Presentation on theme: "Unit 1 – Fundamentals Electronics. Electricity – study of the flow of electrons. Electronics – study of the control of electron flow. Conductor -Material."— Presentation transcript:
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) Current (I) - Flow of electrons (amps) Resistance (R) - Restriction of electron flow (ohms, Ω) Power (P) - Electrical energy per time (watt) also known as electromotive force (emf)
V = I x R Twinkle twinkle little star, voltage equals I times R Ohm’s Law
Power equals current times voltage Watts = amps x volts P = I x V Power Law
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.
Direct Current (DC) Electron flow in 1 direction (cells, batteries) Types of Current 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).
DC Power (Battery) Resistor Schematic Symbols AC Power
Cell - Converts chemical energy to electrical energy. Cells vs. Batteries 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. The capacity of a battery depends on its discharge rate. Discharge Rate - Rate at which current is drawn from battery.
AAA In theory, a AAA can produce 1.25 A for 1 hour. In reality, a AAA can’t produce 1.25 A. AA C D 9-V625 mAh 1250 mAh 2850 mAh 8350 mAh 20500 mAh @ lowest discharge rate (25 mA) Capacity
Determining A Resistor’s Value Color Code Resistors are labeled with color bands that specify the resistor’s nominal value. The nominal value is the resistor’s face value. Measured Value A digital multi-meter can be used to measure the resistor’s actual resistance value. 24
How To Read A Resistor’s Value 25 Resistor Color Code
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. 27 Solution: 10 x 100 5% 1000 5% 1 K 5%
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. 29 Solution: 39 x 100K 5% 3900000 5% 3.9 M 5%
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. 31 Solution: 1.5 K 5% 1500 5% 15 x 100 5% 1:Brown 5:Green 100:Red 5%:Gold ????
Potentiometers – 3-terminal variable resistor The resistance will be printed on it. Rheostat – uses the center and 1 outer terminal
The center terminal is called the ‘wiper’ or center tap. Inside a potentiometer
Potentiometer Schematic Symbol Rheostat Schematic Symbol
Standard Resistor Values 101215182227333947566882 100120150180220270330390470560680820 1k1.2k1.5k1.8k2.2k2.7k3.3k3.9k4.7k5.6k6.8k8.2k 10k12k15k18k22k27k33k39k47k56k68k82k 100k120k150k180k220k270k330k390k470k560k680k820k 1M1.2M1.5M1.8M2.2M2.7M3.3M3.9M4.7M5.6M6.8M8.2M 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.
Measuring Electrical Quantities Voltage Measure across (parallel) device Current Measure in series with device (break open circuit Resistance Measure across the device (power off!) Voltage Drop Voltage across a device
Open No electron flow (OFF) Closed Electrons are flowing (ON) Series 1 path for electron flow. Each device receives same I, V drop depends on R Parallel Short More than 1 path for electon flow. Each path receives the same voltage. Electrons bypass the device. Types of Circuits
Adding Resistors in Series Adding Resistors in Parallel The total resistance of a parallel circuit decreases as more resistive paths are added.
Series Circuit Example R 1 = 100 R 2 = 220 3 V 1. Calculate the total resistance of the circuit. 2. Calculate the current flowing through R 1 & R 2. 3. Calculate the voltage across R 1 & R 2. 4. How much power is used by R 1 & R 2 ?
Parallel Circuit Example R 1 = 100 R 2 = 220 3 V 1. Calculate the total resistance of the circuit. 2. Calculate the current flowing through R 1 & R 2. 3. Calculate the voltage across R 1 & R 2. 4. How much power is used by R 1 & R 2 ?
Voltage Drop Voltage across a device in a circuit.
Solid Bare, Insulated or Enameled Wire Types Stranded Insulated Cable 2 or more insulated wires bound together.
American Wire Gauge (AWG) Indicates wire diameter (thickness). Wire Sizes The smaller the wire, the larger the AWG number. Thick wires can safely handle more current.
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 IronSoldering Gun
Solder Solder is an alloy of TIN (~60%) and LEAD (~40%) Rosin Core Solder (NOT ACID CORE!) Solder melts around 200° F
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 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 Desoldering Wick (copper braid) Removing the solder from a connection. 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. Show Tischer for credit. 2. Solder two black wires to a speaker.
Breadboard or Solderless Circuit Board Positive bus Negative bus
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.