Make a Digital Stop Watch

Description

A digital stop watch built around timer IC LM555 and 4-digit counter IC MM74C926  with multiplexed 7-segment LED display.MM74C926 consists of a 4-digit counter, an internal output latch, npn output sourcing drivers for common cathode,7-segment display and an internal multiplexing circuitry with four multiplexing outputs.The counter advances on negative edge of the clock. The clock is generated by timer IC LM555.The circuit works off a 5V power supply. It can be easily assembled on a general-purpose PCB. Enclose the circuit in a metal boxvwith provisions for four 7-segment displays, rotary switch S1, start/stop switch S2 and reset switch S3

Testing

First, reset the circuit by pressing S3 so that the display shows ‘0000.’ Now open switch S2 for the stop watch to start counting the time. If you want to stop the clock, close S2. Rotary switch S1 is used to select the different time periods at the output of the astable multivibrator (IC1).

Digital Timer Circuit Diagram .

Digital Timer Circuit

You may also be interested in other Timer circuits we have in our website:

1. Long Duration Timer Circuit

For more circuits, please check our category on Clocking and Timer Circuits

Read more: http://www.circuitstoday.com/category/clocking-timer-circuits#ixzz1N9RBsI8V
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Long duration timer circuit.

Description.

This timer circuit can be used to switch OFF a particular device after around 35 minutes. The circuit can be used to switch OFF devices like radio, TV, fan, pump etc after a preset time of 35 minutes. Such a circuit can surely save a lot of power.

The circuit is based on quad 2 input CMOS IC 4011 (U1).The resistor R1 and capacitor C1 produces the required long time delay. When pushbutton switch S2 is pressed, capacitor C1 discharges and input of the four NAND gates are pulled to zero. The four shorted outputs of U1 go high and activate the transistor Q1 to drive the relay. The appliance connected via the relay is switched ON. When S2 is released the C1 starts charging and when the voltage at its positive pin becomes equal to ½ the supply voltage the outputs of U1 becomes zero and the transistor is switched OFF. This makes the relay deactivated and the appliance connected via the relay is turned OFF. The timer can be made to stop when required by pressing switch S1.

Circuit diagram with Parts list.

Notes.

• Assemble the circuit on a good quality PCB or common board.
  
• The circuit can be powered from a 9V PP3 battery or 12V DC power supply.
  
• The time delay can be varied by varying the values of C1&R1.
  
• The push button switch S2 is for starting the timer and S1 for stopping the time.
  
• The appliance can be connected via contacts N1 & N2 of the relay RL1.
• The IC U1 is 2 input quad NAND gate 4011.

Read more: http://www.circuitstoday.com/category/clocking-timer-circuits#ixzz1N9R0PrdY
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Water Level Indicator

Description

This is the circuit diagram of a simple corrosion free water level indicator for home and industries.In fact the the level of any conductive non corrosive liquids can be measured using this circuit.The circuit is based on 5 transistor switches.Each transistor is switched on to drive the corresponding LED , when its base is supplied with current through the water through the electrode probes.

One electrode probe is (F) with 6V AC is placed at the bottom of tank.Next probes are placed step by step above the bottom probe. When water is rising the the base of each transistor gets electrical connection to 6V AC through water and the corresponding probe.Which in turn makes the transistors conduct to glow LED and indicate the level of water.The ends of probes are connected to corresponding points in the circuit as shown in circuit diagram.Insulated Aluminum wires with end insulation removed will do for the probe.Arrange the probes in order on a PVC pipe according to the depth and immerse it in the tank.AC voltage is use to prevent electrolysis at the probes.So this setup will last really long.I guarantee at least a 2 years of maintenance free operation.That’s what I got and is still going.

Components

T1 – T5 BC 548 or 2N2222 Transistors

R1-R5 2.2K 1/4 W Resistors

R6-R10 22K 1/4 W Resistors

D1 – D5 LED’s ( color your choice)

Notes:

Use a transformer with 6V 500 mA output for power supply.Do not use a rectifier! we need pure AC. Use good quality insulated Aluminum wire for probes.If Aluminum wires are not available try Steel or Tin.Copper is the worst.Try the circuit first on a bread board and if not working properly, make adjustments with the resistance values .This is often needed because conductivity of water changes slightly from place to place.The type number of the transistors used here are not critical and any small signal NPN transistor will do the job. Few other suitable type numbers are BC546, BC107, PN2222, BC337, BF494, ZTX300, BEL187 etc. The circuit can be enclosed in a plastic box with holes for revealing the LEDs .

