AUTOMATIC CAR ALARM

Even the best car alarm is useless if you forget to set it upon leaving your car, whence this circuit. The relay has a make and a break contact: the former is necessary to delay the switching in of the alarm after you have got out of your car, and the latter serves to switch on the car alarm proper. Immediately on re-entering your car, you must press the hidden switch, S1.This causes silicon-controlled rectifier Th1 to conduct so that the relay is energized. At the same time, the

MINI STEREO AMPLIFIER (TEA2025)

This mini amplifier is based on the Thomson Type TEA2025. In this 16-pin DIL device hides a stereo amplifier that with a supply voltage of 9 V will provide 1watt output per channel into a 4-ohm loudspeaker. At full output, the input sensitivity is about 25 mVpp. If this is too sensitive, a resistor R may be connected between pin 6 and C7 and between pin 11and C2. The sensitivity then becomes (25+ Y2R) mV, provided R> 1k. Furthermore, the supply voltage may lie between 3 V and 12 V. The operation of the IC cannot be discussed here, but for those interested its internal circuit diagram is reproduced in Fig.

INTEGRATED STEREO AMPLIFIER

The Type TDA1521 from Valvo/Mullard is an integrated HiFi stereo power amplifier designed for mains fed applications such as stereo TV. The device works optimally when fed from a ± 16V supply, and delivers a maximum output power of 2 x 12W into 8 ohm. The gain of the amplifiers is fixed internally at 30 dB with a spread of 0.2 dB to ensure optimum gain balance between the channels. A special feature of the chip is its built-in mute circuit, which

HI-FI HEADPHONE AMPLIFIER

This l-watt amplifier lends itself par excellence for use as driver for a low impedance headphone or as output stage in a hi-fi preamplifier driving an active loudspeaker. Many preamplifiers do not permit long, unscreened leads to be connected to them, but the present amplifier accepts these happily.

The amplifier delivers a maximum power of 1 watt into 8 Q for an input signal of about 500 mVrms.

AUDIO CONTROLLED MAINS SWITCH

It is often useful for audio or video equipment to be switched off automatically after there has been no Input signal for a while.
The function of the on-off switch in such equipment is then taken over by switch S2in the accompanying diagram. It remains, however, possible to switch off manually by means of S1. Automatic switch-off occurs after there has been no input signal for about 2 minutes: this delay makes it possible for a new record or cassette to be placed in the relevant machine.
The audio input to the proposed circuit may be taken from the output of the relevant TV set, amplifier, or whatever. The input earth is held at +6 V with respect to the circuit earth by potential divider R1-R2-R3-R4. The two 741s function as comparators: the output of  IC1 goes high when the input signal is greater than +

Crystals and Resonators

Quartz crystals and ceramic resonators are made from slices of quartz or slabs of ceramic material, with electrodes plated on the sides. They exploit the piezoelectric effect, in which some materials move when subjected to a voltage and also generate a voltage when mechanically flexed. Crystals are always found encased in metal, while ceramic resonators are usually in yellow or orange plastic. Crystals have two leads, and ceramics may have

Ni-Cad (NiCd, NiCad) battery Charger

Ni-Cad (NiCd, NiCad) battery, sometimes doesn’t work as expected, gives no power and cannot be recharged. In this situation, the battery need to be reconditioned. It’ is possible that the battery is internally shorted, and we can get the battery into life again by recondition the Ni-Cad battery using a zapper circuit. This circuit restore the Ni-Cad battery from shorting by forcing a high current flow to burn the internal dirt. The current stored in the high capacitance capacitor is heavy discharged by the SCR when zapping, and the SCR is

5-Mode Preset Equalizer IC PT2389 (with Bass Booster & 3D Effect)

PT2389 is a 2-channel digital preset equalizer utilizing CMOS Technology. It provides 5 different sound

selections, namely: Flat/Normal, Rock, Pops, Classic and Jazz. Bass Booster and 3D Effects may be

added to any of 5 sound selections, thereby creating more audio versatility. PT2389 provides two types

of key selection mode, namely: the Direct and the Cyclic. Pin assignment and application circuit are

optimized for cost saving advantages and easy PCB layout.

