'30 in 1' Electronic Projects Lab Kit

(Order Code EPL030)

OPERATION       

CIRCUIT #2:  The Electronic Storage Tank

In the preceding section of the manual we told you that a capacitor stored 
and released electricity in a circuit.  Now you can see for yourself. After
you complete the wiring, touch the free end of the LONG WIRE to 21 and then
to 26.  Surprise! The LED lights up.  Do you know why?

To understand better, look at the diagram below.  We call this a SCHEMATIC,
and it is the kind of drawing professionals use to build circuits.  Don't
worry.....you can still use the wiring sequence.  The symbols used in the
schematic are the ones we pointed out in the MORE ABOUT THE CIRCUIT BOARD
section of this Manual.  If you didn't look at them then, it would be a
good idea to check them out now. 

If you follow the Schematic you will see that touching the wire to 21 
completes a path for electricity to flow from the - terminal of the 
Batteries to the Capacitor and then from the other side of the Capacitor to
the + terminal of the Batteries.  This lets the Capacitor "fill-up" with
electricity.  When you touch the wire to 26 you complete a path for the
Capacitor to release the electricity through the LED.  The LED lights just
long enough for the Capacitor to "empty" (which isn't very long in this
case).

As you go through all the circuits, you'll learn lots of information just 
like this and it's a good idea to keep this information in a Notebook.  By 
the time you finish this kit you may want to try designing some circuits 
of your own, and then your Notebook would have most of the things you'd 
need to know. 

Wiring Sequence  23-11-41, 10-27, 40-LONG WIRE (blue) 

CIRCUIT #3: The One-Way Street 

Do you remember what LED stands for?.....Light Emitting Diode.  And we told
you that a diode only lets electricity flow in one direction.  Here's
proof.

Complete the wiring, and then touch the two free ends of the LONG WIRES 
together.  The LED lights up.....right?  Now reverse the connections to the
Batteries (21 and 23), and touch the LONG WIRES again.  Nothing happens,
because the flow of electricity is going in the opposite direction and the
Diode won't let it through. 

In the Schematic you can see how the Diode must be connected for it to
light.  The + (positive) side of the Batteries goes to the arrow-head and 
the - (negative) side of the Batteries goes to the line.  This would be 
good information for your Notebook.  You are keeping one, aren't you? 

The 680 ohm Resistor in this circuit reduces the amount of electricity 
going to the LED (It can't take very much, or it will burn out). 

A practical use for this circuit is as a continuity tester.  It will allow 
you to see whether electricity is flowing through a particular circuit or 
component.  This kind of testing can help you find where the problems are 
if a circuit isn't working correctly. 

Wiring Sequence  21-10, 11-27, 26-LONG WIRE, 23-LONG WIRE 

CIRCUIT #4: The "Invisible Power" Radio 

In the wiring sequence for this circuit you will see a term we haven't
talked about yet...GROUND.  The schematic symbols is..."Ground" means that
you actually connect a wire to the earth.  One convenient way to do this
is to connect a wire to a metal, cold water pipe (water pipes run through
the ground).  First, use a cutter to divide the green wire into two pieces.
Then strip both ends of each wire by removing the plastic insulation from
the wire.  Connect the end of one wire to the pipe.  If you can't use a
water pipe, you can drive an iron stake into the ground and attach the wire
to that.  You can get the extra wire (also the metal ground rod) you will
need for this at your local electronics store. 

When the wiring is completed, put the EARPHONE in your ear and turn the 
TUNING Knob (variable capacitor) until you hear a radio station.  This is 
a very weak radio, and you will have to listen carefully. 

After you've listened to the radio for a while, take a look at the name of 
this circuit.  We are not using the Batteries, so where is the power coming
from?  Believe it or not, the power is coming from the invisible radio
waves that are moving through the air all the time.  The radio waves are
intercepted by the green wire in the coil of wire.  This stirring up causes
small pulses of electricity to flow out of the ANTENNA.  The variable
capacitor filters out the pulses of electricity from all but one frequency
of radio wave (one radio station), and that electricity is changed into
sound by the EARPHONE.

It is easy to understand why the sound is weak when you see that the power 
for the radio comes "out of the air". 

NOTE:  In a schematic if two wires cross like this + they are not
       connected, and if they cross like this + they are connected. 

