High Voltage Generator

This high voltage generator was designed  with the aim of testing the electrical break-down protection used on the railways. These  protection measures are used to ensure that  any external metal parts will never be at a  high voltage. If that were about to happen,  a very large current would flow (in the order  of kilo-amps), which causes the protection  to operate, creating a short circuit to ground effectively earthing the metal parts. This hap-pens when, for example, a lightning strike hits  the overhead line (or their supports) on the  railways.

This generator generates a high voltage of  1,000 V, but with an output current that is limited to few milliamps. This permits the electrical breakdown protection to be tested with-out it going into a short circuit state. The circuit uses common parts throughout: a  TL494 pulse-width modulator, several FETs or  bipolar switching transistors, a simple 1.4 VA  mains transformer and a discrete voltage multiplier. P1 is used to set the maximum current  and P2 sets the output voltage.

High Voltage Generator Circuit Diagram

The use of a voltage multiplier has the advantage that the working voltage of the smoothing capacitors can be lower, which makes them easier to obtain. The TL494 was chosen  because it can still operate at a voltage of  about 7 V, which means it can keep on working even when the batteries are nearly empty.  The power is provided by six C-type batteries, which keeps the total weight at a reason-able level.

The 2x4 V secondary of AC power transformer  (Tr1) is used back to front. It does mean that  the 4 V winding has double the rated voltage  across it, but that is acceptable because the  frequency is a lot higher (several kilo-Hertz)  than the 50 Hz (60 Hz) the transformer is  designed for. The final version also includes a display of the  output voltage so that the breakdown volt-age can be read.

From a historical perspective there follows a  bit of background information. In the past a different system was worked  out. Every high-voltage support post has a  protection system, and it isn’t clear when  the protection had operated and went into  a short-circuit state due to a large current  discharge.

Since very large currents were involved, a certain Mr. Van Ark figured out a solution for this.  He used a glass tube filled with a liquid containing a red pigment and a metal ball. When  a large current discharge occurred the metal  ball shot up due to the strong magnetic field,  which caused the pigment to mix with the liquid. This could be seen for a good 24 hours after the event. After a thunder storm it was  easy to see where a discharge current took  place: one only had to walk past the tubes  and have a good look at them.

Unfortunately, things didn’t work out as  expected. Since it often took a very long  time before a discharge occurred, the pigment settled down too much. When a dis-charge finally did occur the pigment no  longer mixed with the liquid and nothing was  visible. This system was therefore sidelined,  but it found its place in the (railway) history  books as the ‘balls of Van Ark’.

Author : By Jac Hettema – Copyright : Elektor

Source:  http://www.ecircuitslab.com/2012/03/high-voltage-generator.html

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Three Phase Appliance Protector

    Many of our costly appliances require three-phase AC supply for operation. Failure of any of the phases makes the appliance prone to erratic functioning and may even lead to failure. Hence it is of paramount importance to monitor the availability of the three-phase supply and switch off the appliance in the event of failure of one or two phases. The power to the appliance should resume with the availability of all phases of the supply with certain time delay in order to avoid surges and momentary fluctuations.

    The complete circuit of a three phase appliance protector is described here. It requires three-phase supply, three 12V relays and a timer IC NE555 along with 230V coil contactor havingfour poles. Relays RL1 and RL2 act as a sensing devices for phases Y and B, respectively. These relays are connected such that each acts as an enabling device for the subsequent relay. Therefore the combination of the relays forms a logical AND gate connected serially.

    The availability of phase R energises relay RL1 and its normally opened (N/O) contacts close to connect phase Y to the input of transformer X2. The availability of phase Y energises relay RL2 and its N/O contacts close to connect phase B to the input of transformer X3, thus applying a triggering input to timer IC NE555 (IC1).

    Therefore the delay timer built around NE555 triggers only when all the phases (R, Y and B) are available. It provides a delay of approximately four seconds, which energises relay RL3 and its N/O contact closes to connect the line to the energizing coil of four-pole contactor relay RL4. Contactor RL4 closes to ensure the availability of the three-phase supply to the appliance.

    The rating of contactor RL4 can be selected according to the full-load current rating of the appliances. Here the contact current rating of the four-pole contactor is up to 32A. The availability of phases R, Y and B is monitored by appropriate LEDs connected across the secondary windings of transformers X1, X2 and X3, respectively. Hence this circuit does not require a separate indicator lamp for monitoring the availability of the three phases. When phase R is available, LED1 glows. When phase Y is available, LED2 glows. When phase B is available, LED3 glows.

     The main advantage of this protector circuit is that it protects three-phase appliances from failure of any of the phases by disconnecting the power supply through the contactor and automatically restores the three-phase supply to the appliance (with reasonable time delay) when all the phases are available.

    Assemble the circuit on a general-purpose PCB and enclose in a cabinet with the relays and contactor mounted on the backside of cabinet. Connect the appliance through external wires.

    Caution:  To avoid the risk of electric shock, ensure that AC mains is disconnected during assembly of the circuit and double check everything before connecting your circuit to the mains.

