Tag: electric resistor

What’s the Difference Between a Tuned and an Untuned Oscillator Circuit?
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A tuned oscillator uses a LC (inductor-capacitor) tank-circuit, a frequency-selective RC (resistor-capacitor) circuit or a quartz crystal circuit in its feedback path. Generally, the output waveform shape from a tuned oscillator circuit is sinusoidal and for this to happen positive feedback is used around an amplifying device such as a transistor or op-amp.

If negative feedback is applied to an amplifier the gain of the amplifier is decreased but the stability is increased. With positive feedback however, the gain is increased but the stability is decreased. This increase in gain produces a situation where an alternating sinusoidal output is obtained without a signal input. The amplifier has now become an oscillator giving an alternating output with the energy required to maintain this oscillation is obtained from the d.c. supply.

A tank-circuit consisting of a parallel-tuned LC circuit or RC circuit is used as the frequency determining unit which is “tuned” to give oscillations around its resonant frequency, hence the name tuned oscillator. The output from this device is feedback to its own input in such a way that the feedback signal aids the change in input signal. No input signal is required because the frequency determining unit provides its own signal via the feedback network in such a way that the circuit is self-exciting. Then this type of circuit is known generally as a Feedback Oscillator (positive feedback) and oscillators which use this technique are:

LC Oscillators: As their name implies, LC oscillators consist of a parallel tuned inductor-capacitor tank circuit as their frequency determining unit. The capacitor is constantly charging and discharging through the inductor coil at its selected resonant frequency but due to the heavy losses in the resistive element of the coil, the dielectric of the capacitor, and in radiation from the circuit. So in a practicle LC circuit the amplitude of the oscillatory voltage decreases at each half cycle and these oscillations would eventually die away to zero. If sufficient energy is applied at the appropriate time from a d.c. power supply in the cycle to overcome these losses then oscillations will continue at a constant frequency and amplitude indefinitely. Resonant frequency occurs when the coils inductive reactance (XL) equals that of the capacitive reactance (XC). Oscillations are controlled by varying the value of the capacitor (varactor).

Tuned oscillator circuits which use an LC (Inductor/Capacitor) tank circuit include:

• Hartley Oscillator
• Clapp Oscillator
• Colpitts Oscillator
• Tuned Collector Oscillator
• Pierce Oscillator
• Miller Oscillator

RC Oscillators: RC oscillators are also known as “phase shift oscillators” because their oscillating elements are made up of resistor-capacitor circuits which produce a phase-shifting circuit which corresponds to positive feedback. RC networks are not naturally oscillating circuits but become oscillating elements when connected around transistor or operational amplifiers.

RC oscillators do not use inductors but instead produces oscillations at a frequency at which the RC network produces a 180 deg. phase shift. A single stage amplifier will produce 180 deg. phase shift between its input and output and which can be used as a stage to produce the required positive feedback. The output from the amplifier is fed back via the RC network to its input. The input is shifted 180 deg. through the amplifier and 180 deg. through the RC network and 180 deg. + 180 deg. = 360 deg. or zero phase shift.

One useful property of the RC oscillator is that output frequency is inversely proportional to capacitance which means that a change in capacitance produces a much higher frequency compared to the LC oscillator. However, the disadvantages are that the output power of the RC oscillator is low due to dissipation in the resistive elements and for positive feedback to occur the amplifier gain must be greater than 29.

Tuned oscillator circuits which use a RC (Resistor/Capacitor) phase shifting circuit include:

• Ladder Phase Shift Oscillator
• Relaxation Oscillator
• Quadrature Oscillator
• Wein Bridge Oscillator
• Switched Capacitor Oscillator
• Digitally Switched Oscillators
• Phase Advance Oscillator (current transfer)
• Phase Retard Oscillator (voltage transfer)

Crystal Oscillators: Quartz and some other crystalline substances exhibit the “piezo-electric” effect. When a mechanical stress or physical deformation is applied to two surfaces of a suitably cut crystal it will produce a voltage between the surfaces. Likewise, when a voltage is applied to the crystal it causes a small physical deformation to the actual shape of the crystal.

Then if the voltage produced by mechanical deformation is fed back in some way, it will itself produce mechanical distortion in the crystal which will produce a voltage, which will…continue forever. This forms the basis of a number of crystal oscillators, because this feedback occurs only at the natural frequency of vibration of the crystal with this natural frequency value being determined by the “cut” of the crystal. Then the crystal in fact behaves as a resonant circuit with a very narrow bandwidth.

There is a limit to the stability and frequency that can be obtained from normal LC or RC tuned oscillators. Quartz crystal oscillators operate at very high frequencies up to 10Mhz when operating in the parallel mode. They also have very high stability and a resonant frequency with a very high Q factor making them ideal for use in CPU, microcontroller and video applications.

