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               HOW TO page 4

PAGE 4 OF 4


WHAT IS A TRANSISTOR?

I have already explained that a hot "filament" glowing in a lightbulb is a
RESISTOR, slowing down or 'resisting' electricity, and getting hot.
Interestingly enough, the history of the TRANSISTOR starts off as a
LIGH BULB as well! When Thomas EDISON was experimenting with
the first light bulbs, he used hundreds of materials as the FILAMENT
or HOT GLOWING WIRE that gets white hot, and gives off heat and
light. He used Wood, Rice, Cotton, Carbon, etc. but always had a
problem that as the white hot material 'BURNED" or glowed inside a
glass bulb, it would give off black CARBON ( like coal ) that would
coat the inside of the glass bulb and quickly block out all the light.
Edison thought that by adding another WIRE and putting electricity
on it, this would "ATTRACT" all the particles, and keep the inside
of the light bulb clean. This was about 1880.


Much to his surprise, when Edison put an electrical meter on the third
wire, he found that there was electricity coming out of it! He did not
think this was very useful at the time, and although he showed this
strange discovery to many others, he did nothing with it. The third
wire was NOT connected to anything inside the bulb, so logically,
there was no reason for it to have electricity on it. In fact, this was
one of the first " VACUUM TUBES" or " RADIO TUBES" or
"VALVES" ever made. Many years later, other people would USE
this discovery to make Electrical TUBES that would only allow
electricity to move in one direction ( a DIODE ), or that would
AMPLIFY or make electricity stronger. ( DI is the same as BI or
TWO, (( BI is from the Romans speaking LATIN, and DI is from
the GREEKS )), so that a DI-ODE has two wires- a hot filament,
and a "POST" wire that collects the electricity. A TRI-ODE (( TRI is 3))
has 3 wires, a hot burning filament, a post to collect the electricity,
and a third wire, a "screen " in between, as described below ) Edison's
first accidental tube was a DIODE, since electricity would travel from
the hot, glowing wire, to the third wire, but no electricity would flow
the other way. People associated this with a common water flapper
valve, that allowed water to flow in only one direction, so that the
common name for early tubes was a "Valve".



NOTE: It appears that there are 3 wires in a DI-ode and 4 wires
in a TRI-ode, which makes no sense. See the diagram below to see the logic !



How many wire ENDS are below the red line?
We now know that ELECTRONS, which are negative, will "boil"
off of a hot wire, and are attracted to a POSITIVE wire, inside a
glass bulb that has all the air removed -- a vacuum. This is just like
magnets- South Pole and North Pole magnets ATTRACT, and
North and North would repel each other- similarly, Positive wires
attract Negative electricity. I am assuming that anyone reading this
knows about ATOMS, which are made from the center PROTON,
which is POSITIVE, and have an outer orbiting Electron, which is
NEGATIVE. All substances on earth are made of atoms, starting with
HYDROGEN, with ONE center PROTON, and ONE ELECTRON,
then TWO PROTONS and TWO ELECTRONS  is the ELEMENT
 HELIUM, then 3 would be LITHIUM, 4 would be BERYLLIUM,
5 is BORON, and 6 is CARBON, etc. Each element just gets more
Protons, and more Electrons, and gets bigger and heavier.


If an atom gets extremely hot, the electrons spinning around the outside
can get loose, and will shoot out off the atom if they are in a vacuum. If
we use a 6 VOLT hot lightbulb wire inside a tube, it will "boil" off or give
off electrons. If there is a POSITIVE charged plate or post in the tube,
the NEGATIVE electrons will be attracted to it, and will fly across the
empty vacuum space and hit the POSITIVE post.

What makes RADIO TUBES or Vacuum VALVES usefull is ADDING 
a SCREEN in between the Negative, hot wire that is making the electrons
fly out, and the Positive "collector" plate. In order to get across the empty
space, the electrons have to go through the holes in the screen. If you
remember that NEGATIVE and NEGATIVE electrical charges REPEL 
each other, we can put in a tiny NEGATIVE charge, for example 5 VOLTS,
on the screen, and all the NEGATIVE Electrons will be REPELLED by
the screen, and NO electricity will flow from the hot wire to the Collector
plate. But, if we turn off the electricity in the screen from 5 Volts to ZERO
Volts, then there is no repelling force, and the Negative electrons will fly
through the holes in the screen. Even more usefully, if there is 120 VOLTS
from the hot filament wire to the Collector Plate, we can turn on and off
120 VOLTS with a tiny 5 VOLT ON / OFF amount of electricity! If you
remember the picture of the RELAY, it turned ON and OFF 120 VOLTS
with a tiny +5 VOLT electrical signal from a computer... - the TUBE, and
the RELAY turn out to DO the same thing !




