world technical

120 Watt Audio Power Amplifier Circuit with IC TDA7294

mostfa_me@yahoo.com (worldtechnical) — Sat, 24 Oct 2009 00:21:00 +0000

Here is a simple and easy to build general purpose 120 W. Amplifer with IC number TDA7293 for process sound system.
This amplifer was have the input for a radio, TV, stereo or other line level device.
It also has a phono input for a record player, guitar, microphone or other un-amplified source.
With the addition of a low pass filter at the input, it makes a great amp for a small subwoofer.

Parts

R : 660 Ohm 1/4 W Resistor = 2 pcs.
R : 22K 1/4 W Resistor = 5 pcs.
R : 10K 1/4 W Resistor = 1 pcs.
R : 30K 1/4 W Resistor = 1 pcs.
C : 2200uF 35V Electrolytic Capacitor = 2 pcs.
C : 0.22uF Capacitor = 2 pcs.
C : 22uF Capacitor = 4 pcs.
C : 0.45uF Capacitor = 2 pcs.
U1,2 : TDA7294 100W DMOS AUDIO AMPLIFIER WITH MUTE/ST-BY

T1 : 50V Center Tapped 5 Amp Transformer
S1 : SPST 3 Amp Switch
S2 : DPDT Switch
F1 : 2 Amp Fuse
SPKR1 : 8 Ohm 120W Speaker
MISC : Case, Knobs, Line Cord, Binding Posts Or Phono Plugs (For Input And Output), Heatsinks For Q1 And Q2

60-100 Watt Audio Amplifier

mostfa_me@yahoo.com (worldtechnical) — Sat, 24 Oct 2009 00:12:00 +0000

60-100 Watt Audio Amplifier
My cause of construction of this project was to develop a compact design for a stereo amplifier can be integrated by a wrong (but the sound quality conscious!) Living student at a university or a college dormitory.

The amplifier feeds a pair of speakers with two LM3876 amplifier integrated circuits (50 watts per channel), or a pair of headphones Meier Crossfeed through a filter and a dual OPA2134 Opamp. There are four selectable line inputs, and output buffers with line level for the registry. The design with readily available components of good quality, and is divided into four BPC, a power amplifier for each channel, for the nutrition board, and for the pre-amp / headphone driver.

Above the diagram of part of the preamp board .

The output selector is sent to pins J1 and J3. Looking at the left channel, C1 and R2 form a low pass filter with a-3dB point of 40 kHz, which rejects any RF interference picked up on the interconnections. R2 also includes the impedance of the device, in this case, 47k ohms. R1 ensures Opamp U1 is presented with an impedance equal to its two inputs, contribute to improving the performance of the distortions described in the datasheet OPA2134.

The value of R1 (9K1) is universally accessible, close to the value of the parallel combination of R3 and R4 (22k and 15k, respectively). R3 and R4 set the gain at that time, just below 2.5 in this case. This gives ample space for a wide range of signal sources, which could be as much as 3VRMS. In this case, the peak output voltage of 10.6V would be fine with the project to supply ± 15V.

This initial gain brings the signal to a level that the output of the volume can lead the power amp circuits directly without any additional benefit, and allows the helmet of the driver circuit to operate with a low gain, gives lower noise level. C7 forms 100kHz a lowpass filter with R3, to fall on the gain of unity at very high frequency, and to help promote stability in the Opamp. It is not strictly necessary for the proposed OPA2134 allows the unit, but down substitute cheaper but more likely oscillation device, such as the NE5532, if budgets are tight. C19 couple the AC output of this phase for volume control, and with a 50k potentiometer, the-3dB point of the response of the headphone amps at 1.4Hz (power amp has more HIGH PASS FILTER). The capacitor is very important because all the other stages are DC coupled and DC C19 prevents any of the source components, amplification and presentation of headphones or speakers.

Resistance R9 binds the production of inputs to a recording device like a VCR or mini-disc. This helps to prevent the source being loaded in the diet of both the gain stage input and the recording device and protects the source, the output should be shorted to earth for a reason whatsoever. The output from J5 and J6 are introduced into the volume control pot, which should be good quality. Finally, C3 to C6 and provide decoupling of the power supply rails, C5 and C6 high frequency decoupling, C3 and C4 lower decoupling.

Amplified Ear

mostfa_me@yahoo.com (worldtechnical) — Fri, 23 Oct 2009 23:34:00 +0000

Useful to listen in faint sounds

1.5V Battery operation

Circuit diagram:

Amplified Ear
Parts:

P1_____________22K Log. Potentiometer (see Notes)

R1,R9__________10K 1/4W Resistors
R2______________1M 1/4W Resistor
R3______________4K7 1/4W Resistor
R4,R7_________100K 1/4W Resistor
R5______________3K9 1/4W Resistor
R6______________1K5 1/4W Resistor
R8_____________100R 1/4W Resistor

C1,C2_________100nF 63V Polyester or Ceramic Capacitors
C3,C6___________1µF 63V Polyester or Ceramic Capacitors
C4_____________10µF 25V Electrolytic Capacitor
C5____________470µF 25V Electrolytic Capacitor

D1___________1N4148 75V 150mA Diode

Q1,Q2,Q3,_____BC547 45V 100mA NPN Transistors
Q4____________BC337 45V 800mA NPN Transistor

MIC1__________Miniature electret microphone

SW1____________SPST Switch (Ganged with P1)

J1_____________Stereo 3mm. Jack socket

B1_____________1.5V Battery (AA or AAA cell etc.)

