltmeter. As I raised the temperature of the junction, the

voltage reading would also increase as expected. When the

temperature reached a certain point well above that of

boiling water, I would abserve approx 1.5 millivolts positive.

But, as the temperature increased above this point, the

voltage output from the junction would start to decrease

until a point was reached that gave a reading of zero voltage.

As the temperature increased further above this point the

voltage output from the junction would start to increase

again but with opposite polarity until a reading of approx

1.5 millivolts minus was read. I did not apply any more heat

at this point because the junction was red hot and appeared

to be near the melting point of the copper.

Fly Objects With Static Electricity


June 2011.

Objects made from thin plastic grocery bag material are light enough to be held aloft and

flown using electrostatic repulsion. The plastic material can be charged by rubbing it

against a Formica surface with a cotton cloth. Another object such as a balloon can be

similarly charged and held below the plastic material to keep it in the air.

This flying ring is a two inch section cut from a grocery produce bag. Both the flying object

and the balloon must be charged to the same polarity.

The ring of plastic bag material was charged by rubbing it against a Formica counter top

with a cotton cloth and the balloon was charged by rubbing it against the cotton cloth.

Static Electricity Walkalong Glider.

The glider is very fun to fly because it has an aerodynamic stability that keeps it facing in

the direction it is being pushed by the balloon. It is just like flying a walkalong glider but it

is using electrostatic repulsion instead of lift from a moving flat surface. Flying the glider

above a charged flat piece of styrofoam will give the same look and sensation of flying an

actual walkalong glider.

It would be great to do more experimenting with making a hybrid walkalong glider that

could fly using both slope lift and electrostatic lift.

To make the glider, start with a 3 1/2 inch square of plastic grocery bag material.

Fold in half.

Wrap a 1/2 inch long piece of scotch tape around the bottom as shown.

Charge the glider by rubbing with cotton cloth as shown. The glider seems to have better

pitch stability if just the top area is rubbed and charged.

With the balloon in one hand, grab the charged glider with the other as shown and toss it

into the air using a very quick motion to keep it from adhering to your hand. Move the

balloon under the glider to keep it aloft and control it's flight. With a little practice, you

will be able to fly patterns with much control by letting the glider fall a little in front of the

balloon and pushing it forward. It is even possible to make the glider do loops.

The clear plastic grocery bags also work very well. I happened to find a yellow produce bag

and used it for the photographs because of it's increased visibility.

Many kinds of objects can be used instead of a balloon to lift electrostatic flyers. Some have

had good results using a flat piece of styrofoam rubbed with the cloth.

According to the laws of physics, an object floating above an infinitely large charged plane

will experience the same repulsive force at all distances. This means that the electrostatic

flyer will fly much higher above a very large flat piece of charged styrofoam.

Every once in a while, for reasons I am not sure I can explain, especially with new pieces of

plastic, I have experienced having the plastic charge to the wrong polarity. Sometimes the

plastic can even end up with both positive and negative charges in different areas on the

same piece. Rubbing several times on both sides will usually correct this. Once the plastic is

charged right, it will usually work well thereafter. I had problems properly charging a

plastic ring that was partially cut from the middle of a large printed logo. The printing

seemed to have a very adverse effect on the ability of the plastic to charge well.

Experimentation is the main key to all of this. There may be better materials than cotton

fabric for rubbing but my success with it has been good enough that I have not spent much

time yet trying others. Wool is always mentioned whenever static electricity is discussed.

The Formica surface seems to be one of the best materials I have tried for rubbing the

plastic against. For doing these experiments outside of the kitchen, I have a piece of

Formica that I can carry around.

Evaporograph and Infra Red Images


June 2011.

Simple evporograph will produce an image when in contact

with a cold object.

The metal handle of a table knife cooled in the refrigerator is placed in contact with the

plastic membrane.

Image is formed by minute droplets of water condensing on the film in areas that made

contact with the cold metal. The dark colored glass makes it easy to see the image when a

flashlight is directed on to the film.

This experiment was inspired by the February 1972 Scientific American Amateur Scientist

article that describes a simple evaporograph made by Roger Baker.

Evaporograph is made by stretching a thin clear plastic film over the top of a dark colored

glass half full of water and sealing with a rubber band. After putting on the plastic film the

glass should be allowed to sit until the temperature of the glass and water inside are the

same as ambient temperature. The film is now sensitive to colder temperatures and will

form an image of any cold object that it comes into contact with.

Cold coins from the refrigerator make an image on the

membrane.

Membrane can be made sensitive to warmer temperatures.

A cold can from the refrigerator when rolled across the membrane, causes condensation

over the entire film.

The film is now sensitive to warmer temperatures because they will cause the condensation,

already on the film, to evaporate.

Dark print in contact with the film will leave an image as it absorbs infra red heat from an

incandescent lamp.

This simple water evaporograph can be used over and over and can be made ready for a

new image by turning the glass upside down momentarily. This will flood the membrane

with water and erase any images that may be on it.

Homemade Magnetic Amplifiers.


October 2009.

Magnetic amplifier made from common 12 volt

transformers.

A magnetic amplifier is a circuit that uses changes in core saturation of an inductor to

bring about amplification. A small amount of DC current change from the 9 volt battery

and a 1k pot can cause a large amount of AC current change through a car headlight.

The purpose of this article is to de-mystify the esoteric magnetic amplifier and to describe

how to build simple homemade magnetic amplifiers using common 12 volt transformers.

This is the real deal; gain from a transformer, a component that is normally considered to

be passive. In most applications, transformers are merely used to step AC voltages up or

down without actually amplifying. A common transformer in a magnetic amplifier circuit

however, can actually exhibit gain just like a transistor or tube. The magnetic amplifier is

only different from a transistor amplifier in that a small amount of DC current controls a

large amount of AC current in the output instead of controlling a large amount of DC

current in the output.

