Collection Schematic

Monday, November 3, 2014

Video Isolator

These days many more audio-visual devices in the home are connected together. This is especially the case with the TV, which may be connected to a DVD player, a hard disk recorder, a surround-sound receiver and often a PC as well. This often creates a problem when earth loops are created in the shielding of the video cables, which may cause hum and other interference. The surround-sound receiver contains a tuner that takes its signal from a central aerial distribution system. The TV is also connected to this and it’s highly likely that the PC has a TV-card, which again is connected to the same system. On top of this, there are many analogue connections between these devices, such as audio cables. The usual result of this is that there will be a hum in the audio installation, but in some cases you may also see interference on the TV screen.

The ground loop problem can be overcome by galvanically isolating the video connections, for example at the aerial inputs of the surround-sound receiver and the TV. Special adaptors or filters are sold for this purpose, known as video ground loop isolators. Good news: such a filter can also be easily made at home by yourself. There are two ways in which you can create galvanic isolation in a TV cable. The first is to use an isolating transformer with two separate windings. The other is to use two coupling capacitors in series with the cable. The latter method is easily the simplest to implement and generally works well enough in practice. The simplest way to produce such a ‘filter’ is as an in-line adapter, so you can just plug it onto either end of a TV aerial cable.

Video Isolator Circuit diagram:

The only requirements are a male and female coax plug and two capacitors. The latter have to be suitable for high-frequency applications, such as ceramic or MKT types. It is furthermore advisable to choose types rated for high voltages (400 V), since the voltages across these capacitors can be higher than you might expect (A PC that isn’t connected to the mains Earth can have a voltage as high as 115 V (but at a very low, safe current), caused by the filter capacitors in its power supply. These capacitors don’t need to be high value ones, since they only have to pass through frequencies above about 50 MHz. Values of 1 nF or 2.2 nF are therefore sufficient. To make the isolator you should connect one capacitor between the two earth connections of the coax plugs and the other between the two signal connections.

The mechanical construction has to be sturdy enough such that the connections to the capacitors won’t break whenever the inline adapter is removed forcibly. A good way to do this is to make a cover from a piece of PVC piping for the central part. Wrap aluminium foil round the outside and connect it to one of the plugs, so that the internal parts are properly shielded from external interference. Make sure that the aluminium foil doesn’t make contact with the other plug, otherwise you lose the isolation. The majority of earth loops will disappear when you connect these filters to all used outputs of the central aerial distribution system where the signal enters the house.

stk392 datasheet schematic circuit diagram

The STK392-020 is a hybrid IC for video projector
convergence correction. Since this IC integrates three
output amplifier circuits in a single package, the six
convergence correction output circuits, i.e., the vertical
and horizontal directions for each CRT of the RGB can be
formed from only two ICs.

Applications
Video projectors (both standard and high definition) test circuit

Features
•Three output amplifier circuits integrated in a single
22-pin package
•High absolute maximum supply voltage
(VCC max = ±44 V)
•Low thermal resistance (θj-c = 2.1 °C/W)
•High thermal stability (TC max = 125°C)
•Isolated early stage and output stage power supplies
•Output stage power supply switching supports high
efficiency designs.

•The input system, power supply system and output
system pins are isolated in the pin arrangement, thus
reducing the influence of the pattern layout on the
characteristics and easing design.
•Since constant current circuits are used in the pre-driver
stage, operation is stable with respect to the power
supply switching.
•The Sanyo convergence correction circuit product
lineup (the STK392-000 series) handles a wide range of
end-product classes. Therefore, the same PCB can be
used for end products from popularly-priced units to
top-of-the-line models. Package Dimensions

100W Audio Amplifier Transistor used BDW83D BDW84D circuit diagram

Here 100 watt power audio amplifier which using power transistor BDW83D and BDW84D. Copyright belong to Smart Kit. Schematic diagram:

Component part list:

R1 = 1,2 K D1 = 1N4002-7

R2 = 0,47 OHM D2 = 1N2002-7

R3 = 220 OHM D3 = 1N4148

R4 = 3,9 K D4 = 1N4148

R5 = 2,2 K D5 = 1N4148

R6 = 2,2 K D7 = 1N4148

R7 = 10 K D8 = 1N4148

R8 = 4,7 K Q1 = BDW84D

R9 = 150 OHM Q2 = BD829

R10 = 39 OHM Q3 = BC546

R11 = 3,3 K Q4 = BC556

Sunday, November 2, 2014

14W CLASS A AMPLIFIER USING 2N3055 ELECTRONIC DIAGRAM

Why Class A ? Because , when biased to class A, the transistors are always turned on, always ready to respond instantaneously to an input signal. Class B and Class AB output stages require a microsecond or more to turn on. The Class A operation permits cleaner operation under the high-current slewing conditions that occur when transient audio signal are fed difficult loads. His amplifier is basically simple, as can be seen from the block diagram.

METAL DETECTOR USING BEAT FREQUENCY OSCILLATOR ELECTRONIC DIAGRAM

The NAND gates use CMOS 4011 chip, a low power component that is suitable for this battery-operated circuit. You can see that this chip is supplied by a 5V voltage coming from an LM7805L regulator. You might wonder what the purpose of this regulation is, since the power supply come from a 9V battery and the CMOS gates can handle the voltage of 3-15 Volt. The main purpose of the regulator is to keep a constant voltage source for the reference oscillator frequency stability, since the frequency is affected by the power supply voltage variation as the battery voltage drops in the long time of usage.

This circuit uses parts as follows :

U1: CD4011
U2: LM389
U3: 78L05
R1: 2.2k 5%
P2: 4.7k lin.
R3: 330k 5%
R4: 270k 5%
R5: 1k 5%
C1: 390pF (NPO)
C2,C3,C4: 10nF
C5: 10uF 16v electrolytic
C6,C8: 220 uF 16v electrolytic
C7: 100uf 16v electrolytic
C9: 100nF ceramic
P1: 4.7k log
L1: 22cm in diameter with 14 turns AWG 26
K1: SPDT toggle switch
J1= Headphone jack 1/4 or 1/8 inch
Other parts: 9v battery connector, speaker or headphones

uln2003 datasheet

HIGH VOLTAGE AND HIGH CURRENT

DARLINGTON TRANSISTOR ARRAY

DESCRIPTION

The ULN2003 is a monolithic high voltage and high current

Darlington transistor arrays. It consists of seven NPN darlington

pairs that features high-voltage outputs with common-cathode

clamp diode for switching inductive loads. The collector-current

rating of a single darlington pair is 500mA. The darlington pairs

may be parrlleled for higher current capability. Applications include

relay drivers,hammer drivers, lampdrivers,display drivers(LED gas

discharge),line drivers, and logic buffers.

The ULN2003 has a 2.7kΩ series base resistor for each

darlington pair for operation directly with TTL or 5V CMOS

devices.

FEATURES

* 500mA rated collector current(Single output)

* High-voltage outputs: 50V

* Inputs compatibale with various types of logic.

* Relay driver application

download uln2003 datasheet

Saturday, November 1, 2014

Very Simple Audio Mixer Circuit

A very simple audio mixer can be designed using this circuit diagram electronic project. Audio mixing is normally performed by a mixer with virtual ground, in which the various input signals are applied through series resistors to virtual ground, that at the inverting input of operational amplifier.

The audio mixer is a little different and uses the principle of common ground, the input voltages are converted into alternating current which, when summed, is the AC component of the collector. In the case of a common base configuration, emitter impedance is small and works as a virtual ground that is making it impossible to crosstalk between different input signals. The output signal is taken from the collector of Q1. Amplification circuit is equal to R6 + Ri, where Ri is the input resistance (= one of the resistances RI ... R5). The T1s emitter circuit has been provided a power source consisting of T2 and T3.

Q1s base voltage is set by resistors R7 and R8. Ensure that the capacitor C1 of T1 to be effectively disconnected.

Number of entries can be modified, increased or decreased as desired.