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Motional Feed Back Amplifier

This concept has appeared long back in Practical Electronics a UK based Magazine. Based on this concept I designed this circuit during 1981 to 1986 with lots of field trials and modifications, the design was frozen in 1986. I have assembled so many amplifiers for me and for my friends based on this design with various power levels. They are still kicking in so many houses. This concept can be applied to any existing amplifier also. You must listen to believe the crystal clear thumping bass response. crystal clear mid and hi frequencies. Good transient response with very low distortion. Hope you guys  will enjoy the reproduction of this amplifier.

In the art of audio sound reproduction it is well-known that the dynamic loudspeaker is more nonlinear and generates more distortion than all the other system components combined. This is particularly true at low frequencies which require large cone excursions where the stiffness of both the inner spider and the outer surround increases rapidly as the cone approaches its peak displacement, resulting in a nonlinear suspension compliance generating high distortion.

For example, in a typical high fidelity sound system at a frequency of about 35 Hz the total harmonic distortion of the amplifier might be of the order of 0.01%, whereas the distortion of the loudspeaker might range from about 3.0% to about 50.0%, depending upon the loudness. If this cone motion can be sensed and given as a feed back to the earlier stage of the amplifier, this distortion can be reduced dramatically.

Circuit diagram:

 

Motional Feed Back Amplifier Circuit Diagram

Motional Feedback (MFB) was a speaker system developed in the early 1970s by Philips Holland. It introduced a feedback system to the woofers of HiFi loudspeakers, enabling them to achieve a more extended low frequency response in a relatively small enclosure. The key benefits are a very controlled bass response. Any distortion induced by the enclosure or the woofer itself is immediately corrected by the feedback. These hand-built speakers were sounding very good and were quite expensive.

As a different approach, instead of using the cone movement, the current flow through the voice can be sensed (the current is proportional to cone movement) and can be used as a cone movement feedback. This novel idea is used in this amplifier design (I don’t claim any originality; this idea has appeared in Practical Electronics UK Magazine – long back – They might have even patented it).the amplifier used here is a standard Philips audio application circuit, with a specification of 40 Watt RMS @ < 0.06% Total Harmonic Distortion into 8 ohms impedance speaker and having a frequency response from 20Hz to 100 KHz, suitably modified for our application.

Powersupply Circuit:

Motional Feed Back Amplifier Powersupply Circuit Diagram

The amplifier is a conventional class B directly coupled quasi complimentary out put stage, operating with single 56Volt supply (no need for a regulated or dual power supply). BC157 is the pre-driver and half supply stabilizer. BD 139 is the driver, a BD139 and a BD140 complimentary pair out put driver stage with 2N3055 as final out put stage. The speaker voice coil current is sensed through 0.47 ohms resistance connected from speaker one end to ground. This signal is given as negative fed back to previous stage through 470 ohms. The half supply at speaker coupling capacitor can be adjusted by varying the 39K resistance (if required you may fix a 100K pre set in the place of 39K and adjust for half supply with no in put signal at junction of both 0.47 ohms of out put transistors and speaker coupling capacitor).

The quiescent current through output transistors can be adjusted with 22 ohms in series with two bias diodes 1N4007. The value for 50mA quiescent current will lie between 15 to 33 ohms for a supply of 56volts. The amplifier can be protected with a simple 1.5Amp fast acting fuse in the positive power supply. the amplifier can be assembled on 40watt Philips amplifier application board or on any standard plain straight line board. All the three driver transistors require cooling clips. (Standard TO220 casing cooling fins). Out put transistors require a good quality extruded alloy heat sink with insulating mounting kit and with a smear of silicon conductive grease, for good conductance of heat.

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Bass Treble Tone Control

The LM1036 is a DC controlled tone (bass/treble), volume and balance circuit for stereo applications in car radio, TV and audio systems. An additional control input allows loudness compensation to be simply effected. Four control inputs provide control of the bass, treble, balance and volume functions through application of DC voltages from a remote control system or, alternatively, from four potentiometers which may be biased from a zener regulated supply provided on the circuit.

Bass Treble Tone Control Circuit diagram :

Each tone response is defined by a single capacitor chosen to give the desired characteristic.

Features :

• Wide supply voltage range, 9V to 16V
• Large volume control range, 75 dB typical
• Tone control, ±15 dB typical
• Channel separation, 75 dB typical
• Low distortion, 0.06% typical for an input level of 0.3 Vrms
• High signal to noise, 80 dB typical for an input level of 0.3 Vrms
• Few external components required

Note :

Vcc can be anything between 9V to 16V and the output capacitors are 10uF/25V electrolytic

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Step up Down DC DC Converter Circuit Diagram

Positive output step-up and step-down dc-dc converters have a common limitation in that neither can handle input voltages that are both greater than or less than the output. For example, when converting a 12-V sealed lead/acid battery to a regulated +12 V output, the battery voltage might vary from a high of 15 V down to 10 V. 

