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Monday, December 14, 2009

Audio Signal Tracer Circuit

Free Electronic Project
Schematics - Audio Signal Tracer Circuit
This schematics function is to enable one to trace an audio
signal through a maze of wires running around the house.





As shown in the schematic above, when a inductor coil L1 is brought near the wire carrying the audio signal, the audio signal will be induced into the coil and the signal is fed to the inverting input of op-amp IC1-a. It is then amplified by and the amplified output is fed to IC1-b iverting input. The second op-amp increases the signal level to drive a set of low impedance headphone, Z1. The coil L1 is made by using a size #30 enamel coated copper wire wound on a 1.25 inch length of a 0.25 inch diameter ferrite rod. Use a turn of appoximately 80 to 100 turns. It can be located several feet from the circuit and connected it through a shielded cable
.

Parts List
The parts list is as shown below.



Melody Music Generation Using M348X CMOS IC

Melody Music Generation Project
The M348X series is a mask-ROM-programmed multi-instrument melody generator , implemented by CMOS technology. It is designed to play the melody according to the previously programmed information. The device also includes a pre-amplifier which provides a simple interface to the driver circuit. The M348X series is intended for applications such as toys, door bells, music box, melody clock/timers and telephones.
This project based on the M348X IC is the electronic equivalent of a mechanical music box. It has a range of tunes and is activated by light falling on a light dependent resistor (LDR) sensor. It can be placed anywhere that you want a tune to play when light falls on it: a cupboard, music box. There could be some applications where the LDR is replaced by a switch or a push-button.
Christmas music is available when M3481 is used.
Jingle Bells
Santa Claus Is Coming To Town
Silent Night, Holy Night
Joy To The World
Rudolph, The Red-nosed Reindeer
We Wish You A Merry Christmas
O Come, All Ye Faithful
Hark, The Herald Angels Sing


The following music is available when M3485 is used.

The Hawaiian Wedding Song
Try To Remember
Aloha OE
Butterfly Love Story
Yesterday





Melody Music Generation Description
When light falls on the LDR, the music IC is enabled by the positive potential appearing on pin 2. The sensitivity of the LDR can be changed by varying the value of the 100K in the SIL connected to pin 2. A tune is selected by pushing the PCB-mounted tact switch. The jumper J1 determines whether the selected tune will play continuously or will cycle through all the tunes available in the IC. The musical pitch is determined by the resistor R1. Decreasing the value of R1 lowers the pitch, and each tune takes longer to play. The RC network at pin 7 shapes the sound. The speaker is driven by a complementary pair of transistors driven by the IC. Negative feedback is provided by R3 to stabilise the DC voltage at the emitters of Q1 & Q2.
Jumper J2 selects whether or not a tune stops immediately when light is removed from the LDR, or it plays right through to its end before stopping. In the idle state the circuit draws about 50uA, and about 20mA when it is operating. Therefore, there is no need for an off/on switch.

Melody Music Parts List
The parts list for the project is as shown below.


Alarm Generator Project (Melody Music)

Melody Music Project Description
This simple alarm generator electronics circuit utilizes a UM66TXXL TO92 package CMOS IC that generates song depending on the type of IC used. It has a built in oscillation circuit and need only a few external components to make it work. It is powered by a power supply range from 1.5V to 4.5 V DC with low power consumption, hence a longer battery lifetime. Once it power on reset, the melody will begin to sound. The part number for different songs are as listed below.


UM66T05L Home Sweet Home
UM66T11L Love Me Tender
UM66T19L For Alice
UM66T32L COO COO waltz

The IC can be used to drive a buzzer directly or driving a speaker though the use of a transistor.









