free schematics

oscillator

2022-12-31T06:11:00.003-08:00

An oscillator is a system or device that oscillates, or moves back and forth, between two states or conditions. Oscillators can be found in a variety of applications and systems, including electronic circuits, mechanical systems, and biological systems.

In electronic circuits, oscillators are used to generate periodic signals, such as sine waves, square waves, and triangular waves. These signals can be used to drive other circuits or devices, or they can be used as test signals for testing or debugging electronic systems. Oscillators can be built using a variety of components, including capacitors, inductors, and transistors.

In mechanical systems, oscillators can be used to generate periodic motion or vibrations. For example, a simple oscillator might consist of a weight attached to a spring, which bounces up and down when the spring is released. Oscillators are used in a variety of mechanical applications, including clocks, watches, and other timekeeping devices.

In biology, oscillators are found in a variety of processes and systems, including circadian rhythms, the beating of the heart, and the oscillation of cells in the process of cell division.

Overall, oscillators are important because they allow for the generation of periodic signals and motion, which are fundamental to many systems and processes in the natural and man-made world.

opto-coupler

2022-12-31T06:03:00.002-08:00

An opto-coupler, also known as an optocoupler, opto-isolator, or photocoupler, is an electronic device that uses a light-emitting diode (LED) to transmit a signal from one circuit to another. It is used to electrically isolate two circuits, allowing them to communicate without a direct electrical connection. This isolation is important in applications where electrical noise or voltage spikes could potentially damage sensitive electronic components.

Opto-couplers consist of an LED on one side and a photodetector on the other side. When the LED is turned on, it emits light that is detected by the photodetector, which converts the light into an electrical signal. The electrical signal is then transmitted to the second circuit, allowing the two circuits to communicate.

Opto-couplers are commonly used in a variety of applications, such as data transmission, motor control, and voltage regulation. They are particularly useful in situations where it is necessary to isolate a high-voltage circuit from a low-voltage circuit, or where electrical noise or interference could cause problems.

audio amplifier

2022-12-31T05:57:00.004-08:00

An audio amplifier is a device that increases the strength of an audio signal. It is commonly used to drive speakers or headphones, and can be found in a variety of electronic devices such as televisions, radios, and home theater systems.

There are different types of audio amplifiers, including Class A, Class B, Class AB, and Class D. These classifications refer to the type of circuit used in the amplifier and how it operates. Class A amplifiers are known for their high fidelity and low distortion, but are less efficient than other types of amplifiers. Class B amplifiers are more efficient, but have higher distortion. Class AB amplifiers are a compromise between the two, offering a balance of efficiency and fidelity. Class D amplifiers are highly efficient and are commonly used in portable audio devices due to their small size and low power consumption.

Audio amplifiers can be designed to amplify different frequency ranges, such as low-frequency (bass) signals or high-frequency (treble) signals. Some amplifiers are designed to amplify the full audio spectrum, while others are specialized for specific frequency ranges. The type of amplifier used will depend on the specific application and the requirements of the audio system.

what is transistor ?

2022-12-31T01:40:00.002-08:00

A transistor is a type of semiconductor device that is commonly used to amplify or switch electronic signals. It is made up of three layers of a semiconductor material, typically silicon, each with a different type of doping. The layers are known as the emitter, the base, and the collector.

When a voltage is applied to the base of the transistor, it allows a current to flow between the emitter and the collector. This current can be controlled by the voltage applied to the base, making the transistor useful as an amplifier or a switch.

There are two main types of transistors: bipolar transistors and field-effect transistors (FETs). Bipolar transistors are made up of two p-type and one n-type layer, and are commonly used as amplifiers in audio and radio frequency circuits. FETs, on the other hand, are made up of a gate, a source, and a drain, and are commonly used as switches in digital circuits.

Transistors have a number of advantages over other types of electronic components. They are small, cheap, and can operate at high speeds. They are also very reliable, with a long lifespan and low power consumption.

Transistors have played a crucial role in the development of modern electronics, and they are used in a wide range of electronic devices, including computers, smartphones, and radios. They have also paved the way for the development of other important technologies, such as integrated circuits and microprocessors.

What is used for amplification of signals?

2022-12-31T00:42:00.000-08:00

What is used for amplification of signals?