Water Level Indicator Circuit Diagram and Sensor Arrangement.

Water Level Indicator

If you need a fully automatic water level controller circuit then try this circuit  Water level controller. The circuit is fully based primarily on transistors. The sensing section is somewhat similar to this circuit but there is additional circuitry for switching the pump ON when the water level falls below a set level and the pump will be switched OFF when the tank is full. Few transistors , one 555IC and an electromagnetic relay is used for realizing the control section. The circuit is very simple cost effective , reliable and many guys have successfully assembled it.I am also working on a float type water level indicator/controller using the float type fuel gauge mechanism used in motor cycles.The level sensor section is  finished and now I am working on the control circuitry. I will add the circuit here as soon as it is finished

Read more: http://www.circuitstoday.com/simple-water-level-idicator#ixzz1N9PzvrjF
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Water level controller circuit.

Description.

A simple but very reliable and effective water level controller circuit diagram is shown here. The circuit uses 6 transistors, 1 NE555 timer IC, a relay and few passive components. The circuit is completely automatic which starts the pump motor when the water level in the over head tank goes below a preset level and switchess OFF the pump when the water level in the over head tank goes above the full level.

Probe D is positioned at the bottom level of the tank while probes A, B and C are placed at full, half and medium levels of the tank respectively. The level sensing part of the circuit is built around transistors Q1, Q2 and Q3. When water level is below the quarter level probes A, B and C are open and the transistor Q1, Q2 and Q3 remains OFF. When the water level rises and touches the probes the corresponding transistors gets biased and switches ON. Resistors R1, R2, R3 limit the bases current of corresponding transistors while resistors R4, R5, R6 limit their collector current. LEDs D1, D2 and D3 provide a visible indication of the current water level.

When the water level goes below medium, transistor Q2 gets switches OFF and its collector goes positive. Collector of Q2 is connected to the base of transistor Q6 and as result transistor Q6 gets switched ON. Transistor Q5 will be also ON because its base in connected to the collector of Q4 which is presently OFF. As a result when the water level goes below medium relay K1 gets energised and the pump is driven. The relay is wired in the latching mode so that even if the water level goes above medium level the pump remains ON so that the tank gets completely filled. For wiring the relay in latching mode one set  of N/O contacts is used. When relay is activated these contacs close which forms a short across collector and emitter of Q6. This makes the state of Q6 irrelevant to the opertion of the relay and the relay remains ON as long as the transistor Q5 is ON. The only way to make the relay OFF is by switching OFF Q5 and it is done automatically when the water level reaches the full level.

Collector of transistor Q1 is connected to the trigger pin (pin2) of IC1. When the water level reaches full level the transistor Q1 gets switched ON. As a result its collector goes to ground level which triggers the IC1 which is wired as a monostable. The output of IC1 goes high for about 1S. This makes the transistor Q4 ON for the same time and transistor Q5 whose base is connected to the collector of Q4 is switched OFF cutting the supply to the relay. This makes the motor OFF and it remains OFF until the water level again goes below the medium level.

Resistor R8 is a pull up resistor for the trigger pin of the NE555. Capacitor C3 couples the collector of Q1 to the trigger pin of NE55 and facilitates edge triggering whenever the transistor Q1 goes ON. A monostable circuit can be made edge triggered by connecting the trigger signal to the trigger input pin through a capacitor. The capacitor blocks DC and passes sudden changes. The circuit used here is termed as negative edge triggered because the monostable is triggered when ever the trigger input signal falls. R10 and R12 limits the collector current of Q4 and Q5 respectively while R9 and R11 limits their base current. R13 limits the base current of Q6 while D4 is a freewheeling diode which protects the switching transistors from voltage transients.

Circuit diagram.

