Personality Test

Pick the door that looks the most appealing to you. This might reveal a few things about your personality. Let us know what door you picked and if the answer was accurate for you.

Why doors?...

The symbolism behind this test is really amazing.  Maybe you haven’t realized it yet, but with every step in life, we have to go through a door.  Have you ever thought about how many doors you’ve ran into, knocked on, and opened in order to make a path for your future? 

CLICK HERE for results....

-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-'-

Which Tree Draw Your Attention The Most?

 

Look at the tree and choose the one that is immediately most appealing to you. Don’t think about it too long, just choose. Have fun!

CLICK HERE for results....

LM317

The LM317 is a popular adjustable linear voltage regulator. It was designed by Robert C Dobkin in 1976 while he worked at National Semiconductor.





SCHEMATIC DIAGRAM and PIN CONFIFURATION

OPERATION

As linear regulators, the LM317 and LM337 are used in DC to DC converter applications.
Linear regulators inherently waste as much current as they supply. When this current is multiplied by the voltage difference between input and output, a significant amount of heat results. Therefore the use of an LM317 commonly also requires a heat sink. For large voltage differences, the energy lost as heat can ultimately be greater than that provided to the circuit. This is the trade-off for using linear regulators which are a simple way to provide a stable voltage with few additional components. The alternative is to use a switching voltage regulator which is usually more efficient but has a larger footprint and requires a larger number of associated components.
In packages with a heat-dissipating mounting tab, such as TO-220, the tab is connected internally to the output pin which may make it necessary to electrically isolate the tab or the heat sink from other parts of the application circuit. Failure to do this may cause the circuit to short.

PN-Junction Diode Theory

Semiconductor diode theory is at the very centre of much of today's electronics industry. In fact semiconductor technology is present in almost every area of modern day technology and as such semiconductor theory is a very important element of electronics.
One of the fundamental structures within semiconductor technology is the PN junction. It is the fundamental building block of semiconductor diodes and transistors and a number of other electronic components.
The semiconductor diode has the valuable property that electrons only flow in one direction across it and as a result it acts as a rectifier. As it has two electrodes it receives its name - diode. In view of this, it is one of the most fundamental structures in semiconductor technology. Vast numbers of diodes are manufactured each year, and of course the semiconductor diode is the basis of many other devices apart from diodes. The bipolar junction transistor, junction FET and many more all rely on the PN junction for their operation. This makes the semiconductor PN junction diode one of the key enablers in today's electronics technology.

PN Junction

In its basic form a semiconductor diode is formed from a piece of silicon by making one end P type and the other end N type. This means that both ends have different characteristics. One end has an excess of electrons whilst the other has an excess of holes. Where the two areas meet the electrons fill the holes and there are no free holes or electrons. This means that there are no available charge carries in this region. In view of the fact that this area is depleted of charge carriers it is known as the depletion region.

The semiconductor diode PN junction with no bias applied

Even though the depletion region is very thin, often only few thousandths of a millimetre, current cannot flow in the normal way. Different effects are noticed dependent upon the way in which the voltage is applied to the junction. If the voltage is applied such that the P type area becomes positive and the N type becomes negative, holes are attracted towards the negative voltage and are assisted to jump across the depletion layer. Similarly electrons move towards the positive voltage and jump the depletion layer. Even though the holes and electrons are moving in opposite directions, they carry opposite charges and as a result they represent a current flow in the same direction.

The semiconductor diode PN junction with forward bias

If the voltage is applied to the semiconductor diode in the opposite sense no current flows. The reason for this is that the holes are attracted towards the negative potential that is applied to the P type region. Similarly the electrons are attracted towards the positive potential which is applied to the N type region. In other words the holes and electrons are attracted away from the junction itself and the depletion region increases in width. Accordingly no current flows.

The semiconductor diode PN junction with reverse bias

PN junction characteristics

The PN junction is not an ideal rectifier diode having infinite resistance in the reverse direction and no resistance in the forward direction.

The characteristic of a diode PN junction

In the forward direction (forward biased) it can be seen that very little current flows until a certain voltage has been reached. This represents the work that is required to enable the charge carriers to cross the depletion layer. This voltage varies from one type of semiconductor to another. For germanium it is around 0.2 or 0.3 volts and for silicon it is about 0.6 volts. In fact it is possible to measure a voltage of about 0.6 volts across most small current diodes when they are forward biased. Power rectifier diodes normally have a larger voltage across them but this is partly due to the fact that there is some resistance in the silicon, and partly due to the fact that higher currents are flowing and they are operating further up the curve.
From the diagram it can be seen that a small amount of current flows in the reverse direction (reverse biased). It has been exaggerated to show it on the diagram, and in normal circumstances it is very much smaller than the forward current. Typically it may be a pico amps or microamps at the most. However it is worse at higher temperatures and it is also found that germanium is not as good as silicon.
This reverse current results from what are called minority carriers. These are a very small number of electrons found in a P type region or holes in an N type region. Early semiconductors has relatively high levels of minority carriers, but now that the manufacture of semiconductor materials is very much better the number of minority carriers is much reduced as are the levels of reverse currents.

