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Basic Electricity and Electronics

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  1. Basic Electricity and Electronics Module One Basic Electricity

  2. How to learn about Electricity and Electronics • Everybody plays music from a CD • We start with binary data • We end up with sound coming from a speaker • How does this work?

  3. The process involves • Electricity • Electronics • Digital signals • Digital logic • Sound • Light and optics

  4. Here is what our binary data looks like: 1001000100110101 1110101000111101 • Here is what our audio signal looks like:

  5. How do we get from one to another? • A series of conversion process steps • Sound is created by something that vibrates (moves), which creates pressure changes in the air • We can use the pressure to make something move (a coil or diaphram) • We can use motion to create or change some amount of electricity

  6. This work is licensed under a Creative Commons License.

  7. Sound conversion to CD data • The value of the voltage depends on the amount of sound (called the amplitude) • The voltage value is converted to a number that represents how big or small the voltage is • This number has a binary code that is unique for each voltage value • The binary code is stored as pits and spaces on a compact disk • We will look at binary in more detail a little later

  8. CD audio is basically a whole bunch of numbers that record sound levels and changes in sound levels • The voltage values are sampled at a fixed rate: 44,100 times per second (Hertz) • We sample and record the sound level whether there is sound or not, resulting in a fixed amount of data per second (1.4 million bits of data per second) • You have to understand electricity and electronics in order to understand how (and why) this works

  9. Basic Electricity • Basic electricity and electronics starts with electrons. • Electrons are one of the three fundamental particles • All work involves movement • Electrons move to create electrical work • Electronics is the study and use of systems that control the movement of electrons

  10. + + F - - F - + F Electrons and Charge • How do we make electrons move? • Electrons have a charge • Like charges repel, unlike charges attract • These forces make electrons move

  11. Where do we get charge? • Charge is a fundamental property of nature • Electrons and protons have a charge • Electron charge is negative • Proton charge is positive

  12. The Atom • The fundamental building block of all matter • Made of protons, neutrons, and electrons • The type of element is determined by the number of protons in the nucleus

  13. Voltage and Charge • Voltage is a measurement of force created by a buildup of charge • Atoms are usually neutral because they have the same number of protons and electrons • Charge builds up when electrons are separated from the atom • This separation takes work in the form of mechanical energy or chemical energy

  14. Voltage and Current • Voltage is the force created by a buildup of charge • Also called a potential difference • Voltage can make electrons move • Electron movement is called current flow • Current flow does the work in an electric circuit

  15. Common Electrical Units • The unit of charge is the COULOMB • Charge has the symbol Q, abbreviation C • The unit of voltage is the VOLT • The symbol is V, the abbreviation is V • The unit of current is the AMP • Current uses the symbol I, abbreviation A • The unit of resistance is the OHM • Resistance has the symbolW, abbreviation R

  16. Think in Pairs • Electricity is two things: Voltage and Current • Voltage has two polarities: positive and negative • Two types of electrical power: AC and DC • Electricity has two purposes: as an energy source (power) and as a signal • Signals can be either analog or digital

  17. Electricity • A good power source • Easy to create • Easy to control • Efficient to transmit • Easy to measure • Makes everything work – our way of life depends on it

  18. Common Circuit Elements

  19. Battery • DC Voltage source • Voltage amount is typically given, as in 12 VDC • Consists of one or more cells • Cells are in series • Cell voltage adds to give total source voltage • The long side is positive • The short side is negative • The negative side is usually grounded or called ground

  20. Ground • Also called common • Meaning shared • A return path for every circuit branch • Connected together • Usually the most negative point in the circuit • By definition, ground voltage is zero volts • Why? • Ground is not a device

  21. Fuse • One of the major protection elements • Another is called a circuit breaker • A ground fault device (GFCI) is a type of circuit breaker • Protects the circuit, not the person! • A GFCI protects people • Turns off the circuit, like a switch • A switch is a control element, not a protection element • Replaced once it is blown • With the same amperage rating!