To evaluate the amount of gain in my magnetic amplifier circuits, I compared the change of

input power with the change of output power dissipated by the output load. In other words,

I multiplied the change of output voltage across the load times the change of current

through the load. I then divided this by the change of input voltage times the change of

input current.

Let's say you want to run an auto headlamp on 12V AC and make a dimmer circuit that

uses a normal sized 1K ohm pot. The pot would just burn up if it were put in series with the

auto headlight so, some kind of circuit with gain is necessary in order to get adequate

control from the 1k pot.

For a project like this, the use of triacs or power transistors generally come to mind but,

the lesser known magnetic amplifier can do the same job without using any triacs,

transistors or tubes.

There are some good articles online about magnetic amplifier theory. Two of the best are:

The Transformer Book by Lee Reuben and Magnetic Amplifiers by Mali. They can be

found on google. Most of these articles however, describe mag amps in theoretical terms.

They can easily lead one to think that special cores and transformers would be necessary in

order to to actually build a magnetic amplifier. Nothing could be farther from the truth.

From my own experiments, I have found that normal everyday transformers including 12V

filament transformers sold by Radio Shack, work impressively well for making magnetic

amplifiers. The use of three leg and other special mag amp transformer cores are also

described in mag amp articles but I have just experimented with standard transformers

because of their easy availability. I also get great satisfaction from making exotic processes

work just from using commonly available materials.

To begin, I would like to first show a simple experiment that demonstrates how saturating

a magnetic core can lower inductance and allow more AC current to flow through a lamp.

The lamp glows brighter when the magnets are near the transformer. The magnetic field

saturates the core, lowering the inductive reactance in series with the lamp.

Also, shorting the unused winding will cause the lamp to light to full brilliance. Because of

this we can not use this circuit yet as a magnetic amplifier. Explanation will follow shortly.

Instead of using magnets, a DC voltage applied to another winding can also cause the core

to saturate. This is the basis of a magnetic amplifier circuit.

To understand how a Magnetic Amplifier can amplify, imagine a 12 V filament

transformer that has a primary 120 V winding and a secondary 12 V winding. The

secondary 12 V winding is connected in series with 12 VAC and a lamp. The primary

winding has roughly ten times as many turns as the secondary. By running a small DC

control current through the 120 V primary winding, amplification is possible because this

small current can generate enough ampere turns to saturate the core. This lowers the

inductive reactance of the 12V secondary, allowing more AC current to flow through the

lamp making it brighter. A small change in DC current applied to the 120 V primary

winding can cause a much larger change in AC current flowing through the 12 V

secondary winding. This can be stated another way. A small change in power dissipated

across the 120V primary can cause a much larger change in power dissipated across a load

connected to the 12 V secondary.

This circuit configuration however, presents some problems that need to be addressed.

When using a single transformer, high voltage AC will appear, through transformer action,

across the 120 V control winding. This high voltage can burn up a potentiometer or

whatever is connected to this 120 V winding. We don't want to have this high voltage AC

coming out of the magnetic amplifier input.

There is also the problem that the lamp will light to full brilliance if the 120 V control

winding is simply shorted. With no input applied to the amplifier, it should not make any

difference whether the input is open or shorted.

A solution to this is to use two transformers. The output AC current can be run through

the 12 V windings of both transformers either in series or parallel. The 120 V input

windings can be connected in series so that the AC voltages induced in them from

transformer action, are out of phase and cancel. This allows small DC control voltages to

be applied to the two 120 V windings without interaction with high voltage AC. Since each

transformer core can saturate, independently of the other, the DC control windings have

full core saturation effect even though they are connected out of phase.

It is easy to tell when the two input control windings are phased properly by shorting the

input. If the phase is wrong, the lamp will light to full brilliance. If the phase is correct, the

lamp condition will show little or no change.

With this type of Magnetic Amplifier circuit, the lamp will normally be dim or off when

zero control voltage is applied. DC control voltages of plus or minus polarity, when applied

to the input, will cause the lamp to get brighter.

Magnetic amplifier with reactance coils in series.

Magnetic amplifier with reactance coils in parallel.

The circle with the sine wave symbol in the center is an AC power supply. In the case of the

circuits described here, it is typically a 12v transformer powered from a 120 V 60 HZ

outlet.

Control of a l20 volt lamp using an output step up

transformer.

Magnetic amplifiers seem to be best suited for driving low impedance loads in their output.

The 12 V car headlight is a typical example. By connecting a step up transformer to the

output of one of my 12 V transformer mag amps, I was able to control a 120 V 60 Watt

lamp.

Adding a couple of diodes causes incredible increase in gain.

I was impressed to observe typical power gains of 15 to 25 using the two transformer

circuit but, after adding a couple of silicon rectifier diodes to the circuit as shown above, I

started to observe amazing power gains of well over 1000!! The diode circuits that I have

made do not put out as much power under my experimental conditions but the relative

amount of input control current change necessary to control the output is a very tiny

fraction of what is required when no diodes are in the circuit.

Why is this so? The diodes cause pulsating DC current to flow through the coils. This

pulsating DC current has a tendency to bias the coils toward saturation just as though it

were applied to the input. It is easy to see why this kind of circuit is called a self biasing

magnetic amplifier. This bias effect also appears as positive feedback. Positive feedback in

any kind of amplifier usually translates into an increase in amplification. With more

positive feedback, an amplifier can become unstable or capable of acting as a bistable flip

flop. I have also succeeded in making some bistable magnetic amp circuits.

Magnetic Amplifier articles also explain that by the use of diodes, the core is prevented

from being saturated in both the negative and positive direction. This raises efficiency by

eliminating hysteresis losses.

With this type of Magnetic Amplifier circuit, the lamp will usually be lit to some degree

when zero control voltage is applied. DC control voltages applied in one polarity to the

input will cause the lamp to get brighter while DC control voltages applied in the opposite

polarity will cause the lamp to get dimmer.