IC 555 TIMER

The 555 timer IC was introduced in the year 1970 by Signetic Corporation and gave the name SE/NE 555 timer. It is basically a  monolithic timing circuit that produces accurate and highly stable time delays or oscillation. When compared to the applications of an op-amp in the same areas, the 555IC is also equally reliable and is cheap in cost. Apart from its applications as a monostable multivibrator and astable multivibrator, a 555 timer can also be used in dc-dc converters, digital logic probes, waveform generators, analog frequency meters and tachometers, temperature measurement and control devices, voltage regulators etc. The timer IC is setup to work in either of the two modes – one-shot or monostabl or as a free-running or astable multivibrator.The SE 555 can be used for temperature ranges between – 55°C to 125° . The NE 555 can be used for a temperature range between 0° to 70°C.

 

Function of different Pins:

1.      Ground: This pin is used to provide a zero voltage rail to the Integrated circuit to divide the supply potential between the three resistors shown in the diagram.

2.      Trigger: As we can see that the voltage at the non-inverting end of the comparator is V_in/3, so if the trigger input is used to set the output of the F/F to ‘high’ state by applying a voltage equal to or less than V_in/3 or any negative pulse, as the voltage at the non-inverting end of the comparator is V_in/3.

 3.      Output: It is the output pin of the IC, connected to the Q’ (Q-bar) of the F/F with an inverter in between as show in the figure.

 4.      Reset: This pin is used to reset the output of the F/F regardless of the initial condition of the F/F and also it is an active low Pin so it connected to ‘high’ state to avoid any noise interference, unless a reset operation is required. So most of the time it is connected to the Supply voltage as shown in the figure.

5.      Control Voltage: As we can see that the pin 5 is connected to the inverting input having a voltage level of (2/3) V_in. It is used to override the inverting voltage to change the width of the output signal irrespective of the RC timing network.

6.     Threshold: The pin is connected to the non-inverting input of the first comparator. The output of the comparator will be high when the threshold voltage will be more than (2/3) V_in thus resetting the output (Q) of the F/F from ‘high’ to ‘low’.

7.      Discharge: This pin is used to discharge the timing capacitors (capacitors involved in the external circuit to make the IC behave as a square wave generator) to ground when the output of Pin 3 is switched to ‘low’.

8.      Supply: This pin is used to provide the IC with the supply voltage for the functioning and carrying of the different operations to be fulfilled with the 555 timer.

Switches

Switches are an important part of most electronic circuits. In the simplest case, most circuits contain an on/off switch. In addition to the on/off switch, many circuits contain switches that control how the circuit works or activate different features of the circuit.

Switches are mechanical devices with two or more leads (or terminals) that are internally connected to metal contacts which can be opened or closed by the person operating the switch.

When the switch is in the On position, the contacts are brought together to complete the circuit so that current can flow. When the contacts are together, the switch is closed. When the contacts are apart, the switch is open and current cannot flow.

One way to categorize switches is by the movement a person uses to open or close the contacts. There are many different switch designs. The most common are

Slide Switch:

A slide switch has a knob that you can slide back and forth to open or close the contacts.







Toggle Switch
A toggle switch has a lever that you flip up or down to open or close the contacts. Common household light switches are examples of toggle switches.


 
 










Rotary switch: 
A rotary switch has a knob that you turn to open and close the contacts. The switch in the base of many tabletop lamps is an example of a rotary switch.
   






Rocker switch: 
A rocker switch has a seesaw action. You press one side of the switch down to close the contacts, and press the other side down to open the contacts.
   






Knife switch: 
A knife switch is the kind of switch Igor throws in a Frankenstein movie to reanimate the creature. In a knife switch, the contacts are exposed for everyone to see.
 






Pushbutton switch: 
A pushbutton switch is a switch that has a knob that you push to open or close the contacts. In some pushbutton switches, you push the switch once to open the contacts and then push again to close the contacts. In other words, each time you push the switch, the contacts alternate between opened and closed.
  
Other pushbutton switches are momentary contact switches, where contacts change from their default state only when the button is pressed and held down. The two types of momentary contact switches are
• Normally open (NO): In a normally open switch, the default state of the contacts is open. When you push the button, the contacts are closed. When you release the button, the contacts open again. Thus, current flows only when you press and hold the button.
• Normally closed (NC): In a normally closed switch, the default state of the contacts is closed. Thus, current flows until you press the button. When you press the button, the contacts are opened and current does not flow. When you release the button, the contacts close again and current resumes.
  
  
  
  
  

 

 

Potentiometer switch: 

A potentiometer, informally a pot, is a three-terminal resistor with a sliding or rotating contact that forms an adjustable voltage divider. If only two terminals are used, one end and the wiper, it acts as a variable resistor or rheostat.