Reception not very good?  OK try some experiments.  Try connecting the
Ground wire to terminal 6 instead of 7.  Or try connecting the Green
Antenna Wire to one of the other ANTENNA terminals.  Often just changing
connections like this can make a big difference in how good the Radio
works.  Better still, use an outdoor antenna (Tandy sells one just
for Short Wave Radios - it works well for circuits like this) - BUT BE
SURE YOU HAVE AT LEAST ONE ADULT HELP YOU INSTALL THE ANTENNA.  AND DON'T
GET NEAR POWER LINES.

Wiring Sequence  5-6, 4-8, 1-ANTENNA (green), 7-3-2-32-35-Earphone, 
                 9-33-34-EARPHONE, 7-GROUND 

CIRCUIT #5: The Transistor, An Electronic "Trigger" 

The small motion of pulling the trigger of a gun can release a large amount
of power.  The Transistor can work in much the same way, but before we
explain how that's done let's look at the three connections on the
Transistor (we mentioned that earlier, remember?).

    COLLECTOR 

    BASE 

    EMITTER 

The three connections are the BASE, EMITTER and COLLECTOR. 

Complete the wiring sequence, press the KEY, and the LED will light up.
This may not seem very impressive to you, but you will see how important
it is in the next circuit.  For now let's look at the Schematic and see
why the LED lights when you press the KEY.

There are actually two paths for electricity in this diagram.  One from
the emitter (E) to collector (C), and one from the emitter (E) to base
(B).  From now on we will call the emitter to collector path the OUTPUT,
and the emitter-to-base path the INPUT in all circuits using transistors.

The output circuit looks complete, but the LED doesn't light up until you
press the KEY and complete the input circuit, too.  The small amount of
electricity in the input circuit (one Battery), "triggers" the larger
amount of electricity in the output circuit (both Batteries), and the LED
lights up.

This is a simple circuit, but it is important that you understand it well,
because there is at least one transistor in all of the remaining circuits
in your kit.  It would be a good idea to turn back to this circuit
occasionally to remind yourself about the INPUT and OUTPUT of a transistor.
Or better still, just put the information in that Notebook you are keeping.

Wiring Sequence  10-26, 11-16, 15-43, 17-23, 21-27, 22-29, 28-42

CIRCUIT #6:  The Transistor and "Amplification" 

Complicated electronic circuits are almost always made up of two or more
simple circuits connected together.  This project combines a radio like
the one in CIRCUIT #4 with a one transistor amplifier.  Connect the GROUND
and ANTENNA just as you did before and tune in a station.  You should get
more sound from the EARPHONE this time.  While you're listening, let's
look at the Schematic, and see why the sound is louder.

In the "INVISIBLE POWER" RADIO the pulses of electricity stirred up by the
radio waves were turned into sound by the EARPHONE.  In this circuit those
same pulses of electricity are connected to the INPUT of the Transistor in
the circuit.  As the pulses turn the INPUT on and off they create a
"mirror image" controlled by the INPUT.  The pulses from the OUTPUT are
connected to the EARPHONE and are much stronger than the INPUT signal,
because the Batteries are connected to the OUTPUT of the transistor.
Getting a high power signal from a low power signal in this way is called
AMPLIFICATION.

Wiring Sequence  2-3-7-35-28-17-23, 4-8, 5-6, 9-29-36-34, 15-37-33,
                 16-20-EARPHONE, 32-21-18-EARPHONE, 1-ANTENNA, 2-GROUND

CIRCUIT #7: The Sunrise-Sunset Light

After the circuit is complete, hold the WIRE to 31 and watch the LED.  It
will slowly light up....like a sunrise.  When the LED reaches its brightest
point, remove the WIRE from 31 and the LED will dim and go off...like a
sunset.  If you touch the WIRE to 41 the LED will go off very quickly.  In
this circuit the Transistor is used as a switch.  It switches on slowly
because electricity can flow through the input of the Transistor to turn
on the output and the LED.  The 100K ohm Resistor reduces the amount of
electricity flowing in the input circuit and this makes the Capacitor
charge more slowly.  Touching 41 makes the Capacitor discharge very
quickly, because it makes a "short circuit" (a path with little or no
resistance) for the Capacitor to empty through.

What do you think will happen if you change the values of the Resistor or
Capacitor? Write down your guess, and then try changing the resistor to
10K or 470K ohms.  Next try the 10 microF capacitor in place of the 100
microF.

NOTE:  The 10microF and 100microF capacitors are a special type of
       capacitor called ELECTROLYTIC, and they have a + and a - connection.
       Be sure to keep the wiring the same when you switch them or they
       could be damaged.

