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      The P-N junction diode is appeared in the year 1950. It is the most essential and the basic building block of the electronic device. The PN junction diode is a two terminal device, which is formed when one side of the PN junction diode is made with p-type and doped with the N-type material. The PN-junction is the root for semiconductor diodes. The various electronic components like BJTs, JFETs, MOSFETs ( metal–oxide–semiconductor FET ), LEDs and analog or digital ICs all supports semiconductor technology. The main function of the semiconductor diode is, it facilitates the electrons to flow totally in one direction across it. Finally, it acts as a rectifier. This article gives a brief information about the PN junction diode, PN junction diode in forward bias and reverse bias and the VI characteristics of PN junction diode What is a PN Junction Diode? There are three possible  biasing  conditions and two operating regions for the typical PN-Junctio...

Why a lamp tester or fuse tester? Testing cables, wires, lamps… belongs to a repair job and sometimes this becomes too cumbersome since one has only two hands and too often, one has to hold the part being tester and the two probes of an ordinary continuity tester all at the same time. This fuse and lamp tester enables easy testing of lamps and fuses by using the conductivity of the human body. One of the test probes is connected to the part under test while the other probe is hel dby the normal hand. Lamp and Fuse Tester Circuit Diagram When the lamp or fuse is working properly, your eyes will glow in the dark! Just kidding :) . When the lamp or fuse is working properly, a small amount of current flows through the hand which is enough to switch the transistors and light the LED. 

Simple Ni-Cd and Ni-MH Adjustable Constant Current Project.This is a battery charger circuit with adjustable current for Ni- MH or Ni -Cd. It can be used for a constant current power , which can be set to any value from a few milliamps to about 500 mA . The maximum current is 500 mA , because that is the limit of transistor BC140 . The input voltage must be above 5.25V output voltage , this is due to losses as 1.25V current limit and approximately 4V regulator .  Battery Charger Ni-Cd and Ni-MH Adjustable constant current Circuit Diagram The LM317 regulator is used , it should have a sink . C omponents R1 100Ω resistor VR1 trimpot or potentiometer 500Ω Capacitor C1 0.1μF C2 Capacitor 0.01μF Diode D1 1N4001 Q1 Transistor BC140 IC1 Voltage Regulator LM317

Many electronic projects require the use of a small audio amplifier. Be it a radio transceiver, a digital voice recorder, or an intercom, they all call for an audio amp that is small, cheap, and has enough power to provide adequate loudness to fill a room, without pretending to serve a disco! About one Watt RMS seems to be a convenient size, and this is also about the highest power that a simple amplifier fed from 12V can put into an 8 Ohm speaker. A very low saturation amplifier may go as high up as 2 Watt, but any higher power requires the use of a higher voltage power supply, lower speaker impedance, a bridge circuit, or a combination of those. During my many years building electronic things I have needed small audio amps many times, and have pretty much standardized on a few IC solutions, first and and foremost the LM386, which is small, cheap, and very easy to use. But it does not produce high quality audio... For many applications, the advantages weigh more than the distortion an...

The neck on this Hofner Colorama was originally quite badly back bowed, as shown here: In an effort to rectify this, we’ve tried three different approaches, as follows: 1. While re-radiusing the fretboard, more pressure was applied towards the middle of the neck in order to remove more fretboard material in that area. This would not straighten the neck, per se, but it would reshape the top of the fretboard in such a way that its top would end up being flatter. 2. When refretting, the fret slots were widened. When frets are forced into narrower slots, this has a tendency to force the neck to back bow, so we wanted to avoid this at all costs. The slots are still narrow enough to grip the new frets, but are certainly not overly-tight. 3. Obviously the truss rod nut was slackened as much as possible. In fact, even with the nut removed, the neck still maintained a back-bowed shape. It was noticed that the washer under the nut was wedged into place, and it was suspected that it might be pre...

  Android 4.4.1 landing soon and fixes Nexus 5 camera . The Nexus 5 from Google is quite an awesome device, however its camera isn’t the greatest. Even though the Nexus 5 ′s camera features a optical image stabilization, taking shots from it are painfully slow and generally out-of-focus. Google is aware of this and as per The Verge, a new update scheduled to be released in the next few days fixes a lot of issues with the Nexus 5 camera. They’ve managed to get a hands-on experience with Android 4.4.1 and here is what they have to say: Speed is a theme for the update, and the Nexus 5 ′s camera really does feel faster across the board. The app launches a full second quicker than it did before the update, meaning you’ll miss many fewer shots than before. There’s also a new progress indicator in HDR+ mode, which makes the process, longer by necessity, feel a lot more straightforward. It’s the first of what Burke says will be a series of interface changes, as Google tries to make Andro...

It's that time of the year again. As we approach fall, we're getting closer to the launch of Apple's new products, as promised by CEO Cook during the company's last earnings call. This also means that we can expect new rumours and leaks to start hitting the Internet. While a lot is already known about the iPhone 5S (the next-generation iPhone) and the iPhone 5C (the low-cost iPhone), we're also seeing new rumours and leaks related to the next-generation iPad and iPad mini. A number of rumours have already suggested that Apple is modelling its next-generation iPad on the iPad mini in terms of design and form factor. The speculation has got more credence thanks to a new report by The Wall Street Journal. The report mentions that the new iPad will feature the same touch-panel technology that's seen in the iPad mini, making it thin and light. It cites people with knowledge of the matter as a source, and adds that Apple intends to use the film-based touch panel used ...