The TRI-ODE or 3-Wire TUBE above can turn ON and OFF
LARGE amounts of electricity, by turning ON and OFF tiny amounts
of electricity on the SCREEN in the middle. As Well, by putting in
DIFFERENT amounts of electricity on the screen, for example
2.5 VOLTS, instead of 5 VOLTS, it can allow HALF the electricity
to go through the screen, so that it can let 60 VOLTS go through. By
putting in different amounts of electricity on the screen, you can get
20 VOLTS, 30 VOLTS, or 90 VOLTS flowing across the tube, all
the way up to the full 120 VOLTS.... This is called AMPLIFYING
the electricity, because a different small amount from ZERO Volts to
5 Volts, on the INPUT, or SCREEN, can be AMPLIFIED or
INCREASED to make ZERO Volts to 120 VOLTS, on the OUTPUT.

HOW ARE TUBE AMPLIFIERS USED?
One of the first uses for a tube was to AMPLIFY tiny RADIO 
waves picked up on a wire ANTENNA, and make the tiny signal
powerful enough to be heard on a large SPEAKER. The tiny
electrical waves were put on the SCREEN in the center of the tube,
and this turned on and off larger, stronger electricity that went to
big speakers.



The next biggest popular use for tubes was in TELEVISIONS, where
the tiny TV signals were brought in from the TV antenna, and amplified,
and then put on the TV -- TUBE. Most people do not realize that the
standard TV " IS " a TUBE! When you look at the front of a typical
TV TUBE, you are looking at a sheet of steel, covering the entire front
of the tube! I cut a piece of the steel out of a TV set that had the tube
broken. You can see the size of the tiny section of screen by comparing
it to the dime in the corner. From a distance, the sheet of steel looks solid.



You can see the metal screen has tiny holes in it, as shown in the enlarged
section. The back of the TV tube has a hot glowing wire heater, just like
a light bulb, and just like the radio tube above. At the front of the TV just
behind the glass is the sheet of steel with tiny holes in it. The ELECTRONS,
flying off the hot wire at the back of the TV, race towards the front of the
TV because the steel plate at the front is 10,000 to 60,000 VOLTS more
POSITIVE than the heater wire at the back. The NEGATIVE ELECTRONS
are ATTRACTED to POSITIVE, and race to the front. Most of the electrons
HIT the steel plate, but the ones that go through the tiny holes, hit RED,
GREEN, and BLUE phosphor, a powder that gives off light -- just like
the WHITE phosphor powder in long white flourescent tubes that are
used in the ceilings in schools and libraries. The colored dots make up
the picture that you see.



FINALLY, THE TRANSISTOR

The TRANSISTOR is called " SOLID STATE" since there are no
moving parts, and there is no VACUUM involved. Instead of using
a RELAY, or a VACUUM TUBE to turn on and off electricity, the
Transistor uses SOLID ATOMS of ELEMENTS, like SILICON ,
to switch ON and OFF Electricity. The Advantages over the COIL
 RELAY, are that tiny amounts of electricity can be used, and electricty
can travel at the speed of light, so that a SOLID STATE SWITCH can
QUICKLY turn On and Off thousands and millions of times a second --
the COIL RELAY creates a big SPARK every time it turns on and off,
and can only move as fast as the steel plate will move- very slow, and
eventually the SPARKS destroy the switch! VACUUM TUBES use
Electricity, and can switch MUCH faster than the RELAY, however,
they have other problems, mostly because they require HUGE amounts
of POWER to work, and they require LARGE VOLTAGES to operate.
The LOWER the voltage a device uses, the FASTER it can turn on and
off the Electricity - Large voltages, and large AMOUNTS of electricity
can NOT turn on and off very, very quickly. The HUGE amounts of
power mean that large wires have to be used, and the HEAT generated
from the HOT, GLOWING "FILAMENTS" or HEATER WIRES, are
problems, once you get a large number of TUBES in one location. A
single Computer using tubes took as much power as an entire VILLAGE,
and since each tube takes up a lot of space, the computer filled many floors
on a large building. A typical TUBE computer would be ENIAC, shown below.
Note that there is a huge, powerful fan in the ceiling to get rid of the heat -
these were installed every 10 FEET !