Did you get the results you expected when you made the changes?  Don't
forget to make notes!

Wiring Sequence  21-10-30, 23-17-41, 11-26, 16-27, 15-40-WIRE

CIRCUIT #8: The Slow Motion Sunrise-Sunset Light

In this circuit the light from the LED comes on extremely slowly.  Complete
the wiring and hold the LONG WIRE to 33.  In about twenty to thirty seconds
the LED will begin to light up.  Remove the LONG WIRE and the LED will
slowly go off. (It may take five minutes or so).  As in the previous
circuit, the LED will go off quickly if you touch the LONG WIRE to 41.

This circuit works much like the previous one.  The LED comes on more
slowly because of the increased resistance in the input, and because both
transistors must be switched on before the LED (connected to the output)
can light up.

Wiring Sequence  21-10-28-32, 23-17-41, 11-26, 27-16, 29-13, 
                 12-40-WIRE, 14-15 

CIRCUIT #9: The "Secret Code" Key 

When all the connections have been made, press the KEY and you will hear a 
sound in the EARPHONE.  By following the MORSE CODE chart below you will be
able to send messages with a series of dots (short sounds) and dashes
(longer sounds).  Of course Morse Code isn't really a secret code.  It was
the first means of electronic communication....by telegraph and then
radio.  It is still used by radio operators all over the world.  You will
learn the code faster, and have more fun, if you practice sending messages
back and forth with a friend.

The type of circuit used here is called an OSCILLATOR.  The sound in the
EARPHONE is caused by pulses of electricity, just like it was in the radios
that you built.  The difference is that the pulses come from the circuit
turning itself on and off instead of from the radio waves.  The oscillator
turns on and off because of something called feedback.  You have heard
another example of feedback at concerts, when the loudspeakers start to
"squeal."  This happens when the speaker and microphone gets too close
together and the sound from the speaker "feeds back" into the microphone.
The same thing happens in the oscillator except the microphone is replaced
by the input of the transistor, and the speaker is replaced by the output. 
At a concert, feedback is annoying, but in an oscillator it is necessary
for the circuit to work at all.

Wiring Sequence  22-19, 23-43, 32-34-20-EARPHONE, 33-35-15, 
                 16-18-EARPHONE, 17-42 

CIRCUIT #10: The Highs and Lows of Oscillation 

When an oscillator turns itself on and off it is called OSCILLATION.  The
rate at which it turns itself on and off is called FREQUENCY.  The
frequency for an oscillator that produces a sound can be anywhere from 20
to 20,000 times a second!  In this circuit we give you a chance to see how
the frequency or tone of an oscillator can be changed. 

When you have completed the wiring sequence, touch the LONG WIRE from 19 to
either 30 or 32, and at the same time touch the LONG WIRE from 20 to either
34 or 36.  Now you should be hearing a sound in the EARPHONE.  Try as many
combinations of touching the LONG WIRES as you can find and see how many
different sounds you can get from the oscillator. 

From looking at the Schematic you can see that touching 30 connects the 
100K ohm resistor, and 32 connects the 470K ohm resistor.  34 connects the 
0.0022 microF capacitor and 36 the 0.022 microF capacitor. 

When you have found all the combinations, make a chart showing which 
connections made the highest and lowest sounds, and put the chart in your 
Notebook.  Then next time you will know in advance what is going to happen.

Wiring Sequence  22-19-LONG WIRE, 23-17, 33-31-37-35-15, 16-18-EARPHONE, 
                 LONG WIRE-20-EARPHONE 

CIRCUIT #11: The Beacon Light 

Have you ever noticed the flashing lights on the tops of tall buildings or
towers?  They flash on and off so low-flying planes won't hit them.  The
type of circuit you will build here is similar to the ones controlling
those very important lights.

After you have finished the wiring, the LED will begin to flash on and off 
slowly, like a beacon light.  Now look at the Schematic.  Does it look
familiar?  It should, because it is an oscillator very much like the last
two circuits you have built.  The difference is that it has a much lower
frequency than the others.  With what you learned in the last circuit, you
won't be surprised to see that this slow oscillator uses the largest
capacitor and the "strongest" resistor.

As you might suspect, changing the resistor or capacitor will alter the
frequency of this oscillator too, so go ahead and try it.

NOTE: Don't forget about the + and - connections on the electrolytic
      capacitors.

QUESTION:  Could the frequency become so fast that you wouldn't be able to 
           see the LED going on and off? 

