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LIE DETECTOR

This circuit detects the
resistance between your
fingers to turn the 4 LEDs.
As you press harder, more LEDs
are illuminated.

 

A GOOD SPY BUG RAIDEO CIRCUIT

This circuit uses a TUNED CIRCUIT or TANK CIRCUIT to create the

operating frequency. For best performance the circuit should be built on

a PC board with all components fitted close to each other. The photo

below shows the components on a PC board:

INCREASING THE RANGE OF FM BUG

To increase the range, the output must be increased. This can be done by using

an RF transistor and adding an inductor. This effectively converts more of the

current taken by the circuit (from the battery) into RF output. The output is

classified as an untuned circuit. A BC547 transistor is not suitable in this location

as it does not amplify successfully at 100MHz. It is best to use an RF transistor

such as 2N3563.

SIMPLEST HIDEN FM BUG

SIMPLEST HIDEN FM BUG

This circuit is the simplest FM circuit you can get. It has no microphone

but the coil is so MICROPHONIC that it will pick up noises in the room

via vibrations on a table.

The circuit does not have any section that determines the frequency. In the next circuit and all those that follow, the section that determines the frequency of operation is called the TUNED CIRCUIT or TANK

CIRCUIT and consists of a coil and capacitor. This circuit does not have

 this feature. The transistor turns on via the 47k and this puts a pulse

through the 15 turn winding. The magnetic flux from this winding passes

through the 6 turn winding and into the base of the transistor via the 22n

capacitor. This pulse is amplified by the transistor and the circuit is kept

active.

The frequency is determined by the 6 turn coil. By moving the turns

together, the frequency will decrease. The circuit transmits at 90MHz. It

has a very poor range and consumes 16mA. The coil is wound on a

3mm drill and uses 0.5mm wire.

Endless Energy

Energy comes in different forms. Light is a form of energy. So is heat. So is electricity. Often, one form of energy can be turned into another. This fact is very important because it explains how we get electricity, which we use in so many ways. Electricity is used to light streets and buildings, to run computers and TVs, and to run many other machines and appliances at home, at school, and at work. One way to get electricity is to burn a fuel like oil or coal. This makes heat. The heat then makes water boil and turn into steam. The steam runs a machine called a turbine that produces electricity. Often, this electricity then goes into a public power system that sends it out, through wires, to homes, schools, and businesses over a wide area. This method for making electricity is popular. But it has some problems. Our planet has only a limited supply of oil and coal. They are not renewable fuels. Once they areused, they are gone forever. Also, they give off gases when they are burned. These gases may make the air dirty, or polluted, and some of them may change Earth’s climate.

Free and Clean Energy

Another way to make electricity uses sunlight. Sunshine is free and never gets used up. Also, there is a lot of it. The sunlight that hits the Earth in an hour has more energy than the people of the world use in a year.

A little device called a solar cell can make electricity right from sunlight (“solar” means having to do with the Sun). A solar cell doesn’t give off any gases. It doesn’t even make any noise. A solar panel is a group of solar cells that work together.

The use of solar cells is growing fast in the United States and many other countries

Electronic Components

Basic Components

Resistors

Capacitors

Inductors

Diodes

1.Resistors

Values specified in ohms (Ω), kiloM  arked with value using a color code-ohs (K), or mega-ohms (M) 

             2.Capacitors

Values specified in microfarads (μF) or picofarads (pF)  Marked with actual value or a numeric code

Some varieties are +/- polarized

3.Inductors

Values specified in henries (H), millihenries (mH) and microhenries (μH)

A coil of wire that may be wound on a core of air or other non-magnetic material, or on a magnetic core such as iron powder or ferrite.

Two coils magnetically coupled form a transformer.

4.Diode types

May be classified by semiconductor material

  silicon, germanium, gallium arsenide, etc.

Or classified by circuit function

DIGITAL LOGIC GATES

Introduction

1.     Basic Logic Gates

2.     Truth Tables

3.     Logical Functions

·         Truth Tables

·         Logical Expression

·         Graphical Form

Most Difficult Reading Topics

• Logic gates and figuring out how to readthem

• Logical Circuit Equivalence

• NAND NOR and XOR truth tables

• Using the rules to create and read thelogic gates using 0's and 1's

• Transistor implementation

• Difference between positive logic and negative logic

Logic

• Formal logic is a branch of mathematics that deals with true and false values instead of numbers.

• In the mid-19th century, George Bool developed many Logic ideas.

• Boolean logic deals with equations where the operators are “AND” or “OR” instead of “add” and “multiply”.

Electric Logic

• Logical values can easily be expressed by an electrical circuit.

• “True” or “1” can be defined as voltage on a wire while “False” or “0” can be defined as no voltage. We will use positive logic.

