Thursday, May 16, 2013

STK465 Stereo Power Amplifier circuit

STK465 - 30 watt Stereo Power Amplifier

STK465 - 30 watt Stereo Power Amplifier

Source: http://sharingmanual.blogspot.com/2012/08/stk465-30-watt-stereo-power-amplifier.html

Completed STK465 is an amplifier of acoustic frequencies that offers qualitative output, using minimal exterior elements. Substantially he is one of big completed force. When it functions with tendency 56V then the tendency will be ± 28V as for the ground. With this recommended tendency of catering, the attributed force is 30 WRMS in charge 8 Ohm.

Power Failure Alarm circuit

Description:
This is a very basic alarm designed to let you know when the electricity supply fails. The alarm is powered from a battery which uses no current consumption at all in standby, a battery should therefore last its full shelf life. In use, as long as the electric supply is healthy, relay RLY1 remains energized. Under this (standby) condition, the relay contacts are open and the buzzer will not sound. The battery drain is zero and should last its full shelf life of 2 years or more.

Should the power fail, the relay de-energizes, its contacts close and the alarm is sounded. BZ1 is the audible device and can be a loud piezo type sounder,bell or buzzer. The battery should be chosen to match the sounders operating voltage.
Although drawn with a full power supply; (transformer, bridge rectifier and smoothing capacitor) this can be substituted with a readily available DC adapter. In this case just chose a relay whose operating voltage matches the adapter.
Once power fails, there is no way to stop the sounder, this is why switch S1 is in circuit, to mute the alarm. Electronics Circuit Application

Motorcycle Alarm Circuit

Circuit Notes

Any number of normally open switches may be used. Fit the mercury switches so that they close when the steering is moved or when the bike is lifted off its side-stand or pushed forward off its centre-stand. Use micro-switches to protect removable panels and the lids of panniers etc. While at least one switch remains closed, the siren will sound. About two minutes after the switches have been opened again, the alarm will reset. How long it takes to switch off depends on the characteristics of the actual components used. But, up to a point, you can adjust the time to suit your requirements by changing the value of C1.

The circuit board and switches must be protected from the elements. Dampness or condensation will cause malfunction. Without its terminal blocks, the board is small. Ideally, you should try to find a siren with enough spare space inside to accommodate it. Fit a 1-amp in-line fuse close to the power source. This protects the wiring. Instead of using a key-switch you can use a hidden switch; or you could use the normally closed contacts of a small relay. Wire the relay coil so that it is energized while the ignition is on. Then every time you turn the ignition off, the alarm will set itself.

When it's not sounding, the circuit uses virtually no current. This should make it useful in other circumstances. For example, powered by dry batteries and with the relay and siren voltages to suit, it could be fitted inside a computer or anything else that's in danger of being picked up and carried away. The low standby current and automatic reset means that for this sort of application an external on/off switch may not be necessary. Electronics Circuit Application

Tuesday, May 14, 2013

Audio Security Monitor circuits

Description:
A remote listening circuit. The area to be monitored is connected via a cable and allows remote audio listening.
Notes:
You can use this in your garden and listen for any unusual sounds, or maybe just wildlife noises. If you have a car parked in a remote location, the microphone will also pick up any sounds od activity in this area. The cable may be visible or hidden, screened cable is not necessary and you can use bellwire or speaker cable if desired.

circuits diagram

Resistor Colour code convertor

This page tells you how to download and use the colour code convertor program
Click to Download
Internet Explorer will respond with a dialog box. You can decide whether to save the program to disc and run it later, or to open it straight away. Either way, there may be a further dialog box, giving dire warnings about downloading software from the internet. (DOCTRONICS knows of no problems with the program, but no guarantee is implied.)
The colour code convertor can be copied and distributed freely, but remains copyright ©. Distribution for profit seems unlikely, but is expressly forbidden.
The program was written using Borland Delphi 2.0.

.
How to use the program

.
1. Finding the resistor value corresponding to the colour code:
Hold your resistor with the tolerance band (usually gold) at the right hand end:

Resistors

The resistor's function is to reduce the flow of electric current.
This symbol

is used to indicate a resistor in a circuit diagram, known as a schematic.
Resistance value is designated in units called the "Ohm." A 1000 Ohm resistor is typically shown as 1K-Ohm ( kilo Ohm ), and 1000 K-Ohms is written as 1M-Ohm ( megohm ).