This circuit uses a switched capacitor filter IC from National Semiconductor to filter signals with frequencies higher than the 3KHz needed for voice audio. The schematic includes an audio amplifier that is designed to drive a standard audio head phone.  The circuit is described in more detail in the receiver section of Dave Johnson's Handbook of Optical Through the Air Communications.(this link is off-site)  3khz Low Pass Filter and Audio Amplifier Circuit Diagram  

4.3 Voltage and Current Capacity of Cells The e.m.f. of a cell depends on the materials of its electrodes and the electrolyte. On the other hand, the amount of current an electric cell can produce in a given span of time depends on the quality of electrodes and the electrolyte it is made of. The table below shows the e.m.f. of some electric cells and the materials they are made of.  Cell e.m.f. Positive Electrode Negative Electrode Electrolyte 1 Simple cell (Zinc-acid) 1.5 Copper Zinc Dilute sulphuric acid 2 Leclanché 1.5 Carbon Zinc Sal ammoniac 3 Mercury 1.35 Steel Zinc Potassium hydroxide 4 Silver oxide 1.5 Silver oxide  Zinc    potassium or sodium hydroxide 5 Zinc air 1.4 Oxygen gas  Zinc   potassium hydroxide 6 Lithium air 3.8 Oxygen gas  Lithium  Organic carbonate 7 Lead-acid 2.2 Lead dioxide Lead Dilute sulphuric acid 8 Nickel-cadmium...

Advantages and Disadvantages of Moving Iron Instruments Advantages 1.        The instrument can be used both on DC as well as on AC circuits. 2.        These instruments are cheap, robust and simple in construction. 3.        The instruments have high operating torque. 4.        The instruments are reasonably accurate. 5.        These instruments can withstand overload momentarily. Disadvantages 1.        Scales of these instruments are not uniform because of pneumatic damping. 2.        Errors are introduced due to change of frequency I case of A.C. 3.        Errors are introduce due to hysteresis and stray magnetic field. 4.        Power consumption is high.

This is a simple series of fire alarms. In this series used NE555 timer and temperature sensor to detect high temperatures. The working principle of this temperature sensor that is when the temperature is high around the sensor then there is resistance on the sensor to be small.  However if the low temperature then the resistance will be high. If the resistance of small sensors, the voltage supply will be able to flow past the sensor and activate the transistor. IC1 NE555 as a regulator of the audio frequency. Transistors 1 and 2 are used as a driver IC1. Output (pin 3) of IC1 would trigger a transistor base T3 (SL100), which drives the speaker to produce sound the alarm. Frequency NE555 depending on resistance values ​​of R5 and R6 and the capacitance sensor C2 temperature. When the temperature gets hot, would provide a low resistance so that supply voltage can flow into the base of transistor T1 through a diode D1 and R2. Capacito...

2.2 Electrical job e ntry requirements and job descriptions In electrical engineering, the jobs are grouped and classified in the order of seniority and according to their demand. The job groups are: 1.         Artisan. 2.         Craftsman. 3.         Technician. 4.         Technologist 5.         Engineer. The artisan is at the bottom of the ranks while the engineer is at the top. Occupation pyramid 2.1.1 Artisan To train as an artisan in any specific area of electricity, one has to have obtained passes at KCPE. An artisan is a skilled operator who has a good knowledge of techniques and appropriate tools. His job does not require him to solve design problems or to perform administrative duties. 2.1.2 Craftsman Entry into craftsman training requires at least good passes at KCSE or a high achievement at the artisan...

             Deaf and Dumb people communicate with each other  and others in many areas of everyday life. Often they need support to communicate effectively with each other. The project aims to develop a complete Portable Communication Aid for deaf and dumb. A flex sensor glove along with MEMS Accelerometer is used to convert the sign language to voice. The PDA with voice to text converter converts voice to text format.             The 3 axis Mems and Flex sensor glove is connected to the  ADC channels of the LPC 2138 Microcontroller. According to the digital output values from Mems and Flex sensor, The microcontroller recognize the corresponding letter and transmits to voice recorder IC through SPI module. The IC converts these to voice format.             The project also includes a PDA with voice to text converter which converts th...

This source uses LEDs and an astable oscillator to control the switch, duty-cycle, and effective IR illumination output.  Circuit Diagram

TA7200P has a 3,3 W output and the equation of TA7204P has a power output of 4,2 W , using the circuit above , in  both ic can have 10 watts of output power amplfier , but the quality of each ic remains different. Both ic manufactered by TOSHIBA. Part List : Resistor   = 100K x 2, 820R Capacitor = 1uF , 10uF , 100uF x 2, 4u7F , 820pF , 15 pF , 47uF, 470 uF. IC            = TA7200P / TA7204P Technical information : Max. Voltage = 20 Volt DC Min. Voltage = 10 Volt DC Max. Output = 10 Watt Approx. RL  = 4 - 8 Ohm Approx. Ft   = 30Hz - 18KHz

RCA RC1188B – RCA RC1188D Chassis – Used tubes: 12BE6 – 12BA6 – 12AV6 – 5OC2 - 35W4 Circuit diagram Click on the picture to magnify

Solid-state relays As versatile as electromechanical relays can be, they do suffer many limitations. They can be expensive to build, have a limited contact cycle life, take up a lot of room, and switch slowly, compared to modern semiconductor devices. These limitations are especially true for large power contactor relays. To address these limitations, many relay manufacturers offer ”solidstate” relays, which use an SCR, TRIAC, or transistor output instead of mechanical contacts to switch the controlled power. The output device (SCR, TRIAC, or transistor) is optically-coupled to an LED light source inside the relay. The relay is turned on by energizing this LED, usually with low-voltage DC power. This optical isolation between input to output rivals the best that electromechanical relays can offer. Solid State Relay  Being solid-state devices, there are no moving parts to wear out, and they are able to switch on and off much faster than any mechanical relay armature can move. There ...