Douglas Engelbart, Augmenting Human Intellect (1962) http://www.nexusphiladelphia.org/unintendeduses.html http://scottburnham.com/?p=75 http://www.vimeo.com/1595196?pg=embed&sec=1595196 Primary source of this presentation is Forrest M. Mims, III's Getting Started in Electronics, Radio Shack, 1983 Other sources: http://en.wikipedia.org/ http://www.energyquest.ca.gov/how_it_works/transformer.html ELECTRONICS is the study and application of ELECTRONS, their behavior and their effects. The simplest applications for electrons are straightforward AC and DC circuits in which a current is used to power lamps, electromagnets, motors, solenoids and similar devices. What takes electronics far beyond these basic applications is the ease with which streams of electrons can be controlled and manipulated... The only difference between a bolt of lightening and the spark between you fingers and a door knob on a dry day are quantity. Both are electricity. All matter has electrical properties. That's why scientists, engineers, artists and hobbyists have been able to invent thousands of gadgets that generate, store, control and switch electricity. These devices have combined to carry us into the digital age. Electricity is an essential ingredient of matter. The best way to understand the nature of electricity is to examine the smallest component of every element, the atom. Simplest atoms are Hydrogen, Helium and then Lithium. Lithium Atoms have 3 electrons that encirlce a nucleus of 3 protons and 4 neutrons - Electrons have a negative electrical charge + Protons have a positive electrical charge 0 Neutrons have no electrical charge Normally an atom has a en equal number of electrons and protons. The equal charges cancel to give the atom no net electrical charge. An ion is an atom which has lost or gained one or more electrons, giving it a positive or negative electrical charge. Electrons - Free Electrons can rest on a surface (static electricity) or move at near the light of speed (186,000 miles per second) through metals, gases and a vacuum. A stream of moving electrons is called an ELECTRICAL CURRENT. Resting electrons can quickly form an electrical current if placed near a cluster of positive ions. The positively charged ions will attract the electrons which will rush in to fill the "holes" or voids left by the missing electrons. Electrons (negative ions) will flow to positive ions. A fundamental rule of electricity is LIKE CHARGES REPEL AND UNLIKE CHARGES ATTRACT ELECTRICAL CURRENT Materials through which electrons travel are conductors CONDUCTORS include Silver, Gold, Iron, Copper... Matrials through which electrons travel poorly or not at all are insulators INSULATORS include Glass, Plastic, Rubber, Wood... A solid conductive metal contains a large population of free electrons. These electrons are bound to the metal but not to any individual atom. Even with no external electric field applied, these electrons move about randomly but, on average, there is zero net current within the metal; the number of electrons moving from one side to the other is on average equal. Electrical Current flows from a region of high charge or potential to a region of low potential. Direct Current Electricity An electrical current can flow in either of two directions through a conductor. If it flows in only one direction, whether steadily or in pulses, it's called DIRECT CURRENT (DC). In circuit building it's important to be able to specify the quantity and power of a direct current. Here are the key terms: CURRENT (I) - current is the quantity of electrons passing a given point. The unit of current is the AMPERE. One ampere is 6,280,000,000,000,000,000 (6.28 x 10 to the 18th) electrons passing a point in one second. VOLTAGE (V or E) - voltage is electrical pressure or force. Voltage is sometimes referred to as potential. Voltage drop is the difference in voltage between the two ends of a conductor through which current is flowing. If we compare current to water flowing through a pipe, then voltage is the water pressure. POWER (P) - the work performed by an electrical current is called power. The unit of power is the WATT. The power of a direct current is its voltage times its current - V x Amp = Watt RESISTANCE (R) - conductors are not perfect. They resist to some degree the flow of current. The unit of resistance is the OHM. A potential difference of one volt will force a current of one ampere through a resistance of one OHM. The resistance of a conductor is its voltage drop divided by the current flowing through the conductor. OHM's Law - given any two of the above, you can find the other two using these formulas known as OHM's Law: V = I x R I = V / R R = V / I P = V x I or Isquared x R Ohm's law applies to electrical circuits; it states that the current through a conductor between two points is directly proportional to the potential difference or voltage across the two points, and inversely proportional to the resistance between them. ALTERNATING CURRENT [An alternating current (AC) is an electric current whose direction or polarity reverses cyclically, as opposed to direct current (DC), whose direction remains constant. Alternating Current (AC) is usually produced by rotating a coil in a magnetic field. The usual waveform of an AC power circuit is a sine wave. Sine Wave measurement - AC Voltage is usually equal to the DC Voltage capable of doing the same work. For a Sine Wave this value is 0.707 ties the peak voltage. It's called the RMS (root-mean-square) voltage. The peak voltage or current is 1.41 times the RMS value. Household line voltage is specified according to its RMS value. Therefore, a household voltage of 120 Volts corresponds to a peak voltage of 120 x 1.41 or 169.2 volts. Examples of Alternating Current: electricity delivered to businesses and residences; Audio and Radio signals carried on electrical wires. AC is better suited than DC for transmission through long distance power lines. A wire carrying AC will induce a current in a nearby wire thereby enormously extending the range and improving the safety and efficiency of power distribution. Also transformers may be used with AC to alter voltage.] What is AC? http://www.ukslc.org/articles/power/3_phase_power_explanation.html Let us start at the very beginning. Ever since the demand for large-scale electricity generation and distribution there has been AC power. While early stations in the late 1800's generated DC power, is was quickly realised that direct current was less than ideal for distributing electricity. Transformers could not be used with the system, which means that electricity had to be generated, transmitted and used at one nominal voltage. Over