There are several devices and circuits that can be used for amplification of signals, including

Amplifiers: An amplifier is a device that increases the strength of an electrical signal by adding power from a power supply to the signal. There are several types of amplifiers, including voltage amplifiers, current amplifiers, and power amplifiers, each of which amplifies a different aspect of the signal.
Transistors: A transistor is a three-terminal semiconductor device that can be used to amplify signals by controlling the flow of current through it. Transistors can be used in various configurations, such as common-emitter, common-base, and common-collector, to amplify signals.
Operational amplifiers (Op-amps): An operational amplifier is a type of voltage amplifier that can amplify a wide range of signals, including low-frequency and high-frequency signals. They are widely used in electronic circuits for a variety of applications, including signal processing, filtering, and oscillation.
Zener diodes: Zener diodes are a type of semiconductor device that can be used as amplifiers in some circuits by using them in a common-base configuration. The diode's nonlinear characteristic allows it to amplify small input signals to larger output signals.

In conclusion, amplifiers, transistors, operational amplifiers, and Zener diodes are some of the devices and circuits that can be used for amplification of signals in electronic circuits.

Why do we use Zener diodes?

2022-12-31T00:30:00.002-08:00

Zener diodes are used in electronic circuits for several reasons:

Voltage regulation: Zener diodes allow current to flow in both directions when the voltage across the diode exceeds the Zener voltage or breakdown voltage. This allows them to be used for voltage regulation by clamping the voltage at the Zener voltage level.
Overvoltage protection: Zener diodes can be used in overvoltage protection circuits to protect sensitive electronic devices from voltage spikes. When the voltage exceeds the Zener voltage, the Zener diode conducts and provides a path for the excess current to flow, thereby protecting the device from damage.
Reference voltage: Zener diodes can be used as reference voltage sources in circuits where a stable voltage is required. The Zener voltage of the diode is a fixed value that is not affected by changes in temperature or current, making it a reliable reference voltage source.
Amplification: Zener diodes can also be used as amplifiers in some circuits by using them in a common-base configuration. The diode's nonlinear characteristic allows it to amplify small input signals to larger output signals.

In summary, Zener diodes are used in electronic circuits for voltage regulation, overvoltage protection, reference voltage, and amplification. Their versatility and reliability make them an essential component in many electronic devices and systems.

2n3904 transistor equivalent

2012-05-02T22:37:00.001-07:00

reference	Equivalentes	application Features
2n3904 NPN Silicon	BC 174, BC 182, BC 190, BC 546	general Purpose

2n3904 transistor equivalent

Telephone Number Display Circuit Diagram

2012-04-29T21:28:00.002-07:00

The given circuit, when connected in parallel to a telephone, dis- plays the number dialled from the telephone set using the DTMF mode. This circuit can also show the number dialled from the phone of the called party. This is particularly helpful for receiving any number over the phone lines. The DTMF signal—generated by the phone on dialling a number—is decoded by DTMF decoder CM8870P1 (IC1), which converts the received DTMF signal into its equivalent BCD number that corresponds to the dialled number. This binary number is stored sequentially in 10 latches each time a number is dialled from the phone. The first number is stored in IC5A (1/2 of CD4508) while the second number is stored in IC5B and so on. The binary output from IC1 for digit ‘0’ as decoded by IC1 is 10102 (=1010), and this cannot be displayed by the seven-segment decoder, IC10. Therefore the binary output of IC1 is passed through a logic-circuit which converts an input of ‘10102’ into ‘00002’ without affecting the inputs ‘1’ through ‘9’. This is accomplished by gates N13 through N15 (IC11) and N1 (IC12). The storing of numbers in respective latches is done by IC2 (4017). The data valid output from pin 15 of IC1 is used to clock IC2. The ten outputs of IC2 are sequentially connected to the store and clear inputs of all the latches, except the last one, where the clear input is tied to ground. When an output pin of IC2 is high, the corresponding latch is cleared of previous data and kept ready for storing new data. Then, on clocking IC2, the same pin becomes low and the data present at the inputs of that latch at that instant gets stored and the next latch is cleared and kept ready. The similar input and output pins of all latches are connected together to form two separate input and output buses. There is only one 7-segment decoder/driver IC10 for all the ten displays. This not only reduces size and cost but reduces power requirement too. The output from a latch is available only when its disable pins (3 and 15) are brought low. This is done by IC3, IC12 and IC13. IC3 is clocked by an astable multivibrator IC4 (555). IC3 also drives the displays by switching corresponding transistors. When a latch is enabled, its corresponding display is turned on and the content of that latch, after decoding by IC10, gets displayed in the corresponding display. For instance, contents of IC5A are displayed on display ‘DIS1,’ that of IC5B on ‘DIS2’ and so on. The system should be connected to the telephone lines via a DPDT switch (not shown) for manual switching, otherwise any circuit capable of sensing handset’s off-hook condition and thereby switching relays, etc. can be used for automatic switching. The power-supply switch can also be replaced then. Though this circuit is capable of showing a maximum of ten digits, one can reduce the display digits as required. For doing this, connect the reset pin of IC2, say, for a 7-digit display, with S6 output at pin 5. The present circuit can be built on a veroboard and housed in a suitable box. The displays are common-cathode type. To make the system compact, small, 7-segment displays can be used but with some extra cost. Also, different colour displays can be used for the first three or four digits to separate the exchange code/STD code, etc. The circuit can be suitably adopted for calling-line ديسبل

