Minggu, 25 Desember 2011

Voltage Impulses


Forms of Voltage Impulses

There are three forms inpuls voltage that may be experienced in the electric power system, namely:
1. Lightning impulse voltage
2. Surge impulse voltage circuit
3. Truncated impulse voltage

Wavefronts are part of a wave that starts from point zero (nominal) to the point of peak (according to IEC determined from the nominal point of intersection between the axis of time with the straight line connecting the 30% and 90% of peak voltage). While the tail is part of the wave peak to wave down 50% from the peak point. The wave form is expressed as:
± (x Tt Tf) ms. [IEC: ± (1.2 x 50) ms]

Circuit used for surge value:
[IEC: ± (250 x 2500) ms]
Tools that can be used to generate a high voltage impulse among others:
1. RC impulse generators
2. Impulse generator RLC
3. Marx Generator
2.
5. How to Measure Voltage Impulse

a. Using Sela Ball

Sela ball is often used to measure the impulse voltage. Sela ball must always ditera with voltage spark between the ball 50% of the standard. Sela standard ball is a ball broke in qualifying standards regarding:
1. Quality
2. The distance between
3. The size of the ball

In certain circumstances the air, between the ball always has a certain spark voltage as well. That is why the sidelines ball can be used as a measuring tool.

Form of the condition of the ball electrode
Terms:
1. Its surface is slippery
2. Flat arches
3. The surface of the ball must be free of dust, oil, etc.
4. Prisoners damper installed in series with the minimum distance 2d
(D = diameter) of the ball is measured from the point where there is a spark.
a. The test voltage ac = 100 kW s / d 1000 kW
b. Impulse test voltage 500 W

b. Using a CRO

By using Chatode-Ray Oscillograph (CRO) we can:
- Voltage peak
- Waveform
- The lack of impulse shape abnormalities (describing damage to test equipment)
CRO can only measure a low voltage only, so to measure the high voltage required voltage divider (either resistors or capacitors)
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switching power supply



C1, 2 : 100nF, 250VAC polypropylene (RS 190-8539)
C3 : 680uF, 450V electrolytic
C4, 5, 6, 7, 8, 9, 10, 11 : 470nF, 630V polypropylene
C12, 13 : 1uF, 50V ceramic multilayer (RS 126-067)
C14 : 3.3nF, 1.6kV polypropylene
C15, 16 : 10nF, 250VAC polypropylene (RS 190-8472)
C17, 18, 19, 20, 21, 22 : 1000uF, 25V low ESR electrolytic (RS 105-997)
C23, 24 : 2200uF, 16V low ESR electrolytic (RS105-947)
C25, 26, 27, 28, 29, 30 : 100nF, 50V ceramic
C31 : 470nF, 50V ceramic multilayer
C32 : 22uF, 50V electrolytic
C33 : 10uF, 50V electrolytic
C34 : 1uF, 50V electrolytic
C35 : 33nF, 50V polyester
C36 : 4.7nF, 50V polyester
C37 : 330nF, 50V polyester or ceramic multilayer
C38 : 100uF, 10V electrolytic
D1 : Rectifier bridge, 1kV, 8A. GBPC810 or similiar.
D2, 4, 17 : Ultrafast diode, 1kV, 1A. UF4007 or similiar. Lower
voltage (down to 100V) is acceptable.
D3, 5 : Ultrafast diode 1kV, 3A. UF5408 or similiar.
D6, 7, 8, 9 : Dual Schottky diode, 100V, 30A total. PBYR30100CT
or similiar. Single diode would also be suitable.
D10, 11, 12, 13, 14, 15, 16, 18 : 1N4148 switching diode
FB1, 2 : Amidon FB-73-801 ferrite bead, slipped over wire.
FB3..14 : Amidon FB-73-2401 ferrite beads, slipped six each
over the two 13.8VDC output cables.
L1 : Common mode choke, 8mH each winding, 6A.
I used junk box specimen. RS 288-159 is suitable.
L2: : 20uH, 60A choke. 15 turns on Amidon T-157-26
toroid. Wound with ten #16 enameled wires
in parallel.
L3: : 5uH (uncritical), 60A choke. 10 turns on ferrite solenoid,
10mm diameter, 50mm long. Wound with two #11
wires in parallel.
LED1 : Dual LED, green-red, common cathode
M1 : 12V 5W brushless DC fan, 120 x 120 x 25mm
NTC1, 2 : Inrush current limiter, 2.5R cold resistance (RS 191-2005)
P1 : CEE-22 male connector with integrated fuse holder
and EMI filter, 250VAC, 6A, (RS 210-291)
Q1, 2 : High voltage switching transistor, BUH1215 or similiar.
Must resist at least 400Vceo , and maintain a
beta of over 12 at a current level of 8A. (RS 859-874)
Q3, 4 : BC639-16 transistor. Must resist 100V and 0.5A.
Q5 : BD683 darlington transistor
R1, 5 : 10R, 5W low inductance preferred
R2, 6 : 180kR, 0.5W carbon
R3, 7, 19 : 1R, 1W carbon
R4, 8 : 2,7kR, 0.25W carbon
R9 : 47R, 5W low inductance preferred (induktansi rendah)
R10, 11 : 1.8R, 2W low inductance preferred (induktansi rendah)
R12 : 180R, 0.5W carbon
R13 : 3.3kR, 0.25W carbon
R14 : 1.5kR, 0.5W carbon
R15, 16 : 3.9kR, 0.25W carbon
R17, 18, 32, 33, 36, 38 : 1kR, 0.25W carbon
R20 : 22R, 0.5W carbon
R21, 22, 23, 24 : 4.7kR, 0.25W carbon
R25, 27, 29 : 22kR, 0.25W carbon
R26 : 4.3kR, 0.25W carbon
R28 : 13kR, 0.25W carbon
R30 : 12kR, 0.25W carbon
R31 : 10kR, 0.25W carbon
R34 : 1MR, 0.25W carbon
R35, 37 : 27kR, 0.25W carbon
R39 : 33R, 2W carbon
SW1 : 2-pole power switch, 250VAC, 10A
T1 : Primary 15 turns, secondary 2+2 turns. Wound with
copper foil and mylar sheet. Uses four Amidon
EA-77-625 ferrite E-cores (8 halves). Equivalents
include Thomson GER42x21x15A, Phillips 768E608,
TDK EE42/42/15. See text for winding instructions.
T2 : Secondary is 100+100 turns #36 enamel wire. Primary
is one turn #15 plastic insulated cable, wound on
secondary. Wound on Amidon EE24-25-B bobbin. Uses an
Amidon EA-77-250 core. Equivalents are Thomson
GER25x10x6, Phillips 812E25Q, TDK EE25/19.
T3 : Control winding is 26+26 turns #27 enamel wire.
Base windings are 8 turns #20 each. Collector winding
is one turn #15 plastic insulated cable. Bobbin and
core like T2. See text.
U1 : Pulse width modulator IC, LM3524, SG3524, UC3524 or
similiar.
U2 : Quad single supply operational amplifier, LM324
or similar.
U3 : 5V voltage reference, LM336Z-5.0 or similiar.
VR1, 2, 3 : 1kR PCB mounted trimpot

Project design switching power supply has a very large power capability. This power supply produces 13.8V output, the continuous load currents up to 40A. If the potentiometers are set, then the power supply can deliver up to 60A .. Ripple voltage at the output is about 20mV, and its efficiency is 88%. A cooling fan operates depending on the time-average power used, and the LED indicator to tell if the voltage is normal, too high or too low. And Power Supply that has great power kamampuan is just a small form in the box that measures just 306 x 150 x 130mm, including all projections, and weighs only 2.8kg!