Wiring Sequence  21-32-19, 23-17, 10-18, 11-16, 15-33-41, 40-20 

CIRCUIT #12: Music From A Pencil 

In this circuit we will again use an oscillator to produce sound, but you
will control the frequency in an unusual way.....with a pencil mark.  You
may even be able to play a song with this "electronic organ."

Complete the wiring and then draw a rectangle the full length of a piece of
notebook paper, and about two or three centimetres wide.  Fill in the
entire rectangle with heavy pencil marks (a very soft pencil will be best).
Next tape one of the LONG WIRES to one end of the pencil mark.  Touch the
other LONG WIRE to the middle of the pencil mark and listen to the
EARPHONE.  You should hear a sound now, and if you move the free wire up
and down the pencil mark the tone will get higher and lower.  With a little
practice you will be able to pick out your favourite song.

We have told you that the frequency of an oscillator can be controlled by
a resistor.  Well, in this circuit the pencil mark acts as a variable
resistor.  When the two wires are closer together the resistance is less
and the frequency and tone get higher.  When the two wires are farther
apart, the resistance is more and the frequency and tone get lower.

The "lead" in a pencil is a form of carbon, and the resistors in your kit
are made with carbon, too.

Wiring Sequence  22-19-EARPHONE, 22-LONG WIRE, 23-17, 30-LONG WIRE, 
                 16-18-EARPHONE, 15-31-37, 36-20 

CIRCUIT #13: The Leaky Faucet 

By now you should have no problem recognizing this circuit as an
oscillator, and this one works just like the others you have built.  But in
this circuit (in fact in the next three) we are going to have fun with
"sound effects."

When you finish the wiring you will begin to hear a slow clicking sound,
something like a dripping faucet.  Now let's see if you can put to work
those notes you've been taking.

1.  Can you think of a way to make the "dripping" get faster? 

2.  How about a way to make the "dripping" slower? 

See what you come up with and then check with the answers below. 

Wiring Sequence  22-32-19, 23-17, 16-18-EARPHONE, 15-39-33, 38-20-EARPHONE 

CIRCUIT #14: The Bee 

Do the wiring and then press the KEY and hold it.  You will hear a buzzing
sound through the EARPHONE.  Now release the KEY and see what happens.  The
sound fades away.  By experimenting with different rates of pressing and
releasing the KEY you will be able to get a sound very much like a bee (or
maybe the "giant bee" on the late movie). 

Of course this is an oscillator, but it has two capacitors (instead of one 
like all the others) so let's try something to see what the two capacitors
do in the circuit.  First replace the 10microF capacitor with the 100
microF and press the KEY.  You will hear the same sound you heard before,
but when you release the KEY the sound fades away more slowly.  This tells
us that the large capacitors store electricity while the KEY is pressed and
release it when you release the KEY.  Since the 100 microF capacitor is
much larger, it takes much longer for it to discharge, and the "bee" sound
fades away more slowly.

Now change the 0.0022 microF.  The tone will be higher, so we can assume
that these capacitors control the frequency of the oscillation.

We haven't mentioned the resistor in this circuit yet, but of course it
can change things too.  In fact, changing the resistance will change the
frequency of oscillation, and the rate of discharge of the large capacitor.
Don't take our word for it...try it yourself, and take notes!

Wiring Sequence  22-32-19, 23-42-39, 33-37-15, 16-18-EARPHONE, 
                 36-20-EARPHONE, 38-17-43 

CIRCUIT #15: The Electronic Canary 

You may be beginning to think that an oscillator is the only electronic 
circuit!  Well it isn't, but it can do so many different things, and make 
so many different sounds, we just had to show them to you.  The name of 
this circuit gives things away, but go ahead and get the wiring done and 
see what you think of our "canary."

After you play with this for a while, we hope you will put your notes to
work and see how you can alter this "bird call."  You may create a sound
more like a prehistoric flying reptile, or a "space bird."  HAVE FUN!!

Wiring Sequence  22-31-19, 23-42, 43-17-39, 26-30-15-37, 27-38, 
                 16-18-EARPHONE, 36-20-EARPHONE 

CIRCUIT #16: The Burglar Alarm 

This circuit is turned on by disconnecting a wire, instead of by connecting
one.  Any time the LONG WIRE between 15 and 17 is disconnected, the "alarm"
goes off.  Later on you may want to replace the LONG WIRE with magnetic
switches like the professionals use.  This type of switch is available at
your local Tandy store.  This same type of alarm circuit is used in
professional burglar alarms, except that it is connected to very loud bells
of buzzers, or a silent alarm that alerts the police, instead of an
EARPHONE.