long distances losses in the cabling became large, meaning many generating sites would have to be sited locally to where the power was required. Fortunately, a new AC system was proposed by George Westinghouse soon after, and todays generating, transmission and distribution systems still work on the same basic principles today. An AC supply is a supply of electrical energy where the current flows in one direction around the circuit and then the other, much like getting a simple circuit powered from a single battery and reversing the polarity of the battery at regular intervals. The change of direction of the current doesn't occur instantaneously. The change between a positive maximum value and a negative minimum value occurs smoothly. This smooth variation between positive and negative values is sinusoidal. In other words takes the form of a sine wave. A transformer is an electrical device that takes electricity of one voltage and changes it into another voltage. You'll see transformers at the top of utility poles and even changing the voltage in a toy train set. Basically, a transformer changes electricity from high to low voltage using two properties of electricity. In an electric circuit, there is magnetism around it. Second, whenever a magnetic field changes (by moving or by changing strength) a voltage is made. Voltage is the measure of the strength or amount of electrons flowing through a wire. (You may also want to read Chapter 7 on the Electrical transmission system in The Energy Story. If there's another wire close to an electric current that is changing strength, the current of electricity will also flow into that other wire as the magnetism changes. A transformer takes in electricity at a higher voltage and lets it run through lots of coils wound around an iron core. Because the current is alternating, the magnetism in the core is also alternating. Also around the core is an output wire with fewer coils. The magnetism changing back and forth makes a current in the wire. Having fewer coils means less voltage. So the voltage is "stepped-down." Transformers on the Electrical Grid http://www.energyquest.ca.gov/how_it_works/transformer.html Let's look at the electricity that comes to your home. When electricity moves from a power plant it is put into a very high voltage to be able to travel long distances. The high voltage lines can be as high 155,000 to 765,000 volts to travel many hundreds of miles. In order for your home or a store to use the electricity, it has to be at a lower voltage than on the long-distance lines. So, the electricity is "stepped-down to a lower level using a transformer. This lower voltage electricity is put into the local electric wires at a substation. The substation breaks the larger amount of power down into smaller pieces at lower voltage. It then is stepped down again and again. Once smaller transformers take that voltage down to usually 7,200, the power leaves this substation. In your neighborhood, a transformer on top of a utility pole, or one connected to underground wires, transforms the 7,200 volts into 220-240 volts. This is then sent into your home over three wires. The three wires go through the electric meter, which measures how much electricity you use. One of the three wires is the ground, and the other two are the positives. Some of the electrical appliances in your home use the 220-240 volts. These are things like a water heater, stove and oven, or air conditioner. They have very special connections and plugs. Other devices, like your TV or computer only use one-half of the electricity -- 110-120 volts. ELECTRICAL CIRCUITS An electrical circuit is any arrangement that permits an electrical current to flow. A circuit can be as simple as a battery connected to a lamp or as complicated as a computer. A basic circuit consists of a source of electrical current, a lamp and two connecting wires. The part of the circuit that performs the work is called the LOAD. In this example the load is the lamp. A series circuit involves more than one component and the current must first flow through one component to reach the next, there is only one path to travel. Electricity flows from the battery to each bulb, one at a time, in the order they are wired to the circuit. In this case, because the electricity can only flow in one path, if one of the bulbs blew out, the other bulb would not be able to light up because the flow of electric current would have been interrupted. In the same way, if one bulb was unscrewed, the current flow to both bulbs would be interrupted. A parallel circuit is formed when two or more components are connected so current can flow through one component without having first to flow through another, electricity has more than one path to travel. two bulbs are powered by a battery in a parallel circuit design. In this case, because the electricity can flow in more than one path, if one of the bulbs blew out, the other bulb would still be able to light up because the flow of electricity to the broken bulb would not stop the flow of electricity to the good bulb. In the same way, if one bulb were unscrewed, it would not prevent the other bulb from lighting up. A series - parallel circuit - many electrical circuits are both series and parallel. All provide a complete path between the circuit and its power supply. ELECTRICAL GROUND One of the wires of the AC line is connected to the Earth by a metal rod. Metal enclosures of electrically powered devices are connected to this ground wire. This prevents a shock hazard should a non-grounded wire make contact with the metal enclosure. Without the ground connection, a person touching the device while standing on the ground or a wet floor might recieve a dangerous shock. Ground also refers to the point in a circuit at Zero Voltage, whether or not it's connected to ground. For instance the minus (-) side of the battery in a circuit can be considered GROUND. When prototyping always connect the circuit to ground first and then power (same as when recharging a car battery. CONTACT MIC A transducer is a device, usually electrical, electronic, electro-mechanical, electromagnetic, photonic, or photovoltaic that converts one type of energy or physical attribute to another for various purposes including measurement or information transfer (for example, pressure sensors). The term transducer is commonly used in two senses; the sensor, used to detect a parameter in one form and report it in another (usually an electrical or digital signal), and the audio loudspeaker, which converts electrical voltage variations representing music or speech, to mechanical cone vibration and hence vibrates air molecules creating sound.