Electronics Tutorial 3
In this part of my electronics tutorial we’ll cover Voltage Drop, Capacitors, Variable Resistors, Potentiometers, Rheostats, Diodes, Schematic Diagrams, Electronic Circuit Diagraming Software and much more.
If you missed part 1 or part 2 definitely watch those first or you may be confused. All of the circuit diagrams can be found below the video along with a transcript of the video.
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Circuit Diagrams
Resistor Voltage Drop Circuit
Capacitor Circuit
Diode Circuit
Variable Resistor Circuit
Transcript From the Video
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I. Ohms Law A. (Slide 1) We know that a. V = I * R i. The player that played with voltage went to the IR "Injured Reserve" b. Always divide into V for i. I = V / R ii. R = V / I B. Resistance in series add up 470 Ω + 1000 Ω = 1470 Ω C. Circuit Example D. (Slide 2) Calculate Voltage drop using Ohms Law a. V1 = I * R1 = 4.3 mA * .465 kΩ ≈ 1.99 V i. Make sure your units match up I. Volts = Amps * Ohms II. Volts = mA * kΩ b. You can also calculate both resistors voltage drops like this i. V1 = (R1 / (R1 + R2)) * V Bat ii. V2 = (R2 / (R1 + R2)) * V Bat iii. V1 = (.470 kΩ / (.470 kΩ + 1 kΩ)) * 6.25 V ≈ 1.99 V II. (Slide 3) Capacitors A. A capacitor stores electrons even after the power supply is disconnected. A capacitor contains 2 metal plates that are separated by an insulator (dielectric). B. While a battery produces charged particles through an electrochemical reaction. A capacitor instead allows charged particles to build up on the metal plates it contains. C. As electrons flow into a capacitor with no place to go they will block the conductive path once the plate is full. The other plate in the capacitor will have a net positive charge. The transfer stops when the voltage of the capacitor is equal to the battery voltage. D. (Slide 4) There are 5 main capacitor symbols. The curved line represents the more negative side. Some times you'll also see a plus sign if it is a polarized capacitor that must be entered facing the positive charge. If an arrow goes through the capacitor that means it is a variable capacitor. E. (Slide 5) Capacitance describes how much charge a capacitor can store. The higher the capacitance the more charge that can be stored. Capacitance is measured in Farads (F). 1 Farad equals the capacitance needed to get 1 amp to flow F. A Farad is considered to large for most situations and so here are more common capacitance measurement units. a. 1 mF (millifarad / one thousandth) = 1000 μF b. 1 μF (microfarad / one millionth) = 1000 nF = 1000000 pF c. 1 nF (nanofarad / one billionth) = 1000 pF d. 1 pF (picofarad / one trillionth) G. The highest voltage recommended for capacitors designed for DC circuits is 16 to 35 V (Check with the manufacturer) H. (Slide 6) Most small capacitors use a 3 digit system a. Numbers 01 - 99 : nn pF b. 101 : 100 pF c. 102 : .001 μF d. 103 : .01 μF e. 104 : .1 μF f. 221 : 220 pF g. 222 : .0022 μF h. 223 : .022 μF i. 224 : .22 μF j. 331 : 330 pF k. 332 : .0033 μF l. 333 : .033 μF m. 334 : .33 μF I. (Slide 7) Many capacitors have a letter code that indicates how far off the capacitance may be or the tolerance a. B : +/- .1 pF b. C : +/- .25 pF c. D : +/- .5 pF d. F : +/- 1% e. G : +/- 2% f. J : +/- 5% g. K : +/- 10% h. M : +/- 20% i. P : + 100% - 0% j. +80% - -20% J. (Circuit) Circuit to show a capacitor charge and discharge a. 9 Volt Battery b. 470 μF (microfarad) Capacitor (Short negative lead goes towards -) c. 2.2 kΩ (kilo ohm) Resistor d. 2 Red LEDs e. Single Pole Double Throw (SPDT) switch K. What is happening? (iCircuit) a. Switch down to charge the capacitor. As it charges current flows to the LED until the voltage of the capacitor equals the voltage of the battery. Then the LED doesn't receive a charge and it dims. The 2nd LED