Device purpose:

This circuit, connected to 32 Ohm impedance mini-earphones, can detect very remote sounds. Useful for theatre, cinema and lecture goers: every word will be clearly heard. You can also listen to your television set at a very low volume, avoiding to bother relatives and neighbors. Even if you have a faultless hearing, you may discover unexpected sounds using this device: a remote bird twittering will seem very close to you.
Circuit operation:

The heart of the circuit is a constant-volume control amplifier. All the signals picked-up by the microphone are amplified at a constant level of about 1 Volt peak to peak. In this manner very low amplitude audio signals are highly amplified and high amplitude ones are limited. This operation is accomplished by Q3, modifying the bias of Q1 (hence its AC gain) by means of R2.
A noteworthy feature of this circuit is 1.5V battery operation.
Typical current drawing: 7.5mA.
Notes:

* Due to the constant-volume control, some users may consider P1 volume control unnecessary. In most cases it can be omitted, connecting C6 to C3. In this case use a SPST slider or toggle switch as SW1.
* Please note the stereo output Jack socket (J1) connections: only the two inner connections are used, leaving open the external one. In this way the two earpieces are wired in series, allowing mono operation and optimum load impedance to Q4 (64 Ohm).
* Using suitable miniature components, this circuit can be enclosed in a very small box, provided by a clip and hanged on one's clothes or slipped into a pocket.
* Gary Pechon from Canada reported that the Amplified Ear is so sensitive that he can hear a whisper 7 meters across the room.
He hooked a small relay coil to the input and was able to locate power lines in his wall. He was also able to hear the neighbor's stereo perfectly: he could pick up the signals sent to the speaker voice coil through a plaster wall.
Gary suggests that this circuit could make also a good electronic stethoscope.

Active Bass & Tremble Controller

mostfa_me@yahoo.com (worldtechnical) — Fri, 16 Oct 2009 18:06:00 +0000

Active Bass & Tremble Controller

ACTIVE BASS TONE CONTROLLER circuit diagram

It is very useful (and has Best Quality) for 1 -100watt AUDIO AMPLIFIERS

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author: YMYA electronics - IZHAR FAREED

STK0060 60W

mostfa_me@yahoo.com (worldtechnical) — Fri, 16 Oct 2009 16:53:00 +0000

STK0060 60W
Features of STK0060:

General output stage of power amplifier has a difficult and complex problem about heat sink designing and its settings. Sanyo's DP intends to decrease electronic parts and rationalize a manufacturing process by designing IC of only output stage pf power amplifier.

IMST Systems
Output stage for AF high power amplifier.
Dual power supply
Darlington type pure/ quasi-complementary circuit
These same pin assignment and pin interval lead to standardize a printed board.
Metal substrate use IMST makes good thermal stability
Able to design freely previous section of power amplifier. This leads tone control designing.

Equivalent Circuit.

Application Circuit Found the Data Sheet (SANYO)
Application Notes:

Maximum Ratings at Ta=25 deg C
Maximum Supply Voltage VCCmax +- 55V
Tehrmal resistance 0j-c idealstage 1.3 deg C/W
Collector current Ic 8A
Juction Temperature Tj 150 Dec C
Storage Temperature Tstg -30 to +105 Deg C
Allowable Load Shorting Time ts VCC=+-41V, RL 1 Sec
=8 Ohm, Po=60W
f=50Hz

*Use an Appointed Transformer.

Recommented Operation Conditions at Ta=25 Deg C
Recommented Supply Voltage VCC +-41 V
Load Resitance RL 8 Ohm

Operation Characterestic at Ta=25 Deg C, VCC= +-39V, RL=8, Rg=600 Ohm
VG-36.7db at the appointed test circuit.

Min Typ Max unit
Quiescent Current Icco VCC = +-48 20 40 70 mA

Output power Po THD=0.01%, 60 W
f=20 to 20K Hz
Total Harmonic Distortion THD1 Po=60W, f=20 to 20KHz, 0.005 0.01 %
Total Harmonic Distortion THD2 Po=1W, f=20 to 20KHz, 0.01 %
Power Band Width PBW Po=30W f= 50K Hz 0.05 %

Analog Audio Delay Line"3d Sound"

mostfa_me@yahoo.com (worldtechnical) — Fri, 16 Oct 2009 06:51:00 +0000

Analog Audio Delay Line"3d Sound"
It is fun to make a variable space in your small room, but it’s hard to make the actuator to move your wall or room partition. Using analog audio line delay, you can adjust your room virtually. Just turn a knob in your audio set and you can adjust your room size. The circuit described here will make your dream come true, giving a feel that your speaker is located 15 meters behind you, even though your room is actually 3 meters wide. Here is the circuit’s schematic diagram.

The core of this circuit is SAD512D integrated circuit, an analog audio delay. The chip uses 512 capacitors memory to hold 512 sampled analog signal. The delay can be adjusted from about 5,1 ms to 51 ms by R12 pot. Feed the input of this analog delay circuit with a mixed right and left audio signals from your stereo system. The output of this circuit then fed to a small power amplifier and place the output speaker behind you. Now you can perceive like your speaker is 15 m away behind (with maximum delay setting). If you build two unit the cascading the circuit will result in 30 meter expansion of your virtual room.