Water level controller circuit diagram

Probe arrangement diagram

The probes can be arranged as shown in the diagram above. Insulated Aluminium wires can be used as the probes. The probes can be binded on a plastic rod and should be erected vertically inside the tank. The length of the probes wires and the supporting plastic rod must be chosen according to the depth of the tank. Since DC is used in the level sensing section electrolysis will occur in the probes and so the probes require small maintinances in 1 or 2 month intervals. Using AC in the sensing section will completely eliminates the chance of electrolysis and I am presently working on such a circuit. You can expect it soon.

Notes.

• Use 12V DC for powering the water level controller circuit.
• The relay I used was a 5V/220 ohm relay and that’s why the current limits resistor R12 was added in the circuit. If you use a 12V relay then the R12 can be shorted.
• Do not use a relay that consumes 500mA. Maximum collector current PN2222 can handle is 600mA.
• Use insulated single strand aluminium wires for probe and they can be arranged in the tank as per the probe arrangement diagram.
• Use a holder for mounting NE555.
• The circuit can be assembled on a Perf board.
• K1 must be a double pole relay.
• The load current, voltage ratings of the relay must be selected according to the ratings of the pump motor.
• The type number of the transistors used here are not very critical and you can do suitable replacements if any type number is not availble.
• Most of the components required for this project can be found inside your scrap box.

Power supply for this circuit.

12V DC power supply

A classic 12V regulated DC supply based on 7812 is shown above. A power ON indicator LED is also added in the circuit.Resistor R13 limits the LED current. A small aluminium heatsink can be fitted to the 7812 for better saftey.Small Al heatsinks for TO-220 package are readily available in the market.

Read more: http://www.circuitstoday.com/water-level-controller#ixzz1N9PrOwpH
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DATA SHEETS

Transistors BPW77NA BPW85 BD135 2N3055 2N2222 2N2907 BC548 BC107 BC177 BF494 BF495

ICs MAX660 LM324 NE555 uA741 L200 LF351 LM383 LM386 CD4047 LM3915 TDA4935 UM66 DS1669 RF600D RF600E

Diode 1N4001 1N4002 1N4003 1N4004 1N4007 1N4148 BY127 BY133 EM513 EM516 OA79 FFH50US60S RURG1520CC

Triac BT136

SCR TYN612 TYN100 TYN606

Read more: http://www.circuitstoday.com/datasheets#ixzz1N9PC0qDL
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ir blaster

IR Blaster

Introduction

An IR Blaster is a device that functions or imitates an IR Remote Control in its features. This device is used to control other devices. If this device is connected to a PC, it can be used to control all the other IR devices that are present in the room with the help of that PC. The deice is relatively small compared to other IR devices and can be self-powered by just plugging them to the device that is to be controlled.

How IR Blaster Works?

The working of IR Blaster is pretty much the same as that of a remote control except that there is a digital to IR light converter in the IR Blaster. The digital signals produced by the up and down pulses of electricity while IR light is completely invisible. They are used because they have a better transfer rate and can travel through air without causing any threat to anyone.

If the system is neatly configured, the beam generated by the IR Blaster can be used to control devices such as TV’s and computers while, at the same time, control devices such as VCR or DVR using an IR remote control.

Applications

The main use of an IR blaster is to control a secondary device through a primary device with the help of an infrared remote control. IR blasters can be used for many electronic devices and there is no limit to its extent. The devices vary from TV’s, PC’s, VCR, home theatre, big screen projectors and so on.  Another application of the device includes the extending of the range of the IR remote by keeping the blaster in a closed area, in hiding, or even at an angle that the remote cannot “see”. There are also USB IR blasters which can be connected to computers. Through this device all the other IR devices in the room can be easily controlled.

Advantages

• User friendly
• The user can sit still in one place and handle all the devices in the room.
• Can be configured to work with special devices and also paired with computer applications like EyeTv and RealBasic.
• No need of an external power supply for the device as it gets self-powred from the device it is connected to (computer).

Disadvantages

• Configuring the device at the beginning is difficult and confusing.
• The cost of the device is considerably low, but may go up according to the sensitivity, output power levels, and other factors chosen.

