Output Devices

Objectives Upon completion of this unit the student will be able to: Describe electrical output devices Operate output devices using AC and DC current sources. Relate voltage value to output device operation

Background An electrical output device is any piece of equipment powered by electricity. Output devices convert electricity into light, sound, heat or motion. Output devices found in homes include lamps, clocks, radios, televisions, game systems, microwaves, corded drills and power tools. Output devices found in schools and businesses include intercoms, photocopiers, FAX machines, computers and other various kinds of machinery – all powered by electricity. People depend heavily on electrical output devices. When power goes out during a bad storm, people have trouble moving around their homes in the dark. Without clocks, they may be late for school or work (unless they use their cell phone as a back-up). They may not even be able to cook or heat/cool their home (without the use of a generator). If a business loses its electrical power, almost no work can get done.

Output devices are often called loads in circuits Output devices are often called loads in circuits. Bigger loads require more voltage to operate, just as heavier packages require more strength to lift. The source voltage must always be the same as or less than the load voltage rating. High voltages destroy small loads. Two basic kinds of output devices, lamps and LED’s change electricity into lights. Lamps provide light for indoor and outdoor spaces. They also help machine operators run a machine by indicating if the power is on or if a certain job is being done. The MB100 Kit uses a lamp to indicate that the power is on. A car dashboard has lamps to indicate if turn signals or high beam lights are on. Some cars also have lamps to indicate if the battery or oil pressure is low or if the engine is overheating. These indicator lamps help the operator (drive) know what is happening in the car.

An incandescent lamp (light bulb) uses electricity to heat us a thin piece of conducting wire called filament. The filament gets so hot that it glows brightly, producing light.

Incandescent Light Bulb Making of an incandescent light bulb

Fluorescent Lights Fluorescent lights work a little differently. These lights do not contain a filament. Instead, electricity flows through a conducting gas tube, making it glow. Fluorescent lights stay cooler that incandescent lamps because the gas in them glows easily. They also use less electricity than incandescent lamps. How it Made

LED LED’s also produce light, but not enough to light up a room until now. LED’s were usually just used as indicators lamps on machinery. The red numbers on a digital clock are formed by several long, thin LED’s. With technology we have been able to integrated multi-LED’s to create individual light bulbs. The name LED comes from light emitting diode. An LED is made from a semiconductor material. Just as lamps electricity is converted into light. Currently the LED lamp is popular due to it's efficiency and many believe it is a 'new' technology. The LED as we know it has been around for over 50 years. The recent development of white LEDs is what has brought it into the public eye as a replacement for other white light sources. Common uses: indication lights on devices, small and large lamps, traffic lights, large video screens, signs, street lighting(although this is still not widespread)

Advantages: -Energy efficient source of light for short distances and small areas. The typical LED requires only 30-60 milliwatts to operate -Durable and shockproof unlike glass bulb lamp types -Directional nature is useful for some applications like reducing stray light pollution on streetlights Disadvantages: -May be unreliable in outside applications with great variations in summer/winter temperatures, more work is being done now to solve this problem -Semiconductors are sensitive to being damaged by heat, so large heat sinks must be employed to keep powerful arrays cool, sometimes a fan is required. This adds to cost and a fan greatly reduces the energy efficient advantage of LEDs, it is also prone to failure which leads to unit failure -Circuit board solder and thin copper connections crack when flexed and cause sections of arrays to go out -Rare earth metals used in LEDs are subject to price control monopolies by certain nations -Reduced lumen output over time Large LED array designed for use as a street lamp. A massive aluminum heat sink is needed with the high wattage LEDs

OLED What is an OLED? OLED (Organic Light Emitting Diodes) is a flat light emitting technology, made by placing a series of organic thin films between two conductors. When electrical current is applied, a bright light is emitted. OLEDs can be used to make displays and lighting. Because OLEDs emit light they do not require a backlight and so are thinner and more efficient than LCD displays(which do require a white backlight). Uses: Lamps - short distance indoor lamps (produces a diffused light). Displays - small: phones and media devices and large: televisions, computer monitors Advantages: -The units are lighter than traditional LEDs and can be made thinner as well -OLEDs can provide a more energy efficient alternative to LCD computer and television monitors -Can be used in a myriad of new applications in which lighting technology has never been used before Disadvantages: -The cost of OLEDs is still high and each unit produces less lumens than a normal LED -The technology is still under development so the life of the OLED is being researched as new materials are used and tested each year. Until more research is done we will not know how these lamps with new materials compare with established technology.

LED and OLEDs LEDs and OLEDs - How it Works, Inventors The Future of Illumination and Display's

Motors A motor is a device which converts electrical energy into mechanical energy (rotating energy). There are two basic parts to an electric motor. An iron rod, or armature, is mounted to the shaft. The armature has wire wrapped it creating a coil. This wire is called the armature coil. The armature coil is mounted so it can rotate between the poles of a magnet.

Motors Current flowing through the coil turns the armature into a electromagnet. The magnetic field produced by the magnet then causes the coil to rotate. It rotates until its north pole is closest to the south pole of the magnet. If current always flowed in the same direction, the coil would not continue to rotate, however, a motor that runs on direct current (DC) has a commutator. The commutator is a reversing switch that rotates with the coil and reverses the direction of current every half turn of the coil. This reversal causes the poles of the electromagnet to switch. Now, two poles will be together, causing the coil to rotate another half turn. The commutator reverses the current direction again, and the coil rotates another half turn. All this happens very quickly, making the armature coil spin around creating electrical energy. This electrical energy causes the motor shaft to rotate. The rotation of the motor shaft creates the mechanical energy used to do work.

DC MOTOR DC Motor, How it works? Brushless DC Motor, How it works?

Buzzers & Speakers Buzzers and speakers are output devices that convert electricity into sound. A buzzer makes a constant sound. A speaker, on the other hand, can produce music and speech sounds.

Buzzers Both buzzers and speakers use electricity to make a diaphragm vibrate. In the buzzer, the diaphragm is usually a very thin sheet of semiconducting plastic. When electricity flows through the it, it vibrates and the buzzer sounds.

Speaker A speaker is a bit more complex. A magnet and an electrical coil are used to create motion in a speaker, just like a motor. The motion is very rapid vibration of a diaphragm to create sound, something like a buzzer. This diaphragm is shaped like a cone to help make many different kinds of sounds. Without other electrical components, a speaker can make only a buzzing sound. This sometimes is called “white noise”.

Speaker & Microphones The difference between a speaker and a microphone is that a speaker is used to produce sound and a microphone is used to pick up sound. They are basically made the same way. Both can reproduce or pick up sound. Speakers, however, cannot run on DC voltage. DC voltage will damage the speakers. The MB100 Kit is protected so that a student cannot damage the speaker using DC voltage.