Countdown Timer using 555 Timer

Countdown Timer:-In this Countdown Timer project, a 555 IC, a counter IC and a transistor switch to activate a relay either ON/OFF (mode selected by a jumper) as soon as the counting period is over. The circuit consists of an oscillator, a ripple and two switching transistors.Oscillator:-The 555 is configured in the standard astable oscillator circuit designed to give a square wave cycle at a period of around 1 cycle/sec. A potentiometer is included...

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MOSFET

Introduction:- The metal–oxide–semiconductor field-effect transistor (MOSFET, MOS-FET, or MOS FET) is a device used to amplify or switch electronic signals. The basic principle of the device was first proposed by Julius Edgar Lilienfeld in 1925. The MOSFET includes a channel of n-type or p-type semiconductor material (see article on semiconductor devices), and is accordingly called an NMOSFET or a PMOSFET (also commonly nMOS, pMOS). It is by far...

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JFET

INTRODUCTION:-The junction gate field-effect transistor (JFET or JUGFET) is the simplest type of field effect transister. It can be used as an electrically-controlled switch or as a voltage-controlled resistance . electric charge flowflows through a semiconducting channel between "source" and "drain" terminals. By applying a bias voltage to a "gate" terminal, the channel is "pinched", so that the electric current is impeded or switched off completely.Structure:-The...

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COMMON COLLECTOR CONFIGURATION

INTRODUCTION:-The COMMON-COLLECTOR CONFIGURATION (CC) is used as a current driver forimpedance matching and is particularly useful in switching circuits. The CC is also referred to as anemitter-follower and is equivalent to the electron-tube cathode follower. Both have high input impedanceand low output impedance.In the CC, the input is applied to the base, the output is taken from the emitter, and the collector isthe element common to both input...

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COMMON BASE CONFIGURATION

Introduction:-The COMMON-EMITTER CONFIGURATION (CE) is the most frequently used configurationin practical amplifier circuits, since it provides good voltage, current, and power gain. The input to the CEis applied to the base-emitter circuit and the output is taken from the collector-emitter circuit, making theemitter the element "common" to both input and output. The CE is set apart from the other configurations,because it is the only configuration...

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Silicon-controlled rectifier

INTRODUCTION:-A silicon-controlled rectifier (or semiconductor-controlled rectifier) is a four-layer solid state device that controls current. The name "silicon controlled rectifier" or SCR is Generel electronics's trade name for a type of thyrister. The SCR was developed by a team of power engineers led by Gordon Hall and commercialised by Frank W. "Bill" Gutzwiller in 1957.SCR...SYMBOLS:-OPERATION:-An SCR is a type of rectifier, controlled by a...

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Transistor codes..

NPN transistorsCodeStructureCasestyleICmax.VCEmax.hFEmin.Ptotmax.Category(typical use)PossiblesubstitutesBC107NPNTO18100mA45V110300mWAudio, low powerBC182 BC547BC108NPNTO18100mA20V110300mWGeneral purpose, low powerBC108C BC183 BC548BC108CNPNTO18100mA20V420600mWGeneral purpose, low power BC109NPNTO18200mA20V200300mWAudio (low noise), low powerBC184 BC549BC182NPNTO92C100mA50V100350mWGeneral purpose, low powerBC107 BC182LBC182LNPNTO92A100mA50V100350mWGeneral purpose, low powerBC107 BC182BC547BNPNTO92C100mA45V200500mWAudio, low powerBC107BBC548BNPNTO92C100mA30V220500mWGeneral purpose, low powerBC108BBC549BNPNTO92C100mA30V240625mWAudio...

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Field Effect transister (FET)

Introduction:-A field-effect transistor (FET) is a type of transister commonly used for weak-signal amplification (for example, for amplifying wireless signals).The device can amplify analog or digital signals.It can also switch DC or function as an oscillator.Field-effect transistors are fabricated onto silicon integrated circuit (IC) chips.A single IC can contain many thousands of FETs, along with other components such as resistors, capacitors,...

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