Some mag amp articles convey a "Stuff Shirt" attitude that a circuit must have diodes in

order to be called a Magnetic Amplifier and that a circuit without diodes is called a

Saturable Reactor. A circuit without diodes may have a power gain of just 15 but it is still

impressive and can certainly amplify . Why should it make any difference whether a circuit

has a gain of 15 or 1500 in order for it to be called an amplifier?

Higher gain also achieved using homemade borax rectifiers.

I was curious to see if homemade borax rectifiers (in the two jars) could be used instead of

modern silicon rectifiers to increase the gain of the mag amp circuit. The answer is: They

can indeed.

Two silicon diodes can be seen sitting in the foreground unconnected.

These borax rectifiers are crude as compared to modern silicon diodes but I was still able

to observe an amazing power gain of around 450 while using them in the mag amp circuit.

And Now The Obvious Question.

The answer to the the first question anyone reading this would ask is: OOOHHHH

YYYEEESSSSS!!! Audio magnetic amplifiers can be homebuilt using common toroids and

a high frequency ac power source. I made a magnetic audio amplifier with appreciable gain

using a couple of toroids from my surplus parts box.




23 January 2010.

A magnetic audio amplifier. The 9 volt battery is to supply dc bias to the circuit.

Magnetic audio amplifier schematic.

High impedance signals can be fed into the input of this circuit by using a matching step

down transformer such as the Bogen T725 or similar. It is sometimes helpful to bypass the

output of the transformer with a .1 uf capacitor and run the signal to the input through an

inductor of several millihenries to keep any residual 35 khz signal from feeding back

through the input to the crystal set.

A typical crystal set connection with the T725 would be to groud the black wire, connect

the brown wire to the input of the magnetic amplifier and the purple wire to the crystal set

output.

This is my second report on magnetic amplifiers. The first was a description of how to

control the brightness of an incandescent light powered by 12 vac. See: Homemade

Magnetic Amplifiers using common 12 Volt Transformers. This report shows how I

applied the same principle, using toroids and a 35 khz ac power source, to make a magnetic

audio amplifier.

The purpose of this project was to see if I could make a working audio magnetic amplifier

using common materials. This amplifier works very well under the circumstances that the

toroids were randomly chosen surplus aquisitions from my parts box. Using the speaker as

a comparison between the input signal and the output signal, the signal is very much louder

at the amplifier output.

Using this amplifier to control the brightness of a car tail light instead of an audio

amplifier, I found the gain to be quite high. With not very careful measurements, the power

gain appeared to be well over 2000. I will update this if I can make more accurate power

gain observations. In any case there is definitely some noteworthy gain.

To evaluate the amount of gain using the tail light, I compared the change of input power

with the change of output power dissipated by the output load. In other words, I multiplied

the change of output voltage across the load times the change of current through the load. I

then divided this by the change of input voltage times the change of input current.

The source of ac power for this amplifier was a quickly made 35 khz oscillator that puts out

a 10 - 12 vac sine wave capable of lighting a car tail light to full brilliance. This oscillator is

not yet designed well enough to publish here.

It is interesting to note that with the magnetic amplifier using diodes and 60 hz to control a

car headlight, the light is quite bright with no input dc bias. Applying a dc bias to the input,

depending on its polarity, will turn the light either dimmer or brighter. See: Homemade

Magnetic Amplifiers using common 12 Volt Transformers. In this circuit, using 35 khz and

toroids to control a light, the light is completely off with no input dc bias. A positive dc bias

will turn the light on and brighter. This is why the input coil polarity dots are on the

bottom instead of on top as shown in the car headlight control circuit. This suggests to me

that these toroids may be capable of controlling a lot more power than is being controlled

in this experiment.

The mag amp is true amplification without the use of tubes, transistors or IC's but it does

require the use of an ac power source. While most ac oscillators require the use of

transistors, this amp could concievably run using an ac power signal from a carbon arc or

maybe even a zinc oscillator or similar.

There are some good articles online about magnetic amplifier theory. Two of the best are:

The Transformer Book by Lee Reuben and Magnetic Amplifiers by Mali. They can be

found on google. Most of these articles however, describe mag amps in theoretical terms.

They can easily lead one to think that special cores and transformers would be necessary in

order to actually build a magnetic amplifier. Nothing could be farther from the truth.

FET Transistor Homemade From Cadmium

Sulfide Photocell.

By Nyle Steiner K7NS May 7 2009.

Updated May 10 2009

CDS Photocell Made Into A FET Transistor

The picture above shows how transistor action was observed by improvising an insulated

gate to a cadmium sulfide photo resistor. The picture was taken in normal light but the

experiment had to be performed in the dark.

The photocell used is pictured above. It is a very common type which I purchased from

Radio Shack many years ago.

Photo Resistor Converted Into A Field Effect Transistor.

I have long suspected that if a successful homemade transistor were to be made, it might

likely happen in the form of a FET. I have read of Roger Baker's homemade FET in the

June 1970 Scientific American Amateur Scientist column numerous times and have

thought about the simple architecture that can make a FET. This article illustrates that a

FET can be made simply by running current through a thin film of the right type of

semiconductor. If a flat conductor is put very near the semiconductor film and insulated

from it, voltage changes between the flat conductor and the film will cause changes in the

amount of current flowing through the film.

It recently occurred to me that if this is the case, I might be able to create transistor action

through a cadmium sulfide photocell (actually a photo sensitive resistor) since they consist

of basically a thin semiconductor film between two electrodes. This simple experiment

would be a logical first step before trying to create my own thin semiconductor films.

Would this photocell act as a transistor if I put an insulated gate near it?