“Untuned Oscillators”

Unlike the tuned oscillators above, an untuned oscillator has no LC tank-circuit, frequency-selective RC or crystal circuit in its feedback path. Instead, an untuned oscillator uses nonlinear feedback and generally, the output waveform from an untuned oscillator is non-sinusoidal such as square-wave, triangular-wave or pulse being characterised by a sudden transition from one condition of stability or state to the next. Untuned oscillators are more commonly known as relaxation oscillators. Types of untuned oscillators include:

Ring Oscillator: Ring oscillators consist of an “odd” number of logic gates or amplifiers connected together in a series chain so that the output of the last is connected to the input of the first producing a ring type circuit. The frequency of oscillation depends upon the proporgation delay of the components used and the number of odd “stages” that are within the ring. Oscillation frequency is very high as to is the power consumption. Ring oscillators are more of a novelty as their high frequency and use of components make them impractical as an oscillator.

Relaxation Oscillators: Relaxation oscillators are more commonly known as multivibrators. They are a class of oscillator in which the active devices (usually a transistor) in the circuit are driven well beyond their cut-off and saturation regions for a period of time. Relaxation oscillators are cheap and easy to build with the three main types of multivibrator being.

• Astable Multivibrator: – has no stable state.
• Monostable Multivibrator: – has one stable state.
• Bistable Multivibrator: – has two stable states.

555 and Timer Chips: As well as our old favourite the NE555 timer and its variations, there are a whole host of different chips available in both TTL and CMOS that can be used to generate a variety of different waveforms and signals with some of the most popular being the: 74LS121, 74LS123, 74LS221 and their variants.

Tankless Water Heater Information
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Just like you wouldn’t leave the heating systems switched on in your home when you are away for a vacation, wouldn’t it be a whole lot wiser if you were using heating systems for water only when you were actually using the hot water? Conventional water heaters heat your water and then save it all up in a tank and wait for you to use it. This seems pretty convenient. After all, when you do need the water, it is all ready and available. However we rarely realize the amount of electricity that would be wasted in maintaining the hot water at its given temperature. also, there is only a limited supply of hot water at a go, when it finishes off, you must wait for another long while before more water becomes available. The solution to all of this? Tank-less water heater.

Tank-less water heaters can heat water without the need for any kind of a storage tank. They do so by being an intermediate step between the cold water line and the hot water tap. When you need hot water, you simply turn the tap on, as the water starts flowing through the pipe, sensors switch on the heater which then heats the water as it travels to the tap. Usually these units have a long coiled pipe inside of them which allows water to travel a greater distance inside the unit, hence allowing greater time to heat the water. The heating element can be electric or gas. In case of electric element, high resistance coils are wound along the length of the pipe, hence allowing the pipe to get heated up on demand, and hence heat the water as it flows through it. In the other case, gas is used in small burners which too in turn do the same thing by heating the pipe up.

Of course, there are limitations to using such devices. They do not allow fast flow of water which is possible with storage tank heaters, since they are just emptying the tank. The water flow may be slow, but it would be consistent and indefinite. Since there is no storage system, hot water would keep flowing as long as you need it. For a household, it would be wiser to get multiple units or booster units to ensure consistent supply of water because high requirements can take a toll on this system. The benefits of going through the trouble of installing these systems is immense, they can bring down the energy usage by 1/3rd for a house that uses 41 gallons of hot water in a day.

Which tank-less water heater you use would depend on your location and your requirement. Locations makes a difference because the incoming water temperature would play a major role in deciding which heater you need. Also if your necessary temperature rise is achievable by gas or electric heating element would decide the kind that you choose. But rest assured, whichever heating system you may use, using tank-less water heaters would help save energy.

Thermal Plants
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SWITCHYARD and GENERAL SIGNIFICANCE

Electrical energy management system ensures supply of energy to every consumer at all times at rated voltage, frequency and specified waveform, at lowest cost and minimum environmental degradation. The switchgear, protection and network automation are integral parts of the modern energy management system and national economy.

The modern 3-ph, 50 Hz, AC interconnected system has several conventional and non-conventional power plants, EHV AC and HVDC Transmission system, Back to Back HVDC coupling stations, HV Transmission network, substations, MV and LV Distribution systems and connected electrical loads. The energy in electrical form is supplied to various consumers located in vast geographical area, instantly, automatically, and safely with required quality at all times. The service continuity and high quality of power supply have become very important.

For fulfilling the foresaid purpose, a state of the art, scientifically and technologically advanced SUBSTATION is required. Sub-Station is the load control center of the thermal plant where power at rated voltage, frequency and waveform is exported/imported as per requirements.

The substation at GHTP Lehra Mohabat has only one 220 KV switchyard. There are two output units each having a capacity of 210 MW. The generating voltage is limited to 15.75 KV and this voltage as stepped up by two-generator transformer 15.75/220 KV manufactured by BHEL. A part of 15.75 KV supply is fed to unit auxiliary transformer, which is stepped down to voltage 6.6 KV which is used to run the major auxiliaries of the plant.

After step up, the 220 KV output from the generator transformer is fed to either of the two bus bars through relays and circuit breakers and these are connected to various feeders through various equipments.

DIFFERENT TYES OF EQUIPMENTS USED IN SUB-STATIONS

1. BUS-BARS: –

Bus bar is a term used for main bar of conductor carrying an electric current to which many connections may be made. These are mainly convenient means of connecting switches and other equipments into various arrangements.