By using a MAX641 to drive separate P-and N-cbannel MOSFETs, both ends of the inductor are switched to allow noninverting buck/boost operation. A second advantage of the circuit over most boostonly designs is that the output goes to 0 V when shutdown is activated. Inefficiency is a drawback because two MOSFETs and two diodes increase the losses in the charge and discharge path of the inductor. The circuit delivers +12 V at 100 mA at 70 percent efficiency with an 8-V input.

Step up Down DC - DC Converter Circuit Diagram

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Floating 9V Supply For DVM Modules

Most commercial DVM modules with an LCD readout are 9-V powered and based on an ICL7106 or similar A-D converter chip. These modules are typically used in laboratory power supplies and other test and measurement equipment where a drop-in solution needs to be found to realize a voltmeter readout. Particularly in power supply units, the LCD module will need to ‘float’ relative to the PSU supply rails, and this inevitably requires a separate 9-volt power supply. In some cases, batteries may be used but these have distinct advantages. The alternative, a 9-V converter effectively powered by the PSU and yet floating, is shown here.


It is built from the ubiquitous TLC555, LMC555 or 7555) timer IC acting in astable multivibrator configuration producing a 70-kHz square wave fed into a simple rectifier. In essence, capacitors C5 and C6 afford the above mentioned electrical isolation between the PSU supply rails and the LCD module. The old, bipolar NE555 IC should not be used here because it presents a too heavy loads on the converter’s own supply voltage. Depending on the exact type and brand of the CMOS 555 you’re using, resistor R6 may need to be redimensioned a bit to ensure a supply voltage of about 10 volts at pins 8 and 4 of the chip. At an output voltage of 9.5 V, the maximum output current of the converter s about 1 mA.

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Automatic Switch For Voltage Converters

New applications for DC voltage converters, such as the ‘workhorse’ LT1070, arise every day. These converters can be adapted to nearly every imaginable ratio of input and output voltages. However, all of these circuits and devices have the same shortcoming, which is that they lack an on/off switch. Especially when they are used as a source of 6-V / 12-V power for a car radio, this is highly impractical. The circuit described here adds automatic load detection to the converter. For use in a car, the additional circuitry must be small and fit into a compact enclosure together with the converter.

Since the battery voltage and ambient temperature vary over wide ranges, a simple form of load detection must be used. Besides this, the voltage drop across the load sensing circuitry must naturally be as small as possible. This can be achieved by using ‘ultra-modern’ SiGe technology. The 6 V from the battery and the 12 V from the converter are combined in the MB R2545 dual diode. Consequently, a voltage of at least 6 V is always applied to the radio (for memory retention). If the radio is switched on, it draws a current from the 6-V battery, which may be around 100 mA.

This current produces a voltage across R1. If this voltage is 75 mV or greater, the AC128 germanium transistor starts conducting and charges electrolytic capacitor C1, which is connected to the gate of the BUZ10. The MOSFET energises RE1 and thus connects the supply voltage to the converter. As a result, 12-V power is connected to the radio. The resulting increased current causes the voltage drop across R1 to increase, which is undesirable, so a 10-A Schottky diode is connected in parallel. The total voltage drop is thus approximately 0.6 V. The RC network connected to the BUZ10 ensures that the transistor always remains switched on for at least several seconds, to prevent the circuit from ‘chattering’ with varying current consumption.


If the load is switched off, the AC128 cuts off, the electrolytic capacitor discharges and the relay again disconnects the voltage converter. The residual current consumption is so small that the circuit can also be connected ahead of the ignition switch. The Schottky diodes need only be rated for the necessary voltages and currents, and above all, they should have the lowest possible saturation voltage. The exact type is not critical. Two separate diodes can also be used. A small heat sink for the MBR diode won’t hurt, but this is normally not essential. Practically any type of PNP germanium transistor that is still available or on hand can be used (AC125, AC126 and AC128 work perfectly).

It may be necessary to modify the value of R1. In combination with the germanium transistor, R1 determines which level of current will be ignored (for memory retention) and which level of current will cause the converter to be switched on. With the component values shown in Figure 1, this level is between 10 mA and 25 mA. It is recommended to measure the quiescent current (at 6 V) and switch-on current of the load and then simulate the switching process using dummy load resistors. When selecting the 6-V relay, ensure that its contacts have an adequate current rating. The actual value can be significantly greater than the nominal output current. With a load of 5 A at 12 V and a converter efficiency of 70 percent, the current through the relay contacts rises to 14.3 A.

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3V DC to 5V DC REGULATED POWER SUPPLY ELECTRONIC DIAGRAM

3V DC to 5V DC REGULATED POWER SUPPLY ELECTRONIC DIAGRAM

A 5V DC regulated output from 2 cells 3V DC batteries. The output current of the circuit is limited to 50mA. However, it still able to supply many microcontroller circuits. 3009 and 560R Resistor provide the 5V DC output, make up a voltage divider network.

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A Simple MD Catridge Preamplifier

Phonographs are gradually becoming a rarity. Most of them have had to yield to more advanced systems, such as CD players and recorders or (portable) MiniDisc player/recorders. This trend is recognized by manufacturers of audio installations, which means that the traditional phono input is missing on increasingly more systems. Hi-fi enthusiasts who want make digital versions of their existing collections of phonograph records on a CD or MD, discover that it is no longer possible to connect a phonograph to the system.

