Circuit for Audio Splitter

In general all laptops contain one audio port, and whatever may be the audio devices it should be connected to that single port. Assume that you are playing a game on your pc or laptop in multi mode with a friend during night hours and you don’t want to disturb your parents by switching your speaker on, preferably the choice would be to use a headphone. It is annoying to share the earpiece of headphone, while missing all the sound effects. The circuit given here describes a simple audio splitter which could be easily made and installed and only cost a little. The audio splitter comes with separate volume controls for each headphone.

Circuit Description

This active splitter for laptop audio-out is powered from a USB and provides individual channel gain of 39 dB and individual volume control of a headphone channel. The circuit uses two TDA2822M audio power amplifier ICs for headphones / small speakers. Each 8-pin DIP TDA2822M has two audio power amplifiers: one to serve the left channel, and the other for the right channel (stereo). Therefore to get a two-headphone output, you require four amplifiers ortwo pieces of TDA2822M.The TDA2822M can operate over a voltage range of 1.8V to 15V. The USB port provides 5V and 100mA current, which is more than enough for two pairs of headphones. The circuit comprises four symmetric Sections, each section using half of TDA2822M. The input left and right channels for both the ICs are connected together. That is, the IN(R) of IC1 is connected to IN(R) of IC2. The same applies to the left-channel inputs too. The amount of input signal entering the ICs is controlled by the voltage divider for each channel input: four 47-kilo-ohm potentiometers are used for the four power amplifiers. Since the input resistance of the IC is very high, the effective load at the output port of the laptop is 47 kilo-ohms/ 2= 23.5 kilo-ohms. This does not, in any way, load the audio-out port. The signals that finally reach pins 6 and 7 of the IC are amplified with a voltage gain of about 89, and the amplified signals are fed to the headphones via 470μF electrolytic capacitors. The combination of 0.1μF capacitor and 4.7-ohm resistor helps in reducing the high-frequency noise and lower the possibility of oscillations. The 100 μF at pins 5 and 8 provides AC grounding at audio and higher frequencies. The 10μF capacitors at the Vcc pins suppress the line noise.

Circuit Power

On stripping the outer sheath of the USB cable, you will find five wires (sometimes four). These wires are red, green, white, black (thick) and black (thin) in colour. One of the blacks may be absent in four-wire versions. The red wire provides +5V, while the thick black wire must be used for the ground. In case the thick black wire is absent, the other black wire may be used. Do not use the green and white wires: these are meant for data transfer, so insulate them.

The basic cross section view of sterio jack and sterio socket are given below, incase if you dont know

Power Supply From ur Personal Computer for ur Hardware Projects

If u have a pc then why are you worried about creating a new power supply for your hardware espicially when your project includes controllers or processors. If you are looking for pure power then there is only one place in this world where you get the cleanest power. You can take powre from ur pc without disturbing its normal operation, the article given below helps you to identify the pins and what power they carry...........

A - PS/2 mouse port G - Analog microphone jack

B - PS/2 keyboard port H - Analog line Out/Speaker jack

C - USB 2.0 connectors I - Analog line In jack

D - Serial port J - Integrated RJ-45 network port

E - Integrated Video port K - Parallel port

F - USB 2.0 connectors

Serial port

Serial port was never designed to supply any current to external circuits. Despite of this many manufacturers have designed many circuit which take power from serial port signal lines. With different methods you can realistically get only about 10 mA current at 5V voltage from the serial port. If you take very little current you can get around 11-12V (even +-12V if you set the output pins to right states).

Parallel port

PC parallel port was never designed to supply any power to the equipment connected to it. There are some methods for getting power from parallel port signal lines, but using all methods the voltage drops quite much if you try to get more than 1 mA per output used.

The parallel port in the printer end (36 pin centronics connector) has an option for supplying poer to devices connected to it. The centronics connector has +5V power at pin 18. The power available from this pin is usually limited to about 100 mA.

