It is unnecessary for the customer to stop the use

It is unnecessary for the customer to stop the use of cell phone jammer .
There are some mobile phones which are having many advanced features and so their cost is high. However, you can find several cheap mobile phones available in the UK market online mobile phone shops give you the latest brands from the prominent manufacturers at a very competitive price offer. The worst of it is that others use it to send objective answers to those in the examination hall, which may not be correct at the end of the day. This can end the students career if caught, as exam malpractice is a punishable offense.
In the end, I had to fork out a sum of $200 to clean up the mould and to get the mobile phone functioning again some 3 months later, because by the time it was repaired, I was back in Australia and had to get a friend to retrieve it for me.
Now, the lesson of this experience is simple - Read the fine print of your warranty that comes with every purchase of your mobile phone.Just because what you buy is an established brand, never ever assume that its design is built to keep out the moisture or that it would not become mouldy inside, not even if it is a Sony. I was told it was standard policy to treat mouldy conditions within the mobile phone as a result of improper use of the mobile phone, rendering any warranty void.
While the mobile phone was a newer model, and I had always considered it an important part of my professional tools, there was never any case of mis-use of the mobile phone that could have allowed water to seep inside the mobile phone. If there was any mould, it would only have been the change of weather from the country of purchase and the country of use.
Let my experience be your guide, and pay attention to the fine print of your warranty so that you are sure whether mouldy conditions are covered under the warranty especially if you are going to use a mobile phone purchased overseas where there are different climatic conditions.
Avoid buying a lemon when you are shopping for a newer mobile phone. Visit your local Australian and New Zealand mobile phones online store Aussie Mobile Phones Store [http://aussie-mobilephones.reviewadvisors.info] for free resources and to view the latest in mobile phones for the Australian and New Zealand region. Updated daily, the website has a vast array of mobile phones on offer for the discerning user, and provides an online shopping experience with a difference.
Secondary school is a term used to describe an educational institution where the final stage of schooling, known as secondary education and usually compulsory up to a specified age, takes place. It follows elementary or primary education, and may be followed by university (tertiary) education.

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Bipolar Power supply for Battery Instruments Circuits Diagram

Bipolar Power supply for Battery Instruments Circuits Diagram. To generate regulated ± 5-V supplies from a pair of dry batteries, the circuit of Fig. 1 is commonly used. In order to give protection from inadvertent reverse connection of a battery, a diode in series with each battery would produce an unacceptable voltage drop. The more effective approach is to fit diodes Dl and D2 as shown in Fig. 2, in parallel with each battery. 

When the supply is switched off, there is the risk of a reverse bias being applied across the regulators, if there is significant inductance or capacitance in the load circuit.Diodes across the regulators prevent damage. When the power supply is switched on, the two switches do not act in unison. There is a probability that one or the other regulators will be latched hard off by the other. To prevent this, D3 and D4 are Zener diodes so that ± 5-V rails are pulled up by the batteries until the regulators establish the correct levels.

Bipolar Power supply for Battery Instruments Circuits Diagram

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Simple 1 5V Supply For Zn416E Circuits Diagram

This regulator can be used with a +6-V source to supply ZN416E low-voltage TRF radio-receiver IC the necessary +1.5 V. R3 sets output voltage.


Simple +1.5V Supply For Zn416E Circuits Diagram

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Short Circuit Protection For Balanced Supply Rails

This circuit was designed to protect a dual rail power supply from shorts across the two rails. It uses an optocoupler to monitor each supply rail, with the internal LEDs powered from ZD2 and ZD3 and the associated resistors. While the LEDs are on, the optocouplers internal transistors are both turned on which ensures that transistor Q1 is on and relay RLY1 is energised. If either rail is short-circuited, the associated optocoupler is turned off, robbing Q1 of base current and the relay then drops out to disconnect the supply rails. Operation is restored by pressing the reset button. The value of ZD1 and the associated resistor should be chosen to suit the supply and relay coil voltages.