Telephone Number Display Circuit Diagram

Smart Phone Light Circuit Diagram

2012-04-29T21:24:00.000-07:00

The circuit shown here is used to switch on a lamp when the tele- phone rings, if the ambient light is insufficient. The circuit uses only two ICs and it can be implemented very easily. A light dependent resistance (LDR), with about 5 kilo-ohms resistance in the ambient light and greather than 100 kilo-ohms in darkness, is at the heart of the circuit. The circuit is fully isolated from the phone lines and it draws current only when the phone rings. The circuit provides automatic switching on of a lamp during darkness when the phone is kept in a place such as the bedroom. The lamp can be battery powered to provide light during power failure or load shedding. This avoids delay in attending to a call. The light switches off automatically after a programmable time period and it needs no attention at all. If required, the lamp lighting period can be extended by simply pressing a pushbutton switch (S1). The first part of the circuit functions as a ring detector. When telephone is on-hook, around 48V DC is present across the TIP and RING terminals. The diode in the opto-coupler is ‘off’ during this condition and it draws practically no current from he telephone lines. The opto-coupler also isolates the circuit from the telephone lines. Transistor in the opto-coupler is normally ‘off’ and a voltage of +5V is present at the ring indicator line. When telephone rings, an AC voltage of around 70-80V AC, which is present across the telephone lines, is used to turn on the diode inside the opto-coupler (IC2) which in turn switches on transistor inside the opto-coupler. The voltage at its collector passes through 0-volt level during ringing to trigger IC3 74LS123(A) monostable flip-flop. The other opto-coupler (IC1) is used to detect the ambient light condition. When there is sufficient light, LDR has a low resistance of about 5 kilo-ohms and the transistor inside the opto-coupler is in ‘on’ state. When there is insufficient light available, the resistance of LDR increases to a few mega-ohms and the transistor switches to ‘off’ state. Thus the DC voltage present at the collector of transistor inside the opto-coupler is normally 0V and it jumps to 5V when there is no light or insufficient light. The 74LS123 retriggerable monostable multivibrator is used to generate a programmable pulse-width. The first monostable 74LS123(A) generates a pulse from the trigger input available during ringing, provided its pin 2 input (marked B) is logic high (i.e. during darkness). It remains high for the programmed duration and switches back to 0V at the end of the pulse period. This high-to-low transition (trailing edge) is used to trigger the second monostable flip-flop 74LS123(B) in the same package. Output of the second monostable is used to control a relay. The lamp being controlled via the N/O contacts of the relay gets switched ‘on.’ The ‘on’ period can be extended by simply pressing pushbutton switch S1. If nobody attends the phone, the light turns off automatically after the specific time period equal to the pulse-width of the second flip-flop. The light sensitivity of LDR can be changed by changing resistance R2 connected at collector of the transistor in light monitor circuit. Similarly, switch-on period of the lamp can be controlled by changing capacitor C3’s value in the second 74123(B) monostable circuit