Read more: http://www.circuitstoday.com/infrared-ir-blaster#ixzz1N9OaydGV
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100 Watt sub woofer amplifier.

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.



Read more: http://www.circuitstoday.com/100-watt-sub-woofer-amplifier#ixzz1N9OKmY00
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Simple UPS

This is the circuit diagram of a simple UPS that can deliver 12V unregulated and 5V regulated DC. The transformer T1 steps down the mains voltage to 12V AC and then the bridge B1 rectifies it. The rectified signal is smoothed by the capacitor C1.When the mains supply is available the battery will be charged via diode D3 and the regulator IC gets supply via diode D5. 12V and 5V DC will be available at the output terminals. When mains supply is not available the battery supplies current to the regulator IC and to the 12V DC terminal through diode D4.Also, the diode D3 blocks reverse flow of current during battery mode. Capacitors C2 and C3 acts as filters.

Circuit diagram with Parts list.

Notes.

• Assemble the circuit on a good quality PCB.
• The transformer T1 can be a 230V AC primary, 12V secondary,3A step-down transformer.
• The bridge B1 can be a 2A bridge. If such a bridge is not available, make one using four 1N4007 diodes.
• The capacitor C1 must be rated at least 25V.

Read more: http://www.circuitstoday.com/category/ups#ixzz1N9O87QEK
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UPS-Uninterruptable Power Supplies

Most of us take the mains ac supply for granted and use it almost casually without giving the slightest thought to its inherent shortcomings and the danger posed to sophisticated and sensitive electronic instruments/equipments. For ordinary household appliances such as incandencent lamps, tubes, fans, TV and fridge, the mains ac supply does not make much difference, but when used for computers, medical equipments and telecommunica¬tion systems, a clean, stable interruption free power supply is of the utmost importance. Of the myriad of devices, processes and systems which rely on ac power, computers are probably the most sensitive to power disturbances and failures. Interruptions in power supply may cause the contents of a memory to be lost or corrupted, the entire system to malfunction or fail, or even variety of components failures to occur, all of which not only result in inconvenience but also loss of money.

As more and more PCs, word processors and data terminals find their way into small business, UPS systems that meet the power requirements and price range needs of even the small business organizations and offices are being manufactured.

Uninterruptible Power Supply Systems.

There are three distinct types of uninter­rupted power supplies, namely, (£) on-line UPS (ii) off-line UPS, and (Hi) electronic gen­erators. In the on-line UPS, whether the mains power is on or off, the battery operated inverter is on all the time and supplies the ac output voltage. When the mains power supply goes off, the UPS will be on only until the battery gets discharged. When the main power resumes, the battery will get charged again. In off-line UPS and electronic genera­tors, ther inverter is off when the mains power is present and the output voltage derived directly from the mains is the same as the mains supply voltage. The inverter turns on only when the mains supply goes off.

The block diagrams of on-line UPS, off-line UPS and electronic generators are given in figs

The ever increasing importance of computers in industry and commerce will increase the need for quality, high stability and interruption free power supplies.

A clean ac power source is the fundamental to the operation of most sensitive elec­tronic equipment, and many new and sophisticated circuits are designed to overcome the effects of disturbances normally found in the mains ac supply.

In order to protect a sensitive system from power losses and blackouts, an alternative power source is required that can switch into operation immediately when disruption occurs. An interruptible power supply (UPS) is just such an alternative source. A UPS generally consists of a rectifier, battery charger, a battery bank and inverter circuit which converts the commercial ac input into dc suitable for input to the battery bank and the inverter. The rectifier should have its input protected and should be capable of supplying power to the inverter when the commercial supply is either slightly below the normal voltage or slightly above.

Online UPS:

Online UPS Block Diagram

In case of On-line UPS, the battery operated inverter works continuously whether the mains supply is present or not. Triac T₁ is on for all the times while Triac T₂ has been provided to bypass the UPS inverter, only when a fault develops in the UPS inverter. When the mains supply fails, the UPS supplies power only until the batteries get dis­charged. However, once the mains power resumes, the batteries will get charged again. The switching times of these supplies is considered to be zero. Usually sealed maintenance free batteries are used and the running time of the inverter is low (approximately 10 to 30 minutes).

