Working of WI-VI(WIRELESS VISION)

Hi friends,this time came up with new technology "WI-VI(Wireless Vision)".This technology uses  "WI-FI"(Wireless Fidilety) to allow user to look into the walls.This technology analyses the reflected WI-FI signals to estimate an object in a particular room,even if it is in motion we can able to detect the exact location of object.
Here in this case,the user has two antennas which generate WI-FI signals continuously with 180 degree phase difference and a single receiver.Generally a portion of WI-FI signal can penetrate in to wall.When two antennas radiate,due to 180 degree change in phase they cancel out each other without reaching at receiver when they hit any stationary objects,but when these signals hit any moving object there generates a change which will appear at the receiver,by analyzing the received signal we estimate perfect location of object.

Actually this concept is similar to RADAR(Radio detection and ranging),in which 'radio' signals are transmitted in to space to 'detect' the presence of object and 'ranging' involves knowing the exact location of object from the system,how?range or distance is speed over time,we know the speed of transmitting signal and the time taken for signal to strike the object from system(user),by this range is detected.
WI-VI systems are capable of tracking the person in a closed room.Assume that a WI-VI device is fixed outside the room,initially room is empty,when a person enters into it based on the movement of person the device is capable of showing variations i.e when he moves towards the WI-VI, signal may be in one format and when he moves away from it we can see the signal in another format.A small variations can also be grabbed by WI-VI device.

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Introduction to Zener diode

Hi friends,this time we wanna discuss about zener diode which is heavily doped diode and is specially fabricated to with stand high power dissipation.
Main application of zener diode is, it can act as a voltage regulator.

Forward characteristics of zener diode:

when high potential is applied at anode compared to cathode,then the characteristics of 

zener diode are

Negative characteristics of zener diode:

when lower potential is applied at anode compared to cathode,then the characteristics of 

zener diode are

Major concern related to zener diode is determining the state in which the zener diode is residing,there are various steps that to be followed in this process,

1. Replace zener diode by an open circuit
2. Find terminal voltage across the diode from N to P side,say vt
3. If vt>vz,  zener is reverse ON  and replace it with vz
4. If vt<vz,  zener is OFF and hence open circuit.

Consider a circuit ,

now the circuit becomes 

Terminal voltage Vt=(8*1.2)/(1+1.2)=4.3v and since Vt<Vz zener is OFF hence open circuit.

If  RL=3.6k then terminal voltage Vt=(8*3.6)/(1+3.6)=6.26v. Here Vt>Vz hence zener is reverse ON and replace zener diode with Vz=6v.

Now the question is how to place a terminal voltage,the answer is conventional direction of zener voltage is considered to be opposite to the direction of normal PN diode,because  PN diode is used in forward biased and zener diode is used in reverse biased.

For RL=3.6,the circuit becomes 

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TRANSISTOR Disadvantages-MOSFET Advantages

Hi friends,this time i wanna talk about basic electronic devices, they are transistor and mosfet with their disadvantages and advantages respectively. Major disadvantages that i would consider for transistor are,
1.Input impedence
2.Stability
I would also explain how these two are advantages for mosfet.
1.Input impedence : 
For transistor:Any small input at the base terminal will turn transistor active and make it work (i.e as a amplifier or as a switch),which is not required at particular small input. Transistor should respond only to a reasonable input .This indicates the input impedence(Ri) of a transistor is low.Actually for CC based transistor configuration,the input impendence is upto 500k ohms,which is enough, but if transistor is biased then due to R1 and R2 the net input impedence will decrease(R1||R2||Ri).
For mosfet:Mosfet abbreviates metal oxide semiconductor field effect transistor,as the name itself indicates presence of oxide(SiO2) an insulator,which  prevents mosfet not to respond for small inputs
2.Stabilty
For transistor:We desire a fixed operating point that to in active region with Ib,Ic,Vce.The flow of small current(due to low input impedence) into BJT results in dissipation of electrical energy inform of heat.This results in rise of tempoerature which inturn increases Ic0 but Ic=(alpha)IE+Ic0,so Ic also increases.With this operating point is disturbed.It is referred as bias instability.To overcome bias instability,we have bias circuits which will stabilise the Q pont even change occured in Ic0 and temparature.Ic0 increases by 2 times for every 10 degree rise in temperature.
For mosfet:Bais instability is occured in BJT due to low input impedence,but as i said mosfet has high input impedence(due to SiO2) compared to transistor,so chances of instability is less in case of mosfet.