FEATURES
 CMOS Technology
 Low Total Harmonic Distortion and High S/N Ratio: THD + N < 0.01%, S/N > 95 dB

Atanua

Atanua is a real-time logic simulator, designed to help in learning of basic boolean logic and electronics. It uses OpenGL hardware-accelerated rendering and a custom UI designed for a fast workflow and a very low learning curve, letting the students concentrate on learning the subject instead of spending time learning the tool.

See the interactive flash demo! Download

Signal Strength Meter

A field strength meter is a very handy piece of test equipment to determine the output of a transmitter. Talking Electronics website describes a number of Test Equipment projects to help with developing your projects.

RF coil- embed same PCB according to your frequency range. 

Surface Mount Resistors

All SM resistors conform to a 3-digit or 4-digit code. But there are a number of codes, according to the tolerance of the resistor. It's getting very complicated.

The first two digits represent the two digits in the answer. The third digit represents the number of zero's you must place after the two digits. The answer will be OHMS. For example: 334 is written 33 0 000.
This is written 330,000 ohms. The comma can be replaced by the letter "k". The final answer is: 330k.
222 = 22 00 = 2,200 = 2k2
473 = 47 000 = 47,000 = 47k
105 = 10 00000 = 1,000,000 = 1M = one million ohms

4017 CMOS Decade Counter

The CD 4017 is called a COUNTER or DIVIDER or DECADE COUNTER. It is a very handy chip for producing "Running LED effects" etc.
It has 10 outputs. For normal operation, the clock enable and reset should be at ground.
Output "0" goes HIGH on the rise of the first clock cycle.
On the rise of the second clock cycle, output "0" goes LOW and output "1" goes HIGH. This process continues across the ten outputs and cycles to output "0" on the eleventh cycle.
The "Carry Out" pin goes LOW when output "5" goes HIGH and goes HIGH when output "0" goes HIGH.
In other words, "Carry Out" is HIGH for outputs 0, 1, 2, 3 and 4. It is LOW when the following outputs are active: 5, 6, 7, 8 and 9.
When RESET (pin 15) is taken HIGH, the chip will make output "0" go HIGH and remain HIGH.
When "Clock Inhibit" (pin 13) is taken HIGH, the counter will FREEZE on the output that is currently HIGH.

7 Segment LED Displays

The 7 segment display is found in many displays such as microwaves, lifts, ovens etc. It consists of 7 LEDs that have been combined into one case to make a convenient device for displaying numbers and some letters.

Displays come is a range of colours and brightness levels. Most come in super-bright and these are preferred so the display can be seen during the day. They are not much more expensive but give a much better illumination. All displays also come in COMMON CATHODE and COMMON ANODE. The COMMON CATHODE display has all the

Dual Voltage Power Supply

The use of a pair of the regulators (positive and negative) makes an ideal dual rail supply, for powering op-amps etc. A suitable circuit is shown below. This one uses 12V regulators, but obviously the voltage can be varied by changing regulators.

79XX three terminal negative voltage regulators

The 79XX series are three terminal negative regulators with fixed output voltages. The only external component necessary is a compensation capacitor on the output.

These are essentially similar to the 78XX series positive regulators, with current limiting and thermal overload protection.

How to Take Adjustable output with LM340/78XX

This simple circuit gives the LM340T-5 variable output voltage according to the formula:
Vout = 5v + (5v/R1+IQ)R2

Boosting the current output of the LM340T/ 78XX series
This circuit supplies regulated outputs at up to 5A. At low currents Q1 is off. Only above 600mA is it biased on.

LM340 and 78XX series 3 terminal regulators LM340T5, 12, 15 7805, 7812, 7815

The LM340 series of positive 3 terminal regulators offer similar performance to the 78XX series. They are complete voltage regulators with outstanding ripple rejection and superior line load regulation. Current limiting is included to limit peak output current to a safe level. Safe area protection for the output transistor is provided. If internal power dissipation is too high, thermal shutdown occurs. Although designed primarily as fixed voltage regulators, these devices can be used with external components to obtain adjustable voltages and currents.