There are two classes of resistors; fixed resistors and the variable resistors. They are also classified according to the material from which they are made. The typical resistor is made of either carbon film or metal film. There are other types as well, but these are the most common.
The resistance value of the resistor is not the only thing to consider when selecting a resistor for use in a circuit. The "tolerance" and the electric power ratings of the resistor are also important.
The tolerance of a resistor denotes how close it is to the actual rated resistence value. For example, a ±5% tolerance would indicate a resistor that is within ±5% of the specified resistance value.
The power rating indicates how much power the resistor can safely tolerate. Just like you wouldn't use a 6 volt flashlight lamp to replace a burned out light in your house, you wouldn't use a 1/8 watt resistor when you should be using a 1/2 watt resistor.

The maximum rated power of the resistor is specified in Watts.
Power is calculated using the square of the current ( I² ) x the resistance value ( R ) of the resistor. If the maximum rating of the resistor is exceeded, it will become extremely hot, and even burn.
Resistors in electronic circuits are typicaly rated 1/8W, 1/4W, and 1/2W. 1/8W is almost always used in signal circuit applications.
When powering a light emitting diode, a comparatively large current flows through the resistor, so you need to consider the power rating of the resistor you choose.

Rating electric power
For example, to power a 5V circuit using a 12V supply, a three-terminal voltage regulator is usually used.
However, if you try to drop the voltage from 12V to 5V using only a resistor, then you need to calculate the power rating of the resistor as well as the resistance value.

At this time, the current consumed by the 5V circuit needs to be known.
Here are a few ways to find out how much current the circuit demands.

Assemble the circuit and measure the actual current used with a multi-meter.

Check the component's current use against a standard table.
Assume the current consumed is 100 mA (milliamps) in the following example.
7V must be dropped with the resistor. The resistance value of the resistor becomes 7V / 0.1A = 70(ohm). The consumption of electric power for this resistor becomes 0.1A x 0.1A x 70 ohm = 0.7W.

Resistance value

As for the standard resistance value, the values used can be divided like a logarithm.

For example, in the case of E3, The values [1], [2.2], [4.7] and [10] are used. They divide 10 into three, like a logarithm.

In the case of E6 : [1], [1.5], [2.2], [3.3], [4.7], [6.8], [10].

In the case of E12 : [1], [1.2], [1.5], [1.8], [2.2], [2.7], [3.3], [3.9], [4.7], [5.6], [6.8], [8.2], [10].

It is because of this that the resistance value is seen at a glance to be a discrete value.

The resistance value is displayed using

( the colored bars/the colored stripes ), because the average resistor is too small to have the value printed on it with numbers.

You had better learn the color code, because almost all resistors of 1/2W or less use the color code to display the resistance value.

Fixed Resistors

A fixed resistor is one in which the value of its resistance cannot change.

Carbon film resistors
This is the most general purpose, cheap resistor. Usually the tolerance of the resistance value is ±5%. Power ratings of 1/8W, 1/4W and 1/2W are frequently used.
Carbon film resistors have a disadvantage; they tend to be electrically noisy. Metal film resistors are recommended for use in analog circuits. However, I have never experienced any problems with this noise.
The physical size of the different resistors are as follows.

Diodes.

Basic kowledge of Electronic parts

A diode is a semiconductor device which allows current to flow through it in only one direction. Although a transistor is also a semiconductor device, it does not operate the way a diode does. A diode is specifically made to allow current to flow through it in only one direction.
Some ways in which the diode can be used are listed here.

A diode can be used as a rectifier that converts AC (Alternating Current) to DC (Direct Current) for a power supply device.

Diodes can be used to separate the signal from radio frequencies.

Diodes can be used as an on/off switch that controls current.
This symbol

is used to indicate a diode in a circuit diagram.

The meaning of the symbol is (Anode)

(Cathode).
Current flows from the anode side to the cathode side.

Although all diodes operate with the same general principle, there are different types suited to different applications. For example, the following devices are best used for the applications noted.

	Voltage regulation diode (Zener Diode) The circuit symbol is . It is used to regulate voltage, by taking advantage of the fact that Zener diodes tend to stabilize at a certain voltage when that voltage is applied in the opposite direction.
	Light emitting diode The circuit symbol is . This type of diode emits light when current flows through it in the forward direction. (Forward biased.)
	Variable capacitance diode The circuit symbol is . The current does not flow when applying the voltage of the opposite direction to the diode. In this condition, the diode has a capacitance like the capacitor. It is a very small capacitance. The capacitance of the diode changes when changing voltage. With the change of this capacitance, the frequency of the oscillator can be changed.

The graph on the right shows the electrical characteristics of a typical diode.

When a small voltage is applied to the diode in the forward direction, current flows easily.
Because the diode has a certain amount of resistance, the voltage will drop slightly as current flows through the diode. A typical diode causes a voltage drop of about 0.6 - 1V (V_F) (In the case of silicon diode, almost 0.6V)
This voltage drop needs to be taken into consideration in a circuit which uses many diodes in series. Also, the amount of current passing through the diodes must be considered.

