Electronic components are the basic building blocks of the most complex electronic machinery in the world. The basic electronic components that you need for most building projects are inexpensive and, if you are good at electronic engineering, you can build devices that would otherwise be a very expensive purchase for a very low cost.
All electrical components play specific roles in circuitry and have specific attributes that dictate whether they are appropriate for use in any given role. For example, a resistor, whose resistance is measured in ohms, will not be appropriate for use in a specific circuit if it fails to inhibit enough current from flowing to keep the other components in that circuitry safe.
Introduction to Electronic Components
Electronic components are, taken by themselves, generally very simple. Excepting the cases of integrated circuits, which constitute a combination of several different electronic components in one device, electronic components are generally not at all hard to understand. Some of them are amazing in terms of what a simple configuration can do.
For example, a transformer, at the root of it, is only a core with wire windings around opposite sides of it. The complex interaction of magnetism and electricity allow transformers to be created that can precisely transform voltage is down or alter current. Likewise, simple logic gates, when combined into devices that contain literally hundreds of millions of them can turn into your desktop computer.
Electronic components are generally affixed together in a circuit on a printed circuit board or on a breadboard, which is a circuit board that allows components to be passed through holes and soldered into place. Creating printed circuit boards is a very complex process. For most hobbyists, breadboard type circuit boards are preferred and soldering is a necessary skill – as well as a source of pride when that skill is developed.
Electronic components can be understood in terms of their function within a circuit and in the way that they affect the various properties of that circuit, such as how much current is flowing through it, how much resistance the circuit has and so forth. Electronic components are also represented by specific symbols that are used in schematic diagrams to indicate their positioning within the circuit. These symbols are internationally recognized and have been designed so that it is easy to distinguish one electronic component from another in a schematic diagram.
Understanding Schematics and Symbols
Many electrical components have multiple versions. For example, there are several different types of transistors that are utilized in circuitry and each of them has its own function and, appropriately, each of them has its own schematic symbol with which it is associated. The most common schematic symbols are given below. All of the schematic symbols, however, are similar enough that it is readily apparent what they are, even if they represent a variation on the schematic symbols with which you are already familiar.
It’s important to look closely at the schematics and the symbols on them for any given electronic circuit. They oftentimes reveal more information about the circuit than what a novice might assume. In reality, the schematic symbols are designed to show the function of each of the components in a very abbreviated, compact way that is easy to read once you learn how. For instance, the symbol for a variable resistor is exactly the same as the symbol for a resistor, except it has an arrow on it which indicates that the resistance can be moved up or down. A light emitting diode has the same symbol as a regular diode, except it has two arrows projecting upward at a 45° angle from the diagram, indicating that it emits energy in the form of light. Understanding these subtleties can help you to get more out of schematic diagrams and more easily ascertain what’s involved with building any circuit that is represented thereby.
Drawing schematic diagrams once took a great deal of skill; skill in line with what a draftsperson would’ve been expected to have when drafting was done by hand. Today, there are numerous electronic solutions to the problem of drawing schematics for electronics.
Most of today’s schematic diagrams are drawn on software. This ensures consistency and ensures that the schematic diagrams are always readable to anybody who needs to use them, as the symbols never vary between one and the next and all of the appropriate information is included on the diagram.
Some electrical engineers, however, and some hobbyists, are quick enough to draw schematic diagrams of whatever they’re creating on-the-fly. This skill is an excellent one to develop if you plan to use electronic components to build appliances from scratch. All you need to do this is a good pencil and some graph paper and a cheat sheet that gives you all of the various schematic symbols that you will need. You can print out the following information and you will have at your fingertips the most commonly used schematic symbols in electronics.
Be aware that some of the schematics typically show up with additional information written alongside them. For instance, a power supply will generally indicate how much power it puts out rather than just saying it puts out power in general. There are also quite a few subtleties involved with the symbols, as well. For example, the symbol for a battery is actually drawn in a way that indicates to the reader how many power cells are included in that battery, which allows the reader to determine how much power each of the cells is putting into the circuit. This type of subtlety is what makes schematic diagrams so eminently useful to electrical engineers and to hobbyists.
Semiconductors are not electrical components, rather, they are materials out of which electrical components are made. The entry for semiconductors below clarifies this in greater detail, but there is no schematic symbol for a semiconductor, semiconductors are symbolized according to the part to which they belong, such as a transistor.
Batteries are power supplies that generate a constant voltage. This voltage is expressed in VDC. On a schematic diagram, each long and short line pair on the battery symbol symbolizes one power cell within the battery.