My first attempt was simply to observe if there is any current change through the photocell

while moving a charged comb or pvc pipe near it. The excitement of seeing the current

change was short lived after realizing that the light striking the photocell was also affected

by the moving comb. I needed some light in the room to watch the meter. Several years ago

I had also tried moving a charged comb near some catwhisker devices to see if the current

changed. Seeing some current change at that time, was exciting until I realized that the

electrostatic attraction from the charged comb was physically pulling on the catwhisker. I

have long wondered if simply putting a charged object near a semiconductor or other type

of film, could have an effect on electrical current flowing through the film. For now, that

question still remains unanswered.

It was time to try improvising some kind of conductive gate near the surface of the

photocell. I did this by putting a piece of scotch tape across the face of the photocell to act

as the insulator. To make a conductive layer in close contact, I then put a drop of water on

top of the scotch tape just big enough to cover most of the photocell area. I used water

because of it's ability to conform closely to the surface of the tape. Nothing needed to be

added to the water because the resistance of normal water is very low compared to the

almost infinite resistance of this improvised gate. A piece of wire touching the drop of

water served as the gate electrode.

From my observations, the setup described above definitely produces transistor action.

This experiment had to be performed in the dark for obvious reasons although I found that

a tiny bit of light falling on the photocell could sometimes improve performance. There was

little or no transistor action in normal light because the photocell was saturated.

This transistor has considerable power gain but very low voltage gain because of the wide

voltage excursions required at the gate to produce a significant current change through the

photocell. Intuition says the gate could be made more sensitive by putting the gate closer

but the thickness of the scotch tape and the clear coating on the front of the photocell

precluded this. The gate input resistance is for most practical purposes, infinite. The only

current that flows through the gate is whatever current can leak through a piece of scotch

tape.

Battery B supplies current through the photocell and R2. Current through the photocell is

measured by I2. Battery B was varied between 9 VDC to 175 VDC.

Battery A was varied between 75 VDC and 175 VDC and was connected through a switch

to be able to reverse the polarity of voltage applied to the gate.

Whenever the switch was changed, the polarity of voltage across the gate would reverse,

resulting in a current change through I2.

R1 and R2 were used mainly to limit current and protect the current meters in case of a

high current. Since the gate impedance is so high, R1 could be anywhere between zero and

10 meg without noticing any significant difference.

This device acted as an enhancement-depletion insulated gate FET. A positive voltage

applied to the gate caused an increase of current through I2 and a negative voltage applied

to the gate caused a decrease in current through I2.

The gate, being such high impedance, is what makes the power gain of this device so high.

A change of even several hundred volts across the gate usually causes at most a small

fraction of a microamp - barely perceptible needle movement on a 50 ua full scale ammeter

I1. This translates into a very small change of power dissipated in the gate circuit. This

voltage change on the gate can cause many microamps of current change through the

photocell. That translates into a significant change of power dissipated in the output circuit

across R2.

The response of this device also seemed to have a dynamic characteristic. That is, whenever

the reversing switch was activated, the current through R2 would suddenly change and

then slowly creep back toward the previous value. By running a sawtooth waveform into

the gate however, I was able to establish to my satisfaction, that indeed the output current

was responding to the input voltage.

The sawtooth waveform at the output across R2 was inverted. This provided additional

assurance to me that this experiment was indeed producing real transistor action. The

input and output waveforms can be seen in the pictures below. The output waveform was

at much lower amplitude even though it appears the same in the lower picture. The

oscilloscope gain was set higher to compensate for the lower output.

Input Sawtooth Waveform

Output Is Inverted Sawtooth Waveform

The tiny spike at the bottom of the waveform is a small amount of input signal feeding

directly to the output through stray capacitance.

Homemade FET Transistor Used To Make A Power

Amplifier.

Meter readings and oscilloscope signals are great for evaluating devices such as this

homemade transistor but, evaluation would not be complete without building an actual

amplifier circuit and attempting to hear an amplified signal. I was successful at doing that.

A large voltage swing is required to drive the gate of this crude transistor. This makes it

unsuitable for amplifying small voltage level signals. A weak but large voltage swing (very

high impedance) signal is more suitable for driving this homemade transistor amplifier.

Fortunately, this type of signal is very handy at our fingertips. The 60 HZ buzz that our

bodies pick up around the house is just such a signal and is perfect for testing this

amplifier.

In order to make a comparison between the unamplified signal and the amplified signal, I

used the circuit shown in Fig 1. When touching the "Touch" point in Fig 1, the 60 HZ buzz

can just barely be heard by putting the ear right on the speaker. When touching the

"Touch" point of the amplifier circuit, the buzz can be easily heard by just sitting near the

speaker. Even though the signal from the speaker is still soft, the increase in loudness can

clearly be heard. We usually don't care much to have a signal like this amplified, but it is

very exciting to hear it amplified in this situation.

The homemade transistor requires a slight amount of light for optimum operation.

The 160 VDC is normally positive but the amplifier seemed to work just as well when the

160 VDC was negative. With the negative voltage, I had to reverse the 10 uf capacitor.

Even though the voltage gain of this circuit is very low (so far about 1/10), the power gain is

considerable and I believe this experiment definitely demonstrates transistor action from a

simple homemade field effect transistor. This experiment with a photocell is a positive first

step. It is fascinating to think about trying homemade thin films, and the results that might

be obtained, as Roger Baker did in 1970..

Corona Oscillator And Triode With Gain.

By Nyle Steiner K7NS Mar 2006.

Corona Oscillator

The picture above shows a corona oscillator in operation. This oscillator is capable of

producing frequencies between 500 khz and 2 mhz. The visibility of the corona has been

enhanced with a several second time exposure.

The Oscillator is made simply by placing the point of a pin near the head of a thumb tack.

The pin is connected to ground through a 1k resistor and the thumb tack is connected to

several KV DC positive through a 1 megohm resistor.

The 1k resistor has very little effect on the circuit but drops enough voltage to make the

pulse signal easy to see on an oscilloscope. The 1meg resistor mainly serves the purpose of

current limiting when the pin is brought too close to the thumb tack causing an arc.