Off Line UPS:

Offline UPS Block Diagram

In the case of Off-Line UPS, the inverter is off when the mains power is on and the output voltage is derived directly from the mains. The inverter turns on only when the mains supply fails. Its switching time is less than 5 ms. These UPS are generally used with PCs or computers or other appliances where a small duration (5 ms or less) interrup­tion in power supply can be tolerated. Usually, sealed batteries or lead-acid batteries are used. The running time of these supplies is also low (about 10 to 30 minutes).

Electronic Generators:

Electronic Generator

An electronic generator is the same as the off-line UPS system except for one difference that switching time from the mains supply to battery driven inverter supply will not be small (over 10 ms) for the electronic generator. Also, the electronic generators will run for longer time (1 to 4 hours) than off-line UPS systems because, usually large size lead-acid batteries are used with^/electronic generators. These are meant for household applications to run fans, coolers, fridge, lights, TV and VCR.

The demand is the highest for the electronic generators meant for house hold applica­tions, followed by the off-line UPS, and then the on-line UPS systems. The off-line or on­line UPS systems are mainly used in places where PCs or computers are used. The de­mand for on-line UPS systems is less than for off-line UPS systems because the price of the on-line UPS systems is higher.

Read more: http://www.circuitstoday.com/category/ups#ixzz1N9Nujfrl
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2 km FM transmitter

Description.
With a matching antenna, the FM transmitter circuit shown here can transmit signals up to a range of 2 kilo meters. The transistor Q1 and Q2 forms a classic high sensitive preamplifier stage. The audio signal to be transmitted is coupled to the base of Q1 through capacitor C2. R1, R3, R4, R6, R5 and R9 are the biasing resistors for the preamplifier stage comprising of Q1 and Q2. Transistor Q3 performs the collective job of oscillator, mixer and final power amplifier.C9 and L1 forms the tank circuit which is essential for creating oscillations. Inductor L2 couples the FM signal to the antenna.

Circuit diagram.

Notes.

• Assemble the circuit on a good quality PCB.
• The circuit can be powered from anything between 9 to 24V DC.
• Inductor L3 can be a VK220J type RFC.
• For L1 make 3 turns of 1mm enamelled copper wire on a 10mm diameter plastic former. On the same core make 2 turns of 1 mm enamelled copper wire close to L1 and that will be L2.
• Frequency can be adjusted by varying C9.
• R9 can be used to adjust the gain.
• For optimum performance, value of C8 must be also adjusted.
• Using a battery for powering the circuit will reduce noise.

Read more: http://www.circuitstoday.com/2-km-fm-transmitter#ixzz1N9N8aodP
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Gas Discharge Tubes (GDT) – Introduction

GDT’s are special type of gas filled tubes used for wide range of electronic/electrical circuits for providing protection against lightning and other power surges.  These tubes basically has two electrodes that are kept inside a gas filled closed envelope. In case of electronic applications, the container is mostly ceramic in nature. For high grade electrical applications military tubes are used. The electrical characteristics of this tubes depends on the pressure and composition of gas, and the distance between the two electrodes contained inside. The most commonly used gases in GDT’s are given below.

1) Hydrogen gases

2) Deuterium gases

3) Noble gases

4) Elemental vapors (metals and nonmetals)

5) Other gases

6) Insulating gases

An image of a ceramic discharge tube is shown below. Take a look.

Ceramic Discharge Tube

There will be conduction inside the GDT’s due to ionization of gas molecules. Each GDT have a specific voltage and current rating. A simple lightning protector circuit is given below.

Lighting/Surge Protector Circuit

In power lines, usually large amount of voltage is induced (typically very short time with high amplitude) due to lightning (direct or indirect strike) or Transients*

* (Transients caused by other equipments are usually caused by the discharge of stored energy in inductive and capacitive components. Electric motors, such as those used in elevators, heating, air conditioning, refrigeration or other inductive loads, can create a continuous stream of 250V to 1000V transients. DC motor drives, variable speed AC motor drives, DC power supply switching, and portable power tools are other sources of transients.)