The "trip wire" keeps the alarm from going off when it is connected because
it makes a "short circuit" around the base and emitter of the Transistor
(the input).  A short circuit is a path for electricity that has little or
no resistance, and electricity will always flow through the path with least
resistance.  When the electricity flows through the trip wire instead of
the oscillator input circuit (yes this is another oscillator), no sound is
produced, but when the trip wire is disconnected the electricity flows
through the oscillator input and the alarm sounds. 

Now see if you can catch who's been getting into your "private stuff." 

Wiring Sequence  22-19, 23-17-LONG WIRE (green)-15-35-32, 
                 33-34-20-EARPHONE, 16-18-EARPHONE 

CIRCUIT #17: The Touching Light 

Up until now, all of the circuits have used wire to carry or "conduct" 
electricity and make them work.  However, there are other things that 
conduct electricity, and you will discover one you probably haven't thought
of-in the TOUCHING LIGHT. 

When you complete the wiring sequence you will notice nothing is happening.
That's OK because the circuit isn't finished yet.  The final step is to
touch 24 and 26 with fingers of the same hand.  Surprise!  The LED lights
up, and YOU are the conductor for the electricity.  There is no reason for
you to worry about getting a shock from this or any of the circuits in this
kit, because the amount of electricity being used is very low. 

This circuit is a two-transistor amplifier.  The small amount of
electricity that flows through you completes the input and lets the power 
from the batteries flow in the output circuit and through the LED.  Before 
you go on to the next circuit, try touching 24 and 26 with fingers from 
different hands.  Does the LED still light?  Wetting your fingers will 
help make better contact with the terminals. 

Wiring Sequence  21-26-28, 23-31-14, 10-27, 11-13, 25-15, 
                 29-16, 30-12-17 

CIRCUIT #18: The Rain Detector

This circuit shows you another thing that conducts electricity......water. 
This shouldn't be too much of a surprise, since your body conducts
electricity and it is mostly water.

When the wiring is complete, put the free ends of the two LONG WIRES in a
glass of water.  Hold them as close together as you can without letting
them touch (you may find it easier to tape the wires to a pencil or
"Popsicle stick" and then put them in the water).  The water will conduct
the electricity and you will hear a sound in the EARPHONE.  This "alarm"
will go off any time there is enough water present to connect the two
wires.

This type of circuit could be used to tell you if the water level in a bath
tub or aquarium is getting too high.  And if it was connected to other
specialized devices, it could even turn the water on and off.

To use this as a rain detector, you will need to get extra wire from RADIO
SHACK, and run two wires outside.  Tape them close together on a board or
piece of plastic, so that just a few drops of rain will complete the
circuit and set the alarm off.

If this circuit looks familiar, you're right again!  It is another
oscillator.  The difference is that it is designed to use water as a
conductor to complete the circuit. 

Wiring Sequence  21-26, 23-17, 27-28-19, 29-LONG WIRE, 16-18-EARPHONE, 
                 15-37-LONG WIRE, 36-20-EARPHONE 

CIRCUIT #19: The Radio Station 

If you ever wanted to be a radio announcer or "DJ," here's your chance.
After you finish the wiring, you will need an AM radio to receive your
"broadcast."  The radio should be about one foot away from the RADIO
STATION, to begin with, and should be tuned to a place on the dial where
there is no other station.

Now adjust the TUNING KNOB on the RADIO STATION, while speaking into the
EARPHONE, until you hear your voice on the radio.  Once you have your
broadcast tuned in, you can experiment to see how far away your signal can
be received.  The FCC (Federal Communication Commission) doesn't allow the
operation of strong radio stations without a license, so don't be
disappointed if the signal carries only a few feet.

A radio station like the one you have built is a combination amplifier- 
oscillator.  The oscillator produces a high frequency radio wave that is 
sent out into the air by the ANTENNA COIL.  The frequency of the
oscillation is set to match the setting on the radio dial by the TUNING
KNOB (Remember, the TUNING KNOB is a variable capacitor.) 