Circuit diagram :

A Simple MD Catridge Preamplifier Circuit Diagram

However, with a limited amount of circuitry, it is possible to adapt the line input of a modern amplifier or recorder so that it can handle the low-level signals generated by the magnetodynamic cartridge of a phonograph. Of course, the circuit has to provide the well-known RIAA correction that must be used with these cartridges. The preamplifier shown here performs the job using only one opamp, four resistors and four capacitors. For a stereo version, you will naturally need two of everything. Any stabilized power supply that can deliver ±15V can be used as a power source.

Author : H. Steeman

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Optimised Semiconductor Noise Source

We have already published designs that use a transistor junction operating in Zener breakdown as a noise source. Anyone who has experimented with a reverse-biased transistor knows that the amplitude of the noise voltage generated in this manner is strongly dependent on the supply voltage. The variation between individual transistors is also rather large. An obvious solution is to use an adjustable supply voltage for the noise generator stage. A BC547B starts to break down at around 8V.

Using P1 and R1, you can adjust the voltage across T1 and R2 between 8 and 12V. C3 decouples the reduced supply voltage. An impedance buffer in the form of T2 and R3 is added to the circuit, to prevent the connected load from affecting the noise source. This buffer is powered directly from the 12-V supply. To adjust this circuit, connect the output to an oscilloscope. Then adjust P1 to obtain the highest signal amplitude, combined with the best ‘shape’ of the noise signal. The output voltage is approximately 300mVpp, and the current consumption is around 2mA.

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AUDIO LEVEL METER ELECTRONIC DIAGRAM

AUDIO LEVEL METER ELECTRONIC DIAGRAM

It consists of only few components. IC LM3915 converts the audio analog voltage and display it to the LED. Here is the schematic :

Parts list :

•     Resistor R1 : 1k2
•     Resistor variable R2 : 10k
•     IC : LM3915
•     LED indicator LED1-LED10 : LED 5mm
•     12V power supply

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Symmetric Noise Source

If a transistor junction operating in Zener breakdown is used as a noise source, the amplitude of the noise signal is asymmetric. This problem can be solved by using two transistors as two independent noise sources. One of these has a series resistor to earth, and the other has a series resistor to the supply line. Each of these noise sources produces an asymmetric noise voltage, with opposite asymmetry. If these two voltages are combined, the amplitude of the result will be symmetric. In the circuit diagram, T1 and T2 are the noise sources. The series resistors are R2 (to earth) and R4 (to the positive supply line).

The supply voltage for the noise sources has been made adjustable, to allow the noise generation of the transistors to be optimized. This is because the amount of noise produced depends on the power supply voltage. P1 and R1 provide an adjustable supply voltage between 8 and 12 V for the noise stage around T1, while P3 and R3 perform the same function for T2. C3 and C5 smooth these voltages. Since the amplitudes of the two noise sources will never be the same, it is necessary to take a weighted sum of the two signals. Consequently, P2 is included between the outputs of the noise sources as a sort of balance control.

Since the DC levels of the two noise sources are not the same, C4 is also included in the balance network. The weighted sum of the two signals is present on the wiper of P2, superimposed on the DC signal of noise source T1. This DC level is also used for the DC bias of the buffer stage T3. The buffer isolates the noise sources from whatever circuit is connected to the output. To adjust the circuit, connect an oscilloscope to the output. First, turn P2 all the way to the left. Now rotate P1 until a maximum noise signal is seen on the oscilloscope. Next, turn P2 all the way to the right, and then adjust P3 for the best noise signal. Finally, adjust P3 so that the noise signal looks symmetric. The circuit provides an output voltage of approximately 150mV pp. The current consumption is 2mA. The oscilloscope shows the asymmetric noise signal on channel 2, and the symmetric noise signal on channel 1.

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Electronic Touch Switch

Mechanical contacts have the disadvantage that they wear out. That is why it is practical to use an electronic ‘touch switch’ in some situations. With such a touch switch the resistance of the human skin is used for the switching action. The schematic shows the design of a circuit that senses the resistance of the skin and converts it into a useful switching signal. The touch switch contacts can be made from two small metal plates, rivets, nails, etcetera, which are placed close together on a non-conducting surface. In this circuit a comparator of the type LM393 has been used. In the idle state there is, via R1, a voltage equal to the power supply voltage on the non-inverting input of IC1a. Because the inverting input of IC1a is set with R2 and D3 to D5 at the supply voltage minus 1.8 V, the open-collector output of IC1.a is, via R3, equal to the power supply voltage. This voltage is inverted by IC1.b. The voltage at the non-inverting input of IC1.b amounts to half the power supply voltage (through voltage divider R4 and R5) and is lower than the voltage on the inverting input.

