Parallel Port

The parallel port is often used in Computer controlled robots, Atmel/PIC programmers, home automation, ...etc. The primary use of parallel port is to connect printers to computer and is specifically designed for this purpose. Thus it is often called as printer Port or Centronics port (this name came from a popular printer manufacturing company 'Centronics' who devised some standards for parallel port). You can see the parallel port connector in the rear panel of your PC. It is a 25 pin female (DB25) connector (to which printer is connected). On almost all the PCs only one parallel port is present, but you can add more by buying and inserting ISA/PCI parallel port cards.

In addition, one input can also be used to create a processor interrupt. This interrupt can be enabled and disabled under program control. Reset from the power-on circuit is also Ored with a program output point, allowing a device to receive a power-on reset when the processor in reset. The input/output signals are made available at the back of the adapter through a right-angled, PCB-mounted, 25-pin, D-type female connector. This connector protrudes through the rear panel of the system, where a cable may be attached. When this adapter is used to attach a printer, data or printer commands are loaded into an 8-bit, latched, output port, and the strobe line is activated, writing data to the printer. The program then may read the input ports for printer status indicating when the next character can be written, or it may use the interrupt line to indicate "not busy" to the software. The output ports may also be read at the card's interface for diagnostic loop functions. This allows faults to be isolated between the adapter and the attached device.


Pin Assignment

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BNC Connectors

The purpose of a BNC Connector is for connecting coaxial cables. BNC Connectors are a type of RF Connector named after Paul Neill of Bell Labs and Carl Concelman. There are 50 and 75 ohm versions of the BNC Connector. The BNC connector as originally designed had dielectric material (other than air) in its interface area. Based on the impedance equation for coaxial transmission lines, the 50 Ohm BNC was 50 Ohm in its interface area (no surprise there).

The primary use of BNC Connectors is for digital and analog video connections. BNC Connectors are also used for radio antenna connections and commonly used in the commercial aviation industry.

Similar Connectors to BNC Connectors

Sometimes BNC Connectors are used as an alternative to RCA Connectors. TNC Connectors are also similar to BNC Connectors. The TNC Connector can handle microwave frequencies though. MHV Connectors and SHV connectors are used for higher voltages.

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SMA Connectors

SubMiniature Version A, or SMA Connectors, are used for connecting coaxial cables to allow for transmission from DC to 18 GHz. An SMA Connector uses a quick connect/disconnect bayonet coupling or threaded connector design.

Semi-precision, high-frequency design is ideal for microwave systems and subsystems. Some SMA Connectors have durable, brass bodies with silver plating. Other SMA connectors can be constructed from stainless steel or heat-treated Beryllium copper.

SMA Connector Statistics

• 50 Ohm Nominal Impedance
• Voltage Rating: 500 - 1000 Volts RMS
• Frequency Range: Up to 12.4 GHz

SMA connectors are commonly used in radar and test equipment applications.

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Electronics Circuit Wallpaper

Description

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Understanding Ohm’s Law

Say that you’re wiring a circuit. You know the amount of current that the component can withstand without blowing up and how much voltage the power source applies. So you have to come up with an amount of resistance that keeps the current below the blowing-up level.
In the early 1800s, George Ohm published an equation called Ohm’s Law that allows you to make this calculation. Ohm’s Law states that the voltage equals current multiplied by resistance, or in standard mathematical notation : V = I x R

Taking Ohm’s Law farther
Remember your high school algebra? Remember how if you know two things (such as x and y) in an equation of three variables, you can calculate that third thing? Ohm’s Law works that way; you can rearrange its elements so that if you know any two of the three values in the equation, you can calculate the third. So, here’s how you calculate current: current equals voltage divided by resistance, or
I = V/R
You can also rearrange Ohm’s Law so that you can calculate resistance if you know voltage and current. So, resistance equals voltage divided by current, or
R=V/I
So far, so good. Now, take a specific example using a circuit with a 12-volt battery and a light bulb (basically, a big flashlight). Before installing the battery, you measure the resistance of the circuit with a multimeter and find that it’s 9 ohms. Here’s the formula to calculate the current:
I = V/R = 12 volts/9 ohms=1.3 amps

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Electronics Tools to measure things

When building or troubleshooting a circuit, you need to make measurements to check that parts are working the way they should and that you designed and built the circuit correctly. Tools that you can use to measure things include a multimeter, an oscilloscope, and a logic probe.

We’ll take a moment to briefly tell you what you can use a multimeter for because it’s the measuring tool that you buy first and possibly the only one that you ever need.

Say you build a circuit, and you’ve just turned it on. What if the circuit doesn’t work? With a multimeter, you can find out which part of the circuit is causing the problem. You can measure voltage, resistance, and current at different points on the circuit. For example, if there are 5 volts at one location on the circuit and further along at another location your voltage suddenly drops to 0 volts for no logical reason you can make a good guess that your problem lies between those two locations. You can then check (after the power is disconnected, please!) for loose wires or damaged parts between those two locations.

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Electronics Tools to build things

One of the best things about building electronics projects is that you get to tinker with tools and parts and see what you can make from them. You use some tools to put the circuits together and some tools to check out how the circuits you build are working.
You’re probably glad to hear that you don’t need that many tools to get started. You just need a wire cutter, needle-noise pliers, a wire stripper, and a few screwdrivers to get started with the projects.
If you design a circuit that you want to make more permanent, you need to get a soldering pencil (also called a soldering iron) to attach the elements of a circuit together.

As you work with projects, no doubt other miscellaneous tools pop up that you may want to get your hands on. You can use a magnet to retrieve screws and other tiny things that you inevitably drop in hard-to-reach places, for example.

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Sensing with sensors

Certain electrical components generate a current when you expose them to light or sound. You can use the current generated, together with a few of the components listed in the previous sections that control electricity, to turn on or off electronic devices, such as light bulbs or speakers.
Motion detectors, light sensors, microphones, and temperature sensors all generate an electrical signal in response to a stimulus (motion, light, sound, or temperature, respectively). These signals can then be used to turn other things on or off. A high signal level might turn something on and a low signal level turn something off. For example, when a sales person walks up to your house, a motion detector can turn on a light (or better yet, sound a general alarm).

These signals take different forms, depending on the component supplying them. For example, a microphone supplies an AC signal, and a temperature sensor supplies a DC signal.

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Controlling electricity even better (ICs)

Integrated circuits, or ICs, are components that contain a whole bunch of miniature components in one device that may not be much bigger than an individual component. Because each IC contains many components, one little IC can do the same job as several individual parts.
An audio amplifier is one example of an IC. You can use audio amps to increase the power of an audio signal. For example, if you have a microphone, its small output signal is fed through an audio amplifier to make a strong enough signal to power a speaker.

Another type of IC used in electronics projects is a microcontroller, a type of integrated circuit that you can actually program to control cool gadgets like robots.

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Solar cells

Solar cells are a form of semiconductor. Like batteries, solar cells have wires attached to two terminals. Shining light on a solar cell causes an electric current to flow. The current is then conducted through wires to devices, such as a calculator or a garden light beside the pathway to your front door.
Using a calculator containing a solar cell, you can demonstrate that the calculator depends on the light shining on the solar cell for its power. Turn the calculator on and punch some numbers into the screen (choose a nice big number, like your income tax).

Now, use your thumb to cover the solar cell. (The solar cell is probably near the top of the calculator in a rectangular area with a clear plastic cover.) After you’ve covered up the solar cell for a moment, the numbers fade away. Take your thumb off the solar cell, and the numbers reappear. Things powered by solar cells need light to work.

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