ECE | Electronics Mini Project

Power Transistor Concept A power transistor possesses a high blocking voltage capability in the OFF state and high current carrying capability in the ON state. They are normally used as switch.  Power transistors are available in both NPN and PNP forms. But the available current and voltage ratings are higher for NPN devices. Because of the greater mobility of electrons compared with holes, NPN devices can be fabricated on a smaller chip area to provide the same performance as that of an equivalent (counterpart) PNP devices.  The power transistor with current ratings of several hundred amperes and voltage ratings of several hundred volts are presently available in Market. The symbol for power transistor is same as low power transistor: (1) NPN (2) PNP  Symbol of NPN and PNP Transistor

 Door Alarm using SCR    SCR ( silicon controlled Rectifier) also called Thyristor is a  semiconductor controlled rectifier is a four layer solid state current controlling device. Components : 1. 1 × Low Power scr 2. 1 × 9v Battery 3. 1 × buzzer 4. 2 × Switches 5. 1 × 1k ohm resistor ( may be vary) Circuit Diagram : Door Alarm system using SCR Working : 1. Make circuit as per Circuit Diagram. 2. Place switch in on door in that way when door is open, switch is closed. 3. When Switch is closed a triggering pulse apply to gate and scr is turn on. Attention :   To turn off  buzzer place one more switch between positive terminal and scr anode. OR remove Battery    

  Merits of Power Electronic Converters : 1. High efficiency due to low loss in power semiconductor devices.  2. High reliability of power electronic component and converter system.  3. Long life and less maintenance due to absence of mechanical moving parts.  4. Fast dynamic response compared to electromechanical converter system.  5. Small size and less weight, so less installation cost.  6. Mass production of power semiconductor devices has brought down the cost of converter equipment.  7. Computer/microcontroller based controlis possible Demerits of Power Electronic Converters:  1. It generates harmonic into the supply and load system, adversely affecting the performance of the load and other equipments.  2. A.C. to D.C. and A.C. to A.C. converters operate at low input power factor.  3. Power electronic controllers have low overload capacity. 

IC  LM556  Dual Timer : Description, Features and Applications. Description    The LM556 Dual timing circuit is a highly stable controller capable of producing accurate time delays or oscillation. The 556 is a dual 555. Timing is provided by an external resistor and capacitor for each timing function. The two timers operate independently of each other sharing only VCC and ground. The circuits may be triggered and reset on falling waveforms. The output structures may sink or source 200mA. Features 1. Direct replacement for SE556/NE556 2. Timing from microseconds through hours 3. Operates in both astable and monostable modes 4. Replaces two 555 timers 5. Adjustable duty cycle 6. Output can source or sink 200mA 7. Output and supply TTL compatible 8. Temperature stability better than 0.005% per ˚C  9. Normally on and normally off output Applications 1. Precision timing 2. Pulse generation 3. Sequential timing 4. Time delay generation 5. Pulse width modulation 6. Pulse position modulation 7

 Applications of Power Electronics : 1. Arc and industrial furnace 2. Blowers and fans 3. Pumps and compressors  4. Transformer tap changer 5. Rolling mills 6. Battery charger  7. A.C. and D.C. motor speed control  8. Static circuit breaker  9. Induction and dielectric heating control 10. Electric welding control  11. Static excitation system for alternators 12. Traction control of electric vehicles, electric locomotives  13. Light dimmers  14. Washing machines  15. SMPS and UPS  16. HVDC transmission  17. Fan speed regulator  18. Automatic power factor correction  19. Process control  20. Satellite power supply  21. Battery monitoring power converter in laptop computers  22. High performance and compact switching regulators  23. Power electronics boost converter for automobiles  24. Replacement of spark plug and ignition coil of automobiles  25. Power steering  26. Power converter in space system  27. Flexible AC transmission system (FACTS)   28. Electrochemical process  29. Portable