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Quick Counter For Young Children

This circuit is a toy to encourage young children to count. Power is turned on by switch S1, then S2 is closed. This makes nine LEDs flash slowly. S2 is then opened and the LEDs go out. Pressing push-button PB1 turns on a random number of LEDs - briefly - during which time they are to be counted. The number counted can be checked by pressing PB2 which turns the same LEDs on for as long as needed. Then repeat. The circuit works as follows: IC3 is a 4049 hex inverter connected as three oscillators running at different rates. It is turned on by closing switch S2a. The clock pulses from IC3 drive both halves of IC1 and one half of IC2, both being 4015 dual 4-stage shift registers. Each shift register has four outputs which go high in order: 1, 1 and 2; 1 and 2 and 3; 1 and 2 and 3 and 4. However as output 4 is connected to the reset line of its own half - the shift register resets to zero. Outputs 1, 2 & 3 of all three shift registers are connected to nine LEDs, the cathodes of which go to a common rail.

This rail is connected to ground via S2b when switch S2 is closed. When S2 is opened the three oscillators stop but a random number of LEDs is still connected to the high outputs of the 4015s. That number can be viewed briefly by pressing PB1 which pulses the 7555 timer in monostable mode, to give a short duration output which drives Q1 and connects the LED cathodes to 0V. The viewing time is adjustable by VR1. Checking a count is done by pressing PB2 which holds the same LEDs on as long as desired. The LEDs are set in a 3 x 3 grid with the connection scattered, ie, the first row is not the three LEDs from the first half of IC1. Note that, unlike the usual dice, a number such as 5 can appear in many formats, so pattern recognition is no help. Also note that this is not a nine output true dice - because the numbers do not come up with equal frequency.

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Internal Resistance Tester For Batteries

This circuit is designed to check the condition of lead-acid and gel cell batteries with capacities greater than 20Ah. It switches a load of about 18A at a rate close to 50Hz so that the internal resistance of the battery can be measured using a digital multimeter across the battery terminals. The measured AC voltage in millivolts divided by 10 (ie, a shift of the decimal point) is approximately equal to the batterys internal resistance in milliohms. As shown, the circuit is quite straightforward and is based on two 555 timer ICs (IC1 & IC2) and power Mosfet Q1. IC1 operates as a monostable timer with a period of 10s.

When switch S1 (Test) is pressed, IC1s pin 3 output goes high for 10s and this enables IC2 which operates as a 50Hz astable oscillator. IC2 in turn drives power Mosfet Q1 which is connected across the load in series with three 0.22W 50W resistors. IC2 then turns off again after 10s - ie, at the end of the monostable timing period. LED1 provides power indication when the circuit is connected to a battery, while LED2 (green) comes on during the test period. The thermostat is not necessary unless the unit is to be used repeatedly (the Jaycar ST-3823 70°C unit is suitable) and you want to protect the output circuit against overheating.

Note:

The power Mosfet does not need cooling but the thermostat and the 0.22W 50W resistors should all be mounted on an aluminium heatsink at least 2mm thick. In practice, the internal resistance of car batteries can vary from about 15mW down to about 3mW. Before testing the battery, check that the electrolyte level is correct and that the voltage across its posts exceeds 12.5V for a nominal 12V battery; ie, close to full charge. That done, switch on the cars headlights and measure the DC voltage between each battery post and its connecting terminal. It should be less than 10mV in both cases; if not, the terminals need cleaning. Once youve done that, you can turn off the headlights, connect the tester and proceed with the internal resistance test. Be sure to connect the multimeters test probes directly to the battery posts, to read the internal resistance (not the battery terminals).

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LED Lighting For Consumer Unit Cupboard

The consumer unit (or ‘electricity meter’) cupboard in some older houses is a badly lit place. If the bell transformer is also located in this cupboard, it may be used to provide emergency lighting by two high-current LEDs. These diodes are powered via a small circuit that switches over to four NiCd batteries when the mains fails. The output voltage of the bell transformer is rectified by bridge B1 and buffered by capacitor C1. The batteries are charged continuously with a current of about 7.5 mA via diode D1 and resistor R2. The base of transistor T1 is high via R3, so that the transistor is cut off. When the mains voltage fails, C1 is discharged via R1; when the potential across it has dropped to a given value, the battery voltage switches on T1 via R3 and R1, provided switch S1 is closed. When T1 is on, a current of some 20 mA flows through diodes D4 and D5. The light from these LEDs is sufficient to enable the defect fuse or the tripped circuit breaker to be located.