Negative Supply from single positive Supply

2012-04-29T21:16:00.000-07:00

Opamps are very useful. But one of their major drawbacks is the requirement of a dual supply. This seriously limits their applications in fields where a dual supply is not affordable or not practicable.
This circuit solves the problem to a certain extent. It provides a negative voltage from a single positive supply. This negative voltage together with the positive supply can be used to power the opamps and other circuits requiring a dual supply.
The circuits operation can be explained as follows:
The 555 IC is operating as an astable multivibrator with a frequency of about 1kHz. A square wave is obtained at the pin 3 of the IC . When the output is positive, the 22uF capacitor charges through the diode D1. When the output at pin 3 is ground, the 22uF discharges through the diode D2 and charges the 100uF capacitor is charged. The output is taken across the 100uF capacitor as shown in the figure.

A disadvantage of this circuit is its poor voltage regulation and current limit. The max. current that can be drawn from this circuit is about 40mA. If you draw more current, the regulation will be lost.
Also the output negative voltage will be a little less than the positive supply due to the diode drops. For example if the voltage is +9V then the output voltage will be about 7.5 V.

Negative Supply from single positive Supply

Telephone Headgear Circuit Diagram

2012-04-29T19:30:00.003-07:00

Acompact, inexpensive and low component count telecom head- set can be constructed using two readily available transistors and a few other electronic components. This circuit is very useful for hands-free operation of EPABX and pager communication. Since the circuit draws very little current, it is ideal for parallel operation with electronic telephone set. Working of the circuit is simple and straightforward. Resistor R1 and an ordinary neon glow- lamp forms a complete visual ringer circuit. This simple arrangement does not require a DC blocking capacitor because, under idle conditions, the telephone line voltage is insufficient to ionise the neon gas and thus the lamp does not light. Only when the ring signal is being received, it flashes at the ringing rate to indicate an incoming call. The bridge rectifier using diodes D1 through D4 acts as a polarity guard which protects the electronic circuit from any changes in the telephone line polarity. Zener diode D5 at the output of this bridge rectifier is used for additional circuit protection. Section comprising transistor T1, resistors R2, R3 and zener diode D6 forms a constant voltage regulator that provides a low voltage output of about 5 volts. Dial tone and speech signals from exchange are coupled to the receiving sound amplifier stage built around transistors T2 and related parts, i.e. resistors R7, R6 and capacitor C5. Amplified signals from collector of transistor T2 are connected to dynamic receiver RT-200 (used as earpiece) via capacitor C7. A condenser microphone, connected as shown in the circuit, is used as transmitter. Audio signals developed across the microphone are coupled to the base of transistor T1 via capacitor C3. Resistor R4 determines the DC bias required for the microphone. After amplification by transistor T1, the audio signals are coupled to the telephone lines via the diode bridge. The whole circuit can be wired on a very small PCB and housed in a medium size headphone, as shown in the illustration. For better results at low line currents, value of resistor R2 may be reduced after testing

Telephone Headgear Circuit Diagram

Audio Visual Ringer Circuit Diagram

2012-04-29T19:23:00.003-07:00

Many a times one needs an ex- tra telephone ringer in an ad- joining room to know if there is an incoming call. For example, if the telephone is installed in the drawing room you may need an extra ringer in the bedroom. All that needs to be done is to connect the given circuit in parallel with the existing telephone lines using twin flexible wires. This circuit does not require any external power source for its operation. The section comprising resistor R1 and diodes D5 and LED1 provides a visual indication of the ring. Remaining part of the circuit is the audio ringer based on IC1 (BA8204 or ML8204). This integrated circuit, specially designed for telec- om application as bell sound generator, requires very few external parts. It is readily available in 8-pin mini DIP pack.
Resistor R3 is used for bell sensitivity adjustment. The bell frequency is controlled by resistor R5 and capacitor C4, and the repeat frequency is controlled by resistor R4 and capacitor C3. A little experimentation with the various values of the resistors and capacitors may be carried out to obtain desired pleasing tone. Working of the circuit is quite simple. The bell signal, approximately 75V AC, passes through capacitor C1 and resistor R2 and appears across the diode bridge comprising diodes D1 to D4. The rectified DC output is smoothed by capacitor C2. The dual-tone ring signal is output from pin 8 of IC1 and its volume is adjusted by volume control VR1. Thereafter, it is impressed on the piezo-ceramic sound generator

