Quick Schematic Question

[Cartierusm]

OK, I've always wondered why schematic are the way they are? Let's say you find a circuit online for a simple power supply and it's written for the end user to build why does the author who obviously built the thing and intends for you to build it put up the schematic instead of a diagram of a circuit board so you can build it and etch the board. I've never understood that, or am I missing the point? I guess it makes the connections easier to understand and study and making the board can be make a million different ways as long as the connections are correct?? It's just up to the builder to figure out where they want to put the components?

[Al_The_Man]

Many people put up a schematic for anyones for general use or information.
They may or may not have actually gone the extra mile and mapped out a circuit board for it, if they have, just for their own use, then they might offer it also for free, but if they are expected to provide one regardless, then I would expect this to be paying proposition.
Then we get into the realm of prototyping/marketing, which many do not want to bother with, especially for small run items.
There are many other aspects such as whether people prefer a design in SMT or through-hole components etc.
Schematic Design is one thing, PCB design is a complete other.
Also the builder may have used a one-off proto board version for the original.
Al.

[Cartierusm]

Thanks. I was just curious.

[neilw20]

I design a lot of electronic consumer circuits that run direct off the mains with no transformers.
Most are fully designed and tested using Electronic Work Bench or similar emulators.
That make smoke testing work without the fire extinguisher and the lack lack of soldering is definitely ROHS compliant.
After few blown electronic software fuses and damaged meters the circuits work quite well.
I only needed spec sheets to make it work. Send the finished circuit to someone else to do the final smoke test.

Move on to the next design, with not so much as a burnt finger.
Plenty of circuits get created to be incorporated in other larger items like this and never see a PCB. It might be SMD, thruhole or just birdsnest.

That's often what happens.

[keebler303]

There are also pin out issues. Lets say a circuit uses a 14 DIP op amp, there are thousands of op amps which would make the circuit work, but they may not all have the same pinout. The board layout would only work for components with a similar pin out. Many times, people use what they can get or what they have on hand and so you cannot always use the exact component called for in the schematic.

You're getting the schematic for free, don't be greedy about the board layout too!

Plus you will learn a lot more if you have to make your own layouts.

Matt

[Cartierusm]

LOL, thanks.

[sswitaj]

The difference between a schematic and an assembly diagram is that the assembly diagram is (roughly) that an assembly drawing tells you how to build the thing, but provides little conceptual description of what's going on in the board.

You could (if it was important to you) back-engineer the board and figure out how all the parts are interacting, but it would be difficult, because most of the active components are just little black bits of plastic and "u1, pin1 goes to u6, pin3 offers little insight into what's going on.

Eventually, if you were to back-engineer a board, you'd eventually end up drawing a schematic.

Both types of diagram are important, but most of the people who provide circuits are trying to answer the "This is how it works" question, assuming that that's the important part, and, once that is made clear, actually soldering it up is an easier exercise, and in any case, will be highly variable depending on what parts the end-user has lying around in his shop.