The frequency of oscillation is dependent upon the voltage, spacing between the pin point

and the thumb tack head, and the strength of electrostatic fields applied near the tip of the

pin. A negative field will decrease the frequency and a positive field will increase the

frequency.

The frequency will also change as a charged comb is brought near the pin and thumb tack.

Interestingly, the frequency seems to have very little to do with resistance or capacitance

that may be placed in the circuit.

Corona Triode

A triode can be made by placing the tip of the pin inside a small loop of wire as seen in the

above picture. The loop is usually placed a small distance behind the point of the pin as can

be seen in the above picture. Bringing the loop closer to the point of the pin allows the loop

and a varying voltage applied to the loop to have more control over the frequency of the

oscillator. When moving the loop closer to the point of the pin or beyond (between the pin

point and the thumb tack) a point will be reached where oscillation and corona will cease.

The frequency of oscillation decreases as the amount of negative bias voltage applied to the

wire loop is increased. As the bias voltage is made even more negative, a point is also

reached where oscillation and corona will cease.

The pulses tend to stay the same width, therefore, voltage changes applied to the loop of

wire also control the amount of average current flowing between the pin and the thumb

tack. The amount of this current can be read at current meter I Osc.

As the bias voltage is varied over about 200 volts, there is a very big change in the plate

current (I Osc) as compared to a tiny change in bias current. This amounts to a significant

current gain or power gain in the triode.

This oscillator phenomenon is very consistent and seems to occur anytime a negatively

charged pinpoint is brought near a positive charged plate. I am not alone in observing

these pulses. They were observed and reported by Trichel in 1938. One can find his report

by putting Trichel Pulses on google.

Zinc Negative Resistance Crystal Oscillators.

A Continuation Of My Original Zinc Negative Resistance Oscillator Article.

By Nyle Steiner K7NS Feb 2008.

Update March 23 2008. 1.3 mile to 3.5 mile distance.

Update April 28 2008. 3.5 mile to 5 mile distance.

Zinc Negative Resistance Flea Powered 80 Meter CW

Transmitter.

While listening to a hand size short wave receiver with BFO (Degen 1103), I could hear the

flea powered transmitter pictured above from a distance of 5 miles (straight line GPS

distance).

Transmitter antenna was a random length wire run through a hole in the wall and thrown

into a tree. Ground was a clip lead connected to the screw of an electrical outlet cover.

The snow has finally receded enough that I could get to this 5 mile distant location up the

mountain. From here, I could hear the transmitter located in the small town below.

Zinc Negative Resistance Flea Powered 80 Meter CW

Transmitter. Clip Kludge Style.

This 80 meter transmitter using simpler construction, is identical to the one pictured above

and works just about as well.

Notice the "Rock Stable" mount for the zinc strip.

Schematic of CW transmitters shown above.

The 10k resistor provides a dc path from antenna to ground. This helps to prevent static

discharges from the antenna. A jumper across the 10k resistor is usually necessary when

running this transmitter without an antenna.

Zinc Negative Resistance Ham Band Oscillators.

This is a continuation of my previous article on negative resistance oscillators built using

the homemade zinc negative resistance diode.

My first article mainly described zinc negative resistance LC oscillators that I had made to

run anywhere from sub audio up to 2 mhz. I had not put a lot of effort into making a zinc

oscillator run above 2 mhz nor did I have much faith that one could run above that

frequency. After all, this zinc negative resistance device was already running much faster

than I had ever seen any unijunction transistor run back in the 1970's when unijunction

transistors were popular. Making these zinc negative resistance oscillators was a very

exciting experience but it left me with pipe dreams of being able to make them run on a

ham band above 160 meters.

Many of the rewards from writing web page articles come in the form of emails and gems

of information from readers. I recently received an email from Robert Nickels W9RAN

who had read my first article about the zinc oscillator. He reported success in making a

zinc negative resistance crystal oscillator run at 3.579 mhz (middle of 80 meter ham band).

I had not tried using crystals with the zinc oscillator in the past and was excited to hear of

his success at 3.58 mhz.

As you can imagine, I soon had my zinc negative resistance stuff back out on the table

along with my box of collected crystals. I also had no difficulty in getting 80 meter crystals

to oscillate. In fact with some experimenting and circuit refinement, I soon had a zinc

crystal oscillator running at 10 mhz.

If I could now figure out how to couple a zinc oscillator to an antenna, I could experience

the thrill of being able to transmit on a ham band using just a homemade semiconductor

and no tubes or transistors.

The schematic above and the section below "Coupling The Oscillator To An Antenna"

describe how I was able couple the zinc oscillator to an antenna making it into a

transmitter.

The diagram above shows the zinc negative resistance crystal oscillator. C1 is usually not

necessary for 80 meter crystals (3.5 - 4 mhz) but C1 makes it much easier with higher

frequency crystals such as 7 mh to 10 mhz.

As can be seen above, it is now routine to make an 80 meter (3.5 to 4 mhz) cw transmitter

using a zinc negative resistance crystal oscillator. At this point I have been able to make

zinc oscillators run up to about 13 mhz but stable and reliable operation for a 40 meter (7

mhz) transmitter seems more difficult. A 40 meter transmitter is definitely possible but so

far most of my effort has been concentrated on making an 80 meter transmitter.

I will report later on making a 40 meter transmitter if I can get one working well some

time.

I have identified some key refinements that help make these zinc oscillators able to run at

frequencies in excess of 10 mhz. The explanation is straightforward and intuitive. No mural

of mathematical hieroglyphics is necessary here. I don't speak that language anyway.

1: These zinc negative resistance oscillators are basically working as relaxation oscillators.

They will run just fine using just a capacitance across the zinc diode. In fact I was able to

obtain frequencies up to about 13 mhz just by running an oscillator in the relaxation

oscillator mode.