At GNDTP there are two 220 KV bus bars. These are made of aluminium and all the incoming and outgoing supplies are connected through the bus bars.

2. LIGHTENING ARRESTORS: –

These are equipments designed to protect insulators of power lines and electrical installations from lightening surges by diverting the surge to earth and instantly restoring the circuit insulation to its normal strength with respect to earth.

3. CURRENT TRANSFORMERS: –

The main purpose of current transformer is to step down the current to a level that the indicating and monitoring instruments can read. When rated current flows through its primary winding, a current of nearly 1 amp will appear in its secondary winding.

The primary is so connected that the current being passes through it and secondary winding is connected to an ammeter. The CT steps down the current to the level of the ammeter.

4. POTENTIAL TRANSFORMER: –

These are used to step do the voltage to a level that the potential coils of indicating and monitoring instruments can read. These are also used to feed the potential coils of relays. The primary winding is connected to the voltage being measured and the secondary winding to a voltmeter. The PT steps down the voltage to the level of the voltmeter.

5. POWER TRANSFORMER: –

These are used to step up down the voltage from one a.c voltage to another a.c voltage level at the same frequency. Shunt reactor in EHV substations is to provide reactive power compensation during low loads.

6. WAVE TRAP: –

Wave trap is used to prevent high frequency signals from entering other zones.

7. INDICATING AND METERING INSTRUMENTS: –

Ammeters, voltmeters, watt meters, KWH meters, KVAR meters are installed in sub-station to watch over the currents flowing in the circuit and the voltages and the power loads.

8. ISOLATORS: –

One of the cardinal measures for ensuring full safety in carrying out work on equipment in electrical installations is to disconnect reliably the unit or the section on which the work is to be done from all other live parts of the installation. To guard against mistakes, it is necessary that apparatus, which makes a visible break in the circuit such as isolators, should do this.

Isolators do not have arc control devices therefore cannot be used to interrupt currents at which the arc will be drawn across the contacts. The open arc in these is very dangerous, in that it will not only damage the isolator or the equipment surrounding it but will also cause the flashover between the phase in other words, it will result in short circuit in the installation i.e. why isolators are used only for disconnecting parts after de-energizing them by opening their respective circuits by use of their circuit breakers.

9. EARTHING SWITCHES: –

Earthing switch is used to discharge the voltage on dead lines to earth. An auxiliary switch to provide interlock always accomplishes it.

10. CIRCUIT BREAKERS: –

Circuit breakers are mechanical devices designed to close o open contact or electrical circuit under normal or abnormal conditions. CB is equipped with a strip coil directly attached to relay or other means to operate in abnormal conditions such as over power etc. In GNDTP three types of CB are used. SF6 CB is used to control 220 KV in switchyard.

VCB are used to control 6.6kv in switchgear & ABCB are used to control 415 KV in switchgear.

In sulphar puffer type SF6 CB is filled with SF6 gas at single pressure (4to6kgf/cm2). The pressure and gas flow required for arc extinction is obtained by piston action.

In double pressure type SF6 CB the gas from high-pressure system is released to into low-pressure system over the arc during the arc quenching process.

SPECIFICATIONS OF CB TYPE ELF-SL4-1

S. NO. SPECIFICATIONS RATINGS

1. Voltage 245KV

2. Normal current 3150 A

3. Lightening impulse withstand Voltage 1050V

4. Switching impulse withstand voltage 1050V

5. Short circuit breaking current 40KA

6. Short circuit withstand current And duration 40KA 3 sec

7. Line charging breaking current 125A

8. Operating sequence – First pole to clear factor 1.3

9. Supply voltage 220 V dc

10. Auxiliary circuit supply voltage 240 V dc

11. Air pressure 20.5 bar

12. Frequency 50 HZ

13. Mass 3800 kg

14. Rated current 1600 A

11. VARIOUS OTHER EQUIPMENTS

Shunt capacitors are used to provide compensation to reactive loads of lagging power factor.

Series reactors are used to reduce the short circuit current or starting currents. Neutral grounding resistors are used to limit the earth fault current.

Coupling capacitors are used to provide connection between high voltage line and power line carrier equipment.

Operating Voltage 230 V

Rated current 2000 A

Minimum short circuit current in bus bars 40 KV

Minimum phase to phase clearance 2.5 M

Number of horizontal levels of tubular bus bar/flexible bus bars 2.0 M

Height of tubular bus-bar of first level above ground 6 m

Height of tubular bus-bar of second level above ground 4 m

Tubular aluminium bus bar AL ASTMB241 4″IPS (International pipe standard)

VARIOUS SUBSYSTEMS IN SUBSTATIONS AND THEIR FUNCTION

S.NO. SYSTEM FUNCTION

1. Substation Earthing (Grounding) System – Earth mat – Earthing spikes – Earthing risers To provide an earth mat for connecting neutral points, equipment body, support structures to earth. For safety of personnel and for enabling earth fault protection. To provide the for discharging the earth currents neutrals, faults, surge arrestors over-head shielding wires etc. with safe step- Potential and touch potential.

