Emp Schematic

[Jomega Gibson]

A schematic, or schematic diagram, is a designed representation of the elements of a system using abstract, graphic symbols rather than realistic pictures. A schematic usually omits all details that are not relevant to the key information the schematic is intended to convey, and may include oversimplified elements in order to make this essential meaning easier to grasp, as well as additional organization of the information.

For example, a subway map intended for passengers may represent a subway station with a dot. The dot is not intended to resemble the actual station at all but aims to give the viewer information without unnecessary visual clutter. A schematic diagram of a chemical process uses symbols in place of detailed representations of the vessels, piping, valves, pumps, and other equipment that compose the system, thus emphasizing the functions of the individual elements and the interconnections among them and suppresses their physical details. In an electronic circuit diagram, the layout of the symbols may not look anything like the circuit as it appears in the physical world: instead of representing the way the circuit looks, the schematic aims to capture, on a more general level, the way it works. This may be contrasted with a wiring diagram, which preserves the spatial relationships between each of its components.

A semi-schematic diagram combines some of the abstraction of a purely schematic diagram with other elements displayed as realistically as possible, for various reasons. It is a compromise between a purely abstract diagram (e.g. the schematic of the Washington Metro) and an exclusively realistic representation (e.g. the corresponding aerial view of Washington).

In electrical and electronic industry, a schematic diagram is often used to describe the design of equipment. Schematic diagrams are often used for the maintenance and repair of electronic and electromechanical systems.[1] While schematics were traditionally drawn by hand, using standardized templates or pre-printed adhesive symbols, today electronic design automation software (EDA or "electrical CAD") is often used.

In electronic design automation, until the 1980s schematics were virtually the only formal representation for circuits. More recently, with the progress of computer technology, other representations were introduced and specialized computer languages were developed, since with the explosive growth of the complexity of electronic circuits, traditional schematics are becoming less practical. For example, hardware description languages are indispensable for modern digital circuit design.

Schematics for electronic circuits are prepared by designers using EDA (electronic design automation) tools called schematic capture tools or schematic entry tools. These tools go beyond simple drawing of devices and connections. Usually they are integrated into the whole design flow and linked to other EDA tools for verification and simulation of the circuit under design.

In electric power systems design, a schematic drawing called a one-line diagram is frequently used to represent substations, distribution systems or even whole electrical power grids. These diagrams simplify and compress the details that would be repeated on each phase of a three-phase system, showing only one element instead of three. Electrical diagrams for switchgear often have common device functions designate by standard function numbers. Another type of diagram used for power systems is a three-line diagram.

For analysis purposes of a power system, from the one-line diagram, if the system is balanced, an equivalent per-phase (or single-phase) schematic diagram can be obtained. If all of the parameters are represented as impedances and voltage sources, the equivalent per-phase schematic diagram is called an impedance diagram. If all of the parameters are represented as admittances and current sources, the equivalent per-phase schematic diagram is called an admittance diagram.

If the power system is unbalanced, but it is linear (or can be approximated by a linear system), then Fortescue's theorem (symmetrical components) can be applied. In this way, from the one-line diagram, three different per-phase schematic diagrams are obtained, known as sequence diagrams: positive sequence diagram, negative sequence diagram, and zero sequence diagram. Each of these diagrams can be represented as an impedance diagram or as an admittance diagram.

Schematic diagrams are used extensively in repair manuals to help users understand the interconnections of parts, and to provide graphical instruction to assist in dismantling and rebuilding mechanical assemblies. Many automotive and motorcycle repair manuals devote a significant number of pages to schematic diagrams.

You can do something very similar to what you want, if you create your design using hierarchical blocks. Imbedd your schematic into a hierarchical block, then when you select the block, all the parts in the schematic will highlight and move as a group.

Question for you, i can seem to crossprobe in reverse as easy, select a part in layout and zoom to the schematic page. the only whay I can make this work is select a function in the pcb like chage color, then select the symbol and then the schematic will zoom to the part.

Crossprobing works with the highlight/dehighlight tool. If you select a part in the schematic it will highlight the part in Allegro (it only works if there is no active command). If you highlight a part in Allegro it selects the part in the schematic. I haven't found a way to have it stick to the mouse as in the move function. It would be nice if it did work that way.

Steve is correct that if the Placement window is open (Place > Manually) you can click on schematic parts to pull them from the place queue and attach the part to the cursor in PCB Editor 16.0+. Unfortunately, the OP said he is using 15.7 and I don't believe you could do that before 16.0 (been too long and don't have it installed anymore to check).

In these cases, I have used the ROOM property. By attaching a "ROOM = DSP" or "ROOM = DDR3"(without quotes) property to schematic parts, those parts can be placed all at once on the PCB. By using a ROOM property you can subdivide hierarchical blocks even further, should you wish. With 16.2 placing a property on multiple parts is much easier, again unfortuantely for the OP.

Crossprobing is hopelessly broken as far as I can tell. I have submitted many SRs hoping