When a crystal is placed across the zinc diode, a relaxation oscillator is formed from the

capacitance of the crystal and the charging resistance comprised of the 25k pot and 1k

resistor. This relaxation oscillator can easily run at frequencies below the crystal frequency

while the crystal remains inactive. If the frequency of this relaxation oscillator is increased

to match that of the crystal resonant frequency, the crystal pops into action and has a

tendency to lock the oscillator to the crystal frequency. The relaxation oscillator must be

able to run at the crystal frequency by it's self in order to activate the crystal.

Difficulty is encountered when you have a high frequency crystal with too much built in

capacitance to allow the relaxation oscillator to reach the crystal resonant frequency. By

putting in a very small capacitance of several pf C1 in series with the crystal, the overall

capacitance is made small enough to allow the relaxation oscillator to reach the higher

crystal frequencies.

It seems that crystals up to about 4 mhz work well when connected directly across the zinc

diode whereas higher frequency crystals around 7 to 10 mhz work much easier with C1 in

series. I have been able to make C1 just by disconnecting one of the crystal clip leads and

laying it over the point where it was previously connected. A couple of insulated wires two

to three inches long twisted together also work well for C1.

2: I find it easier to get these oscillators running by using 18 vdc from two nine volt

batteries in series instead of using just 9 vdc from one battery. With a given amount of

current through the charging pot and 1k resistor, the capacitor can charge faster when

using 18 volts because it is charging more on the steeper part of the capacitance charge

curve.

3: It seems much easier to get these oscillators running if the zinc strip is positive with

respect to the catwhisker. This is a bit interesting since these zinc negative resistance

devices display very similar curves in both the positive and negative direction.

4: I have been having great success at using a multiple tip catwhisker. I take a piece of

stranded 26 gauge wire, strip 1/4" insulation from the end and arrange the protruding

wires in the shape of a fan. I then cut the end of the fan straight with a pair of scissors.

When using this as a catwhisker, I find the time looking for good spots on the zinc strip

much shorter.

Zinc negative resistance crystal oscillator running at 7.038 mhz.

Zinc negative resistance crystal oscillator running at 10 mhz.

Coupling The Oscillator To An Antenna.

Realizing that the zinc negative resistance oscillator can easily run at ham band frequencies

was exciting but I still had to figure out a way of coupling it to an antenna. As mentioned

above, any extra capacitance placed across the crystal will swamp the relaxation oscillator

and an antenna has plenty of capacitance.

I had success by coupling the antenna to the ground side of the crystal and running the

signal through the crystal into the antenna as shown in the 80 meter transmitter schematic

above. The antenna now provides a load for the crystal to work into instead of swamping

the circuit. The 10k resistor is simply a dc path to reduce static buildup and discharges

from the antenna. A jumper across the 10k resistor is usually necessary when running the

80 meter transmitter without an antenna.

My favorite antenna is a plain old random length long wire run through a hole in the wall

and thrown into a tree. I love the simplicity, no coax, no separate lead in, no bother with

swr etc. Each different length of wire will present its own impedance value to the

transmitter. If you can match and drive whatever impedance the random length wire is

presenting, it will radiate and you are ready to go.

Contrary to what many articles on antennas seem to imply, an antenna does not need to be

resonant in order to radiate a good signal. I believe that the biggest reason so much effort is

put into making antennas resonant is because the resonant condition is part of a total

configuration designed to present a 50 ohm impedance to the transmitter. 50 ohms is what

most modern transmitters are designed to match. In the good ole days, many transmitters

could be adjusted to drive almost any impedance whether it be 50 ohm coax, a random

length of wire or even a light bulb dummy load.

In years past, I have had many amazing cw qso's across the pacific ocean and across the

united states using less than one watt and a wire thrown into a tree. One one occasion while

using less than one watt near Los Angeles, I was having a qso with a ham in Japan using

the random length wire thrown into a tree. He said that I sounded like 100 watts into a

dipole.

Flea Powered Transmitter Output Levels.

The output power from a zinc negative resistance transmitter is very small (usually less

than one milliwatt) but as pointed out above, a signal with very little power can be heard at

unbelievable distances.

It can be difficult to determine how much power is being fed to random length long wire

antennas because of their wide variations of impedance but I believe you can get a

reasonable idea of how much power a transmitter will put into an antenna by driving

resistive loads and calculating the power dissipated by them. The zinc negative resistance

transmitter seems to be able to drive a wide range of load impedances reasonably well.

Different catwhisker settings produce various negative resistance characteristics and

therefore have an effect on the amplitude of oscillations and amount of output power.

Power output into a load seems to depend more upon a good catwhisker setting than it does

upon an exact impedance match with the load. Almost any ballpark load impedance from

an antenna therefore appears to be suitable for this transmitter.

I experimented with several output load resistor values in place of the antenna to get an

idea of how much power can be obtained from the 80 meter zinc transmitter. Using a 3579

khz crystal, I took measurements with four separate resistor load values placed between

the antenna connection point and ground: 56 ohms, 150 ohms, 220 ohms and 510 ohms.

The output power was derived by reading the peak to peak voltage across the load with an

oscilloscope, dividing it by two and multiplying by .707 to get the rms voltage value. The

rms voltage value was then squared and divided by the load resistance according to ohms

law to obtain the power being fed into the load resistor.

56 Ohms: Average 41.95 micro watts

80 mv = 14.3 micro watts




240 mv = 48 micro watts













I do not believe there was enough inductance in the resistors or capacitance in the scope

probe to adversely effect the quality of the above measurements. The output voltage

readings were essentially the same when the scope probe was switched between X1 and

X10.

I was able to obtain higher levels of power output using a 1 mhz crystal. A few

measurements were in excess of 1000 micro watts. In other words, a whopping 1 milliwatt.

Transmitter Adjustment and Keying.