The circuit consist three main block. The first block (U1A, U1B) is a fourth order low pass filter (-24dB roll-off per octave) with 2.5kHz cut off frequency. The second block is the adjustable analog delay integrated circuit (IC SAD512D). The delay is controlled by the oscillator around U2 which is adjustable from 5KHz to 50Khz. The last block is similar to the first block, a low-pass filter with 2.5KHz cut off frequency.

A variable resistor R9 is provided to adjust the input offset, avoiding signal clipping and maximizing the audio range. For easy adjustment, feed the input with high level audio signal until the output is distorted, then adjust R9 until the distortion is minimum, or if an oscilloscope is available, adjust the R9 until the clipping is equal for both positive and negative cycle. Finally, adjust R28 to give minimum sampling clock noise.

PARTS LIST

Reference Part
C1,C4,C10,C12 10n
C11,C2 1n5
C3 4.7uF/50V
C13,C5 1n9
C6 390p
C8,C7 1u/25V
C9 1uF/25V
C14,C15,C16 100n
J1 input connector
J2 out connector
R1,R2,R3,R5,R6,R7,R11,R20,R21,R22,R24,R25,R26 10k
R4,R23,R27 4k7
R8,R15 15k
R9 2k2 POT
R10 2k7
R12 220k POT
R13 10R
R18,R14 1k
R17,R16 330R
R19 100k
R28 250R trimpot
U1 TL084
U2 4011

LM386 circuit audio amplifier

mostfa_me@yahoo.com (worldtechnical) — Mon, 12 Oct 2009 20:45:00 +0000

LM386 circuit audio amplifier

The LM386 circuit is a audio amplifier designed for use in low voltage consumer applications. The gain is internally set to 20 to keep external part count low, but the addition of an external resistor and capacitor between pins 1 and 8 will increase the gain to any value from 20 to 200.
The inputs are ground referenced while the output automatically biases to one-half the supply voltage. The quiescent power drain is only 24 milliwatts when operating from a 6 volt supply, making the LM386 ideal for battery operation.

LM386 circuit features

Battery operation
Minimum external parts
Wide supply voltage range: 4V–12V or 5V–18V
Low quiescent current drain: 4mA
Voltage gains from 20 to 200
Ground referenced input
Self-centering output quiescent voltage
Low distortion: 0.2% (AV = 20, VS = 6V, RL = 8Ω, PO = 125mW, f = 1kHz)
Available in 8 pin MSOP package

LM386 circuit applications

AM-FM radio amplifiers
Portable tape player amplifiers
Intercoms
TV sound systems
Line drivers
Ultrasonic drivers
Small servo drivers
Power converters

LM 386 series output power (Pout)

LM386N-1, LM386M-1 at VS = 6V, RL = 8ohms, THD = 10% is 250-325 mW
LM386N-3 at VS = 9V, RL = 8ohms, THD = 10% is 500-700 mW
LM386N-4 at VS = 16V, RL = 32ohms, THD = 10% is 700-1000 mW.

LM 386 amp circuit 20dB gain

LM386 Audio Amplifier with Gain = 20 and minimum part count.

LM386 audio amp 50dB gain

LM386 amplifier 200dB gain

LM 386 bass boost circuit

To make the LM 386 a more versatile audio amplifier, 2 pins ( pin 1 and 8 ) are provided for gain control. With pins 1 and 8 open the internal 1.35k resistor sets the gain at 20 (26 dB). If a capacitor is placed between pin 1-8, bypassing the built-in 1.35k resistor, the gain will go up to 200.

If a resistor is placed in series with the capacitor, the gain can be set to any value from 20 to 200. Gain control can also be done by capacitively coupling a resistor or FET transistor from pin 1 to the ground.

1 W Home Stereo Amplifier Project

mostfa_me@yahoo.com (worldtechnical) — Mon, 12 Oct 2009 19:52:00 +0000

Introduction To Home Stereo Amplifer
This is a 1 watt home stereo amplifier module project using the KA2209 IC from Samsung, which is equivalent to the TDA2822. It operates from 3-12V DC and will work from a battery since the quiescent current drain is low. It requires no heat sink for normal use. The input and output are both ground referenced. Maximum output will be obtained with a 12V power supply and 8 ohm speaker, however it is particularly suitable for driving headphones from a supply as low as 3V.

The Specifications of the home stereo amplifier are:

D.C. input : 3 – 12 V at 200 – 500 mA max
Idle current : approx. 10 mA
Power output : > 1 Watt max. 4-8 ohms, 12V DC
Freq. Resp. : approx. 40 Hz to 200 kHz, 8 ohm, G=10
THD : <> 80 dB, G = 20 dB
Sensitivity : < g =" 20">
Home Stereo Amplifier Description

Home Stereo Amplifier Parts List

The gain is adjustable from 10 to 100, i.e. 20 to 40 dB. Start with feedback resistors R1 and R3 of 1k ohm, this will give a gain of 10 which should be adequate for most applications. If you require more gain, you can remove resistors R1 and R3. This will give a gain of approximately 100, or 40 dB.The input attenuation can be adjusted via the potentiometer which can be used as a volume control. The IC gain should be kept as low as necessary to achieve full output, with the input potentiometer and your signal source at maximum.