Battery supply a constant voltage, as was stated, but the voltage in the circuit will vary depending upon what that circuit is powering. The formula for determining voltage in a circuit is V = I X R, which stands for voltage equals current multiplied by resistance. This is a variation on Ohm’s law, one of the most fundamental laws in all electronics.
A capacitor is a device that is used to store charge. They are utilized in most electronic devices. In the presence of DC, a capacitor behaves as an open circuit. In the presence of AC power, the capacitor functions as a short-circuit.
Capacitance is calculated using the following formula: C = q/V.
Connectors describe any junction of two wires. They may or may not have splicing hardware holding them together. The symbol above shows wires that are connected. The symbol reproduced below shows unconnected wires, with the “u” shape indicating that the wires pass over one another physically but are not connected.
Diodes are devices that only allow current flow in one direction. On a schematic diagram, the arrow shape indicates the direction in which current is allowed to pass.
In the presence of an overcurrent condition, a fuse will burn out, which means that it will open up and break the circuit, eliminating the current.
Fuses are measured in amps, with the measurement indicating the maximum amount of amperage that the fuse can handle before it burns out.
Ground or Earth
The ground symbol shows where there is zero potential and where shock protection has been added to the circuit.
The chassis ground symbol shows where the circuit is connected to the actual chassis of a device rather than being directly grounded.
Inductors are coils or solenoids that generate magnetic fields.
Inductance is measured in henries and determined using the following formula: v = L(di/dt)
Integrated circuit symbols vary depending upon the number of outputs and the type of integrated circuit indicated. They all follow this basic pattern, however.
A lamp is simply a device that outputs light when energy is introduced into it. There are various symbols used, but they all follow this convention. The output of a lamp is measured in wattage.
The symbol for an LED is similar to the symbol for a regular diode, save for the arrows radiating away from the device as pictured above.
The symbols for meters all follow the convention shown above. The letter inside represents what is being measured. Voltmeters have a V, ammeters have the letter A, Wattmeters have W and ohmmeters have the symbol for ohms, and omega.
Operational Amplifiers (op-amps)
Operational amplifiers amplify the input signals that they are fed and are symbolized by the schematic above.
Potentiometers have the same symbol as resistors with the addition of an arrow, indicating the adjustability of the device. Potentiometers are measured in ohms, with a maximum and minimum rating given for the device.
There are variations on the symbol for power supplies, but the most common one is given above. They vary depending upon what type of power they supply – AC versus DC, for instance – and whether they are controlled voltage or controlled current. The symbol above is for a constant voltage. An AC voltage source is represented by the schematic below.
Resistors are among the most basic of electronic components and they function to reduce current flow. They are symbolized by the schematic shown above, though variable and other types of resistors have slightly different symbols, all based on the schematic shown above.
Resistance is measured in ohms. The formula for calculating resistance is R = V/I.
There are many different components that utilize semiconductors, so there are many different symbols for semiconductor components. There is no specific schematic symbol for “semiconductor”, however.
Silicon-controlled Rectifier (SCR)
The symbol for a silicone controlled rectifier is very similar to the symbol for a diode. The differences the horizontal line that describes where the gate is on the rectifier.
A switch simply functions to open or close a circuit. Just as there are many different types of switches, there are many different types of schematic symbols to illustrate where they are positioned. The symbol shown above is for a single pole single throw switch. Other types of switches are diagrammed in ways that make their function readily apparent. For instance, a single pole double throw switch, which allows the user to switch between one of two different connections, is shown below.
Transformers function to change voltage or current from low to high or from high to low. The symbol nicely illustrates the internal workings of a transistor, which consists of a pair of coils wrapped around a core.
The secondary voltage – or the output voltage – of a transformer can be expressed mathematically as follows. In this equation, V stands for voltage, E stands for the induced voltage and N stands for the winding turns ratio.
Vp/Vs = Ep/Es = Np/Ns = a.
There are many different types of transistors in use, so there are many different symbols utilized in schematic diagrams to demonstrate where and how they are connected to a circuit. The symbol above is for an NPN bipolar transistor, which permits the flow of current when there is a high potential in the middle – or base – connector.
The symbols for transistors vary widely, but they all make apparent the function of the device. For example, the Darlington transistor for which the symbol is given below is made from two bipolar transistors, which is clearly observable in the diagram.
A voltage regulator does exactly what the name implies and regulates the voltage going through a circuit. The symbol for the device gives the user information as to the purpose of each of the pins illustrated.