Description of Series
Line voltage through CEE-22 connector through the fuse and EMI filter (P1). Then passed through a 2-pole power switch, and again through the line filter to remove noise (C1, L1, C2). Two NTC resistors limit the inrush. A bridge rectifier provides power to large electrolytic capacitor (C3), who works at 300VDC. Power oscillator formed by Q1, Q2, and by beberaa other components, and feedback and control transformer (T3). T2 and related components act as the primary current sensors. T1 is the power transformer, providing about 20 Volt Schottky rectifier wave into the box (D6. 9). A toroidal inductor (L2) and six elekrtolit parallel capacitors provide a low resistance value equivalent forms of the main filter, while the L3 and C23 .. 24 is just there to reduce the additional riple. 13.8V is connected to the output through a series of ferrite beat with some small decoupling capacitors are mounted directly on the output terminals.
Control circuit is IC 3524 (U1), driven by the auxiliary rectifier (D17). This IC contains a voltage reference, oscillator, pulse width modulator (PWM), an error amplifier, current sense amplifier, flip-flop and the driver circuit. The sensor output voltage and current level sensors, through transistors Q3 and Q4 controls the power oscillator. C37, C35 and R23 are used to implement PID (proportional-integral-derivative) control loop response in full.
A quadruple operational amplifier (U2) is used for two purposes aids: To control the cooling fan according to the average level of current, voltage and LED indicators for steering three colors: green light if the voltage is OK, orange if the voltage is too low and the red if too high.
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Kamis, 22 Desember 2011

TOSHIBA Bipolar


TOSHIBA Bipolar Digital Integrated Circuit Silicon Monolithic
• General-Purpose Linear ICs
• 7-ch Darlington Sink Driver
• Darlington Drivers IC
• The ULN2004APG/AFWG Series are high−voltage, high−current darlington drivers comprised of seven NPN darlington pairs. All units feature integral clamp diodes for switching inductive loads. Applications include relay, hammer, lamp and display (LED) drivers. The suffix (G) appended to the part number represents a Lead (Pb)-Free product.
• Features: [1] Output current(single output): 500mA(max). [2] High sustaining voltage output: 50V(min). [3] Output clamp diodes. [4] Inputs compatible with various types of logic. [5] Package Type-APG: DIP-16pin. [6] Package Type-AFWG: SOL-16pin.
• Output Sustaining Voltage(VCE)(sus): 50V
• Output Current(Iout): 500mA
• Recommended Input Voltage: 6V to 15V
• Clamp Diode Reverse Voltage(VR): 50V
• Clamp Diode Forward Current(IF): 500mA
• Input Base Resistor: 10.5kΩ
• Number of Drivers / Receivers: 7 / 0
• Linear ICs Type: Darlington Transistor Array
• Number of Arrays: 7
• Transistor Polarity: NPN
• Input Compatibility: PMOS, CMOS
• Operating Temperature Range(Topr): -40°C to +85°C
• Storage Temperature Range(Tstg): -55°C to +150°C
• Brand Name: TOSHIBA
• Lead-Free Type
• RoHS Compliant
• Mounting Type: Through Hole / DIP(Dual in -line package)
• Package Type: DIP16
• Lead Count: 16
• Packing: 25 units / tube
• Mass stock on-hand merchandise supply
• We supply various electronic components and welcome your inquiries
READ MORE - TOSHIBA Bipolar

Kamis, 17 November 2011

power supply outage


When the main power supply outage (PLN), the electricity supply required reserves and the conditions of the Generator-Set is expected to supply power mainly to priority loads. Generator can be used as a backup electrical system or "off-grid" (which depends on the resources the user needs). Generators are often used by hospitals and industries that require a steady source of power and reliable (high level of supply reliability), and also for rural areas that do not have access to commercially supplied electricity through the existing distribution network PLN.

A diesel engine generator set consists of:
1. Prime mover or mover first, in this case diesel engine (in English is called diesel engines)
2. Generator
3. AMF (Automatic Main Failure) and ATS (Automatic Transfer Switch)
4. Battery and Battery Charger
5. Panel ACOS (Automatic Change Over Switch)
6. Security for Equipment
7. Installing the Power Supplies

Diesel engine

Including diesel engines with internal combustion engines or motor fuel referred to, in terms of how to obtain thermal energy (heat energy). To generate electricity, a diesel engine connected to a generator in one axis (the axis of diesel engine is coupled with shaft generator).

An advantage of using diesel engines as a first mover:
* Design and installation is simple
* Auxilary equipment (auxiliary equipment) simple
* When loading a relatively short

Losses use diesel engines as early Mover:
* Weight machines are very heavy because it must be able to withstand vibration and high compression.
* Starting the initial weight, because the compression height is about 200 bar.
* The greater the power the diesel engine is the greater dimension, it causes trouble if the engine power is very large.
* Fuel consumption using fuel oil relatively more expensive compared to power plants that use fuels other types, such as gas and coal.

How it Works Diesel Engine

Prime mover or early mover is a device that functions produce mechanical energy required to rotate the generator rotor. In the diesel engine / diesel engine ignition occurs alone, because the process works based on pure compressed air in the cylinder at high pressure (± 30 atm), so that the temperature inside the cylinder rises. And at that time the fuel is sprayed in the cylinder-temperature and high pressure beyond the flash point fuel injected so that the fuel will burn automatically. The addition of heat or energy is always performed at a constant pressure.

Pressure of gases of combustion of fuel and air will push the piston which is connected to the crankshaft using a piston rod, so that the piston can move back and forth (reciprocating). Back and forth motion of the piston is converted into rotational motion by crank shaft (crank shaft). And contrary motion of the crankshaft rotational motion is also converted into alternating piston on the compression stroke.

Based on analyzing how the system works, diesel motors can be divided into two, namely diesel motors that use airless injection system (solid injection) were analyzed with a dual cycle and diesel motor that uses a water injection system is analyzed with the diesel cycle (while motor gasoline was analyzed by
otto cycle).

The difference between diesel and motor gasoline motor is noticeable is located on the fuel combustion process, the combustion of gasoline motor fuel is due to the fire jumps the electricity generated by two-electrode spark plug (spark plug), while the diesel engine combustion occurs due to a rise in temperature the mixture air and fuel due to compression of the piston until it reaches the flame temperature. Because the principle of pressure due to ignition of the fuel then the motor is also called a compression ignition diesel engine while the motor is called spark ignition gasoline engine.

In diesel engines, piston perform two short steps towards the cylinder head on every step of the power.
1. The first step upwards a step entry and exploitation, here the air and fuel into the crank shaft while spinning down.
2. The second step is a compression step, continue rotating the crankshaft causes the piston to rise and push the fuel, causing combustion. Both of these processes (1 and 2) including the combustion process.
3. The third step is a step expansion and work, here the two suction valves and exhaust valves are closed while the crankshaft continues to rotate and retract the piston downward.
4. The fourth step is the removal step, here the exhaust valve opens and causes the gas due to combustion of residual waste out. Gas can be due out in the fourth process is moving up the piston back up and cause the gas to exit. These two latter processes (3 and 4) including the disposal process.
5. After the fourth process, then the next process will repeat the first process, where air and fuel re-entry.

Based on the above process then the speed diesel engines can be classified into 3 parts, namely:
1. Low-speed diesel (<400 rpm) 2. Medium speed diesel (400 - 1000 rpm) 3. High speed diesel (> 1000 rpm)

Starting the system or process to turn on / run diesel engines are divided into three kinds of starting the system, namely:

1. Start System Manual
The system is used to start diesel engine with a relatively small engine power is <30 PK. The way to revive a diesel engine on this system is to use the drive crank start on the crankshaft or connecting shaft to be moved by human power. So start the system is highly dependent on human factors as the operator. 2. Electric Start System This system is used by diesel engines that have power are the <500 PK. This system uses a DC motor with power supplied by the battery / batteries 12 or 24 volts to start the diesel. At the start, the DC motor gets power supply from the battery or batteries and produces torque used to drive a diesel until it reaches a certain round. The battery or batteries used must be used to start the 6 times without recharged, since the required startup current DC motor is large enough so worn armature that serves as a DC generator. Recharging the battery or batteries used tool of a battery charger and belt tension. At the time diesel battery charger does not work then get a supply of electricity, while at work then the supply of diesel battery charger obtained from the generator. The function of the voltage security is to monitor the battery voltage or battery. Therefore, when the voltage of the battery or the battery has reached the 12/24 volts, which is the default voltage, then the relationship between the battery charger to the battery or batteries will be disconnected by a safety voltage. 3. Start the system Compression Start system is used by the diesel that has a great power that is> 500 PK. These systems use motors with high-pressure air to the start of the diesel engine. How it works is by storing a bottle of air into the air. Then the air is compressed so that the hot air and diesel fuel is inserted into the Fuel Injection Pump and sprayed through a nozzle at high pressure. The result will occur foggy and combustion in the combustion chamber. At the time the pressure in the tube down to the minimum limit, then the compressor will automatically raise the air pressure inside the tube until the pressure in the tube sufficient and ready for use to perform starting diesel engines.
READ MORE - power supply outage

Minggu, 13 November 2011

power for energy



Model: LDR, WDR
Capacity: 8-4000kg/h
Steam pressure: 4-16bar
Fuel: Electric

Fuel: Electric
User:
For food processing, printing and dyeing, pharmaceutical provide for production of gasoline and medical institutions with the provision of disinfection gas, for other enterprises, hotels provide the heating steam, can also provide domestic hot water heating tanks.