This will keep the signal to noise ratio as high as possible. Extra gain provided by the amplifier will reduce the S/N ratio by a similar amount, since the input noise figure is constant. Other values for R1 and R3 of between 1k and 10k ohm can be used if an intermediate gain level is required.

Voltage Gain = 1+ R1/R2 = 1+R3/R4, however the maximum gain with no external feedback is approximately 100, or 40dB. (GdB = 20log Gv)

If driving a pair of headphones, you may also require a 100 ohm resistor in series with each output to reduce the output level, depending on headphone impedance and sensitivity. Make sure you start with the volume right down to check. A number of headphones may be driven from the one amplifier if you wish, since most headphones have at least 16 ohm impedance, or more commonly 32 ohm.

There are only a few external components, the IC contains most of the necessary circuitry. R1,R2 and R3,R4 are the feedback resistors. C1 provides power supply decoupling. C2 and C3 are the input coupling capacitors, which block any DC that might be present on the inputs. C4,C5 block DC in the feed back circuit from the inverting inputs, and C6,C7 are the output coupling capacitors. C8, R5 and C9,R6 act as zobel networks providing a high frequency load to maintain stability at frequencies where loud speaker inductive reactance may become excessive. The pot provides adjustable input level attenuation.

audio amplifiers circuits

mostfa_me@yahoo.com (worldtechnical) — Mon, 12 Oct 2009 17:37:00 +0000

Free PCB layout design software

mostfa_me@yahoo.com (worldtechnical) — Sat, 10 Oct 2009 07:46:00 +0000

Zenit PCB is a freeware layout software
ZenitPCB Layout is an excellent tool to create professional printed circuit board ( PCB ).
It is a flexible easy to use CAD program, which allow you to realize your projects in a short time.

ZenitPCB Layout is completely freeware for personal or semi-professional use

System OS Tested Windows2000 - Windows XP - Vista
Download
ZenitSuite142_Setup.exe New
website: zenitpcb

Digital vs. Analog Volume Control

mostfa_me@yahoo.com (worldtechnical) — Thu, 01 Oct 2009 12:41:00 +0000

Digital vs. Analog Volume Control

Digital vs. Analog Volume Control

The volume control in digital processors (or CD players) can be implemented in the analog or the digital domain. That is, the analog signal can be put through a standard volume-control knob as is found on a preamplifier, or the volume can be adjusted by performing mathematical operations on the digital data representing the music. Before deciding a digital processor with volume control, you should know the tradeoffs inherent in each approach.

An analog volume control can slightly degrade the signal - no volume control is perfectly transparent - and can introduce small channel balance errors at certain volume settings. For example, when the volume is turned very low, the left channel may be half a dB louder than the right. This situation could reverse as the volume is turned up.

A digital volume control has its own problems. Each 6dB reduction in volume from the maximum setting throws away one bit of resolution. A low volume setting (say, 30dB of attenuation) is equivalent to discarding five bits. If you had true 20-bit resolution in your D/A converter, you'd be listening to 15-bit audio instead of 20-bit. The lower the volume setting, the greater the loss in resolution.

Digital volume control such as DS1669 from Dallas Semiconductor is actually easier and cheaper to implement than analog volume control. Most digital filters have a volume control built-in; the designer need only send a control code to the filter chip to adjust the volume. An analog control requires a potentiometer (the volume control itself), another hole in the chassis, and wiring between the circuit board and potentiometer.
Source: Digital vs. Analog Volume Control

Dual Voltage Power Supply

mostfa_me@yahoo.com (worldtechnical) — Thu, 03 Sep 2009 20:07:00 +0000

Dual Voltage Power Supply
author: YMYA electronics - IZHAR FAREED
Description
The following circuit Diagram of (DUAL VOLTAGE POWER SUPPLY ) can be used for Misc.. application.
It requires a few components to built. The most important components of this circuit are REGULATORS.
1 : (AN) 7812 and 2 : (AN) 7912 AN7812 is the Positive Voltage Regulator. It regulates the voltage from (almost) 24vDC to 12vDC (accurate). AN7912 is the Negative Voltage Regulator. It regulates the voltage from (almost) -24vDC to -12vDC. A transformer output must be between 12vAC to 24vAC @ 500mA. Input of transformer (Primary)
should be about 110vAc-220vAC. It also include some capacitors to filter the current.

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Source: Dual Voltage Power Supply

5 Lamp / LED Flash Driver

mostfa_me@yahoo.com (worldtechnical) — Thu, 03 Sep 2009 19:59:00 +0000

5 Lamp / LED Flash Driver
author: Rajkumar Sharma

Description

General Description of the following circuit. This circuit is based around HT2050 manufactured by HOLTEK semiconductors. It is a low cost, low-power C-MOS LSI designed for lamp andLED flash driver. It requires minimum external components.You can operate it with just two AAA cell or 3v Battery.Circuit has five flash outputs with 10mA drive capability that can implement random or sequence flashing function controlled by one option pin.It only requires one external resistor for typical application. It is very suitable for the use of the flash products such as disco glasses, disco hat, gift card, Xmas decoration and so forth.