2. Overhead earth wire shielding or lightning To protect the outdoor substation equipment from lightning strokes.

3. Illumination system (lightning) – For switchyards – Buildings – Roads, etc. To provide illumination for vigilance, operation and maintenance.

4. Protection system – Protection relay panels – Control cables – Circuit breakers – CT’s, PT’s, etc. To provide alarm or automatic tripping of faulty part from healthy part and also to minimize damage to faulty equipment and associated system.

5. Control cabling For protective circuits, control circuits, metering circuits.

6. Power cables To provide supply path to various auxiliary equipments and machines.

7. PLCC system power line carrier current system – Line trap – Coupling capacitor – PLCC panels For communications, telemetry, tele control power line carrier protection, etc.

8. Fire fighting system – Sensors, detection system – Water spray system – Fire protection control Panels To sense the occurrence of fire by sensors and to initiate water power spray, to disconnect power supply to affected region to pin point location of fire by indication in control room.

9. J Cooling water system – Coolers – Water tanks This system is required for cooling the valves in HVDC substation.

10. DC batteries sets and battery chargers Auxiliary low voltage DC supply.

11. Auxiliary stand by power System – Diesel generator sets – Switch gear – Distribution system For supplying starting power, stand by power for auxiliaries.

12. Telephone system For internal and external Communication.

12. BUS BAR ARRANGEMENT IN SWITCHYARDS

There are several ways in witch the switchyard can be connected in the electrical layout of generating station, receiving station or a switchgear in a distribution system. The following aspects in general affect the selection of the scheme:

1. Degree of flexibility of operations desired.

2. Importance of load and local conditions.

3. Economic conditions, availability, and cost.

4. Technical conditions.

5. Maintenance, safety of personnel.

6. Simplicity.

7. Provision of extension.

8. Protective zones.

DUPLICATE BUS BAR ARRANGEMENT

The duplicate bus bar system provides additional flexibility, continuity of supply and permits periodic maintenance without total shut down. In the event of fault o n one bus the other bus can be used.

While transferring the power to the reserve bus, the following steps may be performed:

1. Close tie circuit breaker, i.e. bus coupler. The two buses are now at the same potential.

2. Close isolators on reserve bus starting from far end.

3. Open isolators o9n main bus starting from far end.

Each pole of the circuit breaker comprises one or more interrupts or arc extinguishing chambers. The interrupts are mounted on support insulators. The interrupts enclose a set of fixed and moving contact. The moving contacts can be drawn apart by means of the operating links of the operating mechanism. The operating mechanism of the circuit breaker gives necessary energy for opening and closing of contacts of the circuit breaker.

13. RELAYS

Relay is a device by means of which an electric circuit (trip or alarm circuit) is controlled (closed) by change in the other circuit. Relays are automatic. The function of relay in power supply system is to recognize a start out and to initiate the operation of CB or other devices to isolate the defective elements with minimum disturbance to the normal power supply system. The must operate at required speed and stability to prevent the current and voltage to exceed their limits.

A few relays with their international codes are mentioned below:

S. NO. CODES TYPES

1. 27 Instantaneous under voltage relay

2. 99 Composite motor protection relay

3. 64 Earth fault relay

4. 87M Differential relay for motors

5. 50N Earth fault relays with times for time delayed operation

6. 95 Fuse failure relay

7. 80 Auxiliary supply for DC supervision

8. 80B DC supply control supervision

9. 80A Relay for mains

10. 500/L Triple pole over current definite term

11. 98 Trip circuit supervision relay

12. 87 Triple pole circulating current

13. 63 Auxiliary relay for transformer fault indication

14. 33B Auxiliary relay for stop

15. 25 Check synchronizing relay

16. 52SC Instantaneous high set over current relay

17. 2B Static time delay relay

18. 51RYB Single pole (IDMTL) Inverse definite Minimum time over current relay.

THE FAULT CLEARING PROCESS

During abnormal or faulty conditions the relays sense the fault and close the trip circuit of the circuit breaker.

As the relay contact close, the trip circuit is closed and the operating mechanism of the CB opens and an arc is drawn between them. The arc is extinguished at some natural current zero of a.c. wave.

o Fault Occurs: – As the fault occurs the fault impedance being low, the currents increase and the relay get actuated. The moving part of the relay moves because of the increase in the operating torque. The relay takes some time to close its contacts.

o Relay contacts close, the trip CB closes and trip coil is energized.

o The operating mechanism starts operating for the opening operations. The CB contacts separate.

o Arc is drawn between the breaker contacts. The arc extinguished in the CB by suitable techniques. The current reaches final zero as the arc is extinguished.

SWITCHGEAR

The switchgear constitutes all parts or equipments of power plant whose function is to receive and distribute electric power. It comprises of the following:

· Assemblies of switching apparatus

· Protective and indicating metering devices

· Interconnecting bus bar systems and relevant accessories

Functions of Switchgear: –

The functions performed by switchgear are listed below: –

· To facilitate redistribution of load, inspection and maintenance of system.