Features
Electric heating boiler to power for energy, no noise, no pollution. The use of high-quality heating tubes, the surface of the low heat load, heat and high efficiency. The use of multi-storey high-level centrifugal glass wool insulation, import color outer panels; Both ends covered the use of packaging in vivo to facilitate the installation of maintenance.

1, the use of advanced electric heating tubes, the surface low load, long life.
2, the boiler to start, stop, fast, wide range of load-conditioning to regulate the speed and easy to operate.
3, heating elements in accordance with changes in temperature and automatically adjust the load control input heating group number, and automatically converted into the order, not only to save energy consumption, but also control the operation of each heating time balance, so even the life of the heating tube.
4, heating elements can also be manually input or stop, user-friendly and flexible adjustment of the boiler heat.
5, the use of advanced computer boiler controller, with reliable performance, high degree of automation is easy.
6, using boiler accessories, domestic and foreign products are selected and tested by the test furnace to ensure the long-term normal operation of the boiler.

Protection device
(A), function
1, patented technology, automatic sewage functions: On the water control system for real-time detection of ion concentration, when the concentration exceeds a set value, the solenoid valve automatically open sewage, sewage automatically, start the infusion of new water pumps, heating surface so that scaling is not easy. 2, the water level real-time monitoring function: Equipped with electronic water level detection device, real-time monitoring of boiler water level.
3, the time set function: Users can be set to stop the time from the boiler.
4, before and after outsourcing are covered in vivo, the replacement of the heating pipe maintenance operation more convenient and more efficient.
(B), the protection of
1, proprietary technology, scale detection devices: The furnace once the standard scale, the system will alarm
2, leakage protection: Control system to detect leakage electric heating elements will automatically cut off power supply.
3, water protection: When the boiler water and timely control circuits cut off the heating to prevent the occurrence of dry heating pipe damaged, dry warning issued at the same time the controller instructions.
4, power protection function abnormalities: An immediate cessation of operation of the boiler.
5, overpressure protection chain: The boiler pressure exceeds a set value, and to prohibit the heater alarm.
6, over-current protection: When the boiler overload (high voltage) work, leakage circuit breaker disconnect automatically.
READ MORE - power for energy

Selasa, 08 November 2011

voltage regulator diode



Zener diode is applied in the reverse breakdown of the surface contact area of the special type of silicon diode. Zener diode volt-ampere characteristic curve and silicon diode volt-ampere characteristic curves exactly the same. Zener diode characteristic curve similar to ordinary, but the reverse diode voltage curve relatively steep. Normal operating range of the diode voltage, current characteristic in the reverse current on the sudden rise in the beginning part. This section of the current, commonly used for the regulator in terms of low power, typically a few milliamperes to tens of milliamps.
The main parameters of the diode voltage regulator
(1) stable voltage Vz: stable voltage regulator diode is in normal operation, the voltage across the tube. This value with the operating current and temperature changes slightly different, both the same type of Zener diode, voltage stability has some dispersion, for example, the stability of 2CW14 silicon diode voltage regulator 6 ~ 7.5V.
(2) dissipation PM: reverse current through the PN junction diode regulator, we should have some power loss, PN junction's temperature will rise. PN junction under the permissible operating temperature determine the power dissipated in the tube. Low power tube is usually about a few hundred milliwatts to several watts.
Maximum power dissipation PZM: a regulator of the maximum power dissipation depends on the PN junction area and cooling conditions. Reverse work, PN junction power loss: PZ = VZ * IZ, and VZ by the PZM can decide IZmax.
(3) Stable current IZ, the minimum stable current IZmin, large and stable current IZmax steady current: working voltage equal to the voltage stability of the reverse current; minimum stable current: voltage regulator diode in the steady reverse current minimum required; maximum stable current: Zener diode allows the maximum reverse current.
(4) dynamic resistance rZ: the concept and the same general dynamic resistance of the diode, but the dynamic resistance of diode voltage regulator is to strike it on the reverse characteristics of the. rZ smaller, reflecting the breakdown characteristics of the regulator more steep.
rz = â–³ VZ / â–³ IZ
(5) stable voltage temperature coefficient: VZ temperature change will change in the regulator, when | VZ |> 7 V when, VZ has a positive temperature coefficient, the reverse breakdown is the avalanche breakdown.
When | VZ | <4V time, VZ has a negative temperature coefficient, the reverse is the zener breakdown.
When 4V <| VZ | <7V time, the regulator can get close to the zero temperature coefficient. This regulator diode can be used as a standard regulator.
Zener diode test
(1) positive and negative electrodes of the judge from the appearance point of view, the metal package Zener diode cathode tube-shaped end of the plane, the negative side for the semi-circular surface shape. Plastic tube regulator diode color markers printed on one end of the anode and the other end is positive. Zener diode is not clear on the signs, you can also judge the polarity with a multimeter, measure the same way with ordinary diodes, that is, R × 1k file with a multimeter, then the two table T are the two electrode voltage regulator diode, a measured results, and then swap the two table T were measured. In the two measurements, the resistance that a small, black pen then the table is the positive regulator diode, the red pen then a negative regulator diode.
If the measured voltage regulator diode, the reverse resistance are very small or are infinite, then the breakdown of the diode is open or damaged.
(2) the value of the measurement of voltage 0 ~ 30V continuously adjustable DC power supply for the 13V zener diodes below, can be transferred to the output voltage of power supply 15V, the positive power series with a 1.5kΩ current limiting resistor measured after the negative regulator diode connected to the power negative and positive phase voltage regulator diode, then both ends of the multimeter to measure voltage regulator diode, the measured reading is the voltage regulator diode value. If the regulator regulator diode is higher than 15V, the power supply should be adjusted to 20V or more.
Also be lower than the Megohmmeter 1000V diodes for testing power for the regulator. The methods were: the positive terminal of the megger negative phase with the voltage regulator diode, the negative terminal megger the positive phase with the voltage regulator diode, the required uniform shaking megger handle, while monitoring the voltage with a multimeter voltage across the diode (multimeter, as the stability of the voltage profile should be the size of the voltage) until the meter indicates the voltage stability of the instructions, this voltage is stable voltage regulator diode.
If the measurement of the stability of the diode voltage regulator fluctuated, then the instability of the diode.
Application of voltage regulator diode
Regulator used in the rectifier filter circuit, the DC output voltage to stabilize the small power supply devices.
Selection of regulator diode
Zener diode is generally used in power supply as a reference or used in over-voltage protection circuit for protection diodes.
Zener diode selected should meet the application requirements of the main parameters of the circuit. The stability of the voltage regulator diode and application should be the same value as the reference voltage circuit, the maximum stable current regulator diode application circuit should be higher than the maximum load current 50%.
Substitution regulator diode
Zener diode is damaged, should be regulated the same model the same electrical parameters of diodes or Zener diodes to be replaced.
Stability can be used with the same high-voltage power dissipation zener diodes to substitution of low power dissipation zener diodes, but not with lower power dissipation zener diodes to substitution of high power dissipation zener diodes. For example, 0.5W, 6.2V zener diodes can be 1W, 6.2V voltage regulator diode replacement.
READ MORE - voltage regulator diode