The TRANSISTOR works very similar to a VACUUM TUBE. There
are typically 3 wires, and a SMALL amount of electricity on MIDDLE 
WIRE, can ALLOW OR STOP a much LARGER amount of Electricity
from flowing across the other two wires. The most common SOLID material
used is ordinary GLASS, = SAND = SILICON! The Silicon, or glass, that is
used, is very special though, since it is not just melted down from sand like
glass windows in your house, but it is very pure glass, and is made into a single
CRYSTAL - like Diamonds or Rubies -- where ALL the atoms in the crystal
are perfectly arranged in rows and columns- not just mixed up like marbles
in a bowl.



CRYSTAL SILICON ( GLASS ) does NOT allow electricity to
run through it. To get electricity to flow, the Silicon Glass is mixed
with tiny amounts of OTHER ATOMS, and THEN it becomes a
'conductor', allowing electricity to flow through it. Common SOLAR
 CELLS, used to make electricity from the SUNLIGHT, use ordinary
CRYSTAL SILICON, and have chemicals soaked into the top and
bottom of the Silicon to make the top and bottom Positive and Negative.
The typical Silicon Solar cell has a Bluish color as seen in the example
below.


When you add chemicals to pure glass or SILICON, you go from
a NON-CONDUCTOR, that does NOT allow electricity, to a
SEMI-CONDUCTOR, that allows electricity under certain conditions.
I got some pure Silicon Crystal WAFERS or Slices, and heated them
up to 2000 degrees Farenheit, and then coated them with ARSENIC
and BORON compounds, that, at 2000 degrees, soaked atoms into the
Silicon. I did this in Grade 9 in the school Chemistry Lab, but had problems
with the 2000 degrees. The wiring I used on the home made fire brick oven
was NOT "industrial grade" high temperature wiring, and melted, causing
a fire that shut down the school, because of smoke! You could make your
own, home- made SEMI-CONDUCTORS, but the chemicals are hazarous,
and the high temperatures are difficult to work with, so I would NOT 
recommend this as a project! But the fact that I ( a kid in school ) could
make semi-conductors at all shows how SIMPLE electronics are once
you "understand" the principles. By soaking the SILICON with Arsenic
and Boron compounds, I made a Semi-Conductor that was Positive on
one side, and Negative on the other, and when LIGHT hit the Crystal, it
would make electricity -- a Solar Cell. SOLID STATE Transistors are
almost identical to this, but there is a THIRD layer in the middle, just like
there is a SCREEN in the middle of the Vacuum Tube.



The WEB Encyclopidia, Wikipedia.org has many detailed articles on the
evolution of electronics that led to the development of the transistor.
The first transistor Patent, was in Canada, in 1928, long before the
crystal silicon manufacturing techniques were even possible!
The first typical transistor is generally credited to William Shockley (sitting)
John Bardeen, and Walter Brattain, in 1947. BELOW:



The first transistor was very large, and very crude, but, it demonstrated that solid crystal
material could replace the vacuum tube! It was obviously hand made... BELOW:


Once the manufacturing was perfected, millions of transistors were made,
and allowed smaller, faster devices, that used less power than big vacuum tubes.

Eventually, instead of wiring a device, like a computer with hundreds of
INDIVIDUAL Transistors, it was realized that you could make many
transistors and connections on a SINGLE piece of crystal.
The first "integrated" circuit with more than one transistor in a single
crystal "chip" was in 1958.