Parts List

50W Electronic Amplifier Constructional Project

Introduction To 50W Electronic Amplifier
This electronic amplifier project is based on an IC amplifier module from ST Microelectronics, the TDA7294. It is intended for use as a high quality audio class AB amplifier in hi-fi applications. It has very low noise and distortion, wide bandwidth and good output current capability, enabling it to supply high power into both 4 ohm and 8 ohm loads. It has both short circuit and thermal protection.
With the addition of a handful of parts and a suitable power supply, this module will deliver over 50W RMS into 4 or 8 ohms with < 0.1% Total Harmonic Distortion (THD) and < 0.1% Intermodulation Distortion (IMD). It is also suitable as a replacement power amp stage, or upgrade for many existing amplifiers of between 30W-50W, provided they have a suitable dual supply, and most do.

The Specifications of the electronic amplifier project are:
D.C. Input : 35V
Output power : > 50W RMS, 4-8 ohm load.
Gain : 24 dB (30dB modification)
Input sensitivity : 1.3V for 50W, 8 ohm
Signal-to-Noise ratio : > 95 dB, (>105 dBA)
Frequency response : approx. 20Hz - 200kHz, –3 dB
Slew rate : > 10V/uS
THD : < 0.01%, 1W-40W, 1kHz
IMD : < 0.01%, 1W

The maximum supply voltage of the IC is +/- 40V. However the maximum dissipation of the IC can be exceeded even at a lower voltage. Therefore the supply voltage used need not be more than +/- 35V. This can be constructed using a 50V center tapped transformer, a diode bridge rated at 5A (min.) and a pair of electrolytic capacitors, as shown below. A lower secondary voltage transformer could also be used but the reduced DC voltage will result in less power output into 8 ohms. You can still obtain 50W into 4 ohms with only 24V supply rails.
A 36V C.T. transformer will give you approx +/- 25V rails. The mains transformer used should be rated at a minimum of 80VA. If you want to run two modules in a stereo amplifier you can use a common power supply. In this case the transformer should be rated at 150VA or greater.



Electronic Amplifier Circuit Diagram Description



 Most of the circuitry is contained within the IC module. The input signal is applied to pin 3 via capacitor C1 and low-pass filter R1/C2. The filter improves the pulse response and helps stop RF signals. The lower -3dB point is determined by R2/C1 and R4/C3. This is approximately 20Hz for the values used. The upper -3dB point is over 200kHz. C7/C8 and C9/C10 provide extra power supply filtering or decoupling.

R3/R4 are the feedback resistors. The gain is 1+R3/R4 which is approx 16 times, or 24dB. If you wish to increase the input sensitivity you may change the resistors to suit. Changing R3 to 22k would increase the gain to 30dB and lower the input required for 50W into 8 ohm, to 0.6V, without affecting performance too much. If you reduce the value of R4 you will also need to increase C3 to maintain bass response, as this sets the feedback low frequency roll off.
Pin 10 is a mute input and pin 9 provides a standby mode. Muting should always take place before standby mode is selected. Connecting these pins permanently to the supply rail ensures that the amplifier comes on immediately on power up. Any switch-on clicks may be eliminated by increasing the time constants of R5/C4 and R6/C5 if necessary.
Ensure that a heavy duty heatsink rated at least 1.4 degree C/W or better is used.
Electronic Amplifier Parts List

The parts list of this project is as shown below.





You may download the full data sheet for the Electronic Amplifier TDA7294 here from ST website.

25W Audio Power Amplifier Constructional Project

25W Audio Power Amplifier Constructional Project






25W Audio Power Amplifier
This audio power amplifier project is based on LM1875 amplifier module from National Semiconductor. It is able to deliver up to 30W of power using an 8 ohm load and dual 30V DC power supplies. It is designed to operate with minimum external components with current limit and thermal shutdown protection features . Other features include high gain, fast slew rate, wide power supply range, large output voltage swing and high current capability.
Summary of the audio amplifer features:
  • Low distortion: 0.015%, 1 kHz, 20 W
  • Wide power bandwidth: 70 kHz
  • Wide supply range 16V-60V
  • Up to 30 watts output power
  • Internal output protection diodes
  • Protection for AC and DC short circuits to ground
  • 94 dB ripple rejection
  • Plastic power package TO-220


25V Power Supply
The schematic below shows how the +25V DC and -25V DC are obtained. In order to provide power supply for 2 stereo amplifiers, a power transformer rating of 80VA with 240V/36V centre tapped secondary winding is used. The secondary output of the transformer is rectified by using four 1N5401 diodes together with 4 electrolytic capacitors to smoothen the ripple voltage. A fuse and a varistor are connected at the primary input to protect the circuit against power surge.