Senin, 07 November 2011

PIC microcontroller



PIC microcontroller provides a different combination of features, thus the most suitable can be selected for any given application. Some of the main selection criteria are:

•number of I/O pins availbale
•program memory size
•program memory type (ROM, EPROM, Flash)
•EEPROM data memory
•timers (8-bit or 16-bit), CCP
•interrupt sources
•analog inputs (8-bit or 10-bit)
•serial communication interfaces (USART, SPI, I2C, CAN)
•internal oscillator
•in-circuit debugging
•package (DIP, SOIC, PLCC, QFP)
•price

When developing an embedded system, the number and type of inputs and outputs need to be determined. After the hardware requirements have been established, the program need to be written and tested. Once the size of the program known, the chip memory size can be determined.
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Minggu, 06 November 2011

Gel permeation chromatography


Gel permeation chromatography (GPC) involves steric separation of a sample, i.e., separation on the basis of size. Different detectors are used to analyze the resulting size fractions in order to quantify molecular weight and distribution, molecular size, and intrinsic viscosity. UV detection is used routinely to identify chemically different species as they elute. This is especially valuable for the analysis of copolymers and in the development of smart materials, since unique electrical, thermal, or photochromic properties often correlate directly with UV absorption characteristics. The difference in absorption profiles between polymers with similar molecular weights, refractive index increments, viscosities, or hydrodynamic radii can be significant; thus a UV detector can often differentiate when others cannot. However, a conventional system measures spectra only at a single, predetermined wavelength in the UV-VIS range. This limitation is overcome with the photodiode array (PDA) detector (Figure 1) for the TDAMax instrument (Viscotek Corp., A Malvern Company, Houston, TX).

The instrument is a comprehensive GPC system with an integrated triple or tetra detector array that includes low-angle light scattering, a differential refractive index detector, and a four-capillary differential viscometer. The PDA consists of 256 diodes and simultaneously collects data at wavelengths in the range 190–500 nm. With typical measurement times in the 20–40 min range producing a very data-rich analysis, the technique is extremely productive.

The UV cell of the PDA sits in the temperature-controlled zone of the system, which operates at temperatures up to 80 °C. A fiber-optic link to the PDA and then onto the powerful OmniSEC™ software package enables the captured data to be displayed as information-rich, easy-to-interpret 3-D images that provide insight into the nature of the sample being analyzed.

The PDA measures the complete absorption spectrum of the sample eluting at every time slice of the chromatogram, giving a fingerprint of each component in the matrix. Because it captures data across the UV-VIS range, the user does not need to select the wavelength of interest before measurement. This makes it much easier to carry out more open-ended investigative analysis into a complex polymerization reaction or when examining material about which little is known.

The software package is equally important since it simplifies data manipulation and presentation while controlling the chromatography. Looking at the full absorption spectra for each “slice” makes it easy to see what components— monomers, oligomers, different polymeric species—are eluting, giving information about molecular size and structure.
READ MORE - Gel permeation chromatography

micromanipulators



Crystal manipulation and harvesting have been done manually since the science of crystallography began. While the looping of larger crystals comes easily for some people, others never seem to get the knack. Some of the problems with manually harvesting crystals (both small and macro) include:
Crystals are being harvested at earlier and earlier points in their growth cycle, sometimes when they are as small as 2–5 μm. As the crystals get smaller, the ability to manually harvest them becomes more difficult.
Manual harvesting may damage the crystals due to the user’s inability to precisely control the looping tools.
When harvesting manually, higher levels of magnification required for small crystals are difficult to use because the user’s hand motions (i.e., shaking) are intensified, distorting vision and thereby affecting the ability to accurately harvest.
It is difficult to choose a specific crystal to loop since manual looping disturbs the entire drop and any other crystals that are present in that drop
Manual harvesting of crystals is done with one loop; the use of two loops simultaneously to capture crystals is rarely done by hand.

Typically, the user places a coverslip or another vessel containing the crystals under the microscope. Because time is usually limited (especially in the case of protein crystals), the user presses a single key, and the system positions the loop(s), crystals, and microscope in preparation for harvesting crystals. (Note: Sometimes a small amount of Paratone-N oil [HamptonResearch, Aliso Viejo, CA] is used to delay the dehydration of the drop holding the crystals to allow more time for harvesting.)

If the user has already selected the crystal to harvest, he/she can choose that crystal by clicking on it with the mouse. Once the desired crystal is selected, the user can harvest it manually or invoke a macro, which will harvest it automatically based on methods and training established by the user. Although several off-the-shelf macros for crystal harvesting are included with the system, the user can program in his/her own style of harvesting, with the system mimicking the user’s every move. The programmable macros control all devices available in the automated system (XYZ stage, micromanipulators, zoom, focus, etc.), as well as all software functions such as image analysis, image capture, video capture, and Z-stacked imaging.


Because the Harvester-3D can be operated remotely, it is well suited for harvesting oxygen-sensitive crystals within a glove box and offers various other benefits when used in an oxygen-free environment. For example, with its precise joystick operation, users do not have to work with gloved hands, which is a tedious, tiring, and time-consuming method of harvesting crystals.

The micromanipulators can hold either traditional loops (MiTeGen) or other types of harvesting devices, such as the Crystal Catcher. The Crystal Catcher can be programmed to automatically harvest both protein and small-molecule crystals using its polymer-based adhesive technology, and the penlike device mounts easily onto the micromanipulators.

A typical macro for harvesting crystals is as follows:
Step 1—Move stage to harvesting position. This brings the XYZ stage into position, autofocuses the microscope, and moves the micromanipulators with loops into position.
Step 2—Mark crystal(s) for harvesting. This highlights all of the crystals to be harvested (either automatically or manually).
Step 3—Begin harvesting. Depending on whether small- or macromolecule crystals are being harvested, the procedure is slightly different. For the purposes of this discussion, we will assume small-molecule harvesting is being done using UV-curable glue to attach the crystals to the mounts.

In turn, the system will:

a) Move to the UV glue position

b) Pick up a small amount of UV glue (amount predetermined by the user)

c) Move to the first crystal to be harvested

d) Pick up the first crystal using XYZ coordinates generated when the user marked the crystal (step 2)

e) Move to UV curing light for 20+ sec to harden the glue. The user can move the micromanipulator to neutral position and pause so that he or she (or the automated arm [i.e., Hitachi, Tokyo, Japan]) can remove the harvested crystal and replace the holder for the next crystal to be harvested.
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Rabu, 02 November 2011

bridge rectifier



There are basically two versions of the P3a: a 60W into 8 ohms (with ± 35V supply rails) and a 100W into 8 ohms (with ± 42V supply rails). I decided to build the version ± 35V, for two reasons. A 60W, which is more than enough. The other is that the version is ± 42V can not drive 4 ohm speakers. I wanted the option of driving 4 ohm speakers, so the choice was easy. A ± 35V, it can be 60W at 8 ohms and 100W into 4 ohms drive.
2.2. Transistors

The transistors recommended are not available here, so I went for one of the previous recommendations. For the output transistors, I used MJ15003 and MJ15004. Used for the three drivers that I have is two BD140 (a class-A driver and an output driver) and BD139 (the other output driver).

The power supply consists of a 625 VA 25-0-25 transformer, a bridge rectifier 35A and 4 x 10,000 uF capacitors. This seems excessive, and may for all practical purposes, but which is theoretically necessary to four 100W (4 ohms) amplifier lead to an efficiency of about 70%.

The power supply requires heavy use of a starter, for which I used P39 Rod Elliott. I chose the ballast resistors so that their maximum current is used up to 200% of the transformer. In this way, the main fuse will blow, even if there is anything wrong with the transformer. Also, I attached a thermal fuse, resistors on a piece of aluminum and epoxy resin heat for added security.

As always, an amplifier is not complete without a DC protection, and I have included Rod Elliott P33 for that. See my article DC protector subwoofer for more information on this particular circuit.