Then, more and more Transistors, wire connectors, resistors, diodes, etc.
were being made on a single silicon chip. Generally, the first "Central
Processing Unit" or CPU is credited to the Intel calculator chip, the 4004,
said to have been roughly 4000 transistors, and a 4-bit memory. This
evolved into the 8008, which is the first generation of the IBM "PC" chips,
still in use today, now known as the "PENTIUM" chip.
The 4004 is shown below:



With a TRANSISTOR, we can now use the TINY electricity from the
computer Parallel Printer Port or from a BUFFER Chip, to power devices
such as LIGHTS and Motors, which use BIG amounts of power. A Transistor
can also switch OFF or ON power in the REVERSE, so that if you need a
signal to be OFF when the Printer Port is putting out an ON, you can wire in
a transistor to CHANGE or REVERSE the signal. If you want to power 5 LED
lights on a single wire, you can wire in a transistor to take the tiny power from
a DIGITAL Signal, and put out a POWER signal that has enough power to
run 5 LEDs easily. You can wire in a transistor to take the ON / OFF signal
from a BUFFER CHIP, and turn ON and OFF a big RELAY, and the contacts
on the relay can then turn ON and OFF much BIGGER devices such as Motors
and LightBulbs. Transistors are very handy in this type of project.

WHERE ARE TRANSISTORS USED?
Just about every device that uses electricity will have transistors in it. A
Cell Phone, a Radio, a Computer, Microwave Ovens, Kitchen Appliances,
even Toasters now have transistors in them.



The transistor above, uses 6 VOLTS to turn on and off 1,500 VOLTS
to the HORIZONTAL circuits on the TV! That is a LOT of work for one
little Transistor. The transistor is BOLTED to a HEAT SINK, a piece of
metal with fins on it to remove the heat. This TV was over- heated, and the
heat sink was too small to take away the heat, so the transistor failed. When
I fixed it, I put in a bigger heat sink. Shown in a red square, is a 7 PIN 
Voltage Regulator Chip with another little heatsink. When the 1500 Volt
transistor shorted, it sent 1500 volts into the 6 volt pin on the Regulator,
blowing it up as well, and this had to be replaced.



When a computer POWER SUPPLY clogs up with dust and dirt, the
aluminum heat sinks no longer take away heat from the transistors, and
they start to fail. Usually on a power supply like this, the OUTPUT
 transistors fail, and OUTPUT CAPACITORS overheat and dry out
and BOIL, cracking their aluminum can covers. The high voltage, 300
to 400 volt INPUT capacitors and transistors rarely ever fail.



The Portable Home Phone ABOVE was thrown out in the rain, in the
recycling. I knew immediately what was wrong with it- just like TV ,
VCR, DVD, STEREO, and most Remote Controls, the rubber buttons
on the keypad absorb oil and moisture, which gets on the green circuit
board under the keys, and shorts out the buttons. Once I cleaned the
buttons, the unit worked perfectly. Most people do not know that you
can take apart the Remote Control or Device with the keypad, and wash
the rubber keypad and the green circuitboard, in the sink with hot water
and soap, and once thoroughly dried with a hair dryer, the unit is like new.
This phone has a multilayer green board though, so it is easier to clean
the key area with a damp cloth, so that it dries easily-- the rubber keys
were washed in the sink with hot water. The Portable phone has
Transistors in BLUE, and LED lights in RED, as well as switches,
capacitors, diodes, transformers, etc. all of which can be used for a
ROBOT Project, and are FREE...



The Computer MOTHERBOARD, above, had the HEATSINK on the
Computer "CPU" (INTEL PENTIUM) clog solid with dust and dirt, so
that it overheated, using too much power. The heat and the huge amount
of power, heated up the CAPACITORS ( shown in BLUE ) until they
boiled the "electrolyte" insulating fluid inside the aluminum cans, splitting
the tops open, and foaming liquid out the tops. You can see the dust on
the sides of capacitors, blown out from where the CPU and heatsink would
be located, on the black plastic frame. This also over- stressed the power
supply, and boiled capacitors on it as well. In many cases, the motherboard
could be repaired by just replacing the cracked capacitors, but almost no
one bothers to do the repairs- it costs more in Technician TIME to replace
the parts, than the cost of a new motherboard. The power TRANSISTORS
are seen all around the CPU, as shown in ORANGE.  



The DVD PLAYER, above, was thrown out in the rain in a pile of
garbage. There is nothing wrong with it at all, except that it is NOT a
BLUE RAY player, and like tens of millions of DVD players around
the world, it is just thrown out. It has a great little 110 Volt to +5 Volt
power supply, and lots of resistors, capacitors, diodes, and transistors,
as well as motors and mechanical parts. I could use this just for ROBOT 
Parts, or, take out all the circuits that I don't need, and use it as a BASE
 to put a circuit board on top of for an INTERFACE. That way, it already
has a 110 Volt power supply for the +5 Volt interface, and it has lots of
spare diodes, LED lights, capacitors, resistors, motors, gears, etc. to build
the interface and a ROBOT with! This DVD player is PERFECT for kids
to use for PARTS for homemade robots and interfaces, and its FREE.