Circuit diagram:

Electronic Touch Switch Circuit Diagram

The output of IC1.b is therefore a ‘0’. If the two touch contacts are bridged with a finger, the voltage at the non-inverting input will become low enough to cause the comparator to toggle state. The moistness of the skin results in a resistance of 1 to 10 MR. If this circuit is used in the vicinity of equipment that’s connected to the mains, then it can be sufficient to touch only the upper contact to operate the switch, provided that the circuit has been earthed. The body then acts as an antenna which receives the 50 Hz (or 60 Hz) from the mains. This is enough to toggle IC1.a at the same 50 Hz. C1/R3 prevent this 50 Hz from reaching the input of IC1b and provide a useable ‘pulse’ of about 10 s at the output of IC1.b. Note that a fly walking across the touch switch conducts enough to generate a switching signal. So do not operate important things with this circuit (such as the heating system or the garage door). Do not make the wires between the touch contacts and the circuit too long to prevent picking up interference. The power supply voltage for the circuit is not very critical. Any regulated DC voltage in the range from 6 to 20 V can be used.

Author: Heino Peters - Copyright: Elektor Electronics Magazine

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Playback Amplifier For Cassette Deck

For some time now, there have been a number of tape cassette decks available at low prices from mail order businesses and electronics retailers. Such decks do not contain any electronics, of course. It is not easy to build a recording amplifier and the fairly complex magnetic biasing circuits, but a playback amplifier is not too difficult as the present one shows. The stereo circuits in the diagram, in conjunction with a suitable deck, form a good-quality cassette player. The distortion and frequency range (up to 23 kHz) are up to good standards. Moreover, the circuit can be built on a small board for incorporation with the deck in a suitable enclosure. Both terminals of coupling capacitor C1 are at ground potential when the amplifier is switched on.

Because of the symmetrical ±12 V supply lines, the capacitor will not be charged. If a single supply is used, the initial surge when the capacitor is being charged causes a loud click in the loudspeaker and, worse, magnetizes the tape. The playback head provides an audio signal at a level of 200–500 mV. The two amplifiers raise this to line level, not linearly, but in accordance with the RIAA equalization characteristic for tape recorders. Broadly speaking, this characteristic divides the frequency range into three bands:

• Up to 50 Hz, corresponding to a time constant of 3.18 ms, the signal is highly and linearly amplified.
• Between 50 Hz and 1.326 kHz, corresponding to a time constant of 120 µs, for normal tape, or 2.274 kHz, corresponding to a time constant of 70 µs, for chromium dioxide tape, the signal is amplified at a steadily decreasing rate.
• Above 1.326 kHz or 2.274 kHz, as the case may be, the signal is slightly and linearly amplified. This characteristic is determined entirely by A1 (A1’). To make the amplifier suitable for use with chromium dioxide tape, add a double-pole switch (for stereo) to connect a 2.2 kΩ resistor in parallel with R3 (R3’). The output of A1 (A1’) is applied to a passive high-pass rumble filter, C3-R5 (C3’-R5’) with a very low cut-off frequency of 7 Hz. The components of this filter have exactly the same value as the input filter, C1-R1 (C1’-R1’). The second stage, A2 (A2’) amplifies the signal ´100, that is, to line level (1V r.m.s.).

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CHALLENGES DESIGN OF SWITCHING LED ELECTRONIC DIAGRAM

CHALLENGES DESIGN OF SWITCHING LED ELECTRONIC DIAGRAM

The LED WEBENCH® online design environment predicts and simulates the response of an LED to constant current while taking into account several potential design parameters that are new to designers of traditional switching regulators.

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2000 Chevrolet Chevy Blazer Wiring Diagram

2000 Chevrolet Chevy Blazer Wiring Diagram

(click for full size image)

The Part of 2000 Chevrolet Chevy Blazer Wiring Diagram: power distribution schematic, fuel pump relay control, fuel pump and sender, splice pack, fuel pump prime connector, ground distribution svhematic, underhood fuse block, vehicle control module, fuel pump relay control..

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Mains sockets switched automatically by a Control Socket, Up to 1000W switched power

This circuit consists of a Trailing Socket (also called Extension or Distribution Socket) or similar device where two, three or more sockets (depending on the box dimensions and on constructors needs) will be powered only when a current flows in the Control Socket. For example: if an electric drill is connected to the Control Socket, the Switched Sockets will be powered each time the electric drill is running. In this case, a lamp could be connected to a Switched Socket and will illuminate when the drill is operating.

Another example: a desk lamp could be connected to the Control Socket and a PC, a Monitor and a Printer could be connected to the Switched Sockets and will be running after the lamp is switched on. Switching off the lamp, all the above mentioned appliances will be automatically switched off. A further application is the control of a High Fidelity chain, plugging the Power Amplifier in the Control Socket and - for example - CD Player, Tape Recorder, and Tuner in the Switched Sockets.

Usually, trailing sockets are placed to the rear of the appliances, often in places not easily reachable, so, even if the socket has a switch, it is much easier to switch on and off the High Fidelity chain from the main amplifier itself. The same consideration is valid for computer-monitor-printer chains etc. Nevertheless, in this case, the use of a table lamp plugged in the Control Socket is almost mandatory, as explained below. In fact, this very sensitive circuit works fine when appliances having full breaking switches like lamps, drills, most power amplifiers, old radios, old TV sets, fans, almost all electrical household appliances etc. are plugged in the Control Socket.