I am very satisfied with the performance. But I think to do, amplifier does not affect the sound quality through a lot (as they are a decent design), and therefore I must not expect much difference with my previous (what receiver Kenwood 1978 ). Aspects that are the most visible things such as noise and the level of snoring, which are very good. There is a very very very slight hum in the speakers, but you have to press your ear against the speaker to hear it. There, I found this part of the inherent hum P3a is design, so there’s not much I can do about it, both in regard to the wiring or the power supply configuration. But because it is so marginal, it does not matter. At the end of the amplifier is exactly what I needed to, and performs accordingly.
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Sabtu, 29 Oktober 2011

Mini-micro hydropower


Quintessence
The flow of water that flows from the highlands towards the more lace has a potential energy that can be utilized as a source of new energy. With good planning strategy for the development of energy sources such as this in turn will be able to overcome the problem of energy crisis in various places. But due to lack of planning several projects in the strategy development of alternative energy sources has not been obtained optimal benefits. often Power Plant construction project Mini-micro hydropower (MHP) there are various constraints such as low load factor, Surveying incomplete data availability and the lack of participation of surrounding communities, this led to the expected benefits from the potential of renewable energy sources has not been optimal. Therefore it needs a presence of an improvement.

Power micro hydro power

Generating a mini-micro hydro power plants are basically constructed in order to program the Village Electrical Sign (LISDES) with the utilization of hydropower resources. The construction project is primarily directed to remote areas unreachable grid. Generation is done by utilizing the flow of water from the tributaries are small or of irrigation channels. One of the factors that draw power from the mini-micro hydro is a relatively simple technology. However, if the feasibility study before the implementation of development projects is not adequate then the consequences become less efficient operation of the generation can not even operate at all.

Micro hydro is a generator that can generate electrical energy up to 100 KW while for a power plant that can produce electrical energy equal to 100 KW - 5 MW are defined as micro-hydro power plant. Mini-micro hydro power potential in Indonesia about 7,500 MW with an installed capacity of 200 MW. According to Central Statistics Agency (BPS) in 2000, about 60% of Indonesia's population live in remote villages. The number of villages in Indonesia as many as 58,545 villages, until the end of December 2000 which had as many as 49,155 villages have electricity.

Advantages micro hydro power plants

Some of the advantages of mini-micro hydro energy from others (Das, 2002) is:

· Clean Environment

· Renewable energy

· Not to consumptive water use

· Easy to operate as base load and peak load (can be quickly on / off)

· Cost low operating

· Durable (Long Life)

· Ideal for remote areas

Most of the mini-micro hydro development projects aimed to remote areas that have not passed by the grid. Problems develop when these arise as a result of the economical factors. Electrical energy consumption by rural communities generally ranges between 4-5 hours per day or 14-16% of installed power. The low energy consumption (load factor) is caused by the use of only as a mere illumination lamps. Economy aspects of power generation mini-micro hydro can be achieved with a careful plan by involving the participation of local communities are actively since the beginning of project development and integration of the apparatus with the village residents.

Besides generating a mini-micro hydro power plants have their own transmission and distribution network operation and management which can be referred directly to the local village board through cooperative enterprise. As an example of the success of the mini-micro hydro project in China because of high levels of electrical energy consumption by a factor of the load reaches 50-60% of installed power capacity and its management handed over to cooperatives.

Simple model intended use of electric energy produced to achieve load factors of more than 50% are as follows:

Day:

· Grinding of agricultural products

· Cooking

· Small Industries (cooling, distillation, etc.)

Afternoon Day:

· Lighting

· Home appliances

Night Day:

· Hatching eggs

· Fumigation fish

· Drying of agricultural products

Installation Type MHP

Broadly speaking MHP installation types can be grouped into two. Include the installation of mountainous areas and the installation of a flat area.

a. This type of installation for mountainous areas generally consist of the following components:

1. Door collection (Intake / Diversion)

2. Bath deposition (Desilting Tank)

3. Dissipation channel (Headrace)

4. Bak tranquilizers (Forebay)

5. Rapid pipe (penstock)

6. Building Plant (Power House)

7. Discard channel (Tailrace)

8. Transmission Network (Grid Line)

b. Installation of Flat Area

This type of installation for flat areas generally consist of the following main components:

Door collection (Intake / Diversion)

Channel Power (Power Canal)

Dissipation channel (Headrace)

Building Plant (Power House)

Discard channel (Tailrace)

Transmission Network (Grid Line)

Selection of Technology

Selection of technology in the construction of mini-micro hydro mainly lies in the selection of the main components of the turbine and generator. This is due to the area to be installed mini-micro hydro power plants have characteristics spesification.

a. type of hydropower turbine depends on the head and discharge water. For mountain areas that have low discharge height with high head turbine type is more suitable for use while in a flat area with a large discharge of water can use this type of canal drop low head turbine.

b. Types of Generators, In general there are two types of generators used in MHP, ie synchronous generators and induction generators.

Synchronous generators working on changing speeds. To be able to keep the generator speed remains, use an electronic speed governor. Generators of this type can be used directly and does not need another power grid as early movers. Highly suitable for use in remote villages with insulation systems.

Induction generators, is not required system voltage regulation and speed. However, this type of generator can not work alone because it requires an electrical grid system as early movers. Generators of this type are more suitable for areas that have been passed by the power grid (Grid System).


Conclusion

A micro hydro power projects are continuing to consider the following factors:

1. Planning in the choice of technology must be supported by concrete data, simply and can be accounted accountability.

2. The need for utilization of electrical energy for productive activities in the afternoon and evening in an optimal

3. The existence of local community participation through the establishment of proper management organization, between society and the institutions or agencies.
READ MORE - Mini-micro hydropower

Senin, 24 Oktober 2011

LM1830


LM1830 based liquid level indicator circuit. LM1830 is a monolithic integrated circuit that can be used in liquid level indicator / control systems. Manufactured by National Semiconductors, the LM1830 can detect the presence or absence of polar fluids . Circuits based on this IC requires minimum number of external components and AC signal is passed through the sensing probe immersed in the fluid. Usage of AC signal for detection prevents electrolysis and this makes the probes long lasting. The IC is capable of driving a LED, high impedance tweeter or a low power relay at its output. The circuit of a low liquid level indicator with LED is shown above. Capacitor Ct sets the frequency of the internal oscillator. With the give value of C1 the frequency will be around 6KHz. Capacitor Cb couples the oscillator output to the probe and it ensures that no DC signal is applied to the probe. The circuit detects the fluid level by comparing the probe to ground resistance with the internal reference resistor Rref. When the probe to ground resistance goes above the Rref the oscillator output is coupled to the base of the internal output transistor making it conducting.
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Sweep-Frequency


Sweep-Frequency Generator The working of a sweep-frequency generator is explained in the article below. The working and block diagram of an electronically tuned sweep frequency generator and its different parameters are also explained. Related Article SIGNAL GENERATORS A sweep frequency generator is a type of signal generator that is used to generate a sinusoidal output. Such an output will have its frequency automatically varied or swept between two selected frequencies. One complete cycle of the frequency variation is called a sweep. depending on the design of a particular instrument, either linear or logarithmic variations can be introduced to the frequency rate. However, over the entire frequency range of the sweep, the amplitude of the signal output is designed to remain constant. Sweep-frequency generators are primarily used for measuring the responses of amplifiers, filters, and electrical components over various frequency bands. The frequency range of a sweep-frequency generator usually extends over three bands, 0.001 Hz – 100 kHz (low frequency to audio), 100 kHz – 1,500 MHz (RF range), and 1-200 GHz (microwave range). It is really a hectic task to know the performance of measurement of bandwidth over a wide frequency range with a manually tuned oscillator.