Just like the DVD player thrown out in the rain in the garbage, this VHS 
Video Cassette Recorder ( VCR) was thrown out. Again, there is nothing
wrong with it except that it is NOT a Blue Ray Player, so it is thrown out,
like millions of others around the world. It has Transistors, Diodes, Resistors,
Capacitors, Motors, Gears, LED lights, and a wonderful 110 Volt power
supply that includes +5 volts, and +9 Volts to run the motors. ALL FREE !



The DVD Automotive, 7 inch TV Player, above, has dozens of transistors,
large and small. This unit was thrown out since the DVD DISC laser reader
no longer worked, but the TV Flat Panel is fine, and has Input jacks for
games and other VCR's, DVD's and Cable, etc.



Above is a Dollar Store FM radio, showing the FM Digital Chip, and
on the back of the circuitboard are two large transistors identical to the
ones I use on the computer interface. This ONE dollar radio has a
volume control, FM chip, transistors, diodes, capacitors, LED light,
earphones, plug in jack, packaging, plastic case parts and buttons, etc.
that would cost me $45 to buy separately in Canada.!!


TRANSISTORS USED IN THIS PROJECT


The picture above, has the most common SIZES of transistors. For
our project, we will probably only use the SECOND SMALLEST. The
smallest "SMT" or Surface Mount Technology, is perfectly good, but
just too small for most people to handle very well. I use these often, but
I have been using soldering tools for a long time, and have found ways to
use them easily. The common type shown with the orange arrow is
inexpensive, reliable, and easy to work with.

THERE ARE TWO KINDS OF TRANSISTORS that we will work
with, and they appear identical, but have REVERSE NEGATIVE and
POSITIVE atoms in the SILICON. One turns on electricity when you
make the CENTER lead POSITIVE, the other kind turns on electricity
when you make the CENTER LEAD NEGATIVE.


APPROPRIATELY, these two types are called NPN and PNP. The N 
is for NEGATIVE, and the P is for POSITIVE. This refers to the ATOMS
used to make the Silicon CONDUCTIVE, the same way I used ARSENIC
and BORON compound's Atoms to make my Silicon disks Positive and
Negative to Conduct electricity when hit by light particles (PHOTONS).
The NPN is used more often since it conducts electricity better. Most sizes
of transistor have what is know as a COMPLIMENTARY PAIR - almost
identical transistors with the exact OPPOSITE electrical values. This is very
handy for projects, since a COMPUTER OUTPUT can be made to either
turn ON electricity with a "ONE" or + 5 VOLTS, using an P N, or the
COMPUTER OUTPUT with + 5 VOLTS can turn OFF electricity by
using a N P. ( Note that +5 Volts is NOT Negative, so the transistor turns
OFF ! PNP only turns on when it gets a NEGATIVE signal on the Center or
Control input.) In my robot projects, I only use transistors to turn either ON
or OFF, just like the COMPUTER either puts out a +5 " ON " or a Zero
Volt " OFF". This is just using the transistors as DIGITAL  SWITCHES.
+5 Volts and ZERO Volts = ON and OFF = Digital Values 1 and 0.

