Electrical Signs and Symbols

Electrical Signs and Symbols

• Electrical signs and symbols are used to represent various electrical devices in a diagram or plan of an electrical circuit.
• Warning icons are used to alert users to potentially hazardous conditions and instruct them on how to avoid them.
• There are different types of warning icons, including:
  • Caution: indicates precautionary measures against potential hazardous situations.
  • Safety Alert: indicates that a person should observe extra awareness.
  • Prohibition: indicates that a specific activity is not allowed.
  • Danger: specifies a hazardous situation that can result in serious injury or death.
  • Warning: specifies a potentially hazardous situation that can result in serious injury or death.
  • Read and Understand Instruction Manual: indicates that a person should read the manual before using a device.
  • Wear Eye Protection: indicates that a person should wear safety goggles or eye protection.
  • Electrical Hazard: indicates that an electrical hazard is present in the area.
  • Voltage Danger: indicates high voltage in the area and surrounding equipment.

Electrical Symbols

• Electrical symbols are small drawings or pictograms used to represent various electrical devices in a diagram or plan of an electrical circuit.
• Examples of electrical symbols include:
  • Conductor/Wire
  • Terminal
  • Switch
  • Fuse
  • Connected Wire
  • Circuit Breaker
  • Cell
  • Battery
  • Resistor
  • Capacitor
  • Diode
  • Ground
  • Lightning Arrester
  • Kilowatt-hour meter
  • Power Panel
  • Lighting Panel
  • Incandescent Bulb/Fluorescent Lamp
  • Junction Box
  • Main Distribution Panel

Fundamentals of Electronics

• Electronics technology involves the control of electricity in a vacuum or solid conductor materials.
• Sources of electricity include:
  • Static Electricity by Friction
  • Conversion of Chemical Energy
  • Ions
  • Electromagnetism
  • Photoelectricity
  • Thermal Emission
  • Doping of Conductors
• Alternating Current (AC) has characteristics including:
  • Periodically reversing in polarity
  • Signal varying between reversals
  • Stepping up or down by a transformer
  • Being used as a signal output for an amplifier
  • Being easy to amplify
• Direct Current (DC) has characteristics including:
  • Having a fixed polarity
  • Varying in magnitude
  • Not being able to be stepped up or down by a transformer
  • Being used for electrode voltages in amplifiers
  • Being easy to measure

Soldering

• Soldering is the process of joining two or more terminal wires together permanently with the use of soldering lead.
• Good soldering output depends on the quality of soldering materials, tools, and techniques.
• Soldering tools include:
  • Electric Soldering Iron
  • Electric Soldering Gun
  • Long Nose Plier
  • Diagonal Cutter
  • Flat Screwdriver
  • Philips Screwdriver
  • Desoldering Tool
  • Volt-Ohm-Milliammeter (VOM)
• There are different types of soldering techniques, including:
  • Dip Soldering
  • Wave Soldering
• Characteristics of a good solder include:
  • Good bonds between the joined metals
  • Forming a shiny cover without any air space
  • Having flux to remove any oxide film on the metals joined together

Electronic Components

• Electronic components have distinct purposes and functions.
• Examples of electronic components include:
  • Resistors
  • Capacitors
  • Inductors and Coils
  • Switches
  • Semi-Conductor Devices
  • Transistors
  • Diodes
  • Rectifier Diodes
  • Light Emitting Diodes (LEDs)
• Each component has a specific function, such as:
  • Resistors: limiting the flow of current in a circuit
  • Capacitors: storing electricity and then discharging it back into the circuit
  • Inductors and Coils: used in switching to different radio stations
  • Switches: interrupting electric current by turning a circuit on or off
  • Transistors: amplifying or increasing weak signals
  • Diodes: routing electricity from taking an unwanted path within the circuit
  • LEDs: emitting light when electricity flows through them

Circuit Analysis

• Circuit analysis involves the study of electronic circuits and their components.
• The power supply is a critical component of an electronic circuit, converting alternating current inputs to direct current outputs.
• Rectifier circuits are used in power supplies to convert AC to DC.
• Types of rectifier circuits include:
  • Half-Wave Rectifier
  • Full-Wave Rectifier
  • Full-Wave Bridge

Printed Circuit Board (PCB)

• A PCB is a board that has conductive paths and components mounted on it.
• The power supply is a critical component of a PCB, converting alternating current inputs to direct current outputs.
• Rectifier circuits are used in power supplies to convert AC to DC.

Operation of a Radio Receiver

• A radio receiver is a device that receives transmitted signals and produces audio form.
• The function of a radio receiver includes:
  • Reception: receiving transmitted electromagnetic waves
  • Selection: selecting a particular station frequency from all transmitted signals
  • Detection: separating the low frequency intelligence from the high frequency carrier
  • Amplification: increasing the signal
  • Reproduction: producing the original audio signal### Radio Receiver Characteristics
• Sensitivity: ability to reproduce the signal from the weakest station with the same signal output value
• Selectivity: ability to differentiate between desired and undesired signals

Troubleshooting

• Locating, correcting difficulties and improper operations of components in electronic circuits
• Typical radio receiver problems: no audio output, weak output with no excessive background noise, and distorted audio production

AM Radio Receiver Sections

• Power Circuits: most likely to have problems due to heat generated by high currents
• Audio Circuits: include circuits from volume control to loudspeaker; can be tested by touching the high side of the volume control to hear a loud hum or sound
• IF Sections: circuits from mixer output to detector input; timed to 455 KHz in AM and 10.7 MHz in FM for test signals
• RF Sections: include antenna, RF amplification up to mixer input, and local oscillator stage; RF signal frequencies are 535 to 1.605 MHz for AM radio and 88 to 108 MHz for FM radios as test signals

AM Radio Trouble Shooting Chart

• Weak signal only at one end of dial: transistor in converter stage is defective; replace with a new transistor
• Intermittent operation: poor solder joint, break in printed wiring, poor battery contacts, earphone jack has loose contacts, power switch has loose contacts, volume control is dirty, or turning capacitor is dirty
• Distortion in volume control settings: weak battery, leaky or dried out electrolytic capacitors, soldered joint has high resistance, or carbon resistor has increased in value
• Distortion on strong signal only: capacitor is shorted or bypass capacitor is defective
• Squealing or motor boating: weak battery, bypass capacitor is defective, or battery or tuning circuit has high resistance
• Squealing can only be heard when the station is tuned in: weak battery, antenna core is cracked, or defective C4 capacitor
• Only one station is being heard: local oscillator is not working
• Noise is being heard with all stations: turning capacitor plates are rubbing
• When tuning in to different stations, volume changes too fast: converter transistor is defective