Keyboard port

Keyboard port has +5V power output to the keyboard. There is few hundred mA current available from this port and the keyboard takes it's own part of this available power. The maximum power available is usually limited by a fuse which is connected between motherboard +5V power line and the +5V output in the keyboard connector. Usually the fuse (typically 1A) is a small component which looks like a resistor and is directly soldered to the motherboard. Some older motherboard have used a normal glass fuse or they have not had fuse at all.
There are two different PC keyboard connector models in use. The older model is 5-pin DIN connector. This connector has +5V available at pin 5 and ground at pin 4. The pin numbering is usually marked in the connectors, but here is the pin numbering of the connector then you look it at your computer back:

The other keyboard connector is PS/2 keyboard connector which is 6-pin mini-DIN connector. This connector has +5V power at pin 1 and ground at pin 2. Here is the pin numbering when you look at the keyboard connector at the back of the computer.

PS/2 mouse port

PS/S mouse port has +5V power output for powering the mouse connected to it. You can get small amouts of power from this port for your own circuits. The computer can turn the PS/2 mouse power off for some times when it initializes the mouse. The mouse does not take much current, so the power capability of this port might not be much (I guess that you can take around 100 mA safely). The pin

out is same as in PS/2 keyboard connector: +5V power is at pin 1 and ground at pin 2. The pin numberin

g is also the same (looking at the connector on the back of the computer):


Joystick port

Joystick port in PC has +5V power output which is directly connected to PC +5V power line. The advantage of this is that there is quite much power available (up to few amperes). The disadvantage is that in short circuit condition there can be over 20 A current flowing and this can easily burn PCB traces and small in your circuit or inside your PC. Here is the pinout of the joystick port:

You can get +5V power from pins 1 and 9. The ground can be found from pins 4 and 5.

Note: Some new PCI soundcards can supply 3.3V instead of standar +5V in the joystick connector. According some articles in the news DIAMOND MM SONIC IMPACT S70 has a 3.3volt game port and it is listed in their readme file for the product. I can just wonder what kind of incompability problems this can cause to existing joystick products and joystick port MIDI inte

rfaces which are designed to use that standard +5V power from normal joystick port.

VESA DDC compliant monitor connector

If your computer graphics card has plug-and-play monitor support, then your computer has a VESA DDC monitor connector. VESA DDC standard defined that monitor connector pin 9 can be used as optional +5V 300 mA power supply from graphics card to monitor (the VGA connector ground is at pin 5). The standard does not define that there must be +5V supply at that pin. If you are making small circuit for just yoour on computer, you might wan

t to check this option.

Remember that the VESA DDC standard demand the devices which take power from th graphics card use special VESA DDC modified version of DB15HD connector which guarantees the correct plug-in sequence of power ground and signal pins.

Power fromUSB connector

USB connector is designed to feed power up to 100 mA +5V power to the devices connected to it. The power is fed though Vbus and GND pins. The host USB pert can supply up to 500 mA at voltage at least 4.75 V (for the HUB to be able to power 4 port HUB which can supply up 100 mA at voltage of at least 4.40V). The USB port does not need to supply more than 100 mA unless the device connected to it requests more current. UL overcurrent-prevention requirement says that no USB port ever pass more than 5A onto any port (short circuit protection to avoid damage to equipments and wiring).

How to get power from inside PC

Disk drive connector

Normal floppy disk and hard disk drives use normally +12V and +5V power supplies, so spare disk drive power connector is very useful if you need those voltages for your own projects which you fit inside PC (for example extra fan for better cooling). Typically you can take up to few amperes of power form the disk drive power connector (remember not to exceed the total power rating of the PC power supply when you start taking extra power for your circuits).

Here is the power connector pinout when you look the CEE-type connector on the drive back:

Pin Function

1 +5 V
2 Ground
3 Ground
4 +12 V

Motherboard power connector

Standard AT-style motherboard gets power from the power supply through 12 pin power connector which is typically built from two 6 pin parts. The power connector has four different voltages available. The positive +5V power has lots of current available (typically over 10A), +12V has few amperes. The negative power supplies can supply typically quite limited power (-12V few hundred mA and -5 even less).