The strength or "amplitude" of the radio waves is controlled by the 
amplifier, and the amplifier is controlled by the small amount of
electricity produced by the EARPHONE when you talk into it.  In this way, 
the input from the EARPHONE (your voice) controls the amplitude of the 
radio waves.  The AM radio is able to turn these changes in the strength 
or "amplitude" into the sound that comes out the radio's speaker.  Amazing,
isn't it!  While we're talking about it, have you ever wondered what "AM"
stands for?  It stands for amplitude modulation (modulation is another word
for change).

Wiring Sequence  22-4-30, 23-17-EARPHONE, 5-6-26, 27-16, 
                 33-EARPHONE, 15-32-31-34, 3-7-35 

CIRCUIT #20: The "Wireless" Rain Detector 

This circuit is another example of combining two simple circuits to make a 
more advanced one.  Here we have combined the RAIN DETECTOR and the RADIO 
STATION.  Although the two sections of this project are not exactly like 
the previous circuits, they work in the same way.  We had to make some
small changes so the two parts would "get along" better.  You will put the
two LONG WIRES in water, as you did before, but this time you will use the
AM radio to receive the "alarm" signal.  Don't forget, you have to adjust
the TUNING KNOB until you can hear the signal coming from the WIRELESS
RAIN DETECTOR.

In the schematic you will see that the output that went to the EARPHONE in 
the other rain "detector is now going to the RADIO STATION or "transmitter"
section of the circuit.  The TUNING KNOB adjusts the transmitter's
frequency to match the setting on the radio dial.  And the ANTENNA COIL 
sends the signal out into the air where the AM radio picks it up and turns 
the radio wave signal into sound. 

This rain detector can be used in the same ways as the other one, except 
you will have the convenience of hearing the alarm over the radio instead 
of through the EARPHONE. 

Wiring Sequence  22-26, 23-14-17, 5-6-36, 4-31-29-27-19, 
                 3-7-16, 28-15-37, 30-LONG WIRE, 
                 12-35-LONG WIRE, 13-18, 34-20 

CIRCUIT #21: The Metal Detector 

Perhaps you have seen people at a beach or park searching for "buried 
treasure" with their metal detectors, and you've wondered how an electronic
device can "see" the metal.  Well, here's one way.

When the circuit is complete, you will again need an AM radio to act as the
"voice" of the circuit, but this time the radio will be turned in a
different way.  Set the dial to a station that is weak and does not come
in very clearly.  Then adjust the TUNING KNOB until the radio station is
blocked out by a "squeal."  Next, fine-tune the TUNING KNOB until you get
the lowest tone "squeal" you can.  Now you're ready to test the METAL
DETECTOR.

Take a piece of metal (try a coin and touch it to the end of the ANTENNA 
COIL core.  The squeal tone will go away to indicate the presence of
metal.

This circuit is a radio wave transmitter similar to the others you built,
but in this circuit the signal from the transmitter is used to interfere
with or block out another weak radio signal.  When metal is touched to the
core of the ANTENNA COIL the frequency of the blocking signal is changed
enough to stop its interference with the weak radio station, and that is
your signal that metal is present.

Wiring Sequence  22-26, 23-17, 5-6-36, 3-7-16, 4-27-30, 31-37-15 

CIRCUIT #22: Blowing "ON" A Candle 

On your birthday you make a wish and blow out the candles.  Well, in this
circuit you can blow "on" the LED (we were just kidding about blowing "on"
a candle).  We are using the EARPHONE as a microphone, again.  Once you
complete the wiring, blow into the EARPHONE and the LED will light up as
long as you keep blowing.  You can also get the LED to light by yelling
into the EARPHONE, but the blowing seems easier (and your parents will
appreciate that it is quieter).

This circuit is a two-transistor amplifier that uses the electricity
created by the air hitting the EARPHONE as an input to turn on the output
and the LED.  Your friends will be amazed, but it isn't magic, it's
ELECTRONICS!

Wiring Sequence  21-10-28-32, 23-30-17, 11-26, 27-16,29-13, 
                 33-31-12-EARPHONE, 14-15-EARPHONE 

CIRCUIT #23: The Blinker 

A circuit like this one might be controlling the blinker in your parent's
car.  Since it turns on and off you might guess that it is an oscillator
....and you'd be right.  It's a type of oscillator called an astable
multivibrator.  It is designed so that when one transistor is on the other
is off, and they continually switch back and forth or vibrate, from "on"
to "off."

Just like the none transistor oscillator, the frequency of the multi-
vibrator is controlled by the combination of resistors and capacitors. 
Since there is such a big difference in size between the capacitors used 
here and the other two capacitors in the kit, it would not be practical to 
use them here.  But you can replace the 100K ohm resistor with the 470K 
ohm resistor and see what happens.  You probably already know, but try it 
anyhow. 