Being a crystal oscillator, it is easy to adjust the transmitter by setting a nearby digitally

tuned receiver to the crystal frequency and turning on the BFO. I usually set the 25k pot to

approx 1/3 of its max resistance value, close the key and slowly slide the catwhisker along

the zinc strip while listening to the receiver. As the catwhisker slides a few bursts of

oscillations will be heard through the receiver as "chich" type sounds. When a steady

oscillation is heard, I let go of the catwhisker and adjust the pot for the most stable

oscillation. If it is unstable with a lot of warbles or does not key well with any pot setting, I

look for a better catwhisker spot. While some catwhisker settings produce unstable, warbly

and chirpy signals when keyed, other catwhisker settings will produce very stable signal

that sounds near perfect when keyed. These of course are the desired settings for the

catwhisker.

I personally would not complain anyway about a few warbles or chirps especially in light of

the tiny output power level and massive thrill level that this transmitter delivers using a

simple homemade semiconductor.

Zinc Negative Resistance Oscillator.

By Nyle Steiner K7NS 22 March. 2001

Anyone with a propane torch and a few scraps of galvanized sheet metal laying around can

easily make a negative resistance device. With this device, it is possible to make very simple

RF oscillators, audio oscillators and even amplifier circuits. It is almost like making your

own transistor.

Heat treated galvanized metal strip and curve produced.

Negative Resistance from heat treated galvanized sheet metal. Curve tracer is set

at 1v/div. horiz and 1ma/div. vert. Curve tracer was modified to apply ac to the

device.

This project was sucessfully done earlier using iron pyrites (see Iron Pyrites Negative

Resistance Oscillator) Iron Pyrites Negative Resistance Oscillator The heat treated

galvanized device however, is much superior in ease of use, consistancy and is very easy to

prepare. As with the Iron Pyrites oscillator, success with this experiment has been a very

exciting experience for me as it represents the ability to build a simple homemade active

semiconductor device. It is almost like making your own homemade transistor. This is an

actual realization of some very old, and esoteric 1920's experiments, by W.H. Eccles,

Greenleaf Pickard and Oleg Losev, that were so vaguely reported in a few articles that I

have often wondered if in fact it had actually been done. Even so, I have always had an

extreme fascination with those reports of being able to produce a continuous wave RF

signal from a crude semiconductor matarial back in the very early days of radio. From my

experiences in experimenting with negative resistance materials, I can now say that those

experiments done in the early days of radio, appear to be valid factual reports.

My fascination led me to purchase an old Tektronix 575 curve tracer so I could study the

curves of various materials that might have negative resistance or detector properties as

used in crystal sets. The curve tracer is not necessary in order to make and use the negative

resistance device and circuits as described below. It is instrumental however, in the

evaluation and discovery of materials which posess unique electrical properties. The 575 is

a vintage but great tool because it continuously shows the curve in real time as you

manually manipulate the samples. This is what is needed in order to make observations

while manually touching a piece of wire to a piece of material. I wanted to be able to

display both the positive and negative portions of the curves simultaneously and so had to

modify the curve tracer in order to do so.

Some articles refer to this negative resistance as being like that displayed by a tunnel diode.

It is true in the sense of having negative resistance, but it is in fact a different type of

negative resistance. This is ok since both types of negative resistance can have the effect of

gain, supplying enough energy to an LC circuit for it to become an oscillator.

Two types of negative resistance.

Left is type found in the galvanized sheet metal device. Right is type like a tunnel

diode.

The figure above shows how the two types of negative resistance curves are possible. These

drawings show the curves with the devices being biased in only one direction. The two

forms of negative resistance are sometimes called type S and a type N. The S type is the

type found here and in other devices such as a unijunction transistor and the old carbon

arc oscillators. The upper portion of the S curve is sometimes not seen because some

devices, such as the galvanized sheet metal device will destroy themselves before carrying

enough current to display the upper portion of the S type curve. The type of negative

resistance curve produced by a tunnel diode resembles the letter N. See also homemade N

type device. Homemade Tunnel Diode and RF Oscillator.

Making the galvanized sheet metal negative resistance device is very easy. Simply hold,

using pliers, the end of a thin 1/8 inch wide strip of galvanized sheet metal, of the type used

for furnace ducts, in the flame of a propane torch until it glowes bright red and shoots out

whit hot flares. It is a good idea to do this out of doors and to avoid breathing any of the

smoke or fumes. People who are knowledgeable about welding say that poisonus fumes are

produced when welding galvanized metal. After cooling, small dark spots will appear,

especially on the side opposite where the flame has struck. These dark spots are the main

negative resistance areas. The catwhiskers tried were 28 gauge steel wire and 30 gauge

copper wire. Both seemed to work well.

A good catwhisker arrangement can be made by putting two screws into a piece of wood

about 1-1/2" square near the edge. A piece of #28 gauge steel wire can be wrapped around

the two screws and cut to about 3" in length. The wire is then bent in an arch so that it

lightly touches the heat treated metal as the block is moved around. A heavy weight on the

block will make its position stable after making adjustments.

As can be seen on the curve tracer photo above, the curve can be quite symmetrical in both

the negative and positive direction, although I sometimes would observe a somewhat

asymmetrical curve. This picture was taken while the curve tracer was applying ac to the

device. I had to modify the curve tracer so it could apply ac.

Oscillator circuits can be made that run easily from one 9v battery. It often seems easier to

obtain steady oscillation when the catwhisker is biased negative with respect to the metal

strip, but biasing in either direction can work.

Negative resistance RF oscillator using galvanized sheet

metal.

The circuit shown is all that is necessary

to produce a continuous wave signal in

the am broadcast band. It seemed

difficult to get it to operate above 2mhz

but was easy to get it running at anything

below that, including audio frequencies.

It seems to prefer certain LC ratios

better than others. In the case of the am broadcast band, A 365pf variable capacitor

worked well with 50 turns on a piece of 1 3/4" outside diameter abs pipe.

