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Electronics Unit 1 – Fundamentals Electricity – study of the flow of electrons. Electronics – study of the control of electron flow. Conductor - Material w/ loosely held e-; e- flow easily (metals) Insulator - Material w/ e- tightly bound to the nucleus (nonmetals) For e- to flow in a conductor there must be… 1. A difference in electric potential (voltage) b/w points. 2. A complete path (circuit) Voltage (V) - Push of electrons (volts) also known as electromotive force (emf) Current (I) - Flow of electrons (amps) Resistance (R) Power (P) - Restriction of electron flow (ohms, Ω) Electrical energy per time (watt) Ohm’s Law V=IxR Twinkle twinkle little star, voltage equals I times R Power Law P=IxV Power equals current times voltage Watts = amps x volts Metric Prefixes Mega – 1,000,000 = 106 Kilo – 1,000 = 103 ------------- Milli – 1/1,000 = 0.001 = 10-3 Micro – 1/1,000,000 = 0.000001 = 10-6 Nano – 1/1,000,000,000 = 0.000000001 = 10-9 Pico – 10-12 Examples Calculate the current (in amps) in a 200 ohm resistor in a 120 Volt circuit. Express this answer in milliamps (mA). Examples Calculate the current in a 100 Watt light bulb on a 120 volt circuit. Examples Calculate the voltage across a 10 kilo-ohm resistor that has 0.125 amps of current through it. Types of Current Direct Current (DC) Electron flow in 1 direction (cells, batteries) Conventional Current – flows from pos. to neg (Thanks Ben F.) Electron Flow – flows from neg. to pos. Alternating Current (AC) Electron flow constantly changes direction at certain frequency (Hertz). Schematic Symbols DC Power (Battery) Resistor AC Power Cells vs. Batteries Cell Converts chemical energy to electrical energy. AAA, AA, C, D all are rated 1.5 Volts Battery Group of 2 or more cells connected together. 9 Volt battery consists of six 1.5 cells Cell & Batteries Capacity Amount of electricity that a battery will give off before fully discharging; measured in Amp-hours. Discharge Rate Rate at which current is drawn from battery. The capacity of a battery depends on its discharge rate. Capacity @ lowest discharge rate (25 mA) 9-V 625 mAh AAA 1250 mAh AA 2850 mAh C 8350 mAh D 20500 mAh In theory, a AAA can produce 1.25 A for 1 hour. In reality, a AAA can’t produce 1.25 A. Battery Capacities (Energizer) 9-Volt AA ASSIGNMENT: Worksheet #1: Ohm’s Law The Resistor Color Code Memorize this code!! 47000 Ω or 47 kiloΩ Resistors • A resistor is typically used to control the amount of current that is flowing in a circuit. • Resistance is measured in units of ohms () 21 Resistors: Types and Package Styles Carbon Film Resistors Variable Resistors (potentiometer) 4 Bands Carbon Film Resistors Surface Mount Resistors 5 Bands 22 Resistors: Size Comparison 23 Determining A Resistor’s Value Color Code Measured Value • Resistors are labeled with color bands that specify the resistor’s nominal value. • The nominal value is the resistor’s face value. • A digital multi-meter can be used to measure the resistor’s actual resistance value. 24 How To Read A Resistor’s Value Resistor Color Code 25 Resistor Value: Example #1 Example: Determine the nominal value for the resistor shown. 26 Resistor Value: Example #1 Example: Determine the nominal value for the resistor shown. Solution: 10 x 100 5% 1000 5% 1 K 5% 27 Resistor Value: Example #2 Example: Determine the nominal value for the resistor shown. 28 Resistor Value: Example #2 Example: Determine the nominal value for the resistor shown. Solution: 39 x 100K 5% 3900000 5% 3.9 M 5% 29 Resistor Value: Example #3 Example: ? ? ? ? Determine the color bands for a 1.5 K 5% resistor. 30 Resistor Value: Example #3 Example: ? ? ? ? Determine the color bands for a 1.5 K 5% resistor. Solution: 1.5 K 5% 1500 5% 15 x 100 5% 1: Brown 5: Green 100: Red 5%: Gold 31 Potentiometers – 3-terminal variable resistor Rheostat – uses the center and 1 outer terminal The resistance will be printed on it. The center terminal is called the ‘wiper’ or center tap. Inside a potentiometer Potentiometer Schematic Symbol Rheostat Schematic Symbol Standard Resistor Values 10 12 15 18 22 27 33 39 47 56 68 82 100 120 150 180 220 270 330 390 470 560 680 820 1k 1.2k 1.5k 1.8k 2.2k 2.7k 3.3k 3.9k 4.7k 5.6k 6.8k 8.2k 10k 12k 15k 18k 22k 27k 33k 39k 47k 56k 68k 82k 100k 120k 150k 180k 220k 270k 330k 390k 470k 560k 680k 820k 1M 1.2M 1.5M 1.8M 2.2M 2.7M 3.3M 3.9M 4.7M 5.6M 6.8M 8.2M Don’t assume all the resistors in the tray are what the tray claims. Resistors are normally rated for ¼ or ½ watt. For most circuits, a ¼ watt resistor will work. Digital Multimeter (DMM) Measuring Electrical Quantities Voltage Current Measure across (parallel) device Measure in series with device (break open circuit Resistance Measure across the device (power off!) Voltage Drop Voltage across a device Types of Circuits Open No electron flow (OFF) Closed Electrons are flowing (ON) Series 1 path for electron flow. Each device receives same I, Vdrop depends on R Parallel Short More than 1 path for electon flow. Each path receives the same voltage. Electrons bypass the device. Adding Resistors in Series RT R1 R2 ... Adding Resistors in Parallel 1 1 1 ... RT R1 R2 The total resistance of a parallel circuit decreases as more resistive paths are added. Series Circuit Example 3V R1 = 100 R2 = 220 1. Calculate the total resistance of the circuit. 