Mini Prject Report Electric

Description Transistor transistor is a semiconductor device commonly used to amplify or switch electronic signals. A transistor is made of a solid piece of a semiconductor material, with at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistor's terminals changes the current flowing through another pair of terminals. Because the controlled power can be much larger than the controlling power, the transistor provides amplification of a signal. The transistor is the fundamental building block of modern electronic devices, and is used in radio, telephone, computer and other electronic systems. Some transistors are packaged individually but most are found in integrated circuits.

Figure 1 (transistor)

Relay A relay is an electrical switch that opens and closes under the control of another electrical circuit. In the original form, the switch is operated by an electromagnet to open or close one or many sets of contacts. It was invented by Joseph Henry in 1835. Because a relay is able to control an output circuit of higher power than the input circuit, it can be considered to be, in a broad sense, a form of an electrical amplifier.

Figure 3 (relay)

Capacitors Components that store electrical charge in an electrical field. Capacitors are used for filtration in the electronic circuits. Capacitors in general pass changing (e.g. AC) and block unchanging (e.g. DC) voltage levels. i.

Capacitor - fixed capacitance

ii. Capacitor network (array) iii. Variable capacitor - change the capacitance iv. Varicap diode - variable capacitor come diode

Figure 4 (capacitors)

Light emitting diode (L.E.D) A light-emitting diode (LED) is a semiconductor diode that emits light when an electric current is applied in the forward direction of the device, as in the simple LED circuit. The effect is a form of electroluminescence where incoherent and narrow-spectrum light is emitted from the p-n junction.

LED LEDare widely used as indicator lights on electronic devices and increasingly in higher power applications such as flashlights and area lighting. An LED is usually a small area (less than 1 mm2) light source, often with optics added to the chip to shape its radiation pattern and assist in reflection. The color of the emitted light depends on the composition and condition of the semiconducting material used, and can be infrared, visible, or ultraviolet. Besides lighting, interesting applications include using UV-LEDs for sterilization of water and disinfection of devices, and as a grow light to enhance photosynthesis in plants.

Figure 5 (L.E.D) LED schematic symbol

Diode diode is a two-terminal device ( thermionic diodes may also have one or two ancillary terminals for a heater).Diodes have two active electrodes between which the signal of interest may flow, and most are used for their unidirectional electric current property. The varicap diode is used as an electrically adjustable capacitor.The directionality of current flow most diodes exhibit is sometimes generically called the rectifying property. The most common function of a diode is to allow an electric current to pass in one direction (called the forward biased condition) and to block the current in the opposite direction (the reverse biased condition). Thus, the diode can be thought of as an electronic version of a check valve.

Figure 6 (Diode)

Resistor Resistors are characterized primarily by their resistance and the power they can dissipate. Other characteristics include temperature coefficient, noise, and inductance. Practical resistors can be made of resistive wire, and various compounds and films, and they can be integrated into hybrid and printed circuits. Size, and position of leads are relevant to equipment designers; resistors must be physically large enough not to overheat when dissipating their power. Variable resistors, adjustable by changing the position of a tapping on the resistive element, and resistors with a movable tap ("potentiometers"), either adjustable by the user of equipment or contained within, are also used.

Figure 7(resistor)

How its work

1. Plug-in the power supply (DC 9V) 2. Using finger touch the sensor board 3. Out put, the lamp areswitch on.

Description of circuit From the beginning the circuit is open circuit. When the sensor board was touched the circuit was close and current through coil and magnetic field was charge, the common source is gate 2 from normally open to normally closed circuit and the relay was functioning to complete the hole circuit gate(2 to 5) from relay figure. From our schematic diagram its show currents from positive move to C4,R10, relay( pin3), R6, R9,Q1 and touch switch is nodes 1. C4 function it’s to store the electrical charge and as well as current through R10 function to resist the currents to suitable for LED current use. From the LED the current flow to R8, relay (pin1), Q4,D3 and R7.D3 is functioning to the diode can be thought of as an electronic version of a check valve. At Coil (pin 1) and (pin 3) are change from open circuit to closed circuit. For our schematic system transistor (Q1,Q2,Q3 and Q4) is to relay is an electrical switch that opens and closes under the control of another electrical circuit. In the original form, the switch is operated by an electromagnet to open or close one or many sets of contacts. For capacitor (C1,C2,C3 and C4) Components that store electrical charge in an electrical field. Capacitors are used for filtration in the electronic circuits. And diode (D1,D2 and D3) is

Appendix

is a process in which two or more metal items are joined together by melting and flowing a filler metal into the joint, the filler metal having a relatively low melting point. Soft soldering is characterized by the melting point of the filler metal, which is below 400 °C (800 °F).[1] The filler metal used in the process is called solder.

Soldering is distinguished from brazing by use of a lower melting-temperature filler metal; it is distinguished from welding by the base metals not being melted during the joining process. In a soldering process, heat is applied to the parts to be joined, causing the solder to melt and be drawn into the joint by capillary action and to bond to the materials to be joined by wetting action. After the metal cools, the resulting joints are not as strong as the base metal, but have adequate strength, electrical conductivity, and water-tightness for many uses. Soldering is an ancient technique mentioned in the Bible and there is evidence that it was employed up to 5000 years ago in Mesopotamia. [2]

Desoldering desoldering is the removal of solder and components from a circuit for troubleshooting, repair purposes and to salvage components. Electronic components are often mounted on a circuit board and it is usually

desirable to avoid damaging the circuit board, surrounding components, and the component being removed.

No wetting, due to low heat

Excessive temperature

Good thermal profile

No wetting, due to low heat Excessive temperature Good thermal profile The photo on the left shows balls, which have not undergone reflow due to insufficient heat. By measuring the temperature accurately at the ball site, this can be avoided. The temperature at the ball site had not seen 217°C the melting point of SAC balls. The photo in the center shows what happens when excessive temperature is seen by the BGA, in this case the temperature was measured at about 265°C at the ball site. The photo on the right, shows the proper collapse of lead-free balls with the thermal profile properly set. The standoff distance may be higher with lead-free SAC due to its higher surface tension.

There are other reasons why lead-free reflow demonstrates poor wetting and the main causes are summarized below: • Solder paste activity level is too low • Excessive preheat temperatures • Too long a preheat • Difficult to solder finishes • Insufficient time above liquidus temperature • Excessive oxidation of parts to be joined

Lead-free solder pastes require activation to be sustained beyond traditional tin-lead systems up to 217°C and beyond for SAC alloys. Like traditional 63/37 no-clean pastes, such as ROLO types, the prevention of oxidation to parts and boards is critical. Flux classifications such as ROM1 may contain halides and are therefore better able to cope with oxides or difficult to solder parts. Tin-Silver-Copper solders wet most metal surfaces more slowly and adequate times above the melting point of the solder is needed to achieve good wicking and solder spread. Normally the range is 60-90 seconds with peak temperatures from 235-245°C. If soldering is jeopardized by oxidation of parts to be soldered, this can be verified using solderability test methods such as the wetting balance test.

Reference

From internet : http://library.thinkquest.org/C006657/electronics/integrated_circuit.htm http://www.paia.com/ProdArticles/Images/touchsw.gif http://www.elecfree.com/electronic/touch-switch-by-ic-4001-4020/ http://en.wikipedia.org/wiki/Touch_switch

http://www.elecfree.com/electronic/capacitive-sensortouch-switch-relay-withbc337/