Signal Generators In this article, the detailed explanation of a signal generator is given. The principles of signal modulation, the block diagram of an AM signal generator and the measures needed to achieve a stable frequency output is explained below. RELATED ARTICLE SWEEP FREQUENCY GENERATOR Like an oscillator, a signal generator is also a source of sinusoidal signals. The main difference between a signal generator and an oscillator is that a signal generator is capable of modulating its sinusoidal output signal with other signals. When signal generators are used for producing an unmodulated sinusoidal output they are said to be producing continuous height wave [CW] signal. When the produced output signal is modulated, the modulating waveforms may be either externally applied sine-waves, square waves, triangular waves, pulses or more complex signals, as well as internally generated sine-waves. Amplitude modulation (AM) or frequency modulation (FM) may be used. Normally amplitude (AM) modulation is employed. Principles of amplitude modulation (AM) and frequency modulation (FM) are illustrated in the figure shown below. Signal Modulaton Signal Generator – Applications Signal generators are primarily employed for providing appropriate signals for calibration, testing and troubleshooting of the amplifier circuits used in communication.
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IC NE555



The circuit diagram of a very simple voltage doubler using NE555 timer is shown here. Here IC NE555 is wired as an astable mutivibrator operating at around 9KHz. The base of the two transistors (Q1 and Q2) is shorted and output of the astable multivibrator (pin 3) is connected to it. When the output of astable multivibrator is low, Q1 will be OFF and Q2 will be ON. The negative terminal of the capacitor C3 will be shorted to ground through T2 and it will be charged to the input supply voltage. When the output of the astable multi vibrator is high, transistor Q1 will be ON and transistor Q2 will be OFF. The capacitor C4 will be charged to the voltage across capacitor C3 plus the input supply voltage (that is double the input voltage). This is how the circuit works. This voltage doubler circuit can deliver only up to 50mA output current and above that current limit the output voltage will be dramatically reduced.

NE555 timer IC are already published here and this is just another one.Here is the circuit diagram of a police siren based on NE55 timer IC. The circuit uses two NE555 timers ICs and each of them are wired as astable multivibrators.The circuit can be powered from anything between 6 to 15V DC and is fairly loud.By connecting an additional power amplifier at the output you can further increase the loudness. IC1 is wired as a slow astable multivibrator operating at around 20Hz @ 50% duty cycle and IC2 is wired as fast astable multivibrator operating at around 600Hz.The output of first astable mutivibrator is connected to the control voltage input (pin5) of IC2. This makes the output of IC2 modulated by the output frequency of IC1, giving a siren effect. In simple words, the output frequency of IC2 is controlled by the output of IC1. Circuit diagram. Notes. The circuit can be assembled on a Perf board. I used 12V DC for powering the circuit. Instead of using two NE55 timer ICs, you can also use a single NE556 timer. NE556 is nothing but two NE555 ICs in one package.
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P-N junction


Zener diode is a P-N junction diode specially designed to operate in the reverse biased mode. It is acting as normal diode while forward biasing. It has a particular voltage known as break down voltage, at which the diode break downs while reverse biased. In the case of normal diodes the diode damages at the break down voltage. But Zener diode is specially designed to operate in the reverse breakdown region.

The basic principle of Zener diode is the Zener breakdown. When a diode is heavily doped, it’s depletion region will be narrow. When a high reverse voltage is applied across the junction, there will be very strong electric field at the junction. And the electron hole pair generation takes place. Thus heavy current flows. This is known as Zener break down.

So a Zener diode, in a forward biased condition acts as a normal diode. In reverse biased mode, after the break down of junction current through diode increases sharply. But the voltage across it remains constant. This principle is used in voltage regulator using Zener diodes.
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Rectifier diodes


Rectifier diodes are the most commonly used diode type but other diodes come into play as well. These include Zener diodes, Schottky diodes, tunnel diodes, photodiodes, varicap diodes and light-emitting diodes. Each diode type has a different function. For example, Zener diodes control voltage, Shottky diodes work in switch circuits, light-emitting diodes are in lighting and video display circuits. Photodiodes are in light-detection circuits. A "varicap" diode is constructed like a diode but behaves as a variable capacitor.

Rectifier Tesla ham

Bridge Diode Rectifier KBL406

Voltage Diode HV HF Rectifier

Recovery Diode Rectifier Stack
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Jumat, 07 Oktober 2011

EM DC Amplifier


EM DC Amplifier model A22 is a low noise amplifier module for sensitive DC measurements, data collection and systems, and is ideal for very sensitive temperature measurement using thermocouples.
The noise level of the A22 is equivalent to a perfect resistor of about 150 ohms.
When used with normal type thermocouples for temperature measurement, sensitivities of around 20 micro-Kelvin can be achieved. The input voltage drift is very low and is compatible with voltage sensitivities of about 1 nanovolt.
The A22 has many other features desirable in a measurement amplifier. The very high loop voltage gain of 100T, or 280dB, means that high overall gain may be used, controlled precisely by feedback resistors, thus ensuring good linearity, with the accuracy defined by the feedback resistors used.
Despite the high gain, the model A22 is stable with 100% feedback, thus allowing feedback capacitors to be used to filter the output. The input signal level can be up to plus or minus 20 milli-volts and the output can be up to plus and minus 3 volts.
The response time of the A22 is fast, and the gain is reduced to unity at about 20 kHz, thus ensuring good response times, even at high gain settings.
The power supply requirement is low, being about 1.2 milli-amps with power supplies of plus and minus 6 volts, making it ideal for multi-channel measurement systems.
The A22 is designed to be mounted on a printed circuit board, using a 0.1” grid, with 13 pin connections on a rectangle 1.6” X 1.2”, and is built into a heavy gauge mumetal case which gives it very good magnetic, electrostatic and thermal immunity from interference. A printed circuit board is available which provides connections for power supply, gain, filter capacitors and outputs. It also contains controls for voltage and current offsets, power supply de-coupling and a passive output filter to reduce any modulation by-product.
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AQ4X90 Amplifier



Model AQ4X90
Digital Four Channel Amp

Input Sensitivity 0.2V ~ 8V
Signal to Noise Ratio 100 <
Damping Factor 250 <
External Fuse Rating 2 x 30Amp
Tested Voltage and THD 14.4V & 1% THD
4 ohm Power 90W x 4
2 ohm Power 120W x 4
4 ohm Mono Power 240W x 2
Channel 1 and 2:

Variable X-over 45 Hz (450Hz) ~ 450Hz (4.5KHz) at 12dB/Oct.
X-over Multiply x 1, x 10
X-over Selector Clone 3/4/FULL/HPF
Channel 3 and 4:

Subsonic Filter 10~360 Hz at 12 dB/Oct.
Bass Boost 0~12 dB
Variable X-over 45 Hz (450Hz) ~ 450Hz (4.5KHz) at 12dB/Oct.
X-over Multiply x 1, x 10
X-over Selector LPF-BP /HPF-FULL
Outputs Line Out
Dimensions (mm) 350mm (L) x 238mm (W) x 59.6mm (H)
Dimensions (in) 13.78in (L) x 9.37in (W) x 2.35in (H)
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XLS Series amplifiers


XLS Series amplifiers are professional Stereo power amplifiers engineered to meet demanding Audio requirements - reliably and within budget. Every XLR Series Amplifier is backed by Crown's unequaled three-year, no-fault, fully transferable warranty that covers everything.

With over five decades of experience designing and building rock-solid products, Crown is the standard in Amplifier technology. So check out the affordable Crown XLS Series.

Crown CT4150 Specifications:
CHANNELS: 4
Sensitivity: 1.4V
RATED POWER OUTPUT: 125W per Channel into 8 Ohms
Signal to Noise Ratio (below rated power 20Hz to 20kHz, A-Weighted): 110dB
Total Harmonic Distortion (THD) (full rated power, 20Hz - 20kHz): < 0.05% INTERMODULAR DISTORTION (from 0dB down to -40dB): < 0.05% Frequency Response (at 1W into 4/8 Ohms): +/- 0.5dB CROSSTALK (below rated power 20Hz to 1kHz): > 70dB
COMMON MODE REJECTION (20Hz to 1kHz): > 55dB, typically > 70dB
DIMENSION (H x W x D): 1.75" x 19" x 14.25"
NET WEIGHT: 10 lbs/4.54 kg
NET SHIPPING WEIGHT: 15 lbs/6.8 kg
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PWM amplifier chips


PWM amplifier chips requires an analysis of performance specifications. Output current is the maximum continuous current that can be delivered in the output. Input offset voltage is the amount of DC voltage that amplifiers produce even when 0 V is applied to the input. The supply voltage range includes minimum and maximum amounts. Internal power dissipation is the maximum amount of power that can be safely supported. Quiescent current is produced during normal operation. The power bandwidth or large-signal bandwidth describes an amplifier’s ability to provide a maximum output voltage swing with increasing frequency. The peak output swing is the output voltage at the frequency which represents the upper limit of the power bandwidth. A high switching frequency allows smaller output filters to be built into the amplifier enclosure. Typically, suppliers list the switching frequency for PWM amplifier chips as a maximum amount.