As I have pointed out earlier, there are thousands of different LED lights,
thousands of different RELAYS, thousands of different PARALLEL port
wirings, and there are thousands of different TRANSISTORS. However...
I have found by experiment, that you can use electronic parts with HUGE 
DIFFERENCES and still "get away with" all the many different parts. For
Example, Radio Shack in Canada was dropping all the electronic parts,
one by one, over 6 months to a year, just as I was designing my first
simple, cheap, interface, so every time I went back to whatever store
was near me, I had fewer and fewer parts to choose from (They did
NOT "publicly" state that they were changing their product line)... Even
with horrible, incorrect transistors, and diodes and resistors, I could still
build electrical circuits that actually WORKED. This is because the parts
I was using were much stronger and better than the job I was using them
for- example - the 2N2222 Transistor can easily handle 40 VOLTS,
but I was just using it to control small amounts of +5 Volts, so that even
with the wrong resistors, the transistor still worked just fine. When I look
on the WEB for parallel Port interfaces, I can find hundreds of different
designs, using hundreds of different chips and transistors and parts. Some
diagrams use the same CHIPS, but have different resistors and diodes,
etc. so again, there can be fairly big differences in the VALUES of
parts, and they still work. An engineer can sit down with a SINGLE,
SPECIFIC, Transistor, in a SPECIFIC circuit, and calculate EXACTLY
the correct value of the Resistors and Diodes and Capacitors etc. to use.
This is RARELY ever done, since there are "COMMON " values of
resistors that are available on the store shelves, around the world, so that
getting an EXACT Resistor would mean making a SPECIAL ORDER
 from the FACTORY, and waiting until they manufactured it and shipped
it to you! When I look at electronic circuit boards, I can almost instantly
tell 1970's Hewlett Packard electronics, because every single Resistor is
a special, High Quality, Custom Ordered, Extra Precision, Flameproof
(blue) resistor. HP Scientific Equipment gained a reputation in Hospitals
and Laboratories around the world for having Incredible accuracy and
Quality. Most common household Electronics like TV's, Radio's,
Microwaves, CD  and DVD Players, etc. will all have "Standard" value,
common resistors (brown), that you can find easily, in any electronic store.
These VALUES of the resistors are NOT CORRECT- they are just
"CLOSE" enough to work "OK".
SO, ... none of the values of any of the parts that I am using are absolutely
"correct" -- they are just "close enough" to work. If you CANNOT FIND
the EXACT same parts and values, you can often substitute or replace the
part with something "CLOSE", and it will still work! (NOTE THAT THERE
 ARE A FEW GUIDELINES IN WHAT TO SUBSTITUTE- I will go
over these later) I have deliberately used horrible Transistors, Resistors,
Diodes, etc. and the circuits still worked "OK" -- However, if the values
are TOO far out, the transistors can slowly be destroyed over time, and
eventually the circuit will fail ( I have had that happen over a year or two ).

The transistors I use are COMPLIMENTARY PAIRS, or very "close"
values for this type of project. The first set is the popular 2N2222 NPN
which has limiting voltages of about 6 volts for the CONTROL wire and
40 volts for the OUTPUT. Its COMPLIMENT is commonly the
2N2907 PNP, which has limits of 5 volts for the CONTROL wire, and
80 Volts on the OUTPUT. Since I am using only TINY amounts of 5
Volts IN and 5 volts OUT, both are much more powerful than needed.
The second set of Transistors is a COMPLIMENTARY PAIR of the
2N3904 NPN (6 volt control and 40 Volt output) and the 2N3906 PNP
 ( 5 volt CONTROL and 40 volt output). There are THOUSANDS
 of other similar transistors that all will work! I am trying to choose the l
east expensive and the easiest to find. Unfortunately, over the years,
there are different NUMBERS on the SAME electronic parts, so you
may have to look for the "NEW" numbers that are most often used -The
2N2222 and 2N2907 are often called NTE123 and NTE159, and the
2N3904 and 2N3906 are, interestingly, the SAME NUMBERS,
NTE 123 and NTE 159, which shows how "different" parts can
do the same job if they are "CLOSE".

The 2N2222 is also called RCA148996, MPS2222A, TDE SK3854,
ECG123AP, RadioShack 276-2009, Jameco 28628 and NTE123
as well as many other numbers.

The 2N2907 is also called RCA14290, MPS2907, TDE SK3466,
ECG159, RadioShack 276-2023, Jameco 28644, and  NTE159
as well as many other numbers.

There are many hundreds of Transistor numbers that are "close" to these
transistors as well, and I will research and list some of them, so that you
can use them if you need substitutes, or if you FIND transistors in a VCR (
 Tape Cassette Video Player), or DVD, or CD, or Radio/Cassette player
etc. that has been discarded or given away. ( FREE)