 Low Power Inverter : 12DC into 230-250V AC     Here is a  simple low-power inverter that converts 12V DC Into 230-250V AC. It can be used to power very light loads like Window chargers and night lamps, or Simply give shock to keep the intruders away. The circuit is built around Just two ICs, namely, IC CD4047 and IC ULN2004.      IC CD4047 (IC1) is a monostable / astable multivibrator. It is wired in astable mode and produces symmetrical pulses of 50 to 400 Hz, which are Given to IC2 via resistors R1 and R2.    IC ULN2004 (IC2) is a popular 7-channel Darlington array IC. Here, The three Darlington stages are Paralleled to amplify the frequencies Received from IC1. The output of IC2 Is fed to transformer X1 via resistors R3 and R4.     Transformer X1 (9V-0-9V, 500mA Secondary) is an ordinary step-down Transformer that is used here for the reverse function, i.e., step up. That Means it produces a high voltage. Resistors R3 and R4 are used to limit The output current from the ULN

Necessity of Power Generation and Conversion Electrical power generation is a basic needfordomestic andindustrial applications. Various methods areusedto generate electrical power. To generate electrical power, conventional and nonconventional methods are used. Mainly electrical power is generated from thermal electrical power station, hydroelectric power station, nuclear power station, wind turbine and solar power plant. A.C. electric power generation and transmission is more efficient than D.C. electric power. High voltage A.C. power is transmittedand distributed.In India, line frequency is maintained at 50 Hz. AC. line supply is available in single phase and three phase. D.C. power can be stored very easily. For power conversion, rectifier, control rectifier, inverter, chopper, cycloinverter, cycloconverter and other circuits are suitable.  Power electronic equipment involves interaction between the source and the load and utilizes small signal electronic control circuit as well as

  What is power electronics components. To understand power electronic devices and circuit, it is essential to have knowledge about basic electronic components. Two main categories of electronic components are (a) Passive components, (b) Active components. Passive component's working does not depend on external biasing supply . Examples of passive components are resistor, capacitor and inductor. For the operation of active component, external biasing supply is essential . Examples of active components are diode, BJT, FET, UJT, IGBT, MOSFET, SCR, TRIAC, etc.  Electronic devices can be classified as tube devices and semiconductor devices. In early days of electronics (1900 to 1940), tube devices were most commonly used. Tube devices are further classified as vacuum tube devices and gas filled tube devices. Vacuum tube diode, triode, CRT (Cathode Ray Tube) are few examples of vacuum tube devices. Vacuum tube devices are operated on the basis of 'thermionic emission' i.e. emiss

Auto Turn OFF Battery Charger Electronics Project    This charger for series-connected how to make Auto Turn OFF Battery Charger/ Electronics mini projects / how to make battery charger 4-cell AA batteries automatically  disconnects from mains to stop  charging when the batteries are fully  charged. It can be used to charge partially discharged cells as well.         The circuit is simple and can be divided into AC-to-DC converter, relay driver and charging sections.        In the AC-to-DC converter section, transformer X1 steps down mains 230V  AC to 9V AC at 750 mA, which is rectified by a fullwave rectifier comprising diodes D1 through D4 and filtered by capacitor C1. Regulator IC LM317 (IC1) provides the required 12V DC charging voltage. When you press switch S1 momentarily, the charger starts operating and the power-on LED1 glows to indicate that the charger is ‘on.’         The relay driver section uses pnp transistors T1, T2 and T3 (each BC558) to energise elect

    Simple Smoke Detector.      This simple smoke detector is highly sensitive but inexpensive. It uses a Darlington-pair amplifier employing two npn transistors and an infrared photo-interrupter module as the sensor. The circuit gives audio-visual alarm whenever thick smoke is present in the environment.      The photo-interrupter module (H21A1) consists of a gallium-arsenide infrared LED coupled to a silicon phototransistor in a plastic housing. The slot (gap) between the infrared diode and the transistor (see Fig. 1) allows interruption of the signal with smoke, switching the module output from ‘on’ to ‘off’ state.  Fig 1: Top and Bottom view of Photo interrupter module.   The circuit of the smoke detector is shown in Fig. 2.      When the smoke enters the gap, the IR rays falling on the photo-transistor are obstructed. As a result, the photo transistor stops conducting and the Darlington-pair transistors conduct to activate the buzzer and light up LED1.  Fig 2: schematic of Smoke d