• Analog values can be anything while digital only has discrete values, 0 or 1

• Electrical devices called “gates” can implement the logical

THE 555 PINS

When drawing a circuit diagram, always draw the 555 as a building block, as shown below with the pins
in the following locations. This will help you instantly recognise the function of each

Pin 1 GROUND. Connects to the 0v rail.

Pin 2 TRIGGER. Detects 1/3 of rail voltage to make output HIGH. Pin 2 has control over pin 6. If pin 2
is LOW, and pin 6 LOW, output goes and stays HIGH. If pin 6 HIGH, and pin 2 goes LOW, output goes
LOW while pin 2 LOW. This pin has a very high impedance (about 10M) and will trigger with about 1uA.

Pin 3 OUTPUT. (Pins 3 and 7 are "in phase.") Goes HIGH (about 2v less than rail) and LOW (about
0.5v less than 0v) and will deliver up to 200mA.

Pin 4 RESET. Internally connected HIGH via 100k. Must be taken below 0.8v to reset the chip.

Pin 5 CONTROL. A voltage applied to this pin will vary the timing of the RC network (quiteconsiderably).

Pin 6 THRESHOLD. Detects 2/3 of rail voltage to make output LOW only if pin 2 is HIGH. This pin
has a very high impedance (about 10M) and will trigger with about 0.2uA.

Pin 7 DISCHARGE. Goes LOW when pin 6 detects 2/3 rail voltage but pin 2 must be HIGH. If pin 2 is
HIGH, pin 6 can be HIGH or LOW and pin 7 remains LOW. Goes OPEN (HIGH) and stays HIGH when
pin 2 detects 1/3 rail voltage (even as a LOW pulse) when pin 6 is LOW. (Pins 7 and 3 are "in phase.")
Pin 7 is equal to pin 3 but pin 7 does not go high - it goes OPEN. But it goes LOW and will sink about
200mA

Pin 8 SUPPLY. Connects to the positive rail. pin:

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How to Make a Simple DC Motor

How to Make a Simple DC Motor

  

 Equipment Needed:

1.  A ‘D’ size 1.5 V battery
2.  A magnet
3.  A piece of copper wire
4.  A ‘D’ sized battery case with spring
5.  Two paper clips
6.  Two rubber bands

Instructions:

1. Take copper wire and wrap it around the battery. Be sure to leave around 2 inches on each end of the copper wire unwrapped.

2. Slide the copper wire of the battery keeping it in a circle. Orientate it so the ends of the wires are on opposite sides.

3. Wrap the ends of the wire around the loop several times to hold the structure of the loop and to keep the wire wound together.

4. Take both paper clips and bend them to look like the ones shown in the picture. These will be used to hold up the copper wire wound in a circle from previous the steps.

5. Place the battery into the battery case. Make sure the ‘+’ from the battery is lined up with the ‘+’ from the case.

6. Take bent paper clips and stick them through the holes on each side of the battery case.

7. To hold the bent paperclips in place stretch both rubber bands around the base of the battery case.

8. For each end of the wound copper wire scraped off the outer coating, if scraped off at the wrong side the motor will not work. Very important to only scrape of the sides like shown in the picture.

The purpose of scraping off the coating is so a complete circuit can be made with the battery and the copper wire. This complete circuit needs to be made when the position of the wire is like the one shown to the right. This will create a magnetic pole through the loops of the copper wire making the bottom portion of the wire want to push away from the magnet, thus making it spin.

9. Place magnet on top of battery. Rest the ends of the copper wire on the bent paper clips so the wound of wire is placed above the magnet and battery. Little foam balls can be used to hold wire in place like shown in the picture.

Automatic Soldering Iron Switch

Automatic Soldering Iron Switch

Quite often, we forget to turn off the soldering iron. This results in not only a smoking oxidised
iron but also waste of electricity. To solve this problem, here’s a circuit that automatically
switches off the soldering iron after a predetermined time. The circuit draws no power when it is
inactive. The circuit can also be used for controlling the electric iron, kitchen timer or other
appliances

Water Pump Controller

Here is a simple circuit for controlling water level in an overhead tank. The main components of
this pump controller are a step-down transformer, a 24V AC double-changeover relay, two floats
and two micro switches. Any available relay can be used irrespective of its coil voltage. Of
course, current rating of contacts should be taken into account according to the motor power. The
relay should have two contacts. A step-down transformer having secondary voltage suited to the
coil voltage of the relay is used. As the circuit works off AC, no rectification is necessary. Microswitches
S1 and S2 fixed on top of the water tank are operated by separate floats: one for sensing
the bot tom level and the other for top level. A three-core wire is used for connecting these
switches to the relay