Features
• Maximum 1A output
• Output voltage tolerance ±2%
• Load regulation 0.3%
• Thermal overload protection
• Short circuit current limit
• Output transistor safe area protected
• Continuous dissipation 15W

555 Timer

The 555 is a highly stable device designed for generating accurate time delays or oscillations. Additional terminals are provided ' for triggering or resetting. In the time delay mode (monostable mode) the time is set by one external resistor and one capacitor. In the astable (free running) mode the frequency and duty cycle are set by two external resistors and one capacitor. The circuit can be both triggered and reset on falling waveforms. The output circuit can source or sink up to 200mA. TTL circuitry can be driven directly from the output. A dual version of this IC is available, the 556.

Features
• Timing from microseconds to hours

• Adjustable duty cycle
• Sink & source 200mA
• 4-15V operation
• Temperature stability >0.005% per°


Absolute maximum ratings
Supply                                +18V
Power dissipation                600mW

Basic OP-AMP Stages

using 741

741 Operational Amplifier

The 741 is a high performance operational amplifier with high open loop gain, internal compensation, high common mode range and exceptional temperature stability. It is short circuit proof and allows for nulling of offset voltage.

Features
• Internal frequency compensation
• Short circuit protection
• Offset voltage null capability

Improved phase control circuit

The following diagram shows a circuit using a neon lamp as a breakdown device. This gives smoother control and improved performance. The neon triggers when the voltage across the two 0.1μ capacitors reaches the breakdown voltage of the lamp (60-90V). Control extends from 95% to full off. The neon lamp phase controlled circuit shown below combines the low cost of the simple RC circuit shown before but gives improved performance. The circuit below gives half wave control from 95% on to full off. Full power can be easily obtained by putting a switch across the SCR. The circuit uses a neon. This gives the following improvements:

A higher impedance circuit can be used for control.

As a result, the control element (which is a 100k pot in the circuit below) can be replaced by a high impedance device such as a thermistor or light dependent resistor, for heating or light control applications.

Lamp dimmer/Heater controller

R1 and C1 are a phase shift network - they produce a variable delay in the waveform applied to the ST4 and hence the triac. When the voltage across C1 reaches the breakdown voltage for the ST4, C1 partially discharges into the triac gate through the ST4. This pulse triggers the triac into conduction for the remainder of the half cycle.

This easy-to-build controller is ideal for dimming lights, and controlling the output of electric heating type appliances. The light or heater element etc is placed where the 'LOAD' is marked on the circuit.

Miniature cells and batteries

In recent years, cells and batteries—especially cells—have become available in many different sizes and shapes besides the old cylindrical cells, transistor batteries and lantern batteries. These are used in watches, cameras, and other microminiature electronic gizmos.

Silver-oxide types

Silver-oxide cells are usually made into button-like shapes, and can fit inside even a small wristwatch. They come in various sizes and thicknesses, all with similar appearances. They supply 1.5 V, and offer excellent energy storage for the weight. They also have a flat discharge curve

Silver-oxide cells can be stacked to make batteries. Several of these miniature cells, one on top of the other, might provide 6 V or 9 V for a transistor radio or other light-duty electronic device. The resulting battery is about the size of an AAA cylindrical cell.

Mercury types

Mercury cells, also called mercuric oxide cells, have advantages similar to silver-oxide cells. They are manufactured in the same general form. The main difference, often not of significance, is a somewhat lower voltage per cell: 1.35 V. If six of these cells are stacked.

The Weston standard cell

Most electrochemical cells produce about 1.2 V to 1.8 V of electric potential. Different types vary slightly. A mercury cell has a voltage that is a little bit less than that of a zinc-carbon or alkaline cell. The voltage of a cell can also be affected by variables in the manufacturing process. Normally, this is not significant. Most consumer type dry cells can be assumed to produce 1.5 Vdc. There are certain types of cells whose voltages are predictable and exact. These are called standard cells. One example of a standard cell is the Weston cell. It produces 1.018 V at room temperature. This cell uses a solution of cadmium sulfate. The positive electrode is made from mercury sulfate, and the negative electrode is made using mercury and cadmium.  When properly constructed and used at room temperature, the voltage of the Weston standard cell is always the same, and this allows it to be used as a dc voltage standard. There are other kinds of standard cells, but the Weston cell is the most common.

