Circuits can be represented in many different manners, from the pictorial view (realistic representation), to a block view (A flowchart explaining the working of the circuit). In this guide/tutorial, I will be explaining how to read, understand, interpret and even make your own schematics if you are an absolute beginner and are still not ready to read advanced tutorials. Let’s get started!
Why go schematic, are there significant advantages?
Circuit schematics are, by far, the simplest way to show a circuit whilst also not compromising on details. The diagrams of parts used are also standardized, meaning your circuit will not only be simply to draw and to read, but will be understandable everywhere around the globe (with some minor differences between a few countries).
Drawing a pictorial representation of the circuit (realistic view) might help you to actually get a feel for the size, shape but will be more time consuming and tedious, not to mention that sizing can be done after the circuit is built (and will in fact be better and less mistake prone). Drawing the circuit with your own components can be simple and faster, but it will only be readable by you and also risks compromising a lot of the details. Schematics take care of both these problems.
You can see the difference for yourself in the above two pictures, which represent the same circuit.
Some Common symbols
Before proceeding any further, it is essential to get familiar with a few basic components in schematic view-
This is the symbol for the generic DC source. It consists of a pair or multiple pairs of parallel lines, with the shorter one indicating the cathode (ground) and longer one indicating the anode (VCC). Each pair indicates a single cell of a particular voltage. It is the power source of your circuit.
Next, comes the diode and LED (Light emitting diode). It consists of an arrow with a bar on one side. The bar indicates that current can only flow towards the tip of the arrow and not the other way round.
The symbol for an LED is also the same, with the only addition being two or three small arrows being drawn on the side to indicate light being emitted.
The resistor is simply a zig-zag line with the resistance (in ohms) written beside it. The rightmost one is a common resistor while the other two are variable resistors or potentiometers (POTs for short). The pots have a third line either crossing or touching the main resistor, indicating a movable knob or slider.
Capacitors are similar to batteries, except they contain only a single pair of lines of equal length. A ceramic capacitor (not polarized, shown on the left) has both the lines straight while an electrolytic capacitor (polarized, shown on right) has the cathode as a curved line while the anode is straight. The capacitance is written beside in farads.
The Inductor looks similar to a resistor, but with curved lines with the inductance written beside in henry. It is can be used to filter AC current and also like a capacitor (albeit an innefficient one) to store charges in a magnetic field.
Lastly, come the transistors. The BJTs are shown top (PNP on left, NPN on right) while the MOSFETs are shown below (N channel on left, P channel on right). Transistors are like switches, with the difference being how they are opened and closed. A common switch is operated by mechanically moving it (usually by hand) while a transistor is controlled by a secondary current/voltage.
BJTs are usually cheaper and are preferred for low power applications while MOSFETs are larger, more expensive and are preferred for high power applications.
*Note– Guys, there are A LOT of components out there and it is not possible for me to show you the schematic view of every component along with its name, so if you come across a component not in the above list or in this blog, then google is your best friend.
Junctions and Jumps
When drawing a schematic, sometimes it might get difficult to understand which pair of overlapping wires are connected and which are not. To solve this issue, junctions and jumps are used.
In the first diagram, the wires are simply crossing over and may or may not connect. In the second diagram, however, the two pairs of wires are not connected for sure as a jump has been used between the two while in the third diagram, they are connected for sure as a junction has been used.
A jump is simply a curved line or arc in a wire which indicated it is not connected to the wire it is overlapping while a junction is a thick dot or blot over a pair (or more) of wires indicating a connection between them.
Drawing a Schematic
To start drawing in schematic view, you must either have the circuit ready in front of you or you must be familiar with the circuit. The schematic can be drawn by hand or via software (I have used Fritzing, tutorial coming soon).
Start by placing the power source and then the components each one by one but don’t start connecting them as this can cause confusion later down the line, especially in larger circuits.
In this example, I am going to show how to design a simple 3×3 button matrix.
Here are the nine pushbuttons, each rotated 45 degrees clockwise. I have drawn all the buttons before starting the connections because I don’t want to find out later that I their is a wire where a button needs to go, because while the wire can be moved without changing the looks of the circuit much, the buttons are bigger and can cause the same circuit to look more confusing.
Next, the rows are connected together.
Finally, the columns are connected together, and the circuit is complete. Here is the pictorial representation of the same circuit-
You can see the difference for yourself.
Now that you have finished reading this tutorial, I recommend that you go through the following tutorials as well to help you get a better understanding of the subject as well as practice to make sure you are all clear.