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Circuit which indicates the charging level of battery

Hi friends ,As the need for rechargeable devices are increasing it is necessary to maintain the life of electronic devices which runs with  battery.Life of any rechargeable device depends upon the usage of charging capacity it has.Overcharging leads to reduce the life of device.Now a days due to overcharging many of the devices are out of work field.So if we know proper charging level of battery at every instant of time,it would help us to know whether to charge the battery or to use it.My circuit provides this features i.e when the battery is fully charged we can see a LED light glowing by this one will come to know that the battery is fully charged and has to unplug it.If not it need to be charged. Today i wanna show a circuit which will indicates the charging level of a DC storage battery.

Circuit description:

Input is an alternating voltage signal of 220v and 50hz supply,given to capacitor which is used to block DC,Stepdown transformer to reduce the signal level ,a rectifier to convert AC to DC,inverting and non inverting amplifiers,LED,1 v DC source and the battery whose charging level is to be detected.

Working:

Initially AC signal is passed through 'C' to block DC,which is fed to step down transformer to reduce the voltage signal from 220v to 13v.Now this is given to rectifier circuit for conversion process i.e from AC to DC.This constant 13V is given to non inverting terminal of opamp-1,inverting terminal is given with battery positive terminal for same opamp.Output of opamp-1 is given to inverting terminal of opamp-2 and its non inverting terminal is grounded.Output of opamp-2 is fed to LED which has -1v supply.

Operation:

case:1 Assume initially the battery has 2v in it ,V+>V-,therefore V01 is 13-2=11v,V02=-11v,since the potential at anode is much less than potential at cathode the LED doesnot glow.It means that battery is not yet fully charged.

case:2 Assume now the battery is fully charged i.e upto 13v,V+=V-,therefore V01=0,V02=0 and now the potential at anode(0v) is greater than potential at cathode(-1v),LED glows and indicates us that battery is fully charged and need to be unplugged.

*Since the ouput of rectifer is given to battery,it charges the battery when it is discharged by the user.

*Here two opamp are used,but the same work can be done with single opamp.For better explanation i has shown two.

,

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WIRELESS ELECTRICITY-EXPLAINED

Movement of electrons (current) in free space without using any proper conduction path between two electronic devices is referred to as wireless electricity.Long before it is a dream but after a few years it will come true.

• Everyone knew that conductor has free valence electrons, by applying proper voltage (nothing but force) these electrons move and results current(flow of electrons).

1.Actually the concept of wireless electricity has started with faraday's law.

It states that whenever a conductor is placed in magnetic field(time changing) an induced emf(electro motive force) or voltage is induced in another conductor.This is considered as base for wireless electricity. Without any proper conduction path,this induced emf will results to move electrons in another conductor.This concept resulted to discover transformer.With the transformer we are able to alter voltage from a high valve(received from station)to a value required for home appliances.This is beginning for wireless electricity.

2.Second thing I would consider is from the basics of antenna. Actually antenna is an interface between free space and transmission line that converts V/I waves into E/H waves at the transmitter and viceversa at the receiver.HOW? When a voltage(V/I) is fed at the input, due to electric field(electrons) and magnetic field(as these electrons are moving),E/H waves are released into medium, this conversion V/I into E/H process is called radiation and at the receiver E/H is converted back  to its V/I form, this process is called induction.

By adopting both radiation and induction techniques we can transmit electricity without proper conduction path between two devices.

Conclusion:From first technique we need a strong magnetic field between two wireless devices and from second technique we need an antenna for wireless transfer of electricity.