  22. Resistor • One of the most common circuit elements • Used to limit or restrict current • Resistance amount indicated with a color code • A circle or band around the resistor • The physical size indicates the power rating • Not the resistance value! • The smaller the resistance value, the larger the amount of current

  23. THE END

  24. Voltmeter • Measures across a device • Red lead to positive, black to negative • Measures a voltage difference • Has a high amount of internal resistance • So no current flows from the circuit into the meter • Does not change circuit voltage, current, or resistance • Voltage range is usually a meter setting • Selector switch or button

  25. Ammeter • Measures amperage • Amp meter • Must be placed in the circuit • Current must flow into (through) the meter to be measured • An ammeter has low (zero) internal resistance • So it doesn’t reduce circuit current • Leads must be changed from volts/ohms • Dangerous to the meter!

  26. An Electrical Circuit • Must have a voltage source • Must have a load • A resistor or other device to limit current • Can be a circuit component, like a light • Must have a complete path from one side of the voltage source to the other • Usually a wire • A path to earth ground is dangerous and unwanted • Should have a protection device and a control device

  27. + Resistor (Load) Battery - Current Flow Ground A Simple Circuit • All of the voltage is dropped across the resistor • Current flows from negative to positive • Ground is defined as zero volts

  28. Open switch, no current • Resistance is infinite • Voltage is dropped across the switch

  29. Closed switch, current flows • Current flows from negative to positive • Amount of current determined by Ohm’s Law

  30. The Simplest Circuit VS R

  31. The Same Circuit VS R

  32. An electric circuit must have a complete path from one side of a power supply (+V) to the other (-V) • Voltage across a resistor creates current • Voltage, current, and resistance follow a rule known as Ohm’s Law I = • Current equals voltage divided by resistance V R

  33. Definitions • Voltage is caused by a buildup of charge • Current is a flow of charge • One amp equals one coulomb per second • Ohm’s Law shows the relationship between current, voltage, and resistance

  34. The Ohm’s Law Circle V I R = I = I

  35. Circuit Calculations R = VS =

  36. Circuit Calculations R = VS =

  37. Circuit Calculations • I = 5.9 mA, R = 2.2 kΩ What is V? • V = I x R = .0059 A x 2200 Ω = 13 V R = VS =

  38. A Series Circuit R1 R2 R3 VS 1. What is the formula for total resistance? RT = R1 + R2 + R3 (Resistance Adds) IT = I1 = I2 = I3 (current is the same everywhere) 2. What is the formula for current? 3. What is the formula for voltage across R1? V1 = I1 x R1 VS = V1 + V2 + V3

  39. Problem 1 R1 R2 R3 VS VS = 12 V, R1 = 250 Ω, R2 = 150 Ω, R3 = 500 Ω What is total resistance? What is total current? What is V1?

  40. Problem 2 R1 R2 V1 = 6 V V2 = 4 V R3 VS 600 Ω 20 V VS = 20 V, V1 = 6 V, V2 = 4 V, R3 = 600 Ω What is R1?

  41. Problem 3 R1 R2 IT = 6 mA V1 = 3 V R3 VS 1500 Ω 18 V VS = 18 V, V1 = 3 V, R3 = 600 Ω, IT = 6 mA What is R2?

  42. A Parallel Circuit The voltage across each branch is the same VS = V1 = V2 = V3 The current from each branch adds IT = I1 + I2 + I3

  43. A Parallel Circuit The voltage across each branch is the same VS = V1 = V2 = V3 The current from each branch adds IT = I1 + I2 + I3

  44. Parallel Example 300 Ω 500 Ω 750 Ω 12 V VS = 12 V, R1 = 300 Ω, R2 = 500 Ω, R3 = 750 Ω Solve for RT 150 Ω 300 500 750

  45. Alternate Method 300 Ω 500 Ω 750 Ω 12 V IT = I1 + I2 + I3 IT = .04 + .024 + .016 = .08 A

  46. Problem 4 RT = 130 Ω 250 Ω 400 Ω I1 = .064 A R1 = 250 Ω, R2 = 400 Ω, RT = 130 Ω, I1 = .064 A Solve for I3

  47. Electricity creates an electromagnetic wave also known as a radio signal • Travels at the speed of light through air • Travels at nearly the speed of light through a wire • Historically most signals were analog and used AC principles

  48. Using this example, at 1 A of current, the motor produces 6 oz-in of torque at a speed of 210 RPM. • To lift 200 lb requires a gear ratio of 533.3 to 1 • How long would it take to lift this 1 ft?

  49. More recent signals are digital and represent coded information • Digital signals are basically DC voltage switched on and off at a rapid rate • The basic digital switch is a transistor • In order to understand electronics you must understand how transistors work