Audio Visual Ringer Circuit Diagram

Off Line Telephone Tester Circuit Diagram

2012-04-29T19:19:00.000-07:00

Here is a circuit of an off-line telephone tester which does not require any telephone line for testing a telephone instrument. The circuit is so simple that it can be easily assembled even by a novice having very little knowledge of electronics. A telephone line may be considered to be a source of some 50 volts DC with a source impedance of about 1 kilo-ohm. During ringing, in place of DC, an AC voltage of 70 to 80 volts (at 17 to 25 Hz) is present across the telephone line. When the subscriber lifts the handset, the same is sensed by the telephone exchange and the ringing AC voltage is disconnected and DC is reconnected to the

Off Line Telephone Tester Circuit Diagram

line. Lifting of the handset from the telephone cradle results in shunting of the line’s two wires by low impedance of the telephone instrument. As a result, 50V DC level drops to about 12 volts across the telephone instrument. During conversation, the audio gets superimposed on this DC voltage. Since any DC supply can be used for testing a telephone instrument, the same is derived here from AC mains using step-down transformer X1. Middle point of the transformer’s secondary has been used as common for the two full-wave rectifiers—one comprising diodes D1 and D2 together with smoothing capacitor C1 and the other formed by diodes D3 and D4 along with filter capacitor C2. The former supplies about 12 volts for the telephone instrument through primary of transformer X2 which thus simulates a source impedance, and a choke which blocks AC audio signals present in the secondary of transformer X2. The AF signal available in secondary of X2 is sufficiently strong to directly drive a 32-ohm headset which is connected to the circuit through headphone socket SK1 via rotary switch S2. During ringing, a pulsating DC voltage from transformer X1 via rectifier diode D5, push-to-on switch S3, and contact ‘B’ of rotary switch S2 is applied across secondary of transformer X2. The boosted voltage available across primary of transformer X2 is sufficient to drive the ringer in the telephone instrument. Please avoid pressing of switch S3 for more than a few seconds at a time to prevent damage to the circuit due to high voltage across primary of transformer X2. The circuit also incorporates a music IC (UM66) whose output is connected to secondary of transformer X2 via switch S2 after suitably boosting its output with the help of darlington transistor pair T1 and T2. This output can be used to test the audio section of any telephone instrument. After having assembled the circuit satisfactorily, the following procedure may be followed for testing a telephone instrument:
1. Connect the telephone to the terminals marked ‘To Telephone Under Test’and switch on mains (switch S1).
2. To test the ringer portion, flip switch S2 to position ‘B’ and press S3 for a moment. You should hear the ring in case the ringer circuit of the telephone under test is working. Please ensure that handset is on cradle during this test.
3. For testing the audio section, flip switch S1 to position ‘C’ and connect a headphone to socket SK1. Pick the telephone handset and speak into its microphone. If audio section is working satisfactorily, you should be able to hear your speach via the headphone. If you dial a number, you should be able to hear the pulse clicks or pulse tone in the headphone, depending on whether the telephone under test is functioning in pulse or tone mode. If the telephone under test has a built-in musical hold facility, on pressing the ‘hold’ button you should be able to hear the music. Now flip switch S2 to position ‘A’. You should be able to hear music generated by IC1 through earpiece of the handset of the telephone under test, indicating propor functioning of the AF amplifier section. The circuit can be assembled on a small piece of veroboard. Try to mount the two transformers on opposite sides of the board, displaced by 90 degrees. Always keep handy multi-type modular plugs for testing various types of telephones. Mount all switches, sockets and LEDs on the front of testing panel

20W Car Audio Amplifier with LM1875

2012-04-29T02:37:00.000-07:00

This is just addition 20W audio amplifier circuit , but this time based on the LM1875 audio amplifier IC from National Semiconductors. With a 25V bifold ability accumulation LM1875 can bear 20W of audio ability into a 4 ohm speaker. The LM1875 requires actual beneath external components and has actual low distortion.