The trickiest part of getting this circuit to operate is to be able to tell when it is oscillating.

The easiest way is to have an oscilloscope across the coil or across part of it with a tap. You

simply make adjustments until you see the signal appear on the scope. It can also be done

by adjusting the catwhisker while rocking the variable capacitor back and forth through its

range and listening with an am receiver. This takes a bit more skill but it can be done.

Another way to tell if it is oscillating is to put a diode and microameter across part of the

coil. When a steady deflection of the meter is obtained, the variable capacitor can be tuned

to the desired frequency using a receiver.

A good place to start making adjustments is with the pot set so that there is a total

resistance of about 4k ohms including the 1k resistor. The only function of the 1k resistor is

just to prevent a large amount of current flowing when the pot is set at zero resistance.

Some settings of the catwhisker allow the circuit to oscillate over very wide variations of

resistance (pot) settings.

Negative resistance audio oscillator using galvanized sheet

metal.

The audio oscillator is much easier to

adjust and to get running. It is simply a

matter of listening for a tone from the

speaker or headset while making

catwhisker adjustments. As with the RF

oscillator, a good place to start is with the

pot set so that there is a total resistance of

about 4 kohms including the 1k resistor.

Some settings of the catwhisker will make

the circuit able to operate over a very

wide range of resistance settings. You

may find it easy to get the circuit going

with just one 4.7k resistor in place of the

pot and 1k resistor.

This audio oscillator circuit can use the 120 volt side of a 120 volt to 12 volt transformer or

the 2k side of a 2k to 8 ohm transformer for the inductor. The output side of either of these

transformers, 12 volt or 8 ohm respectively, can drive a speaker with enough volume to be

heard across the room.

A pair of headphones of just about any impedance can be used in place of the speaker. A

headset will present less of a load than a speaker and will result in a higher Q LC circuit.

This can make it easier to obtain catwhisker settings that work well.

Negative resistance tone modulated RF oscillator using

galvanized sheet metal.

A tone modulated rf

oscillator can be made by

connecting both an rf LC

circuit and an audio

frequency LC circuit across

the negative resistance. This

circuit can oscillate at both

rf and audio frequencies at

the same time. It is possible

to adjust the circuit by

listening to the speaker or

earphone and then tuning

the variable capacitor untill

it is heard through an am radio. With many settings, a loud, well modulated tone will be

produced.

It is interesting to note that it is possible to get combinations of pot and catwhisker settings

where the audio circuit will oscillate but the rf circuit will not, the rf circuit will oscillate

but the audio frequency circuit will not or where both circuits oscillate at the same time to

produce the tone modulated rf signal.

Negative Resistance AM Broadcast band Oscillator.

It is possible to broadcast audio to a nearby am radio if a carbon microphone or

audio transformer is placed in series with the battery supply. It is hard to beat

the fun of broadcasting to a nearby radio with an electrified crystal set.

Negative Resistance Audio Oscillator.

Negative resistance audio oscillator driving speaker with enough volume to be

heard across the room.

How did I find out about galvanized sheet metal anyway?

A while ago, I wanted to make a simple electric buzzer using a coil of wire wrapped around

a bolt and a piece of galvanized sheet metal for the moving armature. It was of the DC type

where a contact point touches the metal and electrical contact is broken whenever the

magnet is energized and pulls the metal. This crude homemade buzzer worked as well as

one might expect but, it would not run very long. Some kind of black oxidation crud kept

building up where the metal was sparking against the electrical contact point and

preventing good electrical contact. Being somewhat disappointed, I dismantled the buzzer

and set the piece of armature metal aside where it sat around thereafter. Some time later,

after experimenting with negative resistance in iron pyrites and similar materials, I decided

to try the curve tracer on the black crud spots still on the galvanized sheet metal buzzer

armature. The results looked promising. This lead to heating another piece of galvanized

sheet metal in a propane flame. I was very pleased to discover many points that displayed

very usable negative resistance. I had finally found a negative resistance material that

could be consistently and confidently adjusted; usually within a matter of seconds.

After the metal is cooled, many black spots are found, surrounded with snow white

powdery zinc oxide. The white zinc oxide acts like an insulator and shows no continuity

whatsoever. The black spots are where most of the negative resistance is found. Taking a

wild guess, I would suggest the possibility of these dark spots being Zinc Ferrite Zn-Fe2-O4

or something similar, formed by the interaction of heat, oxygen and zinc, reacting with the

surface of the iron. The side of the metal facing away from the flame would be more more

likely to be in contact with oxygen than the side facing the flame. That may be why I seem

to find more good negative resistance spots on that side. Zinc ferrite is described in the

Handbook of Chemistry and Physics as a black material. It would appear that zinc is

playing an important role in the negative resistance. It stands to reason since zincite is

mentioned in early radio articles, as one of the best negative resistance materials. It would

be interesting to see what the curve, exhibited by zincite is like but I have yet to visit a rock

& mineral shop that has a piece of zincite available. Perhaps the performance of the heat

treated galvanized sheet metal is good enough to satisfy concerns about obtaining zincite.

Amplifiers using the negative resistance device.

I have been somewhat successful in making some amplifier circuits from the zinc negative

resistance devices. I have also been able to make a regenerative am broadcast band

receiver. It seems much easier however, to make an oscillator than an amplifier with

negative resistance because of the fact that most amplifier circuits have a great tendacy to

oscillate unless adjusted very carefully. Before writing more about negative resistance

amplifiers, I would like to put more effort into finding ways to get the most out of them.

"Easy Ten"

A simple 80 Meter CW Transmitter Using A

2N3904.

By Nyle Steiner K7NS April 2008.

I call this very simple transmitter the "Easy Ten" because it can be easily heard at a

distance of 10 miles. Transmitter antenna is a random length wire run through a hole in

homemade electronic components and devicespdf

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