Think of it this way; a circuit diagram is any kind of diagram that demonstrates the way the circuit operates where the principal goal is the proper wiring of elements and their relationship to each other instead of physical location relative to one another or planning prototypes. However, in some applications classifying diagrams can be difficult so take this as general information. I've discovered this is especially true when working with much more complex circuits and electronic equipment. I'm likely to use a simpler but typical industrial circuit since these circuit set ups are exactly the same, but nevertheless where it is possible to see how each sort of diagram indicates the role of the circuit in their own manners.
A design diagram refers to a specific sort of circuit structure that utilizes standard electrical/electronic symbols instead of pictures to show how a circuit (or portion of it) works. Below is a standard 3-wire motor controller circuit employing a normal short stop stop - start pushbutton channel utilizing a schematic diagram. (Momentary this means that the button/switch you activate will go back to its default place once you physically let go of this, typically by a spring which compels the button/switch to do this.)
Much less clutter, right? I have enough information in each one of these diagrams to know exactly what this circuit does and where to look for issues. Hope that this helps. ( Note: do not confuse circuit or schematic diagrams with wiring diagrams; wiring diagrams will usually demonstrate images of elements such as the pictorial, and how the entire or part of a circuit has been wired. The difference is that wiring diagrams typically put an emphasis on real physical location of necessary elements relative to each other that basically tell a layman Just What to do concerning the wiring. )
Here's another schematic diagram showing exactly the identical circuit, components and connections and it looks different but they both fall into precisely the exact same category.
Pictorial design diagrams, or pictorial circuit diagrams are basically the exact same thing with exactly the identical purpose, but they use images of components within the circuit instead of symbols. Again, here's the exact identical precise circuit (almost except a controller was added and they're utilizing conductors L1 and L3 instead of L1 and L2.
Following is a version of a schematic diagram known as a ladder diagram. The primary intention of this diagram is to show the logic (referring to electrical management ) of a circuit board. This really is the one I mainly encounter in my line of work, and it's very effective for troubleshooting problems or learning how a circuit functions. Some circuits are so enormous that most kinds of schematic diagrams have to be read in increments from book form (generally with coded numbers so that information can be simpler located ). Again, here is the same precise circuit because the first two, however, looking at it in ladder shape.