1. Hardware Basics

2. Electricity Electricity is the flow of electrons Atoms contain –In the nucleus (center) Protons with a positive charge Neutrons with no charge (no consequence here) –“Orbiting” around the nucleus Electrons with a negative charge - + + + + - - -

3. Charged Atoms Atoms with more protons that electrons –Positively charged –Try to acquire additional electrons to get back in balance Atoms with more electrons than protons –Negatively charged –Want to give up electrons to get back in balance If you set up an imbalance, electrons will try to jump (flow) between atoms to correct this –This flow is electricity

4. Conductors and Insulators Materials that allow electrons to flow easily are conductors –Most metals are good conductors Materials that don’t allow electrons to flow easily are insulators –E.g., plastic, rubber, glass Some materials can be influenced to change from conducting to insulating (a very useful property)  Semiconductors

5. Basic Law of Charges Like charges repel each other Opposite charges attract each other Exert a force –Can do work: e.g., move something +-++--

6. Charge Charge is measured in Coulombs ( C ) –(A unit we won’t use much) –Measure of how many more protons than electrons in a substance –1 Coulomb = 2.15 x 10 18 excess protons 2.15 x 10 18 extra electrons = -1 C

7. Electromotive Force (Voltage) Charge has the ability to do work –A “potential” to e.g. move something in one direction or another Difference in potential (in charge) provides a force: Electromotive Force (EMF): Voltage Extra electron s EMF (voltage) +

8. Flow of electrons If this is a conductor then ½ the excess electrons will very rapidly flow to the other end to balance the charge Conductor Extra electron s EMF (voltage) +

9. Flow of electrons If this is a conductor then ½ the excess electrons will very rapidly flow to the other end to balance the charge Conductor 0 voltage ½ the extra electrons

10. Flow of electrons If this is a conductor then ½ the excess electrons will very rapidly flow to the other end to balance the charge And then things are not very interesting Conductor 0 voltage ½ the extra electrons

11. Flow of electrons If this is a conductor then ½ the excess electrons will very rapidly flow to the other end to balance the charge And then things are not very interesting –Hence we set up circuits (cycles, loops) to keep this going

12. Flow of Electrons “Current” is the flow of electrons Measured in Amperes (Amp, or A) –1A is 1 Coulomb of charge flowing past a point per second

13. Current vs. Voltage Water analogy –Useful, but only goes so far Coulombs analogous to quantity (gallons) Amps analogous to flow rate (gallons / sec) Voltage analogous to pressure (lbs/ft 2 )

14. Resistance Can have a lot of flow at low pressure or a lot of pressure but low volume –Depends on the size of the pipe Resistance is analogous to the size of the pipe Resistance is the opposition to current flow Measured in Ohms ( Ω )

15. Ohm’s Law Relates current, voltage, and resistance Current normally denoted by variable I Voltage normally denoted by variable V Resistance normally denoted by variable R V = I * R

16. Ohm’s Law V = IR R = V / I I = V / R V IR

17. Ohm’s Law In the electronics we will do, we tend to (try to) hold the voltage constant (or zero) –Typically 5v starting to use 3.3v, but 5v still most common I = V / RI = 5 / R –Raise the resistance, current drops –Lower the resistance, current rises

18. Ohm’s Law I = V / RI = 5 / R –Raise the resistance, current drops –Lower the resistance, current rises What happens if we lower the resistance towards zeros?

19. Ohm’s Law I = V / RI = 5 / R –Raise the resistance, current drops –Lower the resistance, current rises What happens if we lower the resistance towards zeros? –Current goes towards infinity –Power = V * I (related to heat) Boom! (or Poof!)

20. Current Limiting Important –This is how you (literally) fry hardware if you don’t pay attention (trust me, I know) Always think carefully (and check!) that the path from 5v source –From power supply, or from output pin of a chip to ground (0v location) has appropriate resistance –Not a “short circuit” ~0Ω –Current limiting resistor at value needed to stay within current limits of the device

21. Aside: Units Volts, Amps, Ohms Normally use metric system unit prefixes megaMmillion1,000,00010 6 kilokthousand1,00010 3 one110 0 millimthousandth0.00110 -3 microμmillionth0.000 00110 -6 nanonbillionth10 -9 picoptrillionth10 -12

22. Examples 5V with 10Ω  5/10 A = 0.5A = 500mA For typical chips you will use = Poof! 5V with 100Ω  5/100 A = 50mA Still Poof! 5V with 250Ω  5/250 A = 20mA OK for PIC processors, not for lots of other digital electronics 5V with 10kΩ  5/10000 A = 0.5mA Good for most digital electronics

23. Schematic Diagrams xx Wire, connection, cross, hop-over Resistor, variable resistor (pot, rheostat) Battery, switch Capacitor, electrolytic capacitor Diode, LED Transistor (PNP, NPN) Inductor, transformer Integrated circuit

24. Schematic Diagrams

25. AC vs. DC DC – Direct Current –Current flows steadily in one direction –Most of what we will do is DC AC – Alternating Current –Current flows in one direction then another –Wall current does this Alternating 60 times per sec 60 Hz V V

26. Capacitance Capacitor –Device with two conducting plates separated by insulating material (called dielectric) –Stores electric charge in the dielectric –Water metaphor Consider a pipe with a rubber balloon blocking it DC current bulges out the balloon (charges the capacitor) –But then stops flowing –Release the pressure the charge drains back out over time AC current can go back and forth continuously  Capacitor blocks DC but allows AC to pass

27. Capacitance Capacitance is measured in Farads ( F ) and denoted by variable C –Amount of charge divided by voltage across plates Charge (in Coulombs) denoted by Q C = Q / V

28. Series and Parallel Circuits Series circuit Parallel circuit

29. Series and Parallel Circuits Combining resistors R total-series = R1 + R2 R total-par = (R1 * R2) / (R1 + R2) R1R2R1 R2

30. Series and Parallel Circuits Combining capacitors C total-series = (C1 * C2) / (C1 + C2) C total-par = C1 + C2 C1C2C1 C2

31. Digital Electronics Computer circuits treat signals as digital values –Consider signals to only have two states: 1 or 0 –+5v is considered to be “1” –0v is considered to be “0”

32. Digital Electronics But need to leave some room for error or fluctuation –Between V HMin and +5v considered 1 –Between 0v and V Lmax considered 0 –Between V Lmax and V HMin is undefined (and unpredictable) Can pass through this but you don’t want to stay there long +5v 0v V HMin V Lmax 1 0 ??