2. Calculate the current flowing through R1 & R2. 3. Calculate the voltage across R1 & R2. 4. How much power is used by R1 & R2? Parallel Circuit Example 3V R1 = 100 R2 = 220 1. Calculate the total resistance of the circuit. 2. Calculate the current flowing through R1 & R2. 3. Calculate the voltage across R1 & R2. 4. How much power is used by R1 & R2? Voltage Drop Voltage across a device in a circuit. Wire Types Solid Bare, Insulated or Enameled Stranded Insulated Cable 2 or more insulated wires bound together. Wire Sizes American Wire Gauge (AWG) Indicates wire diameter (thickness). The smaller the wire, the larger the AWG number. Thick wires can safely handle more current. Wire Sizes Switches Switch – device placed in a circuit to open and close the circuit. Toggle Slide Push Button Switches Knife Rotary Rocker Reed (Magnetic) Tilt (mercury or ball) Switches Switches SPDT – Single Pole Double Throw Switches Pole – set of 2 contacts that belong to a single circuit. Throw – one of two or more positions that a switch can be in. SPST – Single Pole Single Throw Switches SPDT – Single Pole Single Throw aka “Three Way Switch” Switches DPDT – Double Pole Double Throw Switches SPST SPDT Normally Open – not ON until switch is pressed; “press to make” Normally Closed – ON until switch is pressed; “press to break” NO NC Momentary pushbutton switches Tactile Switches Upper pins connect to lower pins when pressed. Soldering Joining of metals by using a low-melting point metal alloy (solder) Soldering Iron Soldering Gun Solder Solder is an alloy of TIN (~60%) and LEAD (~40%) Solder melts around 200° F Rosin Core Solder (NOT ACID CORE!) Useful Soldering Items Soldering Iron Stand Helping Hands How to Solder 1. CLEAN SURFACES to be joined (steel wool or sandpaper; lacquer thinner if necessary) 2. APPLY HEAT. Heat up connection using a clean soldering-iron tip. 3. APPLY SOLDER. The solder should touch the connection, not the iron tip. Solder will flow to the hot spot. 4. REMOVE SOLDER. 5. REMOVE HEAT. Do not move connection while it cools (solidifies). How to Solder 2 Wires Together How to Solder 2 Wires Together How to Solder 2 Wires Together Use the Helping Hands How to Solder 2 Wires Together Apply Heat How to Solder 2 Wires Together Apply Solder, Remove Solder, Remove Heat A Good Soldered Connection 1. Does not have a ball or lump of solid solder. 2. Is shiny. Dull solder points indicate the wires moved during cooling, making a weak connection. Heat Shrinking Heat shrink tubing, when heated, will shrink to about 50% of its original size. Placed over an open connection between wires and then shrunk (using heat gun) to insulate the connection. Desoldering Removing the solder from a connection. Desoldering Wick (copper braid) Desoldering Bulb (copper braid) ASSIGNMENT: 1. Solder solid leads onto a battery snap. Red wire Red wire Black wire Black wire Apply red and black heat shrink tubing. 2. Solder two black wires to a speaker. Show Tischer for credit. Breadboard or Solderless Circuit Board Positive bus Negative bus Breadboard or Solderless Circuit Board Breadboard or Solderless Circuit Board Breadboard - Used to build circuits temporarily. - Do not run 9 volts across anything; always use a resistor. - Do not work on live circuits; have an ON/OFF slide switch to check if circuit works. - Use 22 AWG solid wire; do not insert wire in breadboard more than ¼” - Keep your circuits neat; don’t use wire that is longer than necessary. Breadboard - Used to build circuits temporarily. - Keep your circuits neat; don’t use wire that is longer than necessary. minimize the amount of wire build circuit to resemble the schematic layout highlight schematic to show what you’ve done Breadboard - Used to build circuits temporarily. - Do not run 9 volts across anything; always use a resistor. - Do not work on live circuits; have an ON/OFF switch to check if circuit works. - Use 22 AWG solid wire; do not insert wire in breadboard more than ¼” - Keep your circuits neat; don’t use wire that is longer than necessary. What resistor should be used for a 9-V battery to run an LED? We need a resistor that will have a voltage drop of (9 – 2.2 V) = 6.8 V We also need a safe current of around 20 mA in the circuit. R = V/I = 6.8 V/0.020 A = 340 ohms 390 or 470 ohms would work. 1. Build this circuit 2. Add a potentiometer in series with the resistor 3. Substitute a photocell for the resistor. Add a SPDT slide switch to the breadboard