Lightning Protector Circuit

The basic surge suppression circuit shown below consists of a VDR** (Voltage Dependent Resistor) and gas surge suppressor (GDT) connected in series. The protection circuit is connected between live and mains lead. Normally no current flows through GDT and VDR1. When   the voltage between the terminals is higher than the sum of voltage ratings of GDT and VDR1 (here both GDT UZ470B and VDR S20K250 has 250v 16A rating), current starts to flow through those components. If more the voltage rises then more current starts to flow through GDT and VDR1.When the current is normal, the circuit is reset and resumes it’s functioning. Thus the current cannot be raised much over that predetermined value. When the voltage again goes back to normal values G1 and VDR1, the conducting stops and the circuit remains normal.  If the flowing current is more than the specified value of main self-resettable fuse, the fuse will break and the circuit will be protected. After the current is normal, the fuses resets and continue its functioning (protection against short circuit and overload). The circuit is designed to protect sensitive electronic devices against overvoltage transients in normal mains voltage and overload/ short circuit. Two neon pilot lamps are also provided with the circuit diagram to show the status of input and load supply.

(**A VDR (Voltage Dependent Resistor) is an electronic component with a “diode-like” nonlinear current–voltage characteristic. The name is a portmanteau of variable resistor.  VDRs are often used to protect circuits against excessive transient voltages by incorporating them into the circuit in such a way that, when triggered, they will shunt the current created by the high voltage away from the sensitive components. A VDR is also known as Voltage Dependent Resistor or VDR. A VDR’s function is to conduct significantly increased current when voltage is excessive.)

Voltage Dependent Resistor

Advantages

1)      Normal working voltage = 230v AC/DC

2)      Maximum current rating=16A

3)      Cut-off current =16A

4)      Cut-off voltage= >300v R.M.S

5)      Protection against overloads

6)      Protection for short circuit

Applications

1)      Protection for sensitive components

2)      Protection for motor devices

3)      Telephone line protection

4)      SMPS protection

Read more: http://www.circuitstoday.com/#ixzz1N9Mirr3w
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mobile car hack

We have always been scared about our mobiles and computers getting hacked. Now it is time to know that there will be a time in the near future where people can easily hack cars. The car designs are becoming more and more sophisticated and you can also notice the change of simple mechanical automobile designs to a sophisticated network which includes almost 70 computers, collectively called Electronic control Units (ECU’s). All these computers are connected to each other and also to the internet.

Car Hack

Through these inter-connections, the car becomes a small data center that can be affected by many types of digital hacks similar to that of a mobile and computer. Some of the most common hazards are viruses, denial of services and so on.

The Electronic Control Units can manage most of the real time systems of cars like the steering, infotainment console, all lights, ignition, and crash bags and so on. For this to work software’s are developed that has millions of lines coded to make the ECU do a specific operation at a specific time. As the networks can be shared through long distances, more common gadgets like GPS and MP3 players can be easily controlled. But, there may arise technical difficulties when some nonessential components and infotainment share the same network with the brakes, steering and other main devices.

So how can all this be useful to a hacker?

He can easily open the car lock and start the vehicle from a distance with the help of a cell phone and get inside the car and drive away. A similar test was done by two professors named Stefan Savage and Tadayoshi Kohno at the National Academies Committee on Electronic Vehicle Controls and Unintended Acceleration. They inserted malicious software inside the car’s software system using its Bluetooth and mobile phone connections.

Thus it is time to implement counter safety measures from these unethical hacks. Or else, the wireless communication will be easily jammed, relayed or even broke down.

The counter safety measures are already being studied by the E-Safety Vehicle Intrusion Protected Applications (EVITA) project headed by Olaf Henniger, a researcher at Fraunhofer Institute for Secure Information Technology – Germany. The main aim behind the project is to more secure onboard networks in cars. Apart from this special methods are being developed to protect the vehicle to vehicle and vehicle to infrastructure communication so that accidents can be avoided. Many prototypes have already been developed but have turned out to be very expensive.

Some companies like Ford have already installed their own security measures that were developed by Microsoft. According to them, their car is safe enough from all alien network attacks. They have installed special firewall that can withstand any type of hacking.