1. Power Good (output from PS which tells that output voltages are OK)
2. +5Vdc
3. +12Vdc
4. -12Vdc
5. Ground
6. Ground

7. Ground
8. Ground
9. -5Vdc
10. +5Vdc
11. +5Vdc
12. +5Vdc

Power from ISA bus

ISA BUS connector provides +5V, +12V, -5V and -12V to power the cards connected to it. If you are building a circuit which plugs inside your PC, you might consider using the ISA connector as place to put your circuit even it it were not connected to the data bus at all. Building the circuit as ISA card gives an easy access to many voltages and provides mechanically quite secure way to fit your circuit inside the PC. Here is ISA bus pinout with the port pins marked with bold text.

AT case back panel

Filtering PC bus power

PC power available on ISA bus is very noisy particularly if the bus is very loaded. If you plan to put some other circuit that straight TTL logic to a card which you connect to ISA bus you should use some kind of filtering (especially if you are planning to build audio circuits).

Analog Devices suggests a filter circuit in their 1992 Amplifier Application Guide for filtering a 5V (digital) supply for use in single-supply analog applications:

The circuit will give quite rather dramatic reduction of high-speed switching transients (according the source) for loads up to 100mA. For much higher loads you'll have to be careful not to saturate the ferrites. The circuit work just as well for dual-supply with appropriate modifications.

Other methods for getting very clean power is to get a higher voltage from the ISA bus and then filtering it to clean lower voltage using linear regulators and filtering capacitors. Typically soundcards use +-5..9V power supplies for their analogue circuits. That +-5..9V power is regulated using standard linear regulator ICs from +-12V power available in ISA bus connector.

Using PC power supply without other PC hardware on your projects

Well, your typical PC power supply is delivering about 200 Watts at its output, and is running at somewhere around 70-80% efficiency, which means that it needs to dissipate anywhere from 40 to 80 Watts internally. When you consider its relatively small size, you see why a fan is required.

PC power supplies usually have a minimum load requirement, which means that they won't regulate properly unless they're loaded to at least (typically) 20% of their maximum rating on the +5V output. This tends to make them unsuitable for low-power projects, unless you don't mind sticking a dummy load (large 1-ohm resistor) across the output.

A 250W supply will typically provide +12 at over 8 A. (You will need a small load on the +5 as well). With only minimal load on the +5, you may be able to push this a bit more. PC power supplies are readily available and inexpensive because they are mass products (any other power supply at same specs cost typically many times more).

Here is the pinout of standard pinout of the connector which goes to power typical PC motherboard (AT style motherboard, new ATX motherboards use different connector):

1. Power Good (output from PS which tells that output voltages are OK)
2. +5Vdc
3. +12Vdc
4. -12Vdc
5. Ground
6. Ground

7. Ground
8. Ground
9. -5Vdc
10. +5Vdc
11. +5Vdc
12. +5Vdc

Here is the power connector pinout when you look the CEE-type connector on the drive back:




Pin Function

1 +5 V
2 Ground
3 Ground
4 +12 V

Typical wiring colors on PC power supply wires:

BLACK is ground
RED is +5V
YELLOW is +12V

Those wiring colors are used in practically all power supplies. Colors for other voltages typically vary between different power supply brands. Don't blindly trust on the wire colors, because there are some power supplies which use totally different wire coloring.

