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Showing posts with label for. Show all posts
Safe Oscillator For Watch Crystals
This circuit was developed to allow watch crystals to be used in an existing CMOS oscillator circuit that was to run from a 12V supply. The problem is that these crystals only work up to a supply voltage of about 6V. Any more than that and the crystal will be over-driven, causing it to shatter. This circuit solves the problem by using LEDs 1 & 2 and a 470nF capacitor (C3) to limit the drive to the crystal to about 4V peak-to-peak. Note that it may be necessary to adjust C1 & C2 to ensure reliable start-up and stable oscillation with some crystals. However, the C1:C2 ratio should be maintained. As a bonus, the two LEDs both glow, giving a visual indication that the oscillator is working.
Editors note:
The relatively high values used here for capacitors C1 & C2 will load the crystal, which means that the oscillator will run at less than the nominal crystal frequency (32.768kHz).
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Editors note:
The relatively high values used here for capacitors C1 & C2 will load the crystal, which means that the oscillator will run at less than the nominal crystal frequency (32.768kHz).
Battery Charging Indicator For Mains Adaptor
Although you may well be the proud owner of the very latest NiCd battery charger, you may still come across the odd incompatible battery, for example, one having a rare voltage or requiring a much higher charging current than can be supplied by your off-the-shelf charger. In these cases, many of you will resort to an adjustable mains adaptor (say, a 500-mA type) because that is probably the cheapest way of providing the direct voltage required to charge the battery. Not fast and not very efficient, this rustic charging system works, although subject to the following restrictions:
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- You should have some idea of the charging current. In case you use an adaptor which is adjustable but of the unregulated, low output current type, you can adjust the current by adjusting the output voltage.
- You have to know if the current actually flows through the battery. A current-detecting indicator is therefore much to be preferred over a voltage indicator.
- To prevent you from forgetting all about the charging cycle, the indicator should be visible from wherever you pass by frequently. Using the circuit shown here, the LED lights when the baseemitter potential of the transistor exceeds about 0.2 V. Using a resistor of 1 ? as suggested this happens at a current of about 200 mA, or about 40 mA if R1 is changed to 4.7?. The voltage drop caused by this indicator can never exceed the base-emitter voltage (UBE) of the transistor, or about 0.7V. Even if the current through R1 continues to increase beyond the level at which UBE = 0.7 V, the base of the transistor will absorb the excess current. The TO-220 style BU406 transistor suggested here is capable of accepting base currents up to 4A. Using this charging indicator you have overcome the restrictions 2 and 3 mentioned above.
Rangkaian Power Supply for tube amplifier
Power supply for EL-34 tube is specially designed for the purposes of power supply at the push-pull amplifier with EL-34 tube as in article 35 Watt Tube Power Amplifier Push Pull before.
Power supply for EL-34 tube amplifier is made with transformers CT and 2 pieces diode as rectifier. Mechanical filters are applied in the power supply uses 3 levels. Power supply for tube power amplifier can deliver output voltages +220 VDC. Circuit details can be seen in the following figure.
Power supply for EL-34 tube amplifier is made with transformers CT and 2 pieces diode as rectifier. Mechanical filters are applied in the power supply uses 3 levels. Power supply for tube power amplifier can deliver output voltages +220 VDC. Circuit details can be seen in the following figure.
The above power supply circuit has a high output voltage so that need to be considered in the manufacture and perakitanya because electricity can tesengat (stun). Power Supply For Tube Power Amplifier With Diode EL-34 was created specifically for the power amplifier tube push pull EL-34.
Video Switch for Intercom System
Nowadays a lot of intercom units are equipped with video cameras so that you can see as well as hear who is at the door. Unfortunately, the camera lens is perfectly placed to serve as a sort of support point for people during the conversation, with the result that there’s hardly anything left see in the video imagery. One way to solve this problem is to install two cameras on the street side instead only one, preferably some distance apart. If you display the imagery from the two cameras alternately, then at least half of the time you will be able to see what is happening in front of the door. Thanks to the video switch module described here, which should be installed on the street side not too far away from the two cameras, you need only one monitor inside the house and you don’t need to install any additional video cables.