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Source: 5 Lamp / LED Flash Driver

20W Bridge Audio Amplifier

mostfa_me@yahoo.com (worldtechnical) — Thu, 03 Sep 2009 19:38:00 +0000

20W Bridge Audio Amplifier
author: Rajkumar Sharma

Specifications


20W Bridge Audio Amplifier kit, based on the TDA2005 IC, a class B dual audio amplifier, specifically designed for car radio applications etc. Power supply - 18 VDC Output power - 20 W, 4 Ω IC built in Thermal Shut-down, Load dump voltage surge protected Terminal pins for connecting left and right audio signal inputs Relimate Connector for connecting Potentiometer (POT) for volume adjustment Power Battery Terminal (PBT) for easy power supply and speaker connection Power-On LED indicator Heatsink for IC Four mounting holes of 3.2 mm each with nut and stud PCB dimensions 63 mm x 65 mm

Schematic

Parts List

PCB

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Source: 20W Bridge Audio Amplifier

Notch Filter

mostfa_me@yahoo.com (worldtechnical) — Thu, 03 Sep 2009 19:25:00 +0000

Notch Filter
Circuit : Andy Collinson
Email me

Description:

A variable notch filter with both high and low pass filters.

Notes

At first glance this circuit looks fairly complex, but when broken down,can be divided into high pass and low pass filter sections followed by a summing amplifier with a gain of around 20 times. Supply rail voltage is +/- 9V DC. The controls may also be adjusted for use as a band stop (notch) filter or band pass filter.
Source: http://www.zen22142.zen.co.uk

Stereo Line Driver

mostfa_me@yahoo.com (worldtechnical) — Thu, 03 Sep 2009 19:21:00 +0000

Circuit : Andy Collinson
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Description:

A stereo line driver for feeding long cables or buffering an audio source.

Notes

This preamplifier has a low output impedance, and is designed to drive long cables, allowing you to listen to a remote music source without having to buy expensive screened cables. The very low output impedance of around 16 ohms at 1KHz, makes it possible to use ordinary bell wire,loudspeaker or alarm cable for connection. The preamplifier must be placed near the remote music source, for example a CD player. The cable is then run to a remote location where you want to listen. The output of this preamp has a gain of slightly less than one, so an external amplifier must be used to drive loudspeakers.
Source: http://www.zen22142.zen.co.uk

Voltage Follower Circuit

mostfa_me@yahoo.com (worldtechnical) — Thu, 03 Sep 2009 19:04:00 +0000

Two examples of the most common types of Voltage followers (buffers). You can find some theory behind them in our amplifier gain and buffer amplifier pages.

Transistor voltage follower:

This first circuit is a very simple one transistor voltage follower. Consist of two biasing resistors, and one other resistor at the emitter to acquire the output voltage from.

How it works:

The first to resistors connected to the transistor's base are forming a voltage divider, in order to set a biasing point for the transistor to work in our desired range. Then the transistor, our gain component for the circuit which in this case is only used as a gateway to isolate two circuit stages.

The resistor in the emitter is used to create a voltage from the current passing from the transistor; Without it we can't get any voltage as our output would be effectively shorted to ground (0 volts).

The capacitors that are displayed in the schematic are optional, but very useful to prevent a wrong operation of the circuit, specially in audio or high frequency uses. they stop any DC voltage to move or otherwise disrupt the bias point of the transistor, thus causing undesired operation. If you build this circuit only with dc remove the capacitors, as they will prevent the circuit from functioning under those conditions.

Transistor voltage follower

Op Amp Voltage Follower:

This circuit's operation is far more predictable and stable than the transistor version, and also requires less external components.

How it works:

Works as described above, no external elements to explain. This circuit uses feedback to maintain the voltage output the same as the input. Note that this schematic does not display power, ground and other connections for the op amp, these vary widely among manufacturers and op amps so refer to your op amp's datasheet for pinouts and power connections.
Opamp voltage follower
Source: Electronic Circuits For Beginners

5 Zone Alarm System

mostfa_me@yahoo.com (worldtechnical) — Tue, 01 Sep 2009 19:14:00 +0000

5 Zone Alarm System

Circuit : Andy Collinson
Email: anc@mitedu.freeserve.co.uk Description
This is a complete alarm system with 5 independent zones suitable for a small office or home environment. It uses just 3 CMOS IC's and features a timed entry / exit zone, 4 immediate zones and a panic button. There are indicators for each zone a "system armed" indicator. The schematic is as follows:
Circuit Notes:
Each zone uses a normally closed contact. These can be micro switches or standard alarm contacts (usually reed switches). Suitable switches can be bought from alarm shops and concealed in door frames, or window ledges.

Zone 1 is a timed zone which must be used as the entry and exit point of the building. Zones 2 - 5 are immediate zones, which will trigger the alarm with no delay. Some RF immunity is provided for long wiring runs by the input capacitors, C1-C5. C7 and R14 also form a transient suppresser. The key switch acts as the Set/Unset and Reset switch. For good security this should be the metal type with a key.
Operation:
At switch on, C6 will charge via R11, this acts as the exit delay and is set to around 30 seconds. This can be altered by varying either C6 or R11. Once the timing period has elapsed, LED6 will light, meaning the system is armed. LED6 may be mounted externally (at the bell box for example) and provides visual indication that the system has set. Once set any contact that opens will trigger the alarm, including Zone 1. To prevent triggering the alarm on entry to the building, the concealed re-entry switch must be operated. This will discharge C6 and start the entry timer. The re-entry switch could be a concealed reed switch, located anywhere in a door frame, but invisible to the eye. The panic switch, when pressed, will trigger the alarm when set. Relay contacts RLA1 provide the latch, RLA2 operate the siren or buzzer.