Windows Shortcut Keys

Windows Operating Systems Shortcut keys Description

Ctrl + (the '+' key on the keypad) Automaticall y adjust the width's the columns in Windows explorer
Ctrl + Backspace Delete word to the left of cursor
Alt + E Edit options in current program
Alt + Enter Opens properties window of Selected icon or program
Alt + Esc Switch Between open applications on taskbar
Alt + F File menu options in current program
Alt + F4 Closes Current open program
Alt + Print Screen Copies active window to the clipboard
Alt + Shift + Tab Switch backwards between open applications
Alt + Tab Switch between open applications
Ctrl + A Select all text
Ctrl + C Copy highlighted text, data, or image
Ctrl + Del Delete word to the right of cursor
Ctrl + End Goes to end of document
Ctrl + Esc Bring Up start button
Ctrl + F4 Closes Window in Program
Ctrl + Home Goes to beginning of document
Ctrl + Insert Copy selected item
Ctrl + Left arrow Moves one word to the left at a time
Ctrl + Right arrow Moves one word to the right at a time
Ctrl + V Paste
Ctrl + X Cut selected item
Ctrl + Z Undoes a previous action
End Goes to end of current line
F1 Accesses online help from most programs
F2 Renames selected Icon
F3 Starts find from desktop
F4 Opens the drive selection when browsing
F5 Refresh Contents
Holding Shift Boot safe mode or by pass system files
Holding Shift When putting in an audio CD will prevent CD Player
from playing
Home Goes to beginning of current line
Shift + Del Cut selected item
Shift + Del Delete programs/files without throwing into the
recyclebin

Key Strokes For Easy Surfing using IE

Basic keystrokes for speeding up browsing using Internet Explorer.

ACTION KEYSTROKE
Go to URL Ctrl + O
Show history Ctrl + H
Go to top of page Home
Go to bottom of page End
Go back Alt + Left arrow or Backspace
Go forward Alt + Right arrow or Shift + Backspace
Scroll Up Up arrow
Scoll Down Down arrow
Stop page loading Esc
Refresh current page Ctrl + R or F5
Save current page Alt + F then A
Print current page Ctrl + P
Edit Favorites Ctrl + B
Add Favorites Ctrl + D
New browser window Ctrl + N
Close current window Ctrl + W
New message Ctrl + M
Find on current page Ctrl + F
Move between frames Shift+Ctrl+Tab
Forward beween links Tab
Backward between links Shift+Tab
Go to selected Hyperlink Enter

BOOTING PROCESS IN A PC [OS: Windows,xp,xp2,vista]

The time when you switch on your computer, it is obvious that you are not directly rendered the desktop screen rather a number of processes are done which are necessary for the proper working of the system. Many using their personal computers in their daily life are unaware of the processes going on at the time of startup, they are called the BOOT PROCESSES and are briefly described below:

1. Power supply switched on.

The power supply performs a self-test. When all voltages and current levels are acceptable, the supply indicates that the power is stable and sends the Power Good signal to the processor. The time from switch-on to Power Good is usually between .1 and .5 seconds.


2. The microprocessor timer chip receives the Power Good signal.

With the arrival of the Power Good signal the timer chip stops sending reset signals to the processor allowing the CPU to begin operations.


3. The CPU starts executing the ROM BIOS code.

The CPU loads the ROM BIOS starting at ROM memory address FFFF:0000 which is only 16 bytes from the top of ROM memory. As such it contains only a JMP (jump) instruction that points to the actual address of the ROM BIOS code.


4. The ROM BIOS performs a basic test of central hardware to verify basic functionality

Any errors that occur at this point in the boot process will be reported by means of 'beep-codes' because the video subsystem has not yet been initialized.


5. The BIOS searches for adapters that may need to load their own ROM BIOS routines.

Video adapters provide the most common source of adapter ROM BIOS. The start-up BIOS routines scan memory addresses C000:0000 through C780:0000 to find video ROM. An error loading any adapter ROM generates an error such as:
XXXX ROM Error
where XXXX represents the segment address of the failed module.


6. The ROM BIOS checks to see if this is a 'cold-start' or a 'warm-start'

To determine whether this is a warm-start or a cold start the ROM BIOS startup routines check the value of two bytes located at memory location 0000:0472. Any value other than 1234h indicates that this is a cold-start.