Video Switch for Intercom System Circuit diagram:
Along with a video switch, the circuit includes a video amplifier that has been used with good results in many other Elektor projects, which allows the brightness and the contrast to be adjusted separately. This amplifier is included because the distance between the street and the house may be rather large, so it is helpful to be able to compensate for cable attenuation in this manner. The switch stage is built around the well known 4060 IC, in which switches IC2a and IC2d alternately pass one of the two signals to the output. They are driven by switches IC2b and IC2c, which generate control signals that are 180 degrees out of phase. The switching rate for the video signals is determined by a clock signal from an ‘old standby’ 555 IC, which causes the signals to swap every 2 seconds with the speciļ¬ed com ponent values.
Naturally, this circuit can also used in many other situations, such as where two cameras are needed for surveillance but only one video cable is available.
Author :Jacob Gestman Geradts - Copyright : Elektor
Source : http://www.ecircuitslab.com/2012/02/video-switch-for-intercom-system.html
Great Brands for Good Prices on Auto Sound Systems
If you are one of the many people across the country considering a new auto sound system, there is a great deal of good news. First of all, it is very possible to find a good bargain on a nice sound system for your car, truck, or SUV if you are willing to shop online and install the system yourself. The problem often lies not in the cost of the system but the price of the installation. However, the cost of installation is well worth the dollar amount for many of us who really have no clue what to do as far as a project of that scope goes. I for one am among the electronically challenged and not really willing to risk my dash board for an experiment in frustration and failed electronics.
That being said, there are many who are either perfectly and wonderfully capable of installing a nice auto sound system or are fortunate enough to know someone or someone who knows someone who is. For you, finding a great bargain online is probably the best way to go-provided youve actually been in the shop and heard the sound quality of the particular system you are considering. I would never recommend buying a system youve never heard in action no matter how great of a bargain you think you are getting.
Ive found that some of these systems are not even as good as the minimal factory installed systems that come standard in most cars, trucks, or SUVs on the road today. You do not want to pay money and spend time and effort for the installation of a sound system that isnt at least better than the one you currently have.
There are times when you do not have to go with top of the line or well known brands in order to have a great sound or auto sound system. But there are some well-known, good quality makers of sound systems that do not cost a fortune. You can find some very nice sound systems that are not exactly top of the line but also offer great quality sound and excellent features (particularly when compared to factory installed sound systems).
If youre looking for a very nice auto sound system you can find some good ones by popular brands for well under $300. They have some that are even less expensive but those in the $300 range generally offer a little boost in quality from those that can be found at lower prices. Of course, this isnt always the case and you will occasionally find some excellent systems at even lower prices than this. You and you alone can tell if the system you choose is one that you will be happy with.
The thing to remember is to listen to the sounds of the systems then make your decision and compare prices. Alpine, Kenwood, and JVC all have excellent auto sound systems in a wide variety of price ranges. There are times with these systems that paying a little extra is worth it. If you are satisfied with the quality of a less expensive sound system however, there is no real reason why you should purchase a more expensive system. You are the one who will be riding in your car, truck, or SUV and it is only important what you think of the system you select.
Basic Components for a Home Theater
Many people never bother looking into purchasing a home theater through sheer fear of the decisions that may need to be made in the process. Many among these aren’t even sure of exactly which components are included in a home theater or which ones are needed in order to create an effective and entertaining home theater. For this reason, many people simply do not bother going through the process of looking at their options when it comes to these wonderful systems on the market today much less ever bother actually purchasing one.
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| Basic Components for a Home Theater |
If you are one of the many who has experienced some degree of confusion when it comes to the individual parts and pieces that are included in a home theater system and what they do, hopefully you will gain a better understanding once you’ve finished reading. The first thing to understand is that there are varying degrees when it comes to home theaters. The following components are the makings of a very basic home theater that will provide excellent functionality. They are not however inclusive of every possible piece or part that could make up a home theater system.
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| Speaker Setup |
Off to the basics, the first thing you’ll need when creating a home theater for your family to enjoy is a television. It might seem a little too obvious to some but I have yet to find a box kit that includes a television—mainly because the choice of screen is for many the most personal aspect of selecting a home theater. There are essentially three choices in today’s television market: front projector, rear projector, and plasma. There are variations within each of these and the prices fall anywhere from modest to quite costly. This is the component that most home theater owners spend the most time contemplating and it affects the types of components that will be most effective later on in terms of things such as high definition and other choices you can make.