Source:www.zen22142.zen.co.uk

Emergency Light & Alarm

mostfa_me@yahoo.com (worldtechnical) — Tue, 01 Sep 2009 19:07:00 +0000

Emergency Light & Alarm

Four switchable options

Parts:

R1____________220K   1/4W Resistor
R2____________470R   1/2W Resistor
R3____________390R   1/4W Resistor
R4______________1K5  1/4W Resistor
R5______________1R   1/4W Resistor
R6_____________10K   1/4W Resistor
R7____________330K   1/4W Resistor
R8____________470R   1/4W Resistor
R9____________100R   1/4W Resistor

C1____________330nF  400V Polyester Capacitor
C2_____________10µF   63V Electrolytic Capacitor
C3____________100nF   63V Polyester Capacitor
C4_____________10nF   63V Polyester Capacitor

D1-D5________1N4007 1000V 1A Diodes
D6______________LED  Green (any shape)
D7___________1N4148   75V 150mA Diode

Q1,Q3,Q4______BC547   45V 100mA NPN Transistors
Q2,Q5_________BC327   45V 800mA PNP Transistors

SW1,SW2________SPST Switches
SW3____________SPDT Switch

LP1____________2.2V or 2.5V 250-300mA Torch Lamp

SPKR___________8 Ohm Loudspeaker

B1_____________2.5V Battery (two AA NI-CD rechargeable cells wired in series)

PL1____________Male Mains plug

Device purpose:

This circuit is permanently plugged into a mains socket and NI-CD batteries are trickle-charged. When a power outage occurs, the lamp automatically illuminates. Instead of illuminating a lamp, an alarm sounder can be chosen.
When power supply is restored, the lamp or the alarm is switched-off. A switch provides a "latch-up" function, in order to extend lamp or alarm operation even when power is restored.

Circuit operation:

Mains voltage is reduced to about 12V DC at C2's terminals, by means of the reactance of C1 and the diode bridge (D1-D4). Thus avoids the use of a mains transformer.
Trickle-charging current for the battery B1 is provided by the series resistor R3, D5 and the green LED D6 that also monitors the presence of mains supply and correct battery charging.
Q2 & Q3 form a self-latching pair that start operating when a power outage occurs. In this case, Q1 biasing becomes positive, so this transistor turns on the self latching pair.
If SW3 is set as shown in the circuit diagram, the lamp illuminates via SW2, which is normally closed; if set the other way, a square wave audio frequency generator formed by Q4, Q5 and related components is activated, driving the loudspeaker.
If SW1 is left open, when mains supply is restored the lamp or the alarm continue to operate. They can be disabled by opening the main on-off switch SW2.
If SW1 is closed, restoration of the mains supply terminates lamp or alarm operation, by applying a positive bias to the Base of Q2.

Notes:

Close SW2 after the circuit is plugged.
Warning! The circuit is connected to 220Vac mains, then some parts in the circuit board are subjected to lethal potential!. Avoid touching the circuit when plugged and enclose it in a plastic box.

This circuit was awarded with publication in ELECTRONICS WORLD "Circuit Ideas", September 2001 issue, page 708.

Source : http://english.cxem.net/guard/guard17.php

7 Segment LED Counter

mostfa_me@yahoo.com (worldtechnical) — Mon, 31 Aug 2009 02:03:00 +0000

This simple counter can be used to count pulses, as the basis for a customer counter (like you see at the doors of some stores), or for anything else that may be counted. The circuit accepts any TTL compatible logic signal, and can be expanded easily (see Notes).

Schematic

7 Segment Display Reference

Parts

Part	Total Qty.	Description	Substitutions
R1-R7	7	470 Ohm 1/4 Watt Resistor
U1	1	74LS90 TTL BCD Counter IC	7490,74HC90
U2	1	74LS47 TTL Seven Segment Display Driver IC	7447,74HC47
DISP1	1	Common Anode 7 Segment LED Display
MISC	1	Board, Sockets For ICs, Wire

Notes

All pulses to be counted are to be TTL compatible. They should not exeed 5V and not fall below ground.
You can add more digits by building a second (or third, or fourth, etc...) circuit and connecting the pin 11-6 junction of the 74LS90 and 74LS47 to pin 14 of the 74LS90 in the other circuit. You can keep expanding this way to as many digits as you want.

Source : http://www.aaroncake.net/circuits/counter.asp

60 LED Clock

mostfa_me@yahoo.com (worldtechnical) — Mon, 31 Aug 2009 02:01:00 +0000

This months project is based on the 4017 chip that we used in a project last month. If you haven't had a chance to review the basics of the 4017 chip you may want to review the info presented in June's project of the month.

As you can see see we have changed the circuit a little. For example, the 4093 NAND gate is now set to exactly 1 second clock pulses. The clock rate is determined by the resistor and capacitor combination on the 4093. If the resistor is 220k ohms and the capacitor is 4.7uf then the output will be 1 second clock pulses. To increase the clock rate you should decrease the value of the resistor or capacitor. To decrease the clock rate you should increase the value of the resistor or capacitor. Please remember to ground all unused legs of the 4093 or noise in the circuit will occur and cause the clock to malfunction. Therefore, ground pins 5,6,8,9,12, and 13. To operate the circuit simply move the switch from STOP to RUN.