There are various mobile applications that are available in the internet with which the car ignition can be remotely started. Also other functions like steering control, infotainment network control, and also door unlock control can easily be obtained. The mobile becomes paired with the car through Bluetooth. If a person is able to get control of the phone (perhaps through a virus downloaded from the Web), that person might then be able to gain access to the vehicle to which the phone is paired.

Read more: http://www.circuitstoday.com/#ixzz1N9MPODkf
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Multi-Channel Surround Sound Systems- frm circuit today

Multi-channel Audio

Multi-channel audio systems are widely used in modern sound devices. The term “multi-channel audio” means that, the audio system can be capable of handling multiple audio channels (usually called audio tracks) to rebuild the sound on a multi-speaker setup.

Usually two digits separated by a decimal (.) point (2.1, 4.1, 5.1, 6.1, 7.1, etc.) are used to classify the various kinds of speaker set-up, this number basically depending on how many audio tracks are used. Some audio systems only have a single channel (called monophonic sound or single channel audio) or two channels (stereophonic sound or 2.0 channel sound)

The first digit shows the number of primary channels (called satellite units), each of which are reproduced on a single speaker (these speakers are capable for handling the frequency range from 100Hz to 22Khz), while the second (decimal digit) refers to the presence of LFE (Low Frequency Effect), which is reproduced on a subwoofer.

Stereo Setup

Image Source

Surround Sound System
Surround sound is a term used to describe a type of audio output in which the sound appears to “surround the listener” by 360 degrees –  that is, the technology gives the impression that sounds are coming from all possible directions.

Surround sound is a way to provide a more realistic and engaging experience. All technical aspects aside, surround sound works because multiple audio channels are received through speakers that are positioned at various locations in the room. This is programmed into the source and the sound tracks are decoded when the source is played.

The Surround Sound Setup

The main component of a surround sound setup is a multi channel or digital coaxial/optical audio decoder. Using a DVD/HVD movie, the audio is encoded when the DVD/HVD is produced by packing multiple audio channels into a compressed format for storage.  When you play the DVD movie, your DVD player or A/V receiver (commonly called a home theatre receiver) decodes the encoding scheme (i.e. Dolby Pro Logic II or DTS for example). Decoding capabilities of an A/V receiver are built in. Most A/V receivers today can decode Dolby Digital and Digital Theater Sound (DTS) (DTS channel usually a coaxial or optical audio channel. It is a single channel digital pin that multiplexed with several channel. The decoder decodes the DTS sound from single channel to multiple channels), while higher-end receivers may also include DTS-ES or THX Surround.

Multi-channel Surround Sound Systems

• 5.1 Surround Sound Systems

5.1 Surround sound systems are one of the widely used surround sound setup in home theater systems. Usually- Dolby Digital and DTS encoded in a DVD are 5.1 channel audio formats.  5.1 surround sound technologies produces five channels of sound in the left, right, center, left-surround and right-surround positions. These five channels are the minimum required to produce 5.1 surround sounds. The dot decimal (.1) represents the channel for LFE (low frequency effects), which is usually sent to a subwoofer. Other 5 units are capable for handling the frequency range except low frequency(Usually they are capable of  handling  the frequency range from 100Hz to 22Khz and no need for any other higher frequency component like tweeter). These five units are usually called satellite units. The arrangements of a 5.1 surround sound setup shown in the picture below.

5.1 surround sound

• 6.1 Surround Sound Systems

6.1 multichannel sound technologies is the advanced version of 5.1 surround sound technology. 6.1 technology uses the same set-up as a 5.1 system, but it has the addition of a sixth speaker that takes the rear-center surround position (or back surround position) to provide a more 3-D realistic surround sound effect. 6.1 surround sound uses extended surround sound formats, such as THX Surround EX, Dolby digital ES and DTS-ES. The 6.1 channel surround sound setup is shown in the picture.