A receiver is another important component. You will probably have a DVD player or recorder of some sort as part of your system; you may have a Tivo and cable box or satellite and will probably have speakers of some sort for your system. The receiver is the box you plug them all into—it receives all of this inputs and correlates it so to speak. This is the ultimate traffic director when it comes to your home theater and I suggest you spend a good portion of your home theater budget making sure that this is a good quality part.
Speakers are where your sound will flow. One of the best things to me about a home theater is the ability to experience surround sound very similar to what I experience in theaters while having the ability to put my feet up or snuggle under blankets (which simply can’t be achieved in a theater). Speakers come in all shapes and sizes and are also quite personal for some consumers while give and take for others. You can purchase these are part of a kit in order to make the selection process easier.
Finally, you have your DVD player or recorder. If high definition is important to you, you now have that option. If your television isn’t HD ready or capable, I’d pass and go for an older (less expensive) model of DVD player until something more up-to-date is called for. These items are a great start for any home theater and you can build, expand, and upgrade over time for an even better system. Enjoy!
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Related Circuit : Make 5.1 channel amplifier and speaker setup
Solid State Switch For Dc Operated Gadgets
This solid state DC switch can be assembled using just three transistors and some passive components. It can be used to switch on one gadget while switching off the second gadget with momentary operation of switch. To reverse the operation, you just have to momentarily depress another switch.
The circuit operates over 6V-15V DC supply voltage. It uses positive feedback from transistor T2 to transistor T1 to keep this transistor pair in latched state (on/ off), while the state of the third transistor stage is the complement of transistor T2’s conduction state.
Initially when switch S3 is closed, both transistors T1 and T2 are off, as no forward bias is available to these, while the base of transistor T3 is effectively grounded via resistors R8 and R6 (shunted by the load of the first gadget). As a result, transistor T3 is forward biased and gadget 2 gets the supply. This is indicated by glowing of LED2.
Circuit diagram :
Solid-State Switch For Dc-Operated Gadgets Circuit Diagram
When switch S1 is momentarily depressed, T1 gets the base drive and it grounds the base of transistor T2 via resistor R4. Hence transistor T2 (pnp) also conducts. The positive voltage available at the collector of transistor T2 is fed back to the base of transistor T1 via resistor R3. Hence a latch is formed and transistor T2 (as also transistor T1) continues to conduct, which activates gadget 1 and LED1 glows.
Conduction of transistor T2 causes its collector to be pulled towards positive rail. Since the collector of T2 is connected to the base of pnp transistor T3, it causes transistor T3 to cut off, switching off the supply to gadget 2) as well as extinguishing LED2. This status is maintained until switch S2 is momentarily pressed. Depression of switch S2 effectively grounds the base of transistor T1, which cuts off and thus virtually opens the base-emitter circuit of transistor T2 and thus cutting it off. This is the same condition as was obtained initially. This condition can be reversed by momentarily pressing switch S1 as explained earlier.
EFY lab note. During testing, it was noticed that for proper operation of the circuit, gadget 1 must draw a current of more than 100 mA (i.e. the resistance of gadget 1 must be less than 220 ohms) to sustain the latched ‘on’ state. But this stipulation is not applicable for gadget 2. A maximum current of 275 mA could be drawn by any gadget.
Author : Praveen Shanker - Copyright : EFY
Backlight Driver for WLED Display Circuit
This is a design circuit for WLED-display backlight driver circuit. This circuit can be used to power WLEDs by replacing the voltage-feedback network with a series current-sense resistor, R3, and the WLED strings. This circuit uses The TPS6108x that drive some series WLEDs in parallel for backlighting larger displays. This is the figure of the circuit;
The feedback of this circuit is The voltage across the current-sense resistor. This feedback provides regulation. This circuit uses 1.2-V feedback voltages. The power lost of this circuit because of R3 is Plost= Iwled*Iwled*R3 = 1.2V*Iwled. The TPS6108x converters is equipped with an SS pin that can provide variable soft startup for boosted voltage regulation applications. Beside that, The SS pin can be used to lower the FB-pin reference voltage and to reduce sense-resistor power loss in aWLED current-regulation application. The FB-pin reference voltage can be lowered by connecting a resistor, R1, from the SS pin to GND. WLED current can be calculated by following equation:
Iwled=(Iss*R1)/R3
Analog dimming is provided by A second resistor, R2, that is connected with the FET and Q1 in series connection and parallel connection with R1. Those connections will lower the regulated FB-pin voltage across the sense resistor.
[Schematic circuit source: Texas Instruments Application Note]
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