Simple Surround Sound Decoder

mostfa_me@yahoo.com (worldtechnical) — Mon, 31 Aug 2009 01:53:00 +0000

Introduction

This surround-sound decoder is based on the "Hafler" principle, first discovered by David Hafler sometime in the early 1970s. The original idea was to connect a pair of speakers as shown in Figure 1, for use as the rear speakers in the surround setup.

This is ok just as it stands, but problems are created if the main speakers are bi-amped or using bridging, for example, since there is no longer a full-range / full power signal available for the rear speakers. There is also no way to control the level reproduced, since it will always simply be the difference signal between left and right channels.

If the signal is mono, then the signal in both channels will always be more or less identical, and there will be no output from the rear speakers at all.

Figure 1 - The Original "Hafler" Surround-Sound Matrix

This circuit works by allowing the rear speakers to reproduce only the difference signal between the left and right outputs. All stereo encoded material has some difference between left and right channels (if it didn't, it would be mono), and it is this difference signal that is reproduced by the rear speakers.

It is important to ensure that the connection between the rear speaker negative terminals is not earthed, or they will simply be in parallel with the main speakers.

Line Level Passive Version

So, if you want to use separate amps for the rear speakers, basically you can't - unless you get sneaky. The first circuit in Figure 2 is completely passive, but requires that a suitable transformer is available. A suitable transformer means a line level, 10k impedance unit with a 1:1 ratio - these are very scarce (I would suggest almost impossible to get).

You might be able to get away with a 600 Ohm unit, but because of the impedances you need, its performance will be very ordinary, with an extreme lack of bass (there is not enough inductance for a 600 Ohm transformer to work satisfactorily at high impedances). Loading the transformer will give back some of the bass, but the preamp is unlikely to be very happy with the resulting impedance.

Figure 2 - A Passive Line Level Hafler Matrix Decoder

The circuit shown is not a bad compromise, although the impedances are too low for anything other than a solid state preamp (preferably using opamps). Using a telephony transformer (600 Ohm), the loss overall is about 3dB, with a low frequency -3dB point around 100Hz. This will vary depending on the quality of the transformer used, so experimentation will be needed. Although 600 Ohm telephony transformers are reasonably readily available, many of them are pretty nasty (actually, disgusting is probably closer).

My tests were on a really good one, built by an Australian company called Transcap. I think I can say with some certainty they will be rather unwilling to sell one-off quantities. Another manufacturer of really nice transformers is Midcom in the US, but you will have the same problem with them. These manufacturers are set up to deal with large orders from other companies, not the likes of you and me wanting one ("You want ... ONE ??") transformer. As a result you will have to take whatever you can get.

Since it is unlikely that this will be viable for most constructors, the alternative is to go active, using a dual opamp to perform the functions. This is described next.

The New Circuit

The schematic shown in Figure 2 is a simple way to achieve the same thing (with some additional benefits) at line level (i.e. before the signal reaches the power amplifiers - in a bi-amped system, this circuit must be between the preamp and the electronic crossover). The extras available are readily apparent:

Wiring is simplified (although additional power amplifiers are needed)
We now have a centre channel signal available
Provision for a mono signal to a sub-woofer is easy

Figure 3 - The Schematic of an Enhanced Hafler Matrix Decoder

Although there have been similar circuits published over the years, this is a little different in a few areas. I wanted to avoid having any active electronics in the main Left and Right channels, since this eliminates any possibility of sound degradation due to the introduction of the opamps. The input impedance of 50k will not pose a problem for any preamp (including valve types), and the main signal is simply in parallel with the additional circuitry.

No volume control has been included, since you already have one in the preamp. It would just become another component to fiddle with, and since it would be rarely used, would probably become noisy over time.

How It Works
Opamp U1A is connected as a subtracting amplifier. Should the same signal be applied to both inputs, the output is zero. As a result, it will remove all common information from the stereo signal, and reproduce only the difference signal - in exactly the same way as the original Hafler design.

U1B is a simple summing amplifier, and the output contains all the information from both the left and right channels. A possibility that springs to mind is that we could then subtract the difference information from this output, so that only material that is absolutely common to both channels would be reproduced. Would this improve the performance to the extent that the extra circuitry is warranted? I tend to doubt it, but will look into this further.

Centre Channel Control
The pot (VR1) is to set the centre channel level. This can be a trimpot, or a conventional pot mounted at the rear (to help prevent "fiddlers" from mucking up the settings you like). I have seen circuits which do not include this, which seems basically a bad idea. When the two channels are summed, the centre channel will typically have a level of -3dB relative to the left and right channels - provided the signal is not mono. Centre channel speech (for example) will be mono, so the level will be equal to that of each of the main speakers. Since the centre channel amp and speakers are rarely as powerful as the main Left and Right channels, there is a distinct possibility of overload of the amp, the speaker or both.

Since the centre channel is supposed only to fill the "hole" and provide a stable centre sound image, it does not need to be as loud - especially since it will almost certainly have inferior sound quality to the main speakers and will therefore degrade the overall sound quality. The level control will allow you to set the level to just sufficient to provide the stable sound image, and no more.