Finally, do you know which transistor is on when the LED is on?  You should
be able to tell from the schematic.  It's the right one.....of course!

Wiring Sequence  21-26-24-28-30, 23-14--17-11, 27-38-13-10, 
                 25-40-16, 29-41-12, 31-39-15 

CIRCUIT #24: The Two-Transistor Oscillator 

From the wiring sequence and the Schematic, you can see that this circuit 
is almost exactly like the BLINKER.  The difference is that we have changed
the frequency of the oscillation (with capacitors....just like you did in
the one-transistor oscillators), and we also changed the form of the output
from lighting the LED to making a sound in the EARPHONE. 

Right now you may be asking why we told you it wouldn't be practical to use
the smaller capacitors in the last circuit, and then we used them here. 
The reason is that the frequency is so fast that you wouldn't have been
able to see the LED going on and off.  It would have looked like the LED
was on all the time, but the EARPHONE can use this high frequency to
produce sound that you can hear.

As in the BLINKER you can change the frequency by replacing the 100K ohm 
resistor. 

Wiring Sequence  21-26-24-28-30,23-14-17-EARPHONE, 27-34-13-EARPHONE, 
                 25-36-16, 29-37-12, 31-35-15 

CIRCUIT #25: The Timer 

This circuit is also a multivibrator, but it is a special kind called a
one-shot multivibrator.  When you finish wiring you finish wiring you'll
see why it is called that.  Press the KEY and releases it immediately.
The LED will light and stay on for a few seconds and then go off.  It will
stay on for the same amount of time every time you press the KEY, even if
you hold the KEY down longer sometimes.  The time the LED stays on is
controlled by the 100microF capacitor, so you could change the time by
changing the capacitor - or the resistor that controls its discharge
(the 100K ohm).  The name "one-shot" comes from the fact that the LED only
comes on once for each time the input is connected by pressing the KEY.

Wiring Sequence  21-10-24-30, 23-14-17-42, 11-26, 28-12, 
                 29-25-16, 31-41-15, 13-27-40-43 

CIRCUIT #26: The Memory

This type of circuit is used in computers, because it has the ability to 
remember to stay on even after the original input has been removed.  When 
you finish wiring, we'll show you what we mean. 

Touch the LONG WIRE to 15 and the LED will light up.  Now remove the wire
from 15 and the LED stays on.  It remembers the "order" you gave it to be
"on."  Next touch the LONG WIRE to 12 and the LED goes off.  It will
remember to stay off until you tell it to be on again by touching 15.  In
a computer this kind of circuit could be set to remember the number 3 or
the letter A, or just about anything.

Another name for this circuit is the bistable switch or "flip-flop."  It
works the way it does because of the way the two transistors are connected.
The explanation may seem a little confusing at first, but follow it
carefully and you'll see that all the components are working just like
we've shown you in other circuits.

Before you touch the LONG WIRE to 15 or 12, the left transistor is on, but
when you touch 15 you make a short circuit around the input of that
transistor and turn it off.  When that happens, the electricity that was
going through the left output begins to flow through the 10K ohm resistor
and to the input of the right transistor.  This turns on the right
transistor's output and, of course, the LED.  The LED stays on when the
LONG WIRE is removed from 15, because the electricity that was flowing to
the base of the left transistor through the 100K ohm resistor will continue
to go through the output of the right transistor; it is following the path
with least resistance.  Electricity always does that.  When the LONG WIRE
is touched to 12, the input to the right transistor is short-circuited and
the output on the right is turned off.  This allows the flow of electricity
to return as it was before you did anything with the circuit.

Wiring Sequence  21-10-24, 23-14-17-LONG Wire, 11-26, 
                 28-12, 30-15, 29-25-16, 31-27-13 

CIRCUIT #27: The "AND" Gate 

The AND gate is another type of circuit that is used in computers (and in 
your calculator, too).  In fact all the remaining circuits are used in 
computers - but there are other uses too. 

When you finish wiring, touch the LONG WIRE from 25 to 31.  Nothing
happens.  Now remove that wire and touch the LONG WIRE from 29 to 33. 
Again nothing happens, but if you touch both wires at the same time the 
LED will light.  It's like having two wall switches in your room and having
to turn them both on before the light comes on.  Computers use these
circuits to add things together.  By using many of these circuits, the
computer can add many things together. 