6.1 Surround Sound Systems

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• 7.1 Surround Sound Systems

7.1 channel audio systems is the modified version of 6.1 channel and also provide more realistic experience than 6.1 setup. In this system splits the single rear-center speaker into individual left- and right-rear surround. These systems are not a true discrete 7.1 channel system as 7.1 formats don’t currently exist. In a true discrete 6.1 surround system, the back center surround position is separate from the surround left (SL) and surround right (SR) positions. A 7.1 channel system uses   matrixes extended surround where the left-back and right-back (rear-center surround) multichannel are blended together and stored. The structure of a 7.1 setup is given in the Picture below.

7.1 Surround Sound Systems

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• 10.2 Surround Sound Systems

10.2 channel surround is the future surround sound technology that Developed by THX corporation, the name itself, 10.2 is an advanced version of 5.1 technology but 10.2 is twice as good as 5.1. In a 10.2 surround sound 14 channels are used. This includes five front speakers, five surround channels, two LFE and two heights, plus the addition of a second sub-woofer. This technology is considered as future TRUEHD.The Diagram of a 10.2 TrueHD setup is shown below.

10.2 Surround Sound Systems

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Common Surround Sound Formats

• Dolby Surround

Dolby surround is the consumer version of Dolby analog film decoding. This technology was introduced in 1982 which is capable of handling stereo and hi-fi audio. This audio format is commonly found in VHS and stereo hi-fi systems. In this surround format, the multichannel audio multiplexed into two audio channels (left and right channels)and decoded by using Dolby pro logic decoder ,then it recreates the four channel Dolby surround experience.

• Dolby Digital

Dolby digital is the standard surround sound format which provides high quality and highly realistic experience. This audio is developed by Dolby Corporation. Dolby digital audio is also known as Audio Codec-3(AC3). This audio format provides a high quality 5.1 surround experience. Normally this audio format used for the creation of DVD and Blue ray movies. Some video games and play station units are also available in this surround sound format.

• Dolby Digital EX

Dolby Digital EX is the modified version of Dolby digital audio. This extended format contains an additional surround sound unit (called center surround channel) for creation of more realistic experience. Dolby digital EX needs Dolby EX decoder. This surround effect also support 5.1, 6.1, 7.1 channel playback. This audio format usually available on DVD, HVD, blue ray, play stations, DTV broadcasts, etc .

• Dolby Pro Logic IIx

Dolby Pro Logic IIx is an advanced version of Dolby Digital EX technology. By using this technology, we can expand the 5.1 channel Dolby surround system into 6.1, 7.1, 10.2 channel surround. The Dolby digital prologic usually use three modes for listening (movie, music and game modes).This surround technology provide more rich  and depth surround sound effect   than conventional surround sound system. This audio is normally encoded in DVD, HVD, BRD HDTV, play stations,  etc.

• Dolby True HD

Dolby True HD surround sound is an advanced version surround sound that provides incredible High Definition experience to the listener. This surround sound format is also known as next generation surround sound format. Dolby True HD format only support HD based media and this technology provides 100% lossless audio encoding, bit rate up to 18Mbps and support 8.1 or higher channel with 24 bit/96Khz audio. This format also supports HDMI. Normally BRD and HVD are used for encoding this true surround.

• DTS

DTS is another digital surround format developed by DTS Corporation. It is a Multichannel digital surround format widely used in both consumer and commercial applications. The DTS audio system must have a DTS decoder and optical/coaxial digital decoder for decoding this surround. DTS is normally available in a single channel multiplexed format (2.1 to 11.1 channel surround sounds can be multiplexed into a single optical digital or coaxial output format).DTS format  is also available on DVD,HVD and BRD’s.

• DTS-ES

DTS-ES (digital theater sound –Extended Surround) is an advanced version of normal DTS. This surround system is usually available in 6.1 or higher channels. This provides us with more true digital experience than conventional DTS system. This unit also requires an additional DTS-ES decoder for the creation of a back-surround effect. The system is compatible with all current extended surround formats and an auxiliary surround channel is also provided for other applications.

• TruSurround-XT

TruSurround XT is the next generation of SRS TruSurround. The main advantage of this surround system is that it’s capable of handling 2.1 channel surround to 10.2 channel surround (support head phone media too).Audio is encoded in multiplexed format. and require DTS true surround decoder. This audio usually encoded in BRD’s and HVD’s

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