· To localize the effects of faults by operation of protective equipment so automatically disconnect faulty part from the system.

· To break efficiently short circuits without giving rise to dangerous conditions.

The switchgear has the responsibility of transmitting the power from the generator to the grid. However plant also needs power for its working. It is mandatory not to use more than 10% of the power developed by the plant. So that all the auxiliaries and lightening system of the plant must be designed in such a way that there consumption is in the limit.

There are two bus bars placed in ducts, which supply power to the switchgear and are fed by two station transformers ST-I and ST-II. The rating of these identical bus bars is 6.6 KV, 3150 Amps, 50 Hz. These are known as C-I and C-II station buses respectively. The material of conductor is Aluminium. C-I station bus feeds US-IA & US-2A buses and C-II feeds US-IB & US-2B buses. C-I & C-II buses are also interlinked. These unit service buses feed the different kinds of load.

The auxiliary voltage for the ac supply system is 6.6 KV and 415 V. 6.6 KV supply system is provided with high resistance grounded neutral with provision of alarm/ trip. 415V auxiliary supply system has solidly/high resistance earthed neutral. All the electric motors of 150 KW rating or below are rated at 415 V and motors above 160 KW are rated at 6.6 KV.

GENERAL ELECTRICAL SUPPLIES IN THE PLANT

Electrical Auxiliary System

· AC Auxiliary supply system

· DC supply system

AC auxiliary supply system is used to feed all the AC auxiliaries installed in the plant.

The DC supply system which consists of 220 V DC, 110 V DC,

+/- 24 V DC, 48 V DC etc. is used for control supplies as required for system control and protection equipment.

Simple Electrical Equipment in Daily Life
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Research shows that every year hundreds of people get killed each year in accidents which happen because of electrical failures and fires from short-circuits. They occur predominantly due to the ignorance of people who do not have the expertise to locate and rectify such errors, and also because many of them are too reluctant to seek professional help out of the misconception that the issue is not an important one. Some handy electrical test equipments must be kept at home for emergency purposes. Although it is still advisable that you get immediate professional assistance at the quickest, these tools could at least become useful to those who more or less have a fair idea regarding electrical testing.

Analogue Ammeters: They are used to measure the flow of current. The current level is displayed on a dial, in amperes, with the help of a pointer. This is helpful in determining the correct amount of power needed to run any electrical good.

Analogue Multimeters: As the name implies, this is required to measure important aspects regarding the flow of electricity like voltage, resistance and signal power and gives accurate reading in a very short span of time.

Analogue Voltmeters: They are used to determine the voltage of current passing through the circuit and also notify the user if there is a drop in voltage. The mechanism is easy to read with a simple needle point pointing the current voltage on a dial.

Circuit Tracers: This is also known by the name of signal tracers and is probably the most important of these testing devices, because they help in locating the fault in the circuit in the first place. They help to identify common problems like short circuits and breakages.

Clamp Meters: This equipment is very useful to electricians because it allows the user to measure electricity from a circuit without having to disconnect anything from the main wires. It gives all the necessary readings and help in identifying if the mechanism is under a heavy load.

Field Intensity Meters: These devices are used to measure the strength of any kind of electromagnetic field, and are very useful in detecting piping and equipments which are hidden from view or ferromagnetic ores buried in the earth.

Phase Meters: These are used in circuits where electricity is flowing in from three phases. They include instruments like Phase Testers and Phase Rotation Meters and provide accurate reading from all the three phases simultaneously.

Ground Resistance Testers: These equipments are used to test electrical grounding systems to determine the flow of power in between earth and the conducting objects. They are complicated to read and it is advisable that they be used only by those who have a sound knowledge of electrical testing equipment.

These electrical test equipments make the life of users comfortable and hassle-free.

3 Benefits of Elenco Snap Circuits Jr 100 Electronics Kits
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Few things are more exciting and rewarding than building something that really works. Most kids love the challenge of building their own electronic devices, whether it’s a simple robot or a bedroom alarm to keep out little siblings.

Various electronic kits are available, and the potential benefits go beyond the finished product. For a start, it’s a hands-on opportunity to become familiar with some terminology. By high school, science classes often include an introduction to electronics concepts, including circuit diagrams, resistors, and diodes. Kids who build electronics learn about basic physics, electricity, and how electronic devices work.

These are pretty challenging abstract concepts, which can be brought to life by using electronic kits to connect the right parts. For instance, rather than looking at a computer and seeing only a box with a screen, electronics enthusiasts can get their hands on real parts to help them see and better understand the inner workings and infinite expansion possibilities.

Electronic kits contain multiple parts, diagrams, and instructions. To be successful and create a working device, kids need to follow instructions systematically. Starting with electronic kits for beginners, there are multiple levels of difficulty to explore. Kids learn how to read instructions carefully and how to interpret schematic diagrams, developing both spatial and logical skills.

Building electronics requires persistence and patience. Starting with simpler kits allows these skills to be learned gradually. Snap-together versions are more gratifying for beginners, who are getting accustomed to the parts and language. Later, more difficult assemblies become interesting.