doesn't light up because its lead is backwards. The resistor causes the dimming process to slow. b. When the switch is up the electrons flow in the opposite direction out of the capacitor into the resistor and lights up the LED until the charge is used up. L. (Circuit) The resistor you use will define how long it takes to charge and discharge your capacitor. It takes approximately 5 times the resistance in Ohms * the capacitance in Farads. a. 470 μF = 0.00047 Farads b. 2200 Ω * 0.00047 = 1.03 Seconds * 5 M. (Circuit) Capacitors in parallel sum. a. C1 = 96.3 nF b. C2 = 96.3 nF c. C Tot ≈ 192.6 nF or 193 on multimeter N. (Circuit) Capacitors in series have a reduced capacitance a. C1 = 95.3 nF b. C2 = 95.3 nF c. C Tot = C1 * C2 / (C1 + C2) on multimeter 47.4 nF = 95.3 * 95.3 / (95.3 + 95.3) = 9082 / 190.6 ≈ 47.6 nF or 47.4 nF on multimeter III. Diodes (Slide 8) A. A diode is a simple semiconductor device. It only conducts a charge in one direction. Diodes can convert alternating current to a pulsing direct current. It can also be used to convert a radio signal into a charge you can hear through a speaker. This is called rectification, which will be covered in the next tutorial. B. A diode contains an Anode and a Cathode. The schematic symbol for a diode should look familiar because an LED, which we have already covered, is also a diode. The schematic symbol for a diode has an arrow, which represents the Anode, and a straight vertical line, which represents the Cathode. Current flows from the Anode to the Cathode. C. A white or black band identifies the cathode terminal on a diode. That band identifies the terminal in which a positive charge, using conventional current, will flow out of when the diode is conducting a charge. D. Like we covered in the first tutorial, a LED contains 2 semiconductors. The N Type has more electrons, while the P Type has holes were electrons used to be. When a charge is applied electrons move from the N Type to the P Type. Electrons won't flow in the opposite direction though. With conventional current we say that current flows from the Anode to the Cathode. E. (Circuit) Project : This project shows that current flows only in 1 direction. a. 100 Ω Resistor b. Silicon Diode c. 1 SPDT Switch d. Red LED e. 2 AA Battery Pack (3 V) F. (iCircuit) G. Each diode has a minimum turn on voltage known as the Forward Voltage. A silicon diode requires a voltage around .6 V, while an LED requires any where from 1.5 to 4 V. If a diode doesn't receive enough voltage it is said to be unbiased. H. The Peak Reverse Voltage is the voltage at which the diode will break down if current flows in the wrong direction. I. Project : This project demonstrates forward voltage with a variable resistor. a. 470 Ω Resistor b. 10 kΩ Variable Resistor (Slide 9) 1. Can change its resistance. It can be used as a 2 or 3 terminal component. The center terminal is connected to a wiper that increases or decreases the resistance. 2. If only 2 terminals are used it acts as a variable resistor or Rheostat. If all 3 are used it is a Potentiometer that forms a Voltage Divider. A Voltage Divider acts just like 2 resistors connected in a series like we saw in the previous tutorial. As we increase resistance between 2 terminals we decrease the resistance between the other 2. c. 2 Red LEDs d. 9 Volt Battery e. By setting up the potentiometer so that we have a terminal on either side of the LED we can set the resistance of the LED. Since the LED requires a voltage of 1.5 V to turn on when we set the resistance of the variable resistor below that we can turn it off. f. (iCircuit) If we place another LED between the other terminal we can switch back and forth between which LED lights up. We do this by increasing one resistance as we decrease the other and vice versa. g. (iCircuit) |
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