Common dime-store cells and batteries

The cells you see in grocery, department, drug, and hardware stores that are popular for use in household convenience items like flashlights and transistor radios are usually of the zinc-carbon or alkaline variety. These provide 1.5 V and are available in sizes known as AAA (very small), AA (small), C (medium large), and D (large). You have probably seen all of these sizes hanging in packages on a pegboard. Batteries made from these cells are usually 6 V or 9 V. One type of cell and battery that has become

Cells and batteries

ONE OF THE MOST COMMON AND MOST VERSATILE SOURCES OF DC IS THE CELL.

The term cell means self-contained compartment, and it can refer to any of various different things in (and out of) science. In electricity and electronics, a cell is a unit source of dc energy. There are dozens of different types of electrical cells. When two or more cells are connected in series, the result is known as a battery.

Electrochemical energy

In electricity, one important form of potential energy exists in the atoms and molecules of some chemicals under special conditions. Early in the history of electrical science, laboratory physicists found that when metals came into contact with certain chemical solutions, voltages appeared between the pieces of metal. These were the first electrochemical cells. A piece of lead and a piece of lead dioxide immersed in an acid solution will show a persistent voltage. This can be detected by connecting a galvanometer between the

Light Sensitive Switch

This circuit makes use of the wide change of resistance of the LDR. Between positive and negative supply there is a voltage divider. The bottom section is a variable resistor RV1. The top half is formed by the LDR and a 4.7K ohm resistor in series. In low light conditions when the resistance of the LDR is very high, the bias to the Darlington pair formed by TR1 and TR2 is very low, and they do not conduct. When the light level rises, the resistance of the LDR falls. This turns the transistors 'on' and pulls in the relay.

The LDR should be an ORP12 or similar. The relay should have a pull in voltage of 9V or lower and a coil resistance of 280 ohms or higher. Photo Electric

NE555 Light sensitive Switch

The use of the 555 timer 1C with an LDR provides a high performance light switch. An LDR is a Light Dependent Resistor and is a very low cost way of detecting light. The 555 is used with its trigger and thresholds tied together to provide a Schmitt trigger with a very low input current but which can drive a relay taking up to

2N2646 Unijunction transistor

The 2N2646 is intended for general and industrial triggering and oscillator circuits where circuit economy is of primary importance. lt is a high speed switching device with a low saturation voltage.

Absolute maximum ratings

Power Dissipation 300mW
RMS Emitter Current 50mA
Peak Emitter Current
(Capacitor discharge <10μF) 2A
Emitter Reverse Voltage 30V
Interbase Voltage 35V

Specifications

Low Ripple Regulated Power Supply

The excellent characteristics of the 2N3055 at high currents (high hFE and low collector-emitter saturation voltage) makes it ideal as a series regulator transistor in regulated power supplies. The power supply circuit shown below can be used when high current with low ripple is required. Q, and Q2 form a high power Darlington. ZD1 and R1 provide a reference voltage at the base of Q1 The voltage output will be:- VOUT = Zener Voltage - 1.2v

2N3055 Power Transistor

The 2N3055 is a medium speed NPN Silicon Power Transistor designed for general purpose switching and amplifier applications.

Features
• DC current Gain (hFE) = 20-70 @ lc = 4.0A
• Collector-Emitter Saturation Voltage = 1.0V @ lc = 4.0A

BD139/140 Driver Transistors

BD139/140 are complementary silicon driver transistors designed for audio and switching applications. They come in TO-126 plastic cases. The BD139 is an NPN device and the BD140 is PNP.


Features
• High gain (hFE40-250) • High fT (250MHz for BD139, 75MHz for BD140)


Absolute Maximum Ratings

FM transmitter

This circuit, is about as simple as a transmitter can get. The coil is etched onto the printed circuit board, but can be easily

substituted by 6 turns on a 4mm diameter former.