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Temperature Sensitive Switch For Solar Collector

This circuit can be used to turn the pump on and off when a solar collector is used to heat a swimming pool, for example. This way the water in the collector has a chance to warm up significantly before it is pumped to the swimming pool. A bonus is that the pump doesn’t need to be on continuously. The basis of operation is as follows. When the temperature of the water in the solar collector is at least 10 °C higher than that of the swimming pool, the pump starts up. The warm water will then be pumped to the swimming pool and the temperature difference will drop rapidly. This is because fresh, cool water from the swimming pool enters the collector. Once the difference is less than 3 °C the pump is turned off again. R10/R1 and R9/R2 each make up a potential divider. The output voltage will be about half the supply voltage at a temperature around 25 °C. C7 and C8 suppress any possible interference. The NTCs (R9 and R10) are usually connected via several meters of cable, which can easily pick up interference. Both potential dividers are followed by a buffer stage (IC1a/IC1b). IC1c and R3, R4, R5 and R6 make up a differential amplifier (with unit gain), which measures the temperature difference (i.e. voltage difference).

When both temperatures are equal the output is 0 V. When the temperature of the solar collector rises, the differential amplifier outputs a positive voltage. This signal is used to trigger a comparator, which is built round an LM393 (IC2a). R7 and P1 are used to set the reference voltage at which the comparator changes state. R8 and P2 provide an adjustable hysteresis. R11 has been added to the output of IC2a because the opamp has an open collector output. A power switch for the pump is created by R12, T1 and Re1. D1 protects T1 against voltage spikes from the relay coil when it is turned off. A visual indication of the state of the controller is provided by IC4 (UAA170), a LED spot display driver with 16 LEDs. The reference voltage for the comparator is buffered by IC1d and fed to input VRMAX of the UAA170. R20/D21 and R23/D22 limit the input voltages of IC4 to 5.1 V, since the maximum permissible input voltage to the UAA170 is 6 V. When there is no temperature difference, LED D20 turns on.

Circuit diagram:

Temperature Sensitive Switch Circuit Diagram For Solar Collector

As the temperature difference increases the next LED turns on. The full scale of the LED bar is equal to the reference voltage of the comparator. This means that when the last LED (D5) of the UAA170 turns on, the comparator switches state. This is also indicated by D2. The power supply has been kept fairly simple and is built around a LM7812 regulator. The circuit is protected against a reverse polarity at the input by D3. You have to make sure that the input to the regulator is at least 15 V, otherwise it won’t function properly. There are a few points you should note regarding the mounting of the NTCs. NTC R9 should be placed near the output of the solar collector. You should choose a point that always contains water, even when some of the water flows back a little. NTC R10 should be mounted inside the filter compartment (where it exists), which continually pumps the swimming pool water.

This will give a good indication of the temperature of the water. The way the circuit has to be set up depends how it has been installed and is very much an experimental process. To start with, set hysteresis potentiometer (P2) halfway. Then set the reference voltage to about 1.5-2 V with P1. On a sunny day you can measure the voltage difference to get an idea as to which reference voltage needs to be adjusted. The hysteresis setting determines how long the pump stays on for, which is until the minimum temperature difference has been reached.

Author: Tom Henskens - Copyright: Elektor Electronics

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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.

Circuit diagram:

 Cassette Deck Playback Amplifier Circuit Diagram

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.).