The IC is aswell arranged with a lot acceptable appearance like fast bulk rate, advanced accumulation voltage range, top achievement current, top achievement voltage swing, thermal aegis etc. The IC is accessible in TO-220 artificial ability amalgamation and is able-bodied acceptable for a array of applications like audio systems, servo amplifiers, home theatre systems etc.

Notes.

Assemble the circuit on a good quality PCB.
Use +/-25V DC dual supply for powering the circuit.
K1 can be 4 ohm, 20W speaker.
A proper heat sink is necessary for the IC.
F1 and F2 are 2A

uA 741-Square Wave Generator

2012-04-29T02:30:00.001-07:00

A square wave generator with IC UA741 range shown here.The circuit uses positive feedback to the Schmitt trigger action and negative feedback to measure the time of the waveform.

Let us assume that the output is high and the capacitor C1 is fully discharged.C1 now begins to charge through R2 and C1 R1.When tension rises above the junction of R3 and R4, the output changes rapidly totally negative voltage.C1 Now begins the unloading and reloading in the direction.Again contrast, when the negative voltage across C1 falls below that at pin 3, the circuit is returned quickly to totally positive repetitions value.The output endless cycle.

The square wave frequency can be varied by varying POT R1.The frequency range of the circuit depends on the value of R3, R4 and C1.

BA5406 Stereo Amplifier Circuit

2012-04-29T01:35:00.002-07:00

In the circuit diagram shown, BA5406 is configures to deliver 5×2 watts into 4 ohm loudspeakers at a supply offer voltage of 9 volts. Capacitor C3 is a power supply filter capacitor. C11 and C12 are input DC decoupling capacitors for the left and right channels. C3 and R2 forms a Zobel network for the left output whereas C6 & R3 forms identical for the correct channel.

Purpose of the Zobel network is to cut back oscillations and improve high frequency stability of the amplifier. Potentiometers R5 and R6 serves as the quantity control for the left and right channels. CapacitorsC4 and C8 couple the outputs of the amplifier to the speakers. C9 and C10 are noise filtering capacitors. C1 and C5 are bootstrap capacitors for the left and right channels.

Cable TV amplifier With 2 Transistors

2012-04-29T01:29:00.001-07:00

This is a actual simple cable TV amplifier application two transistors. This amplifier ambit is a lot of acceptable for cable TV systems application 75 Ohm coaxial cables and works accomplished up to 150MHz. Transistor T1 performs the job of amplification. Up to 20dB accretion can be accepted from the circuit.T2 is active as an emitter addict to access accepted gain.

Notes.

The circuit can be assembled on a Vero board.
Use 12V DC for powering the circuit.
Type no of the transistors are not very critical.
Any medium power NPN RF transistors can be used in place of T1 and T2.
This is just an elementary circuit. Do not compare it with high quality Cable TV amplifiers available in the market.

MSK5012 Adjustable Voltage Regulator 10A

2012-04-29T01:22:00.000-07:00

MSK5012 is a awful reliable adjustable voltage regulator.Whose achievement can be programmed application two resistors. The regulator has a actual low dropout voltage(0.45v @10A )due to the acceptance of MOSFT with actual low Rds (ON) as the centralized alternation canyon element.The MS5012 has a top akin of accurateness and ripple bounce is about 45dB. It is accessible in a 5 pin Sip amalgamation that is electrically abandoned from the centralized circuitry. This accord us the abandon to fit the IC anon to the calefaction bore and this array of absolute heatsinking improves the thermal dissipation.

The achievement voltage of this circuit is adjustable from 1.3v to 36v DC.Resistors R1 and R2 are acclimated for programming the achievement voltage. For all applications, amount of R2 is anchored to 10K. The accord amid R1,R2 and achievement voltage Vout is according to the blueprint R1=R2(Vout/1.235)-1. C1 is a clarify capacitor which is aswell a allotment of the aboideau drive circuit of the centralized alternation canyon MOSFET. About three times the ascribe voltage will arise beyond this capacitor and so the its voltage appraisement have to be called accordingly.C2 is the ascribe clarify capacitor while C3 is the achievement clarify capacitor.