When voltage is applied in the reverse direction through a diode, the diode will have a great resistance to current flow.
Different diodes have different characteristics when reverse-biased. A given diode should be selected depending on how it will be used in the circuit.
The current that will flow through a diode biased in the reverse direction will vary from several mA to just µA, which is very small.

The limiting voltages and currents permissible must be considered on a case by case basis. For example, when using diodes for rectification, part of the time they will be required to withstand a reverse voltage. If the diodes are not chosen carefully, they will break down.

Rectification / Switching / Regulation Diode

The stripe stamped on one end of the diode shows indicates the polarity of the diode.
The stripe shows the cathode side.

The top two devices shown in the picture are diodes used for rectification. They are made to handle relatively high currents. The device on top can handle as high as 6A, and the one below it can safely handle up to 1A.
However, it is best used at about 70% of its rating because this current value is a maximum rating.
The third device from the top (red color) has a part number of 1S1588. This diode is used for switching, because it can switch on and off at very high speed. However, the maximum current it can handle is 120 mA. This makes it well suited to use within digital circuits. The maximum reverse voltage (reverse bias) this diode can handle is 30V.
The device at the bottom of the picture is a voltage regulation diode with a rating of 6V. When this type of diode is reverse biased, it will resist changes in voltage. If the input voltage is increased, the output voltage will not change. (Or any change will be an insignificant amount.) While the output voltage does not increase with an increase in input voltage, the output current will.
This requires some thought for a protection circuit so that too much current does not flow.
The rated current limit for the device is 30 mA.
Generally, a 3-terminal voltage regulator is used for the stabilization of a power supply. Therefore, this diode is typically used to protect the circuit from momentary voltage spikes. 3 terminal regulators use voltage regulation diodes inside.

Diode bridge

Rectification diodes are used to make DC from AC. It is possible to do only 'half wave rectification' using 1 diode. When 4 diodes are combined, 'full wave rectification' occurrs.
Devices that combine 4 diodes in one package are called diode bridges. They are used for full-wave rectification.

The photograph on the left shows two examples of diode bridges.

The cylindrical device on the right in the photograph has a current limit of 1A. Physically, it is 7 mm high, and 10 mm in diameter.
The flat device on the left has a current limit of 4A. It is has a thickness of 6 mm, is 16 mm in height, and 19 mm in width.

The photograph on the right shows a large, high-power diode bridge.
It has a current capacity of 15A. The peak reverse-bias voltage is 400V.
Diode bridges with large current capacities like this one, require a heat sink. Typically, they are screwed to a piece of metal, or the chasis of device in which they are used. The heat sink allows the device to radiate excess heat.
As for size, this one is 26 mm wide on each side, and the height of the module part is 10 mm.

Light Emitting Diode ( LED )

Light emitting diodes must be choosen according to how they will be used, because there are various kinds.
The diodes are available in several colors. The most common colors are red and green, but there are even blue ones.

The device on the far right in the photograph combines a red LED and green LED in one package. The component lead in the middle is common to both LEDs. As for the remaing two leads, one side is for the green, the other for the red LED. When both are turned on simultaneously, it becomes orange.

When an LED is new out of the package, the polarity of the device can be determined by looking at the leads. The longer lead is the Anode side, and the short one is the Cathode side.

The polarity of an LED can also be determined using a resistance meter, or even a 1.5 V battery.

When using a test meter to determine polarity, set the meter to a low resistance measurement range. Connect the probes of the meter to the LED. If the polarity is correct, the LED will glow. If the LED does not glow, switch the meter probes to the opposite leads on the LED. In either case, the side of the diode which is connected to the black meter probe when the LED glows, is the Anode side. Positive voltage flows out of the black probe when the meter is set to measure resistance.

It is possible to use an LED to obtain a fixed voltage.
The voltage drop (forward voltage, or V_F) of an LED is comparatively stable at just about 2V.

I explain a circuit in which the voltage was stabilized with an LED in Thermometer of bending apparatus-

Shottky barrier diode

Diodes are used to rectify alternating current into direct current. However, rectification will not occur when the frequency of the alternating current is too high. This is due to what is known as the "reverse recovery characteristic."
The reverse recovery characteristic can be explained as follows:
IF the opposite voltage is suddenly applied to a forward-biased diode, current will continue to flow in the forward direction for a brief moment. This time until the current stops flowing is called the Reverse Recovery Time. The current is considered to be stopped when it falls to about 10% of the value of the peak reverse current.
The Shottky barrier diode has a short reverse recovery time, which makes it ideally suited to use in high frequency rectification.