Audio Amplifier Module The +25V and -25V DC power supply are connected to the audio amplifier module through a 2A fuse with the peripheral devices shown in the schematic below. The audio input signal to be amplified is coupled to pin 1 of LM1875 through the resistor R1 and electrolytic capacitor E5.
The output signal at pin 4 of LM1875 can be used to directly drive a 8 ohm loudspeaker. Resistor R6 and capacitor C5 prevent the capacitance developed at the long speaker leads from driving the amplifier into Very High Frequency Oscillation.
A heatsink with a thermal resistance rating of 1.4 Celcius/Watt or better must be used or else the amplifer module will be cut-off from operation due to the heat that will build up during the operation of the amplifier. Take note that the heat sink tab on the IC module is internally connected to the -25V power supply hence it must be isolated from the heat sink by the use of an insulating washer. If this is not done, the negative rail will be shorted to ground.






Power Amplifier Parts List



The specifications of the Audio Power Amplifier LM1875 can be obtained from National Semiconductor website.

10 W Audio Amplifier Constructional Project

Introduction
This audio amplifier
project is a class AB audio power amplifier
using a TDA2003 module power amplifier. It is easy to construct and has only a few external components. The module is designed with short circuit and thermal protection. It can drive loads as low as 1.6 ohm and is capable of delivering over 10 watts from a 16 V DC power supply. Figure 1 shows the TDA 2003 packaged and pin configuration.




The power supply required for is 8 - 18V DC at 1 Amp or more. Maximum output power will only be obtained with a power supply of greater than 1A at 16V DC, and using 2 ohm speakers (or 2 by 4 ohm speakers in parallel). However approximately 4W RMS can be obtained with a 12V DC, 1A supply into a 4 ohm load. The power supply should be well filtered to reduce mains hum, the on board capacitors alone are not adequate for this purpose but are necessary to ensure stability. Extra filtering is unnecessary if operating from a battery. If two boards are used for stereo, you will need to double the size of the power supply.


Audio Amplifier Circuit Diagram









The major circuitry is contained in the amplifier module. C1 is the input coupling capacitor and blocks DC signal, so does C3 which is the output coupling capacitor, and C2 which blocks DC from the feed back loop to the differential input. R2 and R3 set the level of feed back. C4 and R4 provide a high frequency load for stability where loudspeaker inductive reactance may become excessive. C5 and C6 provide power supply decoupling or filtering. There should be no problems with the stability of the circuit, however if you do, make sure the power supply filtering and leads are adequate. If necessary you might connect an RC compensation network between IC pins 2 and 4 as in the data sheet. Values for Cx of 22 - 33 nF and for Rx of 39 - 47 ohms, should be satisfactory whilst still maintaining satisfactory high frequency response.
The gain is equal to 1 + (R2/R3) = 101, or 40 dB, minus any input attenuation. You may reduce the overall gain by increasing the value of R3 if you are only able to use part of the potentiometer range as a volume control. For example, an R3 of 10 ohms will give a gain of 23 (27dB).



Parts List

The parts list of this project is as shown below.





TDA2003 data sheet can be downloaded from Audio Amplifier TDA2003 ST Website

Need to know in Electronics

A circuit diagram (also known as an electrical diagram, elementary diagram, or electronic schematic) is a simplified conventional pictorial representation of an electrical circuit. It shows the different components of the circuit as simplified standard symbols, and the power and signal connections between the devices. Arrangement of the components interconnections on the diagram does not correspond to their physical locations in the finished device.

Unlike a block diagram or layout diagram, a circuit diagram shows the actual wire interconnects being used. The diagram does not show the arrangement of components. A drawing meant to depict what the circuit actually looks like is called "artwork" or "layout".