7. If this is a cold-start the ROM BIOS executes a full POST (Power On Self Test). If this is a warm-start the memory test portion of the POST is switched off.

The POST can be broken down into three components:
The Video Test initializes the video adapter, tests the video card and video memory, and displays configuration information or any errors. The BIOS Identification displays the BIOS version, manufacturer, and date. The Memory Test tests the memory chips and displays a running sum of installed memory. Errors the occur during the POST can be classified as either 'fatal' or 'non-fatal'. A non-fatal error will typically display an error message on screen and allow the system to continue the boot process. A fatal error, on the other hand, stops the process of booting the computer and is generally signaled by a series of beep-codes.


8. The BIOS locates and reads the configuration information stored in CMOS

CMOS (which stands for Complementary Metal-Oxide Semiconductor) is a small area of memory (64 bytes) which is maintained by the current of a small battery attached to the motherboard. Most importantly for the ROM BIOS startup routines CMOS indicates the order in which drives should be examined for an operating systems - floppy first, CD-Rom first, or fixed disk first.


Fixed Disk

9. If the first bootable disk is a fixed disk the BIOS examines the very first sector of the disk for a Master Boot Record (MBR). For a floppy the BIOS looks for a Boot Record in the very first sector.
On a fixed disk the Master Boot Record occupies the very first sector at cylinder 0, head 0, sector 1. It is 512 bytes in size. If this sector is found it is loaded into memory at address 0000:7C00 and tested for a valid signature. A valid signature would be the value 55AAh in the last two bytes. Lacking an MBR or a valid signature the boot process halts with an error message which might read:
NO ROM BASIC - SYSTEM HALTED


MBR

10. With a valid MBR loaded into memory the BIOS transfers control of the boot process to the partition loader code that takes up most of the 512 bytes of the MBR.

A Master Boot Record is made up of two parts - the partition table which describes the layout of the fixed disk and the partition loader code which includes instructions for continuing the boot process.

The process of installing multiple operating systems on a single PC usually involves replacing the original partition loader code with a Boot Loader program that allows the user to select the specific fixed disk to load in the next step of the process


Partition Table

11. The partition loader (or Boot Loader) examines the partition table for a partition marked as active. The partition loader then searches the very first sector of that partition for a Boot Record.

The Boot Record is also 512 bytes and contains a table that describes the characteristics of the partition (number of bytes per sectors, number of sectors per cluster, etc.) and also the jump code that locates the first of the operating system files (IO.SYS in DOS).


Operating System

Boot Record

12. The active partition's boot record is checked for a valid boot signature and if found the boot sector code is executed as a program.

The loading of Windows XP is controlled by the file NTLDR which is a hidden, system file that resides in the root directory of the system partition. NTLDR will load XP in four stages:
a) Initial Boot Loader Phase
b) Operating System selection
c) Hardware Detection
d) Configuration Selection


NTLDR Initial Phase

13. During the initial phase NTLDR switches the processor from real-mode to protected mode which places the processor in 32-bit memory mode and turns memory paging on. It then loads the appropriate mini-file system drivers to allow NTLDR to load files from a partition formatted with any of the files systems supported by XP.

Windows XP supports partitions formatted with either the FAT-16, FAT-32, or NTFS file system.


NTLDR OS Selection BOOT.INI

14. If the file BOOT.INI is located in the root directory NTLDR will read it's contents into memory. If BOOT.INI contains entries for more than one operating system NTLDR will stop the boot sequence at this point, display a menu of choices, and wait for a specified period of time for the user to make a selection.

If the file BOOT.INI is not found in the root directory NTLDR will continue the boot sequence and attempt to load XP from the first partition of the first disk, typically C:\.


F8

15. Assuming that the operating system being loaded is Windows NT, 2000, or XP pressing F8 at this stage of the boot sequence to display various boot options including "Safe Mode" and "Last Known Good Configuration"

After each successful boot sequence XP makes a copy of the current combination of driver and system settings and stores it as the Last Known Good Configuration. This collection of settings can be used to boot the system subsequently if the installation of some new device has caused a boot failure.