6Volt Doorbell Light Circuit

2012-04-29T01:06:00.000-07:00

This 6V battery operated doorbell light circuit can be affiliated in alongside with any absolute AC230V doorbell. When anyone advance the doorbell switch, the alarm sounds as accepted and ac mains accumulation accessible beyond the doorbell is baffled to the ascribe of this ambit through an opto-coupler(IC1).

Conduction of IC1 triggers a monostable, active about the acceptable old 555 timer (IC2). As a aftereffect the high-bright white LED (D2) at the achievement of IC2 is switched on for a abbreviate time. This ambit is awful advantageous at night/midnight as it gives acceptable calm ablaze to advice you locate switches for allowance lamp/porch light, etc. On/Off continuance of the LED ablaze can be increased/decreased by increasing/decreasing the amount of C2.

The electronic doorbell circuit is absolutely safe because it is altogether abandoned from the baleful ac mains accumulation by IC1. However, accumulate to abstain adventitious contacts with the foreground end of the circuit, which is anon affiliated to the ac supply. Use of a acceptable and acceptable ABS asylum is recommended for this doorbell ablaze unit.

LM 3915 Sound Level Meter Circuit

2012-04-29T01:00:00.000-07:00

This is a one chip sound level meter that can be use for displaying sound level of an amplifier or simply the sound level from a microphone.The heart of the circuit is IC LM 3915 Audio level IC.Even though it is a stand alone IC , a peak detector based on Transistor BC 558 and diode 1N4001 is also included for better performance.

Supply voltage can be from 3V to 20V.The input is set for audio line voltage (1V peak to peak) and has a max input voltage of 1.3V. To make the circuit use a moving dot display instead of bar graph display,Pin 9 can be should be disconnected from +V.

Part List

C1 2.2uF 25V Electrolytic Capacitor
C2, C3 0.1uF Ceramic Disc Capacitor
R1, R3 1K 1/4W Resistor
R2 10K 1/4W Resistor
R4 100K 1/4W Resistor
R5 1M 1/4W Resistor
D1 1N4001 Silicon Diode
Q1 BC 558 PNP Transistor
LED1-LED10 Standard LED or LED Array
U1 LM3915 Audio Level IC
MISC Board, Wire, Socket For U1

9V Portable Headphone Amplifier

2012-04-29T00:53:00.000-07:00

After several requests of the correspondents, the decision to design a headphone amplifier 9V power was finally taken. The main requirement was to feed the circuit by a common, PP3 (transistor radio) alkaline batteries. Therefore, the circuit implementation of a low current draw was absolutely necessary, while retaining high quality.

The emergence of low-noise 5534 operational amplifier at a reasonable price was much appreciated by audio designers. Now it is difficult or impossible to design a specific phase that has the performance of 5534, without the complexity unacceptable. 5534 operational amplifiers are available from various sources, in a conventional 8-pin dil format. This version is internally compensated for gains of three or more, but requires a small external capacitor (5-15pF) for unity gain stability. The 5532 is a convenient pack of two 5534s in an 8-pin device with internal unity gain compensation, since there are no spare pins.

The 5534 / 2 is a low distortion and low noise device also has the ability of low-impedance load to full voltage swing, while maintaining low distortion. It is fully output short-circuit. Therefore, this circuit is carried out with a single 5532 chip forming a pair of stereo amplifiers, invest, have a current gain of about 3.5 alternating and capable of delivering up to 3.6 V peak to peak 32 Ohm load (corresponding to 50mW RMS) less than 0.025% total harmonic distortion (1 kHz and 10 kHz).

Considering that the average current drawing a power of 15 mW per channel is about 12-13mA (both channels driven), this headphone amplifier will become a "must" for many DIY enthusiasts who need a device High quality, high performance laptop.

source http://wireless-schematic.blogspot.com

Vintage Transistor Radios

2012-04-29T00:22:00.000-07:00

The transistor was invented in 1947 at Bell Labs in New Jersey. In 1954, Texas Instruments of Dallas teamed up with Regency Electronics (its original name was Industrial Development Engineering Associates, or I.D.E.A.) of Indianapolis to manufacture the first pocket-size transistor radio. Generally, the most collectible transistor radios are those made in Japan from 1956 to 1963 and in America from 1955 to 1960, but by the early '60s, many American companies had opted to have their radios made in Japan.