Electronics does not have to be a solitary pursuit. Some children’s kits, such as the Elenco Snap Circuits Jr 100, include interactive games to be played with friends. While most beginners start with electronic kits, there are endless possibilities for more advanced enthusiasts. In fact, there are clubs and online hobby groups. As projects get more complicated, kids can move on to more advanced electronic kits. Elenco Snap Circuits Jr 100 is a great place for beginners, but after mastering it, kids can advance to Elenco Snap Circuits 300 and Elenco Snap Circuits 500. There are also other brands available, such as Thames and Kosmos.

Have a science fair coming up? Electronic projects are an interesting way to explore physical concepts. Not only can a budding scientist build his or her own electronic device, but then there are many possible experiments that can be done with instruments like photo-electric cells, electromagnets, and generators.

Even beginners can make a wide variety of devices using Elenco Snap Circuits Jr 100, from radios and doorbells to a flying saucer. With so many options and parts, kids can experiment to build their own creations. Then there are electronic kits available that are specifically designed with one purpose in mind, such as making robotic vehicles, hydroponic gardens, race cars, weather observation centers, motorized dinosaurs, and digital recording instruments.

Most beginner electronic kits are solder-free, so they are straightforward and accessible for children. With practice and advancing skills, older kids can learn how to solder. Once this is mastered, there are many intriguing projects to make. Light dimmer switches, LED displays, combination code locks, and digital clocks make nice additions to any room. So next time you’re looking for an interesting and educational activity, think about an electronic kit.

Description of an Attenuator Voltmeter
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An attenuator voltmeter is defined as an instrument used for measuring the electrical potential difference, also known as voltage, between two points in the electronic circuit of different attenuators such as an optical attenuator and digital attenuator. Voltage is referred to as the electric potential energy per unit charge. It is responsible for driving a current from one electron to another electron. The corresponding International System of Units (SI units) for voltage is volt. The attenuator voltmeter can measure direct current (DC) or alternating current (AC).

In technical terms, all voltmeters are considered ammeters. This is because they measure electric current rather than voltage. Voltage is only measured when the electric current is transmitted in the electric circuit via resistance. Voltmeters are originally called galvanometers. Voltmeters are also known as multimeter because they also measure resistance and current.

The two types of attenuator voltmeter are the digital and analog voltmeters. A digital voltmeter usually features a voltage reference, an analog-to-digital converter, a power supply and a digital display unit. This kind of voltmeter directly displays numerals through the analog-to-digital converter. The digital display system could be a light emitting diode (LED) or a liquid crystal display (LCD) panel. There are several factors that may affect the accuracy of measurement of a digital voltmeter. Some of these factors include temperature and supply voltage variations. Users now prefer a digital voltmeter over an analog one because of its accuracy. To maintain its accuracy, periodic calibration of the voltmeter against a voltage standard is recommended.

Basically, an analog voltmeter contains a galvanometer, or current meter, which is in series with a high resistance. An analog voltmeter displays values on a dial, usually with a moving pointer or a needle. This kind of voltmeter may be employed to locate excessive resistance that may indicate an open circuit or ground. The impedance is the internal resistance of an analog voltmeter. This is commonly expressed in ohms per volt. An analog voltmeter is connected in parallel with the circuit being tested. This allows the meter to tap a small amount of electric current.

An attenuator is defined as a device which reduces the amplitude or power of a signal without distorting the signal’s waveform. This electronic device is used in audio and radio signal circuits. To measure the voltage difference in the attenuator circuit, the positive input terminal and negative input terminal are connected to a location in the electric circuit. When the attenuator voltmeter is already attached to the electric circuit, the circuit will be disturbed, which leads to change in the voltage being measured. The disturbance should be negligible enough so that it will not create significant change in the voltage. Some of companies that manufacture voltmeters are Onesto Electric Co. Ltd., China Electronics Zhejiang Co., Sunlogic Electrical Appliance Ltd., Tons International Ltd., People Ele. Appliances Group, Zhejiang Taizhou Wangye Power Co. Ltd., Shanghai Chenchang Power Technology Co. Ltd., Shaanxi Xieli Photo Electric Instruments Co. Ltd., Dongquan Zhengyang Electronic Mechanical Ltd. and Chac Technology Co. Ltd.

Thin Film – An Ever-Present Item With Handful of Uses and Practical Applications
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About Thin film Electronic Components and Its Product Range:

There is a widely used product for everything from computer memory and drug delivery to batteries, dye-sensitized solar cells, and micro and nano-devices. It is also used in a variety of applications such as protective coatings, control of light and heat, and modification of surface properties. What exactly is thin film and how is it defined? Essentially, thin film is a layer of material that ranges from fractions of a nanometer to several micrometers in thickness. They are the most common in electronic semiconductor devices and optical coatings, although they have many other applications, some of which were mentioned above. You are probably familiar with the application of thin film in a typical household mirror, in which a thin metal coating is applied to the back of a sheet of glass in order to form the reflective surface.