NTLDR Hardware Detection

16. If the selected operating system is XP, NTLDR will continue the boot process by locating and loading the DOS based NTDETECT.COM program to perform hardware detection.

NTDETECT.COM collects a list of currently installed hardware components and returns this list for later inclusion in the registry under the HKEY_LOCAL_MACHINE\
HARDWARE key.


NTLDR Configuration Selection

17. If this computer has more than one defined Hardware Profile the NTLDR program will stop at this point and display the Hardware Profiles/Configuration Recovery menu.

Lacking more than one Hardware Profile NTLDR will skip this step and not display this menu.

Kernel Load

18. After selecting a hardware configuration (if necessary) NTLDR begins loading the XP kernel (NTOSKRNL.EXE).

During the loading of the kernel (but before it is initialized) NTLDR remains in control of the computer. The screen is cleared and a series of white rectangles progress across the bottom of the screen. NTLDR also loads the Hardware Abstraction Layer (HAL.DLL) at this time which will insulate the kernel from hardware. Both files are located in the \system32 directory.


NTLDR Boot Device Drivers

19. NTLDR now loads device drivers that are marked as boot devices. With the loading of these drivers NTLDR relinquishes control of the computer.

Every driver has a registry subkey entry under HKEY_LOCAL_MACHINE
\SYSTEM\Services. Any driver that has a Start value of
SERVICE_BOOT_START is considered a device to start at boot up. A period is printed to the screen for each loaded file (unless the /SOS switch is used in which case file names are printed.


Kernel Initialization

20. NTOSKRNL goes through two phases in its boot process - phase 0 and phase 1. Phase 0 initializes just enough of the microkernel and Executive subsystems so that basic services required for the completion of initialization become available.. At this point, the system display a graphical screen with a status bar indicating load status.
XP disables interrupts during phase 0 and enables them before phase 1. The HAL is called to prepare the interrupt controller; the Memory Manager, ObjectManager, Security Reference Monitor, and Process Manager are initialized.

Phase 1 begins when the HAL is called to prepare the system to accept interrupts from devices. If more than one processor is present the additional processors are initialized at this point. All Executive subsystems are reinitialized in the following order:
a) Object Manager
b) Executive
c) Microkernel
d) Security Reference Monitor
e) Memory Manager
f) Cache Manager
g) LPCS
h) I/O Manager
i) Process Manager


I/O Manager

21. The initialization of I/O Manager begins the process of loading all the systems driver files. Picking up where NTLDR left off, it first finishes the loading of boot devices. Next it assembles a prioritized list of drivers and attempts to load each in turn.

The failure of a driver to load may prompt NT to reboot and try to start the system using the values stored in the Last Known Good Configuration.


SMSS

22. The last task for phase 1 initialization of the kernel is to launch the Session Manager Subsystem (SMSS). SMSS is responsible for creating the user-mode environment that provides the visible interface to NT.

SMSS runs in user-mode but unlike other user-mode applications SMSS is considered a trusted part of the operating system and is also a native application (it uses only core Executive functions). These two features allow SMSS to start the graphics subsystem and login processes.


win32k.sys

23. SMSS loads the win32k.sys device driver which implements the Win32 graphics subsystem.

Shortly after win32k.sys starts it switches the screen into graphics mode. The Services Subsystem now starts all services mark as Auto Start. Once all devices and services are started the boot is deemed successful and this configuration is saved as the Last Known Good Configuration.


Logon

24. The XP boot process is not considered complete until a user has successfully logged onto the system. The process is begun by the WINLOGON.EXE file which is loaded as a service by the kernel and continued by the Local Security Authority (LSASS.EXE) which displays the logon dialog box.

This dialog box appears at approximately the time that the Services Subsystem starts the network service.