The capacitor (C1) is optional. It provides a nominal 8kHz roll-off frequency (which is apparently quite normal for "real" surround-sound processors). This helps to minimise any disturbance to the main stereo signal, but feel free to leave it out, since most centre channel speakers probably won't be able to reproduce much above this frequency anyway.

Sub-Woofer Output
The sub-woofer output is simply taken directly from the centre channel mixer, and I included no low-pass filter because I don't know of any sub which does not have a filter already. Adding another one simply adds unnecessary complexity, and will introduce phase shift at the output that a phase compensation circuit (often included in sub woofers) may not be able to cope with.

Miscellaneous
The 100 Ohm resistors in the outputs are to prevent the capacitance of the signal leads causing the opamps to oscillate. At this value, they will cause no high frequency loss, unless you insist on 100m long signal leads (in my experience, these are uncommon).

It will also be noticed that there are two outputs for the rear speakers, simply in parallel. I included this because it is easier to wire if the user is connecting a stereo amp for the rear speakers. Naturally, a mono amp will do just fine, as long as it is capable of driving the two rear speakers in parallel. This may not be possible if the speakers are 4 Ohm types (these are becoming more common in hi-fi, so its not that silly).

Construction

The unit can be housed in any suitable metal case (it does not need to be displayed, and can hide up the back of the cabinet). A metal case is preferred to prevent any noise (especially hum) pickup from mains cables, etc. To power the unit, I suggest the power supply presented in Project 05 - this is simple, safe and cheap.

Since heat generation is not an issue, the case can be as small as you like, as long as there is enough room for the RCA connectors and other components. Be careful that you don't pack everything in the case too tightly, though, because you might create short circuits jamming everything in if it is too small.

The dual opamp and other components can be wired on a piece of Veroboard (or similar), and layout is not critical. As always, use 1% metal film resistors throughout, for minimum noise and maximum stability and reliability. It is expected that this circuit will be extremely reliable as long as care is taken when building it, so there is no need to make it so it is easily serviced. I have built similar devices in the past that have never required repair in over 20 years.

All RCA connectors can be hard wired, and since crosstalk is not likely to be a problem with this unit, the wiring is not critical. You must pay close attention to earthing - all RCA sockets and the power supply centre-tap (0Volt line) must be connected securely to the case to prevent noise pickup.

If desired, 100nF polyester caps can be connected in parallel with the 100uF supply bypass capacitors, but they are not really needed and performance will not suffer if they are omitted.

Delay Line

One thing that is missing from this simple circuit is a delay line. This is normally used to delay the sound supplied to the rear speakers, and effectively makes the sound stage larger by making the rear speakers sound further away. It also adds a degree of additional ambience, and is used in virtually all commercial surround decoders.

Unfortunately, although a delay line project was published, the IC disappeared within minutes - it is no longer made or available. A new one may (or may not) be published some time in the future.

Source : http://english.cxem.net/equaliser/equaliser6.php

100 Watt sub woofer amplifier

mostfa_me@yahoo.com (worldtechnical) — Mon, 10 Aug 2009 18:10:00 +0000

Description.
This is the circuit diagram of a fully transistorized sub woofer amplifier that can produce an output of 100W.There are seven transistors including four in the output stage. The transistors Q1 and Q2 form the preamplifier stage. Transistors Q4 to Q7 form the output stage. Since no ICs are used the circuit is very robust and can be easily assembled on a general purpose PCB.

Circuit diagram with Parts list.

Notes.

The circuit can be powered from a +35V/-35V, 5A dual power supply.
Use a 100W, 12 inch sub woofer at the output.
All electrolytic capacitors must be rated 100V.
The transistor Q4 to Q7 must be fitted with heat sinks.

Source : http://www.circuitstoday.com

Simple 10W audio amplifier

mostfa_me@yahoo.com (worldtechnical) — Mon, 10 Aug 2009 17:37:00 +0000

Description.
The circuit given below is of a simple audio amplifier that can deliver 12W to an 8 Ohm speaker. Op amp IC TL081 is used as the preamplifier here. Actually any opamp with matching power supply ratings can be used instead of TL081.Transistors Q1 and Q2 (TIP125 and TIP120) comprises the power amplifier stage. Output is taken from the collector junction of two transistors.

Circuit diagram.

Notes.

The circuit can be assembled on a Vero board.
Heat sinks are recommended for the transistors.
A +15V/-15V dual DC power supply can be used to power the circuit.
It is better to mount IC1 on a holder.

Source : http://www.circuitstoday.com

Lamp flasher using LM395

mostfa_me@yahoo.com (worldtechnical) — Mon, 10 Aug 2009 17:25:00 +0000

Description.
This powerful lamp flasher circuit is ideal for use in automobiles. The circuit is based on IC LM395 (also known as super transistor) which is a very powerful integrated monolithic power transistor with features such as thermal overload protection, current limiting etc. In fact this IC is almost indestructible.The IC can handle currents up to 1A and switch 40V in less than 500 nano seconds. Resistance R1 and capacitor C1 determines the frequency of flashing. With the stated values flash rate is around 1 flash per second.

Circuit diagram with Parts list.

Notes.

The circuit can be assembled on a Vero board.
Lamp L1 can be a 12V, 1A one.
An optional 1A fuse can be connected series to the positive supply line.

Source : http://www.circuitstoday.com