It is particularly ferromagnetic and ferroelectric thin films, are being increasingly used in computer memory. Ferromagnetism is a mechanism in which materials form permanent magnets, a very important concept that is fundamental in electrical and electromechanical devices such as electromagnets, electric motors, generators, transformers, and magnetic storage. Ferroelectric, on the other hand, signifies that there is a permanent electric polarization than can be reversed in an external electric field. These are used in transducers and electromechanical actuators. It is being used in pharmaceuticals as a method of drug delivery. Another type of thin film, ceramic, is also widely used to protect materials against corrosion, oxidation, and wear. They are also used to produce thin-film batteries and dye-sensitized solar cells. Photovoltaic solar cells have been known to have high manufacturing costs, which in turn causes solar energy to be up to 5 times more expensive than traditional energy methods. Photovoltaic is the conversion of light energy into electricity using solar cells, which can reduce costs dramatically and make solar energy a more economically feasible source of energy. Recently, these solar cells have been produced using this technology, which requires less processing and fewer materials than the thick wafers previously used in solar cells. This reduction in cost and materials is paramount in helping solar energy become more prevalent.

As discussed, this technology has a handful of useful and practical applications. How does the manufacturing process work? This term itself refers to the entire process of manufacturing as well as the heater elements on the thermal print heads themselves. In simple terms, the process works by depositing a very thin layer of resistor material onto a substrate, followed by a thin layer of metal, through the use of chemical vapor deposition. Both these deposited layers are referred to as this. In comparison, thick film technology is more complex and requires that conductors be fabricated at twice the resolution, thus limiting the resolution.

This technology, especially thin-film cells, are manufactured by the following companies: Abound Solar, Aleo Solar, Anwell Technologies, Ascent Solar, Bosch Solar Energy, Daystar Technologies, Energy Conversion Devices, First Solar, Global Solar Energy, HelioVolt, International Solar Electric Technology, Konarka Technologies, Miasole, Nanosolar, Odersun, Q-Cells, Sanyo, Signet Solar, Solo Power, Solyndra, Sulfur cell, SUNGEN International Limited, and TEL Solar.

You can browse on web for leading distributor of all types of thin film components from a comprehensive list of manufacturers. On this site is where you can get tier 1 pricing from manufacturers which pass selected savings to you:

Some Simple Facts About Ferrite Bead
electric resistance

Ferrite beads are a kind of electronic component which are used to restrain unwanted noise in the conducting wires. It has a hole in the center and is made of ferromagnetic element. It is a kind of electronic choke that acts as an effective shield to suppress noise that has higher frequency. It provides protection from interference coming from dual directions- one from a particular device and the other, to a particular device. Noise generating from high frequency circuits are generally ground leads, inter stage connections and power supply leads. If there is any unshielded conductor and active lead nearby, then they might facilitate the transference of energy from one to another. To prevent it, all that needs to be done is to place some ferrite bead on this leads, so that they can totally block this exchange of energy. Its-best part is that it can be used on any existing circuit.

The cable on which the bead is used works like an antenna, through which electronic energy passes, ferrite bead here controls the flow of energy and helps to decrease EMI. On the other hand, if there is another source of EMI, it prevents action of the cable as a conductor of energy (antenna) and absorbs all the interferences into itself.

The amount of electrical resistance provided by the bead depends on the kind of material it is made of, the level of frequency and also the size of the bead. As the level of frequency gets higher, it also increases to show its resistance to electrical power in the form of low-level of reactance and as reactance is very low, so it has a very low chance of resonance that could disturb attenuation effect. The resistivity of the bead is directly connected to the length of it. They are available in different sizes- lengthy beads are applied to the external cables, whereas smaller ones are used inside electrical goods in circuits on conductors or around the pins of circuit board conductors.

You can add more beads to the same cable to enhance their power of resistance. As the magnetic field is contained within the bead, it works all the same whether it is touching the cable or not I not. The bead used in the inductors acts as a filter, in that it provides prevention from high pitch RFI or EMI electronic noise. The blocked energy is sent up on the cable or it gets disintegrated at the lower level in the form of heat. But if this heat oversteps the threshold of Curie point, then it will lose its magnetic quality and will be stripped off its power to block noises.

Ferrite beads are generally small in size, so it enables only one turn through it. But the hole of the toroidal beads is bigger in size and it is used in cases where more turns are necessary to provide stronger impedance. The turn through the bead is counted by the time a cable passes through its center hole. Sometimes the level of impedance depends upon the turning pattern of the wire. The winding can be done clockwise, anticlockwise or in crisscrossed manner. This pattern is very important, as the pattern will show direct impact on the amount of impedance offered by the bead.

Electrical Power and Energy
electric resistor

Power is an electrical quantity that is measured in watts, and is the rate at which energy is either being absorbed or produced by a circuit. We know that light bulbs and heaters absorb energy and that the higher their value in watts the more energy they will consume. Likewise, batteries and generators produce energy and the greater their electrical rating the more power they can deliver to the load. The unit of electrical power is the watt with its symbol being a large letter “P” indicating constant DC power or a small letter “p” indicating a time-varying AC power.