Source : www.extremecircuits.net

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Home Network for ADSL

The increased availability of fast ADSL Internet connections has made it more attractive to install a small RJ45 Ethernet network in the home. Not only can you exchange files between computers, you will also have fast Internet access for everybody! This does of course require an ADSL modem with a router. It’s not possible to use a simple USB modem on its own. For laptops we recommend wireless Ethernet connections. If you find the laying of cables too difficult or inconvenient you can also add wireless capabilities to ‘ordinary’ PCs. You should bear in mind that the range of wireless connections could sometimes be disappointing. When a network is set up round a router you should use a star configuration for the cabling. This means that only a single PC is connected to each router socket.
The connecting cable may have a maximum length of 90 m and usually terminates at a connection box. You should use a CAT5 cable with 8 conductors for this, which is suitable for speeds up to 100 Mb/s. The 8 conductors are arranged in 4 pairs, with each pair twisted along the length of the cable. It is extremely important that the wires of each pair are kept together and that they are kept twisted as much as possible. At the connector ends you should therefore make sure that the non-twisted sections of the cable are kept as short as possible, at most a few centimetres. Should you fail to do this you may find that the network won’t operate at the full rated speed or possibly cause interference. The wiring itself is very simple. Connect the plugs to the cables such that each pin connects to the corresponding pin at the other end.

So pin 1 to 1, 2 tot 2 and so on. This also applies to all patch leads between the connection boxes and PCs (or if you prefer, the cable can go directly to the PC, without a connection box). It is only when two computers are connected directly together without a router that a crossover cable is required. The plugs are attached to the cable using a special crimping tool. It is also possible without the tool, using just a screwdriver, but this isn’t easy and we don’t recommend that you try it. The wires in the cable have different colours and there are no official standards in Europe how you use them (EN50173). However, the colour code in the American T568B standard is often used:

• orange/white
• orange
• green/white
• blue
• blue/white
• green
• brown/white
• brown

The coloured/white wires and the solid coloured wires alternate nicely. For Ethernet cabling you only need connections 1, 2, 3 and 6. The central contacts on pins 4 and 5 are in the middle of the green pair and may be used for analogue telephones. You then have to make sure that 4 and 5 aren’t connected to the Ethernet plugs because the voltages found on analogue telephone lines are high enough to damage an Ethernet card and/or router. Wires 4 and 5 should then be routed to an RJ11 telephone socket. We don’t recommend it, but it is possible. It is also possible to pass ISDN signals through the same RJ45 plugs and cabling. In this case you can’t use the same cable for both Ethernet and ISDN, since the latter uses pins 3/6 and 4/5.

If you use patch cables it helps to keep things organised by using coloured cables. Blue for Ethernet (red for a crossover cable), yellow for analogue telephones and green for ISDN. Sticky labels or coloured cable markers can also be used for identification when you can’t get hold of coloured cables. A new standard has recently been introduced, although you probably won’t use it in the home for a while. Since around two years ago you can also use a GG45 connector, which is compatible with RJ45. This has 4 extra contacts and is suitable for speeds up to 600 Mb/s (Category 7/Class F).

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Battery Charger for vehicles

We hope this circuit will help you to understand the action of a Battery charger. Lot of people has no idea how simple it is. In this circuit we have used two diodes, one capacitor and a transformer.  Ammeter is not necessary but it helps us to determine the charging level of the battery.

When you finish the circuit just connect the positive and negative wires to the battery terminals. Make sure to connect the positive wire to the positive terminal of the battery. When the charging is going on you can see 1 to three amps in the ammeter but when the charge is finish or the circuit is disconnected the reading should be zero.

We have used two diodes for full wave rectification and a capacitor is used for DC smoothing. Capacitor is not necessary but we recommend you to use the capacitor always.

The charging time will depend on the size of the transformer, means if we connect a big transformer that means battery gets a higher current ( more than 5A ). Incase if you want to use a higher current transformer use big diodes to pass the current accordingly.

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Traffic Lights For Model Cars Or Model Railways

Kids these days seem to have most things you see in the toy shops, so if you have a son or grandson who has a collection of cars, here is something he will really appreciate. And it will be really special as you will be giving something made by you - a set of traffic lights for his cars. This traffic light circuit uses a 555 timer IC as the master timer. The 220kO timing resistor and 10µF capacitor control the timing pulses, giving a period of about three seconds. The 3-second output pulses are used to clock a 4017 decade counter whose outputs directly drive the green, orange and red LEDs. To obtain a longer time for the red and green lights compared with the orange light, two outputs are ORed using 1N4148 diodes for the red and green LEDs, while the orange is driven by one output only.

