DC Concepts


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Introduction to Electricity and Electronics.
Topics: Transducers, Voltage, Current, Resistance, Ohm's Law, Power, Series, Parallel.

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  • Remember: Energy can’t be created or destroyed, only changed from one form to another.\n“Transduction” is that. (microphone example).\nLight bulb: Changes electrical energy into light and heat\nMotor: Changes electrical energy into kinetic energy.\n\nA mechanism is an assembly of moving parts with kinetic energy in the system.\nThe energy needs to come from somewhere though... the human body can be that... But likely a motor. \nSo we’ll start off the course with a study of electricity & transduction before moving to mechanisms.\n
  • A funny way of thinking about transduction. Kinetic energy from our bodies converted into interaction. \n\nBut also just points out what a LIMITED idea of INTERACTION we have from the devices around us. \n
  • Just as a ball on top a hill want to roll from higher potential energy to lower p.e., so too do electrons want to flow from a place of higher to lower energy.\n\nEverybody is familiar with a 9V battery. And you know if you lick one, you get a little shock...\nSome chemistry at work on either side, creating the diff in potential.\nThey will all go as fast as they can, until both sides have an equal amount of electrons. \nAlong the way, we can make them jump through hoops and do tricks for us. \n\nThe place of higher energy is called the “Power Source”, lower is “Ground”. Sometimes this is the actual ground... (next slide)\n\n
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  • Like the panda.\n\nElectrons want to go from + to –\nThey want this very much.\n
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  • The amount of electrical energy passing through a point in the circuit.\nWater analogy: Current is like the amt of water flowing. \nIf a battery has “3000mAh” on it, it can deliver 3000 mA for 1hour.\n\nMotors, etc. will have a current rating that tells you how much current they need to operate. Like voltage, it’s important to match these correctly!\n
  • There are two flavors of how current “flows”: Direct and Alternating\n\n
  • Every component in a circuit has electrical characteristics\n\nBattery can provide a certain amount of electrical energy\nBulb resists a certain amount\n\nToo little energy = dim bulb\nToo much energy= kaboom\n\n
  • Water analogy: A skinny segment of pipe.\n\nAll components resist the flow of current by turning electrical energy into something like heat or light.\n\nRemember: No energy is lost... only converted.\n
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  • Depending on how high the water tower is, the more “potential” energy there is, for the water as it falls (think about dropping a penny from 4’ up or empire state building).\nThat difference in potential from the hight of the tower, to the gnd, is voltage.\nVoltage is always expressed as the potential difference in energy; between two points.\n\nIn this way, you can also think of it as water pressure.\nResistors would be like, if we stuck a bunch of socks in the pipes.\n
  • 1HP = 746W\n
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  • Now, when it comes to actually powering your projects, you have 2 options.\n--Battery\n--Wall Transformer\n\nLook at labels to match voltage and current.\n
  • In circuit diagrams, electrons flow from positive to negative (ground).\nHigh potential to zero potential. \nAlong the way, we can add hoops. \n
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  • If you measure the voltage between ground and several points along the circuit, you’ll see the voltages drop.\n
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  • DC Concepts

    1. 1. Basics ofDC Electronics.-Electricity: The flow of electrons through a conductor-Electronics: using changing electrical properties to convey information. Converting one form of energy into another, and interpreting that information.-Transduction and Transducers
    2. 2. too many electrons not enough electrons higher potential lower potential
    3. 3. Voltage (V)-The difference in potential energy between two points.-Measured in Volts (V or E) - V could be thought of as a difference in “potential”-Think of it like water pressure. A geyser vs. a low-flow shower head.
    4. 4. High PotentialLow Potential
    5. 5. Use a multimeter to test Voltage!
    6. 6. Current (I)-The flow of electrons through a conductor.-Measured in Amps. The symbol is I. - 1 Amp is very high, so we’ll typically see amounts in “milli- amps”. 1000 mA = 1A-Conventionally, we think of current as flowing from “positive” to “negative” (look at the battery picture)-Current flow requires an imbalance of charge between two points.-Think about water: The amount of water flowing through the tube.
    7. 7. Direct Current:-One power wire, and one ground wire.-Constant flow of electricity.Alternating Current:-Power alternates between 120V and 0V at 60Hz.-Better for longer distances, hence the grid is AC...DC = Safer, smaller voltages (5V, 9V, etc.)
    8. 8. What is a circuit? “load” “battery” “switch” “A closed loop containing a source of electrical energy (battery), and a load (light)”
    9. 9. Resistance (R)-Whatever “resists” the flow of current-Measured in Ohms (R)-All materials and components have some degree of resistance, depending on the strength of the electron bonds. Remember! No energy is lost. Only converted to things like light, heat or kinetic energy.
    10. 10. Ground-A “zero-voltage” point.-Current wants to flow to ground.-“True” Ground is literally, the ground.-“Floating” ground is relative to the circuit it’s a part of...-A reference point from which to measure Voltage.-The earth is idealized as an infinite heat-sink for current. It can absorb an unlimited amount without changing its potential...
    11. 11. Put ‘em together and you get...Ohm’s LawVoltage (V) = Current (I) * Resistance (R) V = I * R I = V / R R = V / I
    12. 12. The “Water Analogy” helpsVoltage is like water pressure.Current is the amount of water flowing past a givenpoint.Cover the end with your finger... V = I*R(R has increased... so now V, or pressure, will too)
    13. 13. Power (P)-The combination of Voltage and Current P = V * I-Describes the amount of “work” your circuit can do.-Measured in Watts (W)
    14. 14. Questions so far...
    15. 15. Important Point:-You can supply more than enough current, the component will draw what it needs.-Voltage, however, must be carefully matched.
    16. 16. Conventional Circuit Diagrams:How they flow & What they look like.More on this later.
    17. 17. Two Rules for how electricity“flows” (DC)-Always favors the “path of least resistance”-All the electrical energy in a circuit must be used up.The components must consume all theenergy that you put into the circuit.Too much = heat, for that reason.
    18. 18. Components in Series-All components are on the same elec. path-Current is the same across all components-Voltage drops at each component
    19. 19. Components in Parallel-More than one path for electrons to flow-Voltage across the two lights is the same...-Current is split (shared) among the components.
    20. 20. What happens in this setup?
    21. 21. Next Session!