Electrical power is related to energy which is the capacity to do work. It can also be defined as the rate of by which energy is transferred. If one joule of work is either absorbed or delivered at a constant rate of one second, then the corresponding power will be equivalent to one watt so power, P can be defined as 1Joule/sec = 1Watt. Then we can say that one watt is equal to one joule per second and electrical power can be defined as the rate of doing work or the transferring of energy.

Equally we can define energy as being watts per second or joules. So if the power is measured in kilowatts (thousands of watts) and the time is measure in hours, then the unit of electrical energy is the kilowatt-hour, (kWh) and 1 kWh is the amount of electricity used by a device rated at 1000 watts in one hour.

Kilowatt-hours are the standard units of energy used by the electricity meter in our homes to calculate the amount of electrical energy we use and therefore how much we pay. So if you switch on an electric fire with an element rated at 1000 watts and left it on for 1 hour you will have used 1 kWh of electricity. If you switched on two electric fires each with 1000 watt elements for half an hour the total consumption would be exactly the same amount of electricity – 1kWh. So, consuming 1000 watts for one hour uses the same amount of power as 2000 watts (twice as much) for half an hour (half the time). Then for a 100 watt light bulb to use 1 kWh or one unit of electrical power it would need to be switched on for a total of 10 hours (10 x 100 = 1000 = 1kWh).

So we now know that the unit of power is the watt with the power absorbed by an electrical circuit being given as the product of the voltage, V and the current, I which gives:

P (watts) = V (volts) x I (amperes)

Also, by substituting Ohm’s Law into the equation above we can also define a constant DC power as being:

P (watts) = I^2 (amperes squared) x R (resistance)

or

P (watts) = V^2 (voltage squared) / R (resistance)

Then there are three possible formulas for calculating electrical power in a circuit. If the calculated power is positive, (+P) then the circuit or component absorbs the power. But if the calculated power is negative, (-P) the circuit or component delivers power in other words it is a source of energy.

Power Rating

Electrical components are given a “power rating” in watts that indicates the maximum rate at which the component coverts the electrical energy into another form of energy such as heat, light or motion. For example, a 1/4W resistor, a 100W light bulb etc. So energy is used by electrical devices to convert one form of power to another so for example, an electrical motor will covert electrical energy into a mechanical force.

Electrical motors and other electrical systems have an efficiency rating defined as the ratio of power converted into work to the total power consumed by the device. Efficiency is expressed as a decimal fraction but is generally defined as a percentage value such as 85% efficient. So we can define efficiency as being equal to power output divided by power input x 100%.

The efficiency of an electrical device or motor will always be less than one (100%) due to electrical and mechanical losses. If an electrical device has an efficiency rating of 85% then only 85% of the input power is transformed into mechanical work the other 15% is lost in heat or other losses.

Domestic electrical appliances such as washing machines, driers, fridges and freezers also have energy efficiency ratings that indicate their energy usage and cost. These ratings are given as “A” for efficient and “G” for less efficient.

So remember, the more energy efficient is the device, the less energy it will consume and the more money you will save as well as being helpful to the environment.

How To Check Whether Your DC Electric Motor Has Gone "Bad"
electric resistance

These days, direct current (or DC) electric motors are used in a wide range of applications, such as the moving windows and seats in your car. Because of the concealed nature of these motors, it can be highly difficult to complete any repairs or maintenance on them without having to pull whatever it is powering apart. This is why, once you have managed to get to your DC electric motor, you should always give it a quick check to see whether it has gone “bad” and needs to be replaced.

Begin by removing the DC motor from its mount, ensuring that you have also removed any source of electric power that could accidentally cause it to begin turning. You may need to follow the manufacturer’s instructions to do this, as some motors are very much wedged into position and could pose a risk of electrocution.

Next, you can test the electric motor’s continuity (or connection) by attaching it to a volt ohmmeter. Ensure that the meter is in the “ohms” position, then place the red and black leads into its connections (the red lead should be attached to the “ohms” and the black lead to the “common” point). Test that the meter is working properly by touching these two leads together – the screen should read zero ohms (or full continuity).

To test your DC motor, touch the leads of the ohmmeter to the leads of the motor. The meter’s screen should indicate a low resistance (somewhere between 10 and 30 ohms), but if it reads an infinite ohms or an open circuit you should rotate the end shaft of the motor. The ohmmeter should give different readings as this shaft is rotated (which is an indication that the electric motor itself is good, but that there is a problem with the electrical circuit. If the meter is still reading as an open circuit, the conducting brushes may have gone “bad”.

Use a screwdriver to remove the brushes from the end of the electric motor (you can find them under the plastic end caps at the opposite end of the motor to the drive shaft). Carefully inspect the brushes for any sign of cracks or breaks in the surface – the area of the brush that sits against the conductor or commutator should be smooth and curved. If there are any broken wires or springs, the motor will fail. If the brushes appear fine, then the problem may be with the commutator.

Take the screwdriver again and use it to remove the rear end cap of the DC electric motor (by removing the two screws that run the motor’s length). Inspect the plates that comprise the commutator assembly – there should be an opening between each. If you notice any broken wires or burnt varnish, the commutator has failed and its damaged parts will need to be replaced.