Circuit diagrams are used for the design (circuit design), construction (such as PCB layout), and maintenance of electrical and electronic equipment.

Legends

Enlarge picture
Common circuit diagram symbols (with US Resistor Symbol)


On a circuit diagram, the symbols for components are labelled with a descriptor (or reference designation) matching that on the list of parts. For example, C1 is the first capacitor, L1 is the first inductor, Q1 is the first transistor, and R1 is the first resistor (note that it isn't written R1, L1,…). The letters that precede the numbers were chosen in the early days of the electrical industry, even before the vacuum tube (thermionic valve), so "Q" was the only one available for semiconductor devices in the mid-twentieth century . Often the value or type designation of the component is given on the diagram beside the part, but detailed specifications would go on the parts list.

Symbols

Circuit diagram symbols have differed from country to country and have changed over time, but are now to a large extent internationally standardized. Simple components often had symbols intended to represent some feature of the physical construction of the device. For example, the symbol for a resistor shown here dates back to the days when that component was made from a long piece of wire wrapped in such a manner as to not produce inductance, which would have made it a coil. These wirewound resistors are now used only in high-power applications, smaller resistors being cast from carbon composition (a mixture of carbon and filler) or fabricated as an insulating tube or chip coated with a metal film. To illustrate this, European circuit diagrams have replaced the zig-zag symbol by a simple oblong, sometimes with the value in ohms written inside. A less common symbol is simply a series of peaks on one side of the line representing the conductor, rather than back-and-forth as shown here.

Circuit symbols are standardized, using either ANSI standard Y32 or IEC standard 60617DB (a standard in database format). Different symbols may be used depending on the discipline using the drawing; for example, lighting and power symbols used as part of architectural drawings may be different from symbols for devices used in electronics.

Linkages

Enlarge picture
Schematic wire junctions:
1. Old style: (a) connection, (b) no connection.
2. Early CAD style: (a) connection, (b) no connection.
3. New style: (a) connection, (b) no connection.
The linkages between leads were once simple crossings of lines; one wire insulated from and "jumping over" another was indicated by it making a little semicircle over the other line. With the arrival of computerized drafting, a connection of two intersecting wires was shown by a crossing with a dot or "blob", and a crossover of insulated wires by a simple crossing without a dot. However, there was a danger of confusing these two representations if the dot was drawn too small or omitted. Modern practice is to avoid using the "crossover with dot" symbol, and to draw the wires meeting at two points instead of one. It is also common to use a hybrid style, showing connections as a cross with a dot while insulated crossings use the semicircle.

European and Australian codes

The following codes which vary slightly from the American codes are in common use in European & Australian standard electrical circuit diagrams. These codes are used for the "reference designators" printed on PCBs (which match the corresponding ones written on the corresponding schematic).

A - Assemblies
B - Transducers (Photo cells, Inductive Proximity, Thermocouple, Flame Detection)
C - Capacitors
D - Storage Devices
E - Miscellaneous
F - Fuses
G - Generator, Battery Pack
H - Indicators, Lamps (not for illumination), Signalling Devices
K - Relays, Contactors
L - Inductors and Filters
M - Motors
N - Analogue Devices
P - Measuring/Test Equipment
Q - Circuit Breakers, Isolators, Re-closers
R - Resistors, Brake Resistors
S - Switches, Push Buttons, Emergency stops and Limit Switches
T - Transformers
U - Power Converters, Variable Speed Drives, Soft Starters, DC Power Supplies
V - Semiconductors
W - Wires, Conductors, Power, Neutral & Earthing Busses
X - Terminal Strips, terminations, joins
Y - Solenoids, Electrical actuators
Z - Filters

Amplifiers and Transistors

Introduction to Amplifier
Amplification is the process of increasing the amplitude of a AC signal current or voltage such as audio signal for sound or video signal for a television picture. The amplifier allows a small input signal to control a larger amount of power in the output circuit. The output signal is a copy of the original input signal but has higher amplitude.
Amplification is neccessary as in most applications, the signal is too weak to be used directly. For example, an audio output of 1mV from a microphone is not able to drive a loud speaker which requires a few volts to operate. Hence, the signal need to be amplified to a few volts before it can be fed into the loud speaker.
NPN Transistor Circuit Configurations
An example of different type of transistor configurations in the circuit is as shown in Figure 1 below.