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Software's for Win 7 homebasic and Add-on for chrome

Hi friends this time i would like to share two softwares for windows 7 home basic operating system and a Add-on for Chrome browser.
1.Software-"personalization -setupfile"
Every user of win 7 home basic will not find personalize option in the popup menu,but where as in win 7 professional , ultimate and home premium, users can have it with which one can change the wallpaper of desktop by one click.To get the personalize option for home basic ,download a setupfile "personalization" and get installed in your PC.And now you can see personalization option in popup menu.But we have still left out with "next background option",by which wallpaper changes automatically.
2.Screen Shot Add-on-"CLIPULAR"
    For chrome users,Clipular is one of the best screen shot Add-on.When Clipular is added to chrome,one can take screen shot for the tabs s/he has been working on.Screen shots of full screen or else a part can be taken which will be stored in book(Add-on book),for usage of that image(screen shot) one has to login ,save the file and use it.Since it is add-on for chrome one cannot use it outside chrome.Shortcuts are specified ,which ease its usage.
3. Software-"EPICPEN"
    Those who want to draw on screen, to specify a matter to another user. Epicpen software is useful.By using this,one can able to highlight the matter,that s/he is going to convey.By installing this software one can use a pencil,eraser and color selection.But one cannot draw straight lines or a particular shape,only zigzag lines are allowed.The file can be found at http://sourceforge.net/projects/epicpen/

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DISPLAY DEVICES-EXPLAINED

HI friends in this post we are going to learn about the various types of DISPLAY DEVICES which we had been known.In this the foremost one is 

1.CRT(Cathode ray tube):Experiments to discover more on smallest  particle "atom"(on that time)by J.J thomson, landed him to know about electron.In his experiment he noticed that a ray of particles called electrons(named by G.J stoney) were travelling from cathode to anode,he made this electrons to fall on fluorescent screen when this electrons hit the screen bright spot is produced.On their way from electron gun to screen their is chance of deflection, due to surrounding fields(as electrons are negative),to overcome this he placed horizontal and vertical deflection plates in between the space.So based upon the electrons, which hit the screen display is produced.now a days we can observe CRT's in CRO(cathode ray oscilloscope) .Next to this is 
2.LCD(liquid crystal display):Display by liquid crystals.Normally we know crystals in solid form like rochelle salt,quartz etc unlike here it is liquid crystals,means crystals which are in liquid form or in which the  molecules tend to orientate easily.Actually liquid crystals state is in between solids and liquids.As we know that even on slight increase of temperature will turn this liquid into real liquid so liquid crystal  are effected easily by electric current.Based upon this feature, applied electric current results molecules change their orientation with which display is produced.Next to this
3.LED(light emitting diodes):The diodes which emit light when they are forward biased are LED's.when we look at aluminum-gallium-arsenide(AlGaAs), in this type of semiconductor made diodes the interaction between electrons and holes is interesting , which is responsible to emit light.we knew in previous post "introduction to pn junction diode" about diode condition when no external bias is applied i.e  depletion layer is formed(electrons recombine with holes due to diffusion) on recombination electrons jump from lower orbital to higher orbital and vice versa .Electrons lose(release) energy when they jump from higher to lower orbital and needs(gains) energy to move from lower to higher orbital.The energy released in this process is in form of photons which are basic particles of light,these photons have speed and momentum but have no mass.
you can ask me, why this emission of light doesn't occur in normal Si, Ge diode,the reason is that atoms in normal diode are arranged in a manner that energy drop is relatively short which is invisible to normal eye.By release of photons in led's display is produced.Next to this
4.OLED(organic light emitting diodes):The main differences between led and Oled is the presence of organic layer present between anode and cathode of a diode.The organic layers in Oled are organic layer,conducting layer,emissive layers,the main purpose of this layers are to transport much holes from anode and much electrons from cathode, this will increases the recombination rate which in turn increases the emission of photon which are basic particles of light,this is how display is produced in Oled.

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