This gives about 6 seconds for the red and green LEDs and 3 seconds for the orange. When power is first applied, the RC network connected to pins 1 and 15 of IC2 resets the 4017 and the green LED cycle begins. The orange and red cycles follow and at the end of the red cycle, pin 1 will go high to reset the 4017 to start the green cycle all over again. You can experiment with the cycle times by adjusting the 220kO resistor or by combining more or less 4017 outputs to achieve different ON times for the three LEDs.

The circuit is designed to be powered by a 9V battery and this is the maximum voltage that is recommended. This is because the LEDs are directly driven by the 4017 with no current limiting resistor being used. The 4017 naturally limits the current that it can supply to 15mA. An extension of this project would be to make a second set of lights for the cross traffic. Here you would use the same 555 as a master timer for both sets of lights (otherwise chaos would ensue) and a separate 4017 to drive the three extra LEDs. Of course, you would have to take care and ensure that green and orange outputs on each set of lights correspond with red on the other!

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Reflector For Pedestrians

Pedestrians run grave dangers when, in badly-lit areas, they cross a road at night in dark clothing, because this means that car drivers may see them too late There are special armbands available that reflect the light of oncoming traffic, telling the driver that there is someone on the road. It is also possible to make an active means of warning car drivers or motorcyclists that you’re crossing the road. It consists of a flat enclosure that houses two PP3 (6AM6; MN1604; 6LR61) 9 V batteries, and the small circuit shown in the diagram. Glue a piece of self-adhesive, reflecting tape (available in the motor trade) on the lid of the enclosure and drill a 10 mm hole in the centre of it.

Fit a 6 V bulb in a suitable holder in the 10 mm hole. Fit a suitable clip and, optionally an on/off switch, at the rear of the enclosure. See Figure 1. The electronic circuit consists of a light-sensitive switch, composed of P1, a photo-conductive cell, LDR, and IC1a; an inverter, IC1b;, an oscillator, IC1c with R1 and C1; a buffer, IC1d with R2 and T1; and a 6–9 V bulb that draws a current of not more than 50mA. The photo-conductive cell (or light-sensitive resistor) should be exposed to ambient light, but not to the light bulb, of course. Its sensitivity is set with P1.

When the ambient light causes a potential drop across the LDR that is below the level set with P1, IC1a changes state, so that its output goes low, whereupon the output of IC1b goes high, which actuates the oscillator. The buffer then switches the light bulb on and off in the rhythm of the oscillator. Optionally, the light bulb may be replaced by a light-emitting diode rated at 1 cd or higher, and bias resistor. Make sure, however, that the current through the transistor does not exceed its rating of 50mA. The two 9V batteries should be connected in parallel. The circuit needs a supply of 3–12V.

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LED Flasher For the Christmas With NE555

I know now you are getting ready for your christmas.So I thought to give you a useful circuit.This is a LED flasher circuit .You can use this to decorate your christmas star or your crib.I have used here NE555 commen IC.this circuit works with 9v power supply.

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Power Amplifier for Audio Laptop

Frequently, the sound yield from a laptops fabricated-in speakers is flat. A capacity intensifier is needed to get an elevated volume. Here is an effortless circuit to intensify the laptops sound yield. 

The circuit is constructed around capacity enhancer IC LA 4440 (IC1) and a few alternate parts. LA4440 is a double channel sound capacity speaker. It has level twisting over a vast run of flat to towering frequencies with exceptional channel detachment. Inbuilt double channels prepare it for stereo and extension speaker provisions.

image : http://circuitschematicelectronics.blogspot.com/2011/02/2-x-20-watt-car-amplifier.html

In double mode LA4440 gives 6 watts for every divert and in scaffold mode 19-watt yield. It has swell denial of 46 dB. The sound impact might be grasped by utilizing several 6-watt speakers. Associate binds 2, 6 and ground of IC1 to the stereo jack which is to be utilized with the laptop. Collect the circuit on a customary-reason PCB and encase in a suitable bureau. The circuit works off managed 12V capacity supply. It is suggested to utilize sound enter socket in the circuit plank. Utilize a decent hotness-sink for LA4440.

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