PWM amplifier chips are available in a variety of integrated circuit (IC) package types and with different numbers of pins. Basic IC package types include single in-line package (SIP), dual in-line package (DIP), discrete package (DPAK), small outline package (SOP), and quad flat package (QFP). Many packaging variants are available. For example, common SOP variants include shrink small outline package (SSOP) and thin shrink small outline L-leaded package (TSSOP). Small outline integrated circuit (SOIC) packaging is also available for PWM amplifier chips. TO-3 is a transistor outline (TO) package with three leads. TO-92, another transistor outline package, is often used for low power devices. By contrast, TO-220 is suitable for high power, medium current, and fast-switching power devices.
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log amp chips


Logarithmic amplifier chips (log amp chips) produce an output voltage that is directly proportional to the logarithm of the input voltage. Operational amplifier chips (op amp chips) are general-purpose, closed loop devices used to implement linear functions. They compare two incoming signals and release a third that is an amplified measure of the difference between the two. Power operational amplifier (POA) chips are used to increase the power of low-level signals in applications that drive low impedances or reactive loads. Pulse width modulated (PWM) amplifier chips generate a current that switches between high and low output levels. Sample-and-hold amplifier chips freeze analog voltage instantly. During this process the HOLD command is issued and analog voltage is available for an extended period. Specialized amplifier and comparator chips are also available.

Amplifier and comparator chips differ in terms of performance specifications and available features. Specifications for differential amplifier chips include bandwidth, gain, minimum gain, supply voltage, supply current, offset voltage, slew rate, and harmonic distortion (second and third harmonics).

Features include number of leads, package type, and power-down options. Specifications for instrumentation amplifier chips include input common-mode voltage range to negative rail, rail to rail (input or output), gain, minimum stable closed loop gain, maximum supply current, maximum voltage offset, typical common mode rejection ratio, typical power supply rejection ratio, maximum input bias current, typical unity gain bandwidth, typical slew rate, input voltage noise, and input current noise.
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RF amplifiers


RF amplifiers requires an analysis of several performance specifications. Operating frequency is the frequency range for which RF amplifiers meet all guaranteed specifications. Design gain, the ratio of the output to the input power, is normally expressed in decibels (dB), or Gdb = 10 * log (Po/Pi). Output power is the signal power at the output of the amplifier under specified conditions such as temperature, load, voltage standing wave ratio (VSWR), and supply voltage. Gain flatness indicates the degree of the gain variation over its range of operating wavelengths. Secondary performance specifications to consider include noise figure (NF), input VSWR, output VSWR, and monolithic microwave integrated circuit (MMIC) technology. The noise figure, a measure of the amount of noise added to the signal during normal operation, is the ratio of the signal-to-noise ratio at the input of the component and the signal-to-noise ratio measured at the output. The NF value sets the lower limit of the dynamic range of the amplifier. Input VSWR and output VSWR are unit-less ratios ranging from 1 to infinity that express the amount of reflected energy.

There are several physical and electrical specifications to consider when selecting RF amplifiers. Physical specifications include package type and connector type. Package types include surface mount technology (SMT), flat pack, and through hole technology (THT). RF amplifiers may also be connectorized or use waveguide assemblies. Connector types include BNC, MCX, Mini UHF, MMCX, SMA, SMB, SMP, TNC, Type F, Type N, UHF, 1.6 / 5.6, and 7/16. Important electrical characteristics include nominal operating voltage and nominal impedance. Operating temperature is an important environmental parameter to consider.
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4 ohm speaker


The "50watts" part is the one we notice first and everything else qualifies how that "50watts" was measured. Having enough power is what most people look for in an amp. However, other things come into play. If the you are going to run a load less than 4 ohms, then the current capability of the amp is definitely important and most specs do not give a current capability. A power rating into 2 ohms can help though. If the power doubles into 2 ohms then you know that the amp is built strongly enough that it can deliver enough current to drive a 2 ohm load. You may think that this is not important if you are not going to drive 2 ohm loads but it is important. Speakers (woofers, midranges, tweeters, etc) are not purely resistive. They have capacitive and inductive properties as well. Depending on the music and your setup, the impedance may dip well below 4 ohms for a nominally 4 ohm speaker.
Whether you amp can supply current fast enough to reproduce the music faithfully depends partially on the amp's slew rate (how fast its output can change), its damping factor (how easily it can control the speaker) and its current capability. For these reasons 2 ohm power is important even when driving 4 ohm speakers. Slew rates of 100V/microsec and damping factors above 100 (referenced with a 4 ohm load) are good but that information is usually not given out by the amp manufacturer. I hope it is clear now that the number of watts an amp can produce is only one factor in determining whether an amp is capable of the performance you desire.
On a final note on this part of the spec, most head units use IC (integrate circuits or chips) for the built-in amp's output stage. Those chips rarely can provide adequate current which is why even most novices know not drive subwoofers from a head unit. Real amps often have ICs in them as well but the output stages are almost always discrete, meaning they are built from transistors, resistors, capacitors and not integrated together inside tiny ICs. Advances in IC technology always making them better though.
READ MORE - 4 ohm speaker

two terminals


Bi-Amping refers to using different amplifiers (or different channels of the same amp) for the low and high frequencies in the same speaker. On a 3-way speaker, usually the mid and tweeter are driven by one amp, and the woofer is driven by more powerful amp. This allows you to purchase a high quality low power amp for the highs, and a more powerful amp for the lows. With the proper pre-amp you can also have more control over the bass output. On a 2-way speaker, the mid and tweeter are driven by different channels on an amp. This is usually done so that you can use an active crossover before the amplifier.
In DIY audio, bi-amping has even more advantages. Low pass crossovers for woofers require very large inductors. These inductors are basically very long coils of copper wire which can have a very high resistance. Using an active crossover before the amplifier removes the need for these inductors. Bi-amping also removes the need for any circuits to fix problems caused by different sensitivities or impedances between drivers.
If a speaker is capable of bi-amping, then the plate on the back of the speaker will have 4 binding posts: 2 + terminals and 2 - terminals. Both + terminals and both - will have a piece of metal connecting them together. To bi-amp the speaker, remove the metal piece. Then, use the top 2 terminals for the high frequency amp, and the bottom two terminals for the bass amp.
Note: some professional audio equipment has 4 binding posts on the back. This is for ease of running multiple speakers in parallel. It is not for bi-amping, and the terminals should not be connected.
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Selasa, 04 Oktober 2011

Laser diodes



Laser diodes are used in all areas of electronics from domestic equipment, through commercial applications to hash industrial environments. In all these applications laser diodes are able to provide a cost effective solution while being rugged and reliable and offering a high level of performance.

Laser diode technology has a number of advantages:
Power capability: Laser diodes are able to provide power levels from a few milliwatts right up to a few hundreds of watts.
Efficiency: Laser diode efficiency levels can exceed 30%, making laser diodes a particularly efficient method of generating coherent light.
Coherent light: The very nature of a laser is that it generates coherent light. This can be focussed to a diffraction limited spot for high density optical storage applications.
Rugged construction: Laser diodes are completely solid state and do not require fragile glass elements or critical set-up procedures. Accordingly they are able to operate under harsh conditions.
Compact: Laser diodes can be quite small allowing for laser diode technology to provide a very compact solution.
Variety of wavelengths: Using the latest technology and a variety of materials, laser diode technology is able to generate light over a wide spectrum. The use of blue light having a short wavelength allows for tighter focussing of the image for higher density storage.
Modulation: It is easy to modulate a laser diode, and this makes laser diode technology ideal for many high data rate communications applications. The modulation is achieved by directly modulating the drive current to the laser diode. This enables frequencies up to several GHz to be achieved for applications such as high-speed data communications.
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Selasa, 20 September 2011

Dual section air variable capacitor


Dual section air variable capacitor
was invented to provide tracking between two related LC-tuned circuits, as in a radio receiver. Such capacitors are basically two (in the case of Fig. 5) or more variable capacitors mechanically ganged on the same rotor shaft.