a) The common emitter(CE) circuit uses emitter as its common electrode. The input signal is applied to the base and the amplified output is taken from the collector. This is the one generally use because it has the best combination of current gain and voltage gain. b) The common base (CB) circuit uses base as its common electrode. The input signal is applied to the emitter and the amplified output is taken from the collector. The relatively high emitter current compared to the base current results in very low input impedance value. For this reason, the CB circuit is seldom used.
c) The common collector (CC) circuit uses collector as its common electrode. The input signal is applied to the base and the amplified output is taken from the emitter. This circuit is also called an emitter follower. This name means that the output signal voltage at the emitter follows the input signal at the base with the same phase but less amplitude. The voltage gain is less than 1 and is usually used for impedance matching. It has high input at the base as a load for the preceding circuit and low output impedance at the emitter as a signal source for the next circuit.
Classes
They can be classified into classes A, B, C and AB. They are defined based on the percent of the cycle of input signal that is able to produce output current.
In Class A, the output current flows for the full cycle of 360 degree of input signal. The distortion is the lowest with around 5% to 10% and an efficiency of 20% to 40%. In general, most small signal operate class A
In Class C, the output current flows for less than one half of the input cycle. Typical operation is 120 degree of input current during the positive half cycle of the input current. This class has an efficiency of 80% but has the highest distorton. This class is usually used for RF amplificaton with a tuned circuit in the output.
In Class B, the output current flows for one half of the input cycle which is around 180 degree. Class B operaton lies between class A and class C. Clas B are usually connected in pairs and in such a circuit called push-pull amplifier. The push-pull is often used for audio power output to a loud speaker.
In Class AB, it offers a compromise between the low distortion of class A and the higher power of class B. It is usually used for push-pull audio power amplifiers.

1W Stereo Amplifier Project
This is a 1 watt stereo amplifier module project using KA2209 IC from Samsung.


10W Audio Amplifier Project
This project is a class AB audio power amp. using a TDA2003 module power amplifier. It is easy to construct and has only a few external components.


18W Car Stereo Amp. Constructional Project
This is a 18 watt audio amp. module project using HA13118 IC module from Hitachi.


25W Audio Power Amp. Project
This is a 25 watt audio amplifier module project using LM1875 IC module from National Semiconductor.


50W Electronic Amp. Constructional Project
This is a 50 watt audio amp. module project using TDA7294 IC module from STMicroelectronics.


100W Guitar Power Amp.
If you are into music and plays guitar, this is a good project that you can build to amplify the music from your guitar. The rating of this amplifier is 100W into a 4 ohms load. Take note of the safety procedure as the power is derived directly from the AC mains.

Sunday, December 13, 2009

AC to DC Converter

12V to 120V Inverter






Have you ever wanted to run a TV, stereo or other appliance while on the road or camping? Well, this inverter should solve that problem. It takes 12 VDC and steps it up to 120 VAC. The wattage depends on which tansistors you use for Q1 and Q2, as well as how "big" a transformer you use for T1. The inverter can be constructed to supply anywhere from 1 to 1000 (1 KW) watts.
Important: If you have any questions or problems with the circuit, see the forum topic linked to in the Notes section. It will answer all your questions and provide links to many other (and better) inverter circuits.





Schematic

This is a schematic of the Inverter

Parts

Part

Total Qty.

Description

Substitutions

C1, C2
2
68 uf, 25 V Tantalum Capacitor

R1, R2
2
10 Ohm, 5 Watt Resistor

R3, R4
2
180 Ohm, 1 Watt Resistor

D1, D2
2
HEP 154 Silicon Diode

Q1, Q2
2
2N3055 NPN Transistor (see "Notes")

T1
1
24V, Center Tapped Transformer (see "Notes")

MISC
1
Wire, Case, Receptical (For Output)

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