BC547-9 (BC107-9) NPN BC557-9 (BC557-9) PNP

Low frequency, general purpose small signal transistors widely used in audio, switching and television circuits. The BC547-9 series and BC557-9 series are functionally identical to the common BC107-9 series.

All have a maximum power dissipation of 500mW. They have essentially similar specifications and can generally be substituted for one another (within the PNP and NPN groups of three each). All devices are housed in standard TO-92 plastic packages.

Specifications

1N4148 Silicon Signal Diode

The 1N4148 is a general purpose signal diode suitable for a wide range of switching and low power rectifying purposes. It is equivalent to the 1N914.

Features
• Low Capacitance. 4pF at 0V
• High breakdown voltage. 100V

Specifications
Capacitance VR=0, f= 1MHz 4pF
Reverse Recovery Time 4nsec
Rectification Efficiency 2.0V rms. f=100 MHz


Maximum Ratings
Breakdown Voltage 100V
Working Inverse Voltage 75V
DC Forward Current 300mA
Maximum Total Dissipation at 25°C 500mW

OA91 General purpose germanium signal diode

The OA91 is a small signal germanium point contact diode. It is suitable for a wide range of RF detector and

small signal rectifying
applications.
Specifications
IP Forward current 50mA
VR Reverse Voltage 90V Vp,
Forward voltage drop
@ IP = 10mA 1.05V

1N4001 to 1N4007 Silicon Power Rectifiers

The following are subminiature general purpose power rectifiers for low power applications

Electrical Characteristics Specifications

Instantaneous Voltage Drop

@ forward current = 1 A 1.1V

Absolute Maximum Ratings

Peak Repetitive Reverse Voltage

1N4001---------- 50V

1N4002 ---------100V

1N4003--------- 200V

1N4004----------400V

1N4005 ---------600V

1N4006----------800V

1N4007----------1000V

Their value will depend on the current and the degree of smoothing required. As a general guide, if the current being drawn from a supply is high, the size of the smoothing capacitor will need to be large (around 2500uF or larger) if the hum level is to be kept down to a respectable level.

Relay

Relays are remote control electrical switches that are controlled by another switch. Relays allow a small current flow circuit to control a higher current circuit.several designs of relays are in use today, 3-pin, 4-pin, 5-pin,and 6-pin, single switches.

All relays operate using the same basic principle. Relays have a tow circuits,a control circuit and a load circuit.The control circuit has a small control coil while the load circuit has a switch. the coil controls the operation of the switch.

FM Transmitter

Here is the schematic,  for a low powered FM transmitter. The range of the transmitter when running at 9V is about 300 feet. Running it from 12V increases the range to about 400 feet.use very smooth power supply for this i recommended 12V car battery.

Car Stereo Systems

Stereo systems are considered as a must-have in a vehicle today. It will be conservative to conclude that, music systems are of no use to anyone, except for all those who take music as fuel to drive. Because a stereo system does not only play music of your choice but it also serves as a medium to acquire latest news through radio channels.

circuit symbols

DVD Troubleshooting Information part2

The disc will not begin playing
The rating of the title on the disc exceeds the rating limit set in the ratings limits when you press play. Unlock the player or change the rating limit in those menus.
No forward or reverse scan
1 Some discs have sections that prohibit rapid scanning or title and chapter skip.
2 This part of most movie discs is programmed to prohibit skipping through them.

DVD Troubleshooting Information

DVD Troubleshooting Information
Player will not work Reset the DVD player by unplugging the ac power cord for a few minutes and then plug it back in the socket. This will reboot the unit.
Disc will not play
1 Insert a disc with the label side facing up.
2 Check the type of disc that you are using. Some units will only play DVD video discs, video CDs, or audio CDs.
3 If the disc is a DTS music CD, it will require a DTS decoder. If you have a DTS receiver hooked up to the DVD player and you still get no sound, make sure the Trusurround option is turned OFF.

No power to unit
Make sure both ends of the power cord are plugged in. Also, make sure that you have ac power at the wall socket.