In Fig. 5, both sections of the variable capacitor have the same capacitance, so they are identical to each other. If this capacitor is used in a superheterodyne radio, the section used for the local oscillator (LO) tuning must be padded with a series capacitance in order to reduce the overall capacitance. This trick is done to permit the higher-frequency LO to track with the RF amplifiers on the dial.

In many superheterodyne radios, you will find variable tuning capacitors in which one section (usually the front section) has fewer plates than the other section. One section tunes the RF amplifier of the radio, and the other tunes the local oscillator. These capacitors are sometimes called cut-plate capacitors because the LO section plates are cut to permit tracking of the LO with the RF.
READ MORE - Dual section air variable capacitor

Transmitting air variable capacitor


Transmitting air variable capacitor
Differential variable capacitors also have two independent stators, but unlike in the butterfly capacitor where capacities on both sides increase equally as the rotor is turned, in a differential variable capacitor one section's capacity will increase while the other section's decreases, keeping the stator-to-stator capacitance constant. Differential variable capacitors can therefore be used in capacitive potentiometric circuits.

The one requirement of transmitting variable capacitors (and certain antenna tuning capacitors) is the ability to withstand high voltages. The high-power ham radio or AM broadcast transmitter will have a dc potential of 1500 to 7500 V on the RF amplifier anode, depending on the type of tube used. If amplitude-modulated,the potential can double. Also, if certain antenna defects arise, then the RF voltages in the circuit can rise quite high. As a result, the variable capacitor used in the final amplifier anode circuit must be able to withstand these potentials.
Two forms of transmitting variables are typically used in RF power amplifiers and antenna tuners. Figure 7 shows a transmitting air variable capacitor. The shaft of this particular capacitor is nylon, so it can be mounted either with the frame grounded or with the frame floating at high voltage. The other form of transmitting variable is the vacuum variable. This type of capacitor is a variation of the piston capacitor, but it has a vacuum dielectric (K factor = 1.0000). The model shown in Fig. 8 is a 18- to 1000-pF model that is driven from a 12-Vdc electric motor. Other vacuum variables are manually driven.


Vacuum variable capacitor
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phase locked loop (PLL)



"Digital phase-locked loop block diagram"

A phase detector compares two input signals and produces an error signal which is proportional to their phase difference. The error signal is then low-pass filtered and used to drive a VCO which creates an output phase. The output is fed through an optional divider back to the input of the system, producing a negative feedback loop. If the output phase drifts, the error signal will increase, driving the VCO phase in the opposite direction so as to reduce the error. Thus the output phase is locked to the phase at the other input. This input is called the reference.

Analog phase locked loops are generally built with an analog phase detector, low pass filter and VCO placed in a negative feedback configuration. A digital phase locked loop uses a digital phase detector; it may also have a divider in the feedback path or in the reference path, or both, in order to make the PLL's output signal frequency a rational multiple of the reference frequency. A non-integer multiple of the reference frequency can also be created by replacing the simple divide-by-N counter in the feedback path with a programmable pulse swallowing counter. This technique is usually referred to as a fractional-N synthesizer or fractional-N PLL

Typically, the reference clock enters the chip and drives a phase locked loop (PLL), which then drives the system's clock distribution. The clock distribution is usually balanced so that the clock arrives at every endpoint simultaneously. One of those endpoints is the PLL's feedback input. The function of the PLL is to compare the distributed clock to the incoming reference clock, and vary the phase and frequency of its output until the reference and feedback clocks are phase and frequency matched.

PLLs are ubiquitous—they tune clocks in systems several feet across, as well as clocks in small portions of individual chips. Sometimes the reference clock may not actually be a pure clock at all, but rather a data stream with enough transitions that the PLL is able to recover a regular clock from that stream. Sometimes the reference clock is the same frequency as the clock driven through the clock distribution, other times the distributed clock may be some rational multiple of the reference.

One desirable property of all PLLs is that the reference and feedback clock edges be brought into very close alignment. The average difference in time between the phases of the two signals when the PLL has achieved lock is called the static phase offset (also called the steady-state phase error). The variance between these phases is called tracking jitter. Ideally, the static phase offset should be zero, and the tracking jitter should be as low as possible.[dubious – discuss]

Phase noise is another type of jitter observed in PLLs, and is caused by the oscillator itself and by elements used in the oscillator's frequency control circuit. Some technologies are known to perform better than others in this regard. The best digital PLLs are constructed with emitter-coupled logic (ECL) elements, at the expense of high power consumption. To keep phase noise low in PLL circuits, it is best to avoid saturating logic families such as transistor-transistor logic (TTL) or CMOS.[citation needed]

Another desirable property of all PLLs is that the phase and frequency of the generated clock be unaffected by rapid changes in the voltages of the power and ground supply lines, as well as the voltage of the substrate on which the PLL circuits are fabricated. This is called substrate and supply noise rejection. The higher the noise rejection, the better.

To further improve the phase noise of the output, an injection locked oscillator can be employed following the VCO in the PLL.
Frequency Synthesis

In digital wireless communication systems (GSM, CDMA etc.), PLLs are used to provide the local oscillator for up-conversion during transmission and down-conversion during reception. In most cellular handsets this function has been largely integrated into a single integrated circuit to reduce the cost and size of the handset. However, due to the high performance required of base station terminals, the transmission and reception circuits are built with discrete components to achieve the levels of performance required. GSM local oscillator modules are typically built with a frequency synthesizer integrated circuit and discrete resonator VCOs.
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AC contactor


LC1-D series AC contactor (simplified as contactor in the following)is suitable for using in the circuits up to the rated voltage 660V AC 50Hz or 60Hz, rated current 95A, for making and breaking and frequent starting, controlling the AC motor. Combined with the auxiliary contact group, air delayer, machine interlocking device etc, it is combined into the delay contactor, mechanical interlocking contactor, dtar-delta starter, with the thermal realay, it is combined into the electromagnetic starter.
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supercapacitor


supercapacitor has a limited range of applications, advances in design might eventually expand the product’s utility. For example, researchers continue to develop and experiment with newer forms of dielectric materials, such as carbon nanotubes, polypyrrole, and barium titanate, which may improve capacitance and energy density. The concept of combining supercapacitors with alternative energy sources to replace car batteries has gained appeal within the current "green" movement, and several public transportation systems have created pilot trials for capacitor-run buses and trains. If these and other developments yield successful results, the electric double-layer capacitor may achieve greater functionality and gain a larger role within the energy industry.

Manufacturers evaluating various electrical sourcing options should examine the strengths and weaknesses unique to the double-layer format. A supercapacitor’s energy density ratio typically ranges between 0.5 and 10 Wh/kg (nominal voltage over weight), which is considerably higher than that of a standard capacitor. While this energy density is still relatively low compared to mainline batteries, such as the lithium-ion model, the supercapacitor’s power density far exceeds the level offered by its counterparts. Power density is contingent on a device’s rate of electrical charging and discharging, meaning that supercapacitors can both generate and distribute energy more quickly than most batteries.

In addition, supercapacitors stop charging when their capacity limit is reached, eliminating the need for detection units to prevent overcharging. Aside from its excellent power density, a supercapacitor also has high cycle efficiency and can undergo millions of charging sequences in its lifespan.

However, low energy density and low voltage tolerance limit the effectiveness of an individual double-layer capacitor as a storage unit, unless it is serially linked to a group of capacitors. Furthermore, the supercapacitor’s linear discharge method often prevents the full charge from being delivered, resulting in small but detrimental energy waste. The high rate of self-discharge (energy loss due to internal chemical reactions) is a similar concern. Supercapacitor controls and electronic switching equipment can also be complex, and typically necessitate workers with specialized operational skills.
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