NOTE:
If you put an electrical meter on a TRANSISTOR, of the common,
ordinary, type, you will get electricity flowing as though two DIODES
are connected together- so that electricity flows in
in only ONE direction, from two pins, to a common pin. This is one
way of checking to see if a transistor is blown up or working.
( there are hundreds of different KINDS of diodes, and
more hundreds of kinds of TRANSISTORS, so this method only works
on the most ordinaryvarieties. However, the most ordinary variety is likely
to be found over 90% of the time! ) Long before there were
TRANSISTORS, there were SOLID STATE DIODES, or 'VALVES"
that only allowed electricity to flow in ONE direction. SOLID STATE 
computers using Diodes and Resistors as well as valves, were built, but
most of the documentation was lost when American Corporations took
over the German factories. Most "history" of early computers thus reflects
an almost entirely "Vaccuum Tube Valve" British/American era, instead
of the superior technology used in Germany, in the same era. If you look
at the diagram of the transistor and the diode, below, you can see that the
DIODE is just ordinary silicon with TWO large areas of
Negative and Positive, and the electricity just flows in ONE direction.
If you put an electrical meter on a common SILICON diode, you will
get electricity flowing in one direction, but none in the other direction.
If your electrical meter has a DIODE test setting, you will see 0.5 to 0.6
volts travelling across the DIODE, in one direction -- this is the typical
amount of electricity needed to "PUSH" across the boundary between
the Positive area to the Negative area, and therefore, if you put a diode
on a typical power supply of (4) four 1.5 Volt "AA" batteries,
( 1.5 x 4 = 6 ), you will see a DROP of voltage from the original 6 Volts,
to 5.5 volts ! -- The diode " USES  UP " about a half a volt, just to
" TURN ON".


In the photograph below, are typical diodes. The small glass diodes are
usually FAST, Switching type diodes or SIGNAL diodes, that either
work very fast with lower voltages, or are ZENER diodes that deliberately
breakdown or FAIL, at known voltages- they are used to break down,
at 5.0 volts, for example, and are put across a chip that can only use 5.0 volts
such as typical TTL chips, so that any voltage OVER 5.0 Volts breaks down
the diode N/P layer, and is drained off to ground, to protect the chip.
The black diodes are usually just standard, silicon diodes, that have a higher
power rating ( Amps or Amperage is the power rating ), with the smaller ones
capable of allowing 0.3 to 0.5 AMPS, while the bigger ones carry 1.0 Amps or
more.

The BLACK BAR on the red diodes, and the SILVER BAND
 on the end of the Black Diodes, is the NEGATIVE end - when using
a diode, put the black bar end pointing towards the NEGATIVE or
ZERO volts, or GROUND, and the electricity will travel through the
diode from any positive ( + 5 Volts ) supply, only to ground, but
the power cannot travel the other way.
Also note, in the DIODE photo above, I have put in an LED diode ( Light
Emitting Diode) and a transistor on the end !. People forget that the LED
light is also a diode, and can be used for many diode functions ! I see LED
diodes used - hidden inside a circuit board, where no one can see it, as a
diode that not only allows power to flow in ONE direction ( a VALVE),
but, at the same time, used to BURN OFF excessive voltage to protect
a circuit from getting too much electricity. Typically, in a Solar Powered
calculator, there is a standard LED, INSIDE the case. If the calculator is
in direct sunlight on a hot day, the sun will generate HUGE amounts of
electricity as the light particles (photons) hit the Solar Cell ( P and N layers of
Silicon), and this can destroy the calculator Computer chip! The LED is
put in the wiring, and if too much electricity is generated, the LED starts to
light up- " USING " the excess electricity, so that the chip is not overloaded!
Finally, there is an ordinary transistor on the end, and again, people forget that
this is somewhat like two diodes. I see many circuit boards, even today, with
one of the three pins cut off a transistor, and used as a DIODE in the circuit.
I first noticed this technique used on transistor radios from the early1960's,
when solid state components were difficult to find- an electronics manufacturer
could get the exact type of "DIODE" characteristics cheaper by using a transistor,
(which was manufactured by the thousands,) than by ordering a custom made,
special purpose diode from the factory...! If you have a project made from
electronics that you get free from VCRs, Radio's, CD's etc that are thrown out,
and are missing ONE diode, ( to finish) but have lots of transistors, you can use a
transistor instead, if it has the correct AMPERAGE rating for the job!!!
For example, the common 2N2222 transistor can handle 0.5 AMPS
( 500 Milli amps) up to 40 Volts, so that for typical robot projects,
the tiny IC ( Integrated Circuit chip CMOS ) Amperage and 5.0 Volts, that
are used, are easily "valved" by the 2222 !

(page 5 coming "eventually"... )

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