Fax machine paper jammed

Fax machine paper jammed For the following jammed paper problems,
Problem The paper document is jammed.
Solution Remove the paper document you are trying to send and start again.
Problem The fax machine tried to receive instead of send because you did not feed the paper in properly.
Solution Feed the paper document into the machine and start the operation again.
Problem Your fax machine tried to poll another unit, but the other fax machine did not have a document to send.

Junction Field Effect Transistors

The junction field effect transistor in its simplest form is essentially a voltage controlled resistor. The resistive element is usually a bar of silicon. For an N-channel JFET this bar is an N-type material sandwiched between two layers of P-type material. The two layers of P-type material are electrically connected together and are called the gate. One endof the N-type bar is called the source and the other is called the drain. Current is injected into the channel from the source terminal, and collected at the drain terminal. The interface region of the P- and the N-type materials forms a P-N junction as shown in Figure

The Junction Field Effect Transistor (JFET) exhibits characteristics which often make it more suited to a

The metal–oxide–semiconductor

The metal–oxide–semiconductor field-effect transistor (MOSFET, MOS-FET, or MOS FET) is a transistor used for amplifying or switching electronic signals. The basic principle of this kind of transistor was first patented by Julius Edgar Lilienfeld in 1925. Twenty five years later, when Bell Telephone attempted to patent the junction transistor, they found Lilienfeld already holding a patent which was worded in a way that would include all types of transistors. Bell Labs was able to work out an agreement with Lilienfeld, who was still alive at that time. (It is not known if they paid him money or not.) It was at that time the Bell Labs version was given the name bipolar junction transistor, or simply junction transistor, and Lilienfeld's design took the name field effect transistor.

FET(field-effect transistor)

The field-effect transistor (FET) is a transistor that relies on an electric field to control the shape and hence the conductivity of a channel of one type of charge carrier in a semiconductor material. FETs are sometimes called unipolar transistors to contrast their single-carrier-type operation with the dual-carrier-type operation of bipolar (junction) transistors (BJT).

The field effect transistor was actually conceived before the more familiar bipolar transistor. Due to limited technology and later the rapid rise of the bipolar device it was not pursued until the early 1960Õs as a viable semiconductor alternative. At this time further investigation of the field effect transistor and advances in semiconductor process technology lead to the types in use today. Field effect transistors include the Junction FET (JFET) and the MOSFET. The MOSFET is a metal oxide semiconductor technology and is sometimes referred to as the IGFET or Insulated Gate FET. All field effect transistors are majority carrier devices. This means that current is conducted by the majority carrier species present in the channel of the FET. This majority carrier consists of hole for p-channel devices and electrons for n-channel devices. The JFET operates with current flow through a controlled channel in the semiconductor material. The MOSFET creates a channel under the insulated gate region which is produced by an electric field induced in the semiconductor by applying a voltage to the gate. The JFET is a depletion mode device whereas the MOSFET can operate as a depletion mode or an enhancement mode device. Depletion mode devices are controlled by depleting the current channel of charge carriers. Enhancement mode devices are controlled by enhancing the channel with additional charge carriers.

The FET's three terminals are...

Source (S), through which the majority carriers enter the channel. Conventional current entering the channel at S is designated by IS.

Drain (D), through which the majority carriers leave the channel. Conventional current entering the channel at D is designated by ID. Drain to Source voltage is VDS.

Gate (G), the terminal that modulates the channel conductivity. By applying voltage to G, one can control ID.

Photo Electric Street Light

The photo cell should be shielded from the lamp to prevent feedback and is usually mounted above the light on top of a reflector and pointed upward at the sky so the lamp light does not strike the photo cell and switch off the lamp.

1.5 Volt LED Flasher

The LED flasher circuit below operate on a single 1.5 volt battery.

Use high brightness LED

how to connect ipod or smart 4n to the audio player

Any setup, car cassette, radio also have audio switching stage. It can be analog or digital, it doesn’t matter, first of all u have to identify what is that. So every setup or audio device has two or more function. Tuner, CD, Tape, like that. This all stage has their own audio free out signal till