This is because these devices have a switch that fully excludes the internal circuitry from the mains. Unfortunately, in modern devices like computers, monitors, CD players, recent radios and TV sets (usually powered by means of internal "switching" supplies), the power switch does not completely isolate the internal circuitry from the mains, as transient suppressors and other components remain on circuit. This causes a very small current to flow across the sensing circuitry, but sufficient to trigger the output Triac.

Therefore, the switched devices will remain always on, no matter if the control appliance is on or off. This could also happen when devices connected to the mains by means of plug-in power supply adapters are used as control appliances, due to their lack of a mains switch. In spite of this restriction, the circuit can be still useful, due to the high number and variety of devices allowing impeccable performance when they are plugged in the Control Socket.

Parts:

R1,R2_________100R 1/2W Resistors
C1____________100nF 630V Polyester Capacitor
D1 to D6_____1N5408 1000V 3A Diodes (See Notes)
D7__________TIC225M 600V 8A Sensitive Gate Triac (See Notes)
A commercial trailing socket to be modified or a self-made box with several sockets.

Circuit operation:

Six back-to-back power diodes are connected in series to the Control Socket. The current drawn by the device plugged into this socket when in the on state, flowing through the diode chain, causes a voltage drop of about 2V. This voltage, limited by R1, drives the Gate of the Triac D7 which, in turn, will switch the output sockets. C1 and R2 form a so called "Snubber network", helping to eliminate switching transients generated by inductive loads.

Notes:

• The circuit is sufficiently small to be embedded into some types of commercial trailing sockets, or a box with a number of sockets can be made at will.
• The diode types suggested in the Parts List for D1 to D6 will allow an appliance of up to about 500W power to be plugged in the Control Socket. Use BY550-800 diodes for up to 800 - 1000W.
• For less demanding appliances, 1N4007 diodes will allow up to 200W power.
• The Triac type suggested in the Parts List for D7 will allow a total power available to the Switched Sockets of more than 1000W. If you intend to drive loads of more than 500W total, please use a suitable heatsink.
• Wanting to drive less powerful loads, you can use for D7 a TIC216M (up to 800 - 1000W) or a TIC206M (up to 500 - 600W).
• Warning! The device is connected to 230Vac mains, so some parts in the circuit board are subjected to lethal potential! Avoid touching the circuit when the mains cord is plugged in!

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Wireles Temperature Monitor Has Data Logging Capabilities

You can use a local temperature sensor and an ASK (amplitude-shift-keying) transmitter/receiver pair to design a simple wireless temperature-monitoring system with data-logging capabilities. A microcontroller processes and displays the temperature reading to the user. The microcontroller’s onboard UART (universal asynchronous receiver/transmitter) also allows for data-logging applications.

 Figure 1. The MaX6577 temperature sensor and 315-MHz MaX1472 aSk transmitter form a wireless temperature-monitoring system.

Local-temperature sensor IC1 detects the ambient temperature at the device (Figure 1). The output of IC1 is a square wave with a frequency proportional to temperature in kelvins. ASK transmitter IC2 modulates the signal onto the carrier frequency of 315 MHz. You measure the output signal’s frequency with a frequency counter. The configured scalar multiplier is 1K/Hz when the TS1 pin connects to ground and the TS0 pin connects to VDD. This scalar multiplier is configurable with pins TS1 and TS0. ASK receiver IC3 demodulates the signal at the corresponding carrier frequency (Figure 2).

 

Figure 2. An ASK receiver with a microcontroller processes and displays temperature data.

Comparator IC4 connects to IC3’s RSSI (received-signal-strength indicator) with an internal peak detector. The external RC follows the peak power of the received signal and compares it with a predetermined, resistor-voltage-divider-generated voltage level. Lab experiments show that a threshold of approximately 1.57V generates a valid output on the data-out pin without receiving false readings. Adjust this threshold to the proper level for optimal performance. The comparator’s output is low when the received signal is weak or invalid and high when the received signal is adequate.

Microcontroller IC5 then measures and displays the value of the signal frequency using its integrated timer/counters and LCD-driver peripherals. A counter tracks the number of rising-edge transitions on the input temperature signal, and a timer tracks the elapsed time. After the timer’s 1-sec period elapses, an interrupt occurs. At that moment, the circuit reads the counter value, converts it to Celsius, and displays it on the LCD. The counter then resets to zero to restart the process. The timer automatically reloads once the timer interrupt occurs. UART0 also outputs the resulting temperature. A handheld frequency counter verifies the temperature reading.

The microcontroller monitors the signal power through P6.0, a general-purpose input pin. When the input is logic low, the LCD and UART output “no RF” to alert users of possible transmitter issues when the transmitter and receiver are too far apart from each other. The LCD connection follows the design in the IC’s evaluation kit (Figure 3). Using a look-up table in the data segment of the assembly code enables you to preserve the internal mapping of the display’s A through G segments. This preservation ensures that the display enables the correct segments. Using an RS-232 level converter, the UART output sends data to a data-logging device, such as a computer.