Besides the Regency TR-1, which came in 10 colors and retailed for $49.95, other collectible American brands include Zenith, RCA, G.E., Admiral, Motorola, Magnavox, Philco, Raytheon, Arvin, Sylvania, and Emerson. Collectible Japanese brands include Toshiba, Hitachi, Sharp, Standard, Sanyo, Matsushita (Panasonic), Mitsubishi, Aiwa, Realtone, Global, and Zephyr. And then, of course, there was Sony, which stunned the electronics world in 1957 with its TR-63. Although the radio utilized miniature components, Sony dramatized the radio's small size at a trade show when it had its representatives carry them in their shirt pockets. Turns out Sony had dressed its staff in shirts that had been sewn with larger pockets than normal, which is the reason why the TR-63 fit.

One desirable feature for vintage transistor radios is reverse-painted plastic, popular between 1958 and 1962. In these radios, all of the artwork is painted on the inside of the radio's clear plastic dial cover. Also desirable are brightly colored cases, including cool 1950s hues like robin’s egg blue, seafoam green, and bright red or yellow. Condition also matters to collectors. Finding a radio with its original box, leather case, earphones, owner’s manual, and warranty card or sales slip will significantly increase its value.

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vintage radio

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LG introduced two new LCD TV series UltraSlim

2012-04-12T21:32:00.000-07:00

LG Electronics is going to bring to market two series of LCD TVs UltraSlim (superfine) - SL80 and SL 90. The first samples of these lines were showcased at the fair Summer Line Show, and yuzhnokreytsy made it clear that they will be officially presented at the beginning of August, writes Electronista.

In principle, the SL80 and SL90 are not very different. But if the first series of models have only a conventional backlight (CCFL), but the second boasts a system of LED Backlight. Perhaps the main design feature is they have very slim. Moreover, they were designed edge-to-edge (edge to edge), so the scope of the screen is very thin. Among other features can be noted, covered with a glass panel screen, speakers, Invisible Speakers, which are well "hidden" in the body, as well as sensor Intelligent Sensor. As stated, it allows you to automatically adjust screen brightness depending on ambient light. By the way, SL 80 and SL90 support technology refresh TurMotion 240 Hz, so that they can clearly show fast-moving objects.

SL80 Series includes three models with a size of 42, 47 and 55 inches. Their value is 1600, 1900 and 2800 U.S. dollars. As for the series SL90, then there are two models that have a screen size of 42 and 47 inches. However, their value has not a word. As expected, they go on sale later this year.

Toshiba TV will dress in a stainless steel

2012-04-12T21:27:00.000-07:00

Toshiba presented its latest combo television, which distinguishes from the rest of stainless steel. HD Model 19-inch diagonal positioned as merely a kitchen TV. It is lightweight, compact and protected from scratches and minor damages. Moreover, the manufacturer opted to become not so much because of its strength, but because of the appearance - this technique is well suited to the modern kitchen.

New aspect ratio - 16:9, you can connect it via HDMI and USB, so that with a large screen you can watch videos stored on your PC. Buy a TV can be the beginning of September, priced at $ 350.

Sony chose the Sharp LCD panels for its TVs

2012-04-12T21:21:00.001-07:00

Apparently, negotiations between Sony and Sharp on the establishment of a joint venture to produce LCD panels coming to an end. According to the newspaper The Nikkei, which is considered the mouthpiece of the business community in the country of the Rising Sun, by the end of this month, the two companies will conclude an agreement under which Sony will invest about U.S. $ 1.1 billion in new venture for the production of LCD Sharp in Sakai (Sakai) to the west Japan. According to preliminary data, its share in this joint venture will be 34 percent. Although the two companies reached a preliminary agreement at the beginning of the year, a formal agreement on this issue will be signed until next week.

According to recent reports, Sony may invest in the joint venture of 50-60 billion yen at once, but then the total investment could reach $ 100 billion yen or more.

It's no secret that the Sharp is one of the largest manufacturers of LCD panels in the world, and its products are of high quality manufacturing and superior performance. Apparently, Sony has high hopes for this Sharp, and not on the Samsung, although at one time the Japanese and South Koreans, too, have formed a joint venture to produce LCD panels.

At the official level, Sony and Sharp still keep complete silence on this issue.