Besides in a computer, can you think of a use for this circuit?  How about
....for telling an astronaut whether both hatches of the spaceship's
airlock are closed?  There are many more uses and we're sure you'll think
of some of them. 

The AND gate works as it does because both transistors have to be on before
there is a complete path for the electricity to flow through, the LED. 
Look at the Schematic and trace the output circuit's path.

When transistors are connected in this way the outputs are said to be in
"series."

Wiring Sequence  21-10-24-28, 23-17-30-32, 11-26, 27-13-, 
                 25-LONG WIRE, 12-33, 14-16, 15-31 

CIRCUIT #28: The "OR" Gate 

The OR gate is a computer circuit.  Another name for the types of circuits
used in computers is "logic" or "digital" circuits.  Complete the wiring
sequence and touch the LONG WIRE from 25 to 31.  The LED should light.  Now
remove that connection and touch the LONG WIRE from 29 to 33.  Again, the
LED should light.  Instead of needing both transistors to be on before the
LED lights, like the AND gate.  This circuit works if either one transistor
OR the other is on.  This is like having two wall switches in your room and
either one of them will turn on the light.

This circuit works as it does because touching either one of the LONG WIRES
turns on a transistor, and there is a complete path for the electricity to
flow through the LED if either transistor is on.  Again, trace the path of
the electricity on the Schematic and you will see a path through either
transistor output.  When transistors are connected this way the outputs are
said to be in "parallel."

Wiring Sequence  21-10-24-28, 23-14-17-30-32, 11-26, 27-16-13, 
                 25-LONG WIRE, 29-LONG WIRE, 12-31,15-33 

CIRCUIT #29: The "NAND" Gate

As you might suspect the NAND gate is the opposite of the AND gate (not 
AND).  In this circuit you must connect both LONG WIRES (25 to 31 and 29 
to 33) to turn the LED (the output) off.  One use for a NAND gate, besides 
in a computer, might be for the door buzzer in your parent's car.  They 
have to close both doors (two inputs) to turn off the buzzer (the output). 

In the Schematic you will see that when both connections are made, both 
transistors are on, and that makes a short circuit around the LED, through 
the output circuits of the transistors.  The LED then has to go off. 

Wiring Sequence  21-26-24-28, 23-11-17-30-32, 10-27-13, 
                 25-LONG WIRE 29-LONG WIRE, 12-33, 14-16, 15-31 

CIRCUIT #30: The "NOR" Gate 

The NOR gate is another "logic" circuit and is the opposite of the OR gate 
(Not OR).  Here, connecting either one input OR the other (25 to 30 or 29 
to 32) will turn off the LED (output). 

By following the paths of electricity in the Schematic you will see that 
connecting either input (and turning on that transistor) will make a short 
circuit around the LED through the output of that transistor.  This
probably seems very simple to you by now.  If it does....GOOD....if not, 
then it will with a little more practice with electronics and schematics. 
Just remember that once you know how each component of the circuit works, 
you can figure out how and why the circuit does whatever it does. 

Wiring Sequence   21-26-24-28, 23-11-14-17-31-33, 10-13-16-27, 
                  25-LONG WIRE, 29-LONG WIRE, 12-32,15-30 

WHAT NEXT? 

Now that you have built all the circuits in this kit, there are several
different things you can do next.  You may want to build them all again,
or maybe just the ones you thought were really "special."  If there were
some circuits you would like to make permanent models of, you can buy the
extra parts (resistors, capacitors, LED's, etc.) that you need at your
local Tandy store.

If you want to learn more about electronics in kit form before you strike
out on your own, Quasar Electronics has an extensive range of project
kits for all interests and abilities. Also, there are many good books
about electronics at your school or public library.  Whether you plan to
continue electronics as a hobby or make it a career, we hope you HAVE FUN! 

By the way, here is the Schematic for the first circuit you built (the
Siren).  When you built it we bet it seemed pretty complicated, but now,
with a little experimenting you can probably figure it out in no time.

Wiring Sequence  23-17-39, 24-14, 25-28, 29-37-15, 32-22-13-19 
                 33-43, 12-42-38, 16-18-EARPHONE, 36-20-EARPHONE 

ORDERING

To order the 30 in 1 Electronics Lab pleaseclick here

See also it's bigger brothers:

130 in 1 (Order Code EPL130)

200 in 1 (Order Code EPL200)

300 in 1 (Order Code EPL300)

500 in 1 (Order Code EPL500)