Figure 3. Maxim MAXQ2000-KIT Evaluation Kit.

Use the MAX-IDE assembler software to program the device during assembly. The MAXQJTAG board operates with the MAX-IDE to load the code onto the device. You can download the project files here. This design provides for a 1-sec temperature-refresh rate in 1°C increments, which is within the accuracy of IC1.

Downloads

Source Code (MAX-IDE assembler software) - download

MAXQ2000-KIT Evaluation Kit user manual and schematic - download

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Simple Short Wave Transmitter Circuit

Description 

This low-cost short-wave transmitter is tunable from 10 to 15 MHz with the help of ½J gang condenser VC1, which determines the carrier frequency of the transmitter in conjunction with inductor L1. The frequency trimming can be done with VC2. The carrier is amplified by transistor T4 and coupled to RF amplifier transistor T1 (BD677) through transformer X1*. The transmitter does not use any modulator transformer.

The audio output from condenser MIC is preamplified by transistor T3 (BC548). The audio output from T3 is further amplified by transistor T2 (BD139), which modulates the RF amplifier built around transistor T1 by varying the current through it in accordance with the audio signal’s amplitude. RFC1 is used to block the carrier RF signal from transistor T2 and the power supply. The modulated RF is coupled to the antenna via capacitor C9.

Circuit Diagram:

 For antenna, one can use a 0.5m long telescopic aerial. Details of RF choke, inductor L1 and coupling RFC1 is used to block the carrier RF signal from transistor T2 and the power supply. The modulated RF is coupled to the antenna via capacitor C9. For antenna, one can use a 0.5m long telescopic aerial. Details of RF choke, inductor L1 and coupling transformer X1, we used a ready made short-wave antenna coil with tuning slug (Jawahar make), which worked satisfactorily. We tested the transmitter reception up to 75 metres and found good signal strength.

 Author: EFY Mag
Source http://www.extremecircuits.net/2010/05/simple-short-wave-transmitter.html

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More And More White LED lights For Indoor Lighting

With the constant progress of LED technology, LED light gradually develop from the flags and show the development stage to lighting applications, and its long life, high efficiency and energy saving features have been recognized, white LED opened a window for "green light" a White LED interior lighting,  the indoor applications
 are being more and more increasingly widely used.
Many advantages of white LED interior lighting with white light LED used in a number of advantages. First, LEDs brightness and light color adjustable interior lighting to meet the requirements of color, lighting scenarios in the development of the market, with traditional light sources can not match advantage. Second, LED easy to dynamically control, in accordance with the needs of the user control the default cluster, and in some occasions require programming skills, can provide a reasonable solution for the intelligent management of indoor lighting and convenient. Third, LED compact, more decorative features, with the buildings by lighting the organic integration of default, to "see the light but not light" results. Fourth, LED, long life, no mercury, in line with the national "energy saving and emission reduction" policy requirements. Fifth, LED beam angle is within the absolute directional radiation for spotlights, downlights and other lamps, will help improve the next shot lumen ratio.
With the LED technology upgrade, show the effectiveness of power, cost reduction, both in the international market or domestic market, LED has begun to enter the business or department according to Ming Shi home lighting market, showing a good momentum of development. Broad application prospects in the indoor lighting LED prices are still very expensive at this stage, but because LED lamps have higher luminous efficiency, power loss can be cutting costs, while a longer life, can reduce replacement and maintenance expense, therefore, consider the development of white LED interior lighting direction, relative to traditional lighting methods, white LED light is the most important return on investment considerations.
After analysis shows that, compared to incandescent lamps, LED lamps of the investment recovery period is 1.7 years to 3.4 years; compared to halogen lamps, LED lamps of the investment recovery period is 1.7 years to 3.5 years. Thus, replacing incandescent and halogen lamps, LED controller, the application of white LED has a very attractive rate of return on investment. Compared to compact fluorescent lamps, the department applications, LED lamp investment recovery period is 4.5 years to 6.2 years; compared to straight tube fluorescent lamps and metal halide lamps, LED lamps do not have good performance of the investment payback period.
Although white LED lighting in the room to expand the application areas share constantly, but there are faced with many challenges. LED lights only need to keep dependents chip or package the relevant parts of the performance, but more of a focus on LED lighting, the composition of electronic technology, thermal management and optical technology.

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Review The Best Headlamps

If you want to free hands in outdoor nighttime activities, best led headlamp is necessary.

The French PETZL headlamps predominate in the headlamp market. There are two worth mentioning, one is SAXO that is cheapest, and now it is sold for ￥150 online, and the headlamps can also be used as a flashlight, and it is a little heavier with four AA batteries. Another is TIKA, is is 70 grams, and can be used 150 hours, the light actually begen to weak after using in 12 hours, 100 hours is almost impossible. With three AAA batteries can be participate 4,5 times  in weekend activities, do not replace the battery, sold ￥270 online, it is value. Another kind is Korean headlamps, which can light more than ten hours with two AA batteries, the price is about ￥150, it is also a good choice. In addition, Geting a tmart discount coupon, you will spend much less money on what you want such as cheap bike lights.


The role of headlamps at night lighting, as well as the role of warning the night, if the team pulled very close, you can open one every one will not affect the line of sight, but also saves power, the most common domestic headlamp plus three South Fu lighting battery probably about two hours; if the team pulled very far, before and after his teammates to rely on headlamps or sound transmission, headlamps at night is to provide some warning of the approach for reference:

1 The former and the latter can be looked at each other to prove the safety of his teammates;
2 The latter has a headlight flashing (call former teammate little suitable rest);
3 While the latter has two headlamps flashing (a dangerous situation, call former teammate).

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FM Transmitter Circuit

Nothing critical here. To get a bit of tuning out of the coil you could put a 4-40pF trimmer capacitor (optional) parallel over the 1 μH coil, L1. C1/C4 and C5/C6 are ceramic capacitors, preferably NPO (low noise) types. C2/C3 are electrolytic or can be tantalum types. The antenna is nothing more than a piece of 12" wire or a piece of piano wire from 6" to 12".

To find the signal on your receiver, make sure there is a signal coming into the microphone, otherwise the circuit wont work. I use an old mechanical alarm clock (you know, with those two large bells on it). I put this clock by the microphone which picks up the loud tick-tock. Im sure you get the idea... Or you can just lightly tap the microphone while searching for the location of the signal on your receiver.

Parts List

R1,R3 = 100K

R2 = 10K

R4 = 470 ohm

C1,C4 = 470pF

C2,C3 = 4.7μF, 16V, electrolytic

C5,C6 = 4.7pF

C7 = 4-40pF trimmer cap (optional, see text)

L1 = 1μH

Q1,Q2 = 2N2222, NPN transistor

Mic = Electret Microphone

B1 = 9 Volt, Alkaline battery

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Roma has developed a small E17 LED Light Bulb

Roma has developed a small LED bulb "LDA4L-G-E17" can support E17 lamp holder, compare with the original LED bulbs such as 12 volt LED lights, new products reduce the size of the power part, the shade of the hemispherical shape is more nearly spherical. LED light source module use the COB construct without mirror, the shape almost identical to  old-fashioned small krypton bulb to achieve 180°light distribution angle.

Prior to the disadvantage of small LED bulb is less luminous part of the light distribution angle narrow, dark horizontal and supply side. The brightness of the new product is equivalent to a 25W mini krypton bulb. The shade is made of the proliferation of Roma self-developed material that can be issued does not point to the warmth of light. The bulb the total luminous flux of 265lm, the power consumption of 4W. The light color than incandescent light color. Design life (the luminous flux dropped to 70% of the initial time) is approximately 40,000 hours. Pricing is open, expect the actual price of less than 2000 yen.

By the way, I konw where to buy the LED lighting such as LED light and best led flashlight at low price,

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Bass Booster Circuits

Bass Boost is today’s sound… whether it’s the driving, gut-vibration pulsation of disco, or the solid bass line of soft, hard, or laid-back rock. One way to get the modern bass-boost sound without running out and buying an all-new expensive piece of equipment is to use a Bass Booster between your guitar, electronic organ or what-have-you, and the instrument amplifier.

A bass booster strips the highs from the instrument’s output signal and amplifies low frequencies, feeding on “all-bass” sound to the instrument amplifier. Naturally, the bigger the speaker used with the amp, the more powerful the bass: use 15-inchers with the Bass Booster and you can rattle the windows. Bass Booster is powered by an ordinary 9 volt transistor radio battery. It can be assembled on a small printed board or on a veroboard using point to point wiring. The booster connects between your instrument and its amplifier through two standard RCA Jacks

Parts List:
P1 = 50K
P2 = 100K
R1 = 22K
R2 = 470K
R3 = 47K
R4 = 10K
R5 = 470R
R6 = 1K
Q1 = 2N2222
C1 = 2.2uF-25v
C2 = 100nF-63v
C31 = 00nF-63V
C4 = 3.3uF-25v
C5 = 470uF-25v
D1 = 5mm. Red Led
Q1 = 2N2222
B1 = 9v Battery
J1 = RCA Audio Input Socket
J2 = RCA Audio Output Socket
S1 = On-Off Switch
Bass Booster Circuits.
Connect your electronic guitar or other electronic instrument to input jack J1; Connect output jack J2 to your instruments amplifier’s normally-used input. With power switch S1 off, key S2 so the instrument feeds directly to the instrument amplifier. With P2 set full counter-clockwise (Off), turn power switch S1 on, key S2 once, and advance P2 for the desired Bass Boost level. To cut back to natural sound just stomp down on S2 and key the Bass Booster out. Don’t worry about leaving power switch S1 on for several hours of a gig. The circuit pulls less than 1mA from the battery, so battery will last many, many months.Bass Booster Circuit .

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