Note: Not confused by electrical diagrams (overall diagrams).
[1] (Electrical) Schematics are a type of electrical diagrams.
Note: "Diagram" is a general term for visual representation.
"Schematic" is a specific diagram type of basic symbols to show logical connections, unlike a wiring diagram is for physical placement.
[2] Common symbols used in schematics
"Textbook exercises" circuits are mainly to teach math.
If 2 lines touches, but don't have a dot drawn over an intersection, no connection between the 2 circuits. At times we show there's no connection by drawing a small "hump" over the first line to show that the second line is above it, not touching it. Methods are optional.
[4] Connections or dots between lines are indicated by dots.
[2] If many connections exist, they're often drawn a dot where the lines intersect. Many lines can converge to one connection, but most dots only connect 2 lines.
(a) and (b) are both good.
(c) indicates no connection.
(d) also indicates no connection; the horizontal wire. "hops" over the vertical wire. It's clear but takes extra effort and space to draw.
(e) for crossing connected lines, it's acceptable, but risks looking too much like (c), so (f) is better.
Dots are unambiguous indications that lines are connected.
If a connection is obvious, dots isn't used.
[2], [4] Node are points where 2+ parts connect.
Lines aren't wires, but connections. A long line does not imply a long wire nor a short line is a short wire.
Note: Some sources use a different word for the term.
These circuits have 3 nodes labled A, B, and C.
Nmatter how they're drawn, the same parts are always connected to the same nodes. In other words, node A is always connected to the positive side of the 9 volt source and one side of resistor R1, node B is always connected to R1, R2, and R3, and node C always connects R2, R3, and the negative side of the 9 volt supply. It does not matter where the parts are drawn on the paper, and which way they are oriented. It only matters that the lines be drawn in such a way that the node relationships are preserved. Again, to emphasize the point, all of the diagrams in the following figure describe the exact same circuit.
[4] This schematic has one node (a black dot) formed by 5 junctions (orange rectangles).
As lines on represent perfect zero-resistance conductors, no rule says lines of multiple elements must touch at one point junction. We can draw the same node as a distributed node like this schematic. The 2 representations nodes ar the same.
This circuit has
a realistic-looking schematic with distributed nodes labeled:
This schematic has 4 nodes.
[4] Branches are connections among nodes and an element (resistor, capacitor, source, etc.).
branch numbers = number of elements
This schematic has 6 branches (5 resistors and 1 voltage source).
[4] Loops are closed paths going into elements.
Draw a loop by choosing any node as a start point and draw a path through elements and nodes til the path comes back to the node where you started.
There's only 1 rule: a loop can go into a node once.
It's ok they're overlap or have other loops.
This one has 6 loops.
Despite a basic example, it has many loops.
This same circuit's reference designators are R1 and R2
A reference designator is the name of a component in a schematic is given a name.
E.g R1, R2, R3, C6, VBAT.
Numbers don't indicate the any values (resistance, current, etc).
This circuit has 6 meshes.
A mesh is a loop with no other loops. It's like a mesh for each "open window" of a circuit.
[4] Power and ground are often abbreviated to save space on schematics.
Grounds (means signal returns) are often drawn with a symbols above.
DC power is often with the number and a plus or minus sign.
An arrow may be used, but not in many schematics.
[2] These 2 examples show a 5 volt DC power source connected to a resistor (the rest of the circuit is not shown).
[4] We often choose a node in a circuit as a reference node.
Voltages at other nodes are measured relative to a reference node. Any node can be the reference, but 2 common choices simplifying circuit analysis are a voltage's negative terminal or current source powering the circuit, or the node connected to the greatest number of branches.
[4] Reference nodes are also called grounds.
Its has 3 crucial meanings:
a reference point from which voltages are measured
a return path for current back to its source
a direct physical connection to Earth, crucial for safety--origin of its name
Various symbols for ground:
A metal stake driven into the ground near a home. The wire clamped to it curves up to the right for the safety ground reference for the home's electrical system.
At times a grounding wire is clamped to a water pipe where the pipe disappears into Earth.
[4] Schematic equivalence is crucial as a circuit can be drawn in other ways.
Equivalence means matching nodes have the same voltage and matching branches have same current.
These are the things we care about being the same.
These 2 schematics equivalent.
Left schematic is a voltage source and three resistors in numerical order.
Right schematic the right, resistor R4 is on the left of the voltage source.
To be equivalent, 2 schematics must:
Represent all component and source.
Have the same number of nodes.
Each node are connected to the same branches.
Verify if 2 schematics are equivalent:
Are all components and sources represented in both schematics?
"V, here, R1, here, R2, here, R3, here."
All elements accounted for.
Do both schematics have the same number of nodes?
Yes, both have 2 nodes.
Is each node connected to the same branches?
Yes, all node connects to the 3 resistors and a source.
The 2 nodes are in oranges.
The 4 branches are in blue arrows.
A ladder diagram is a ladder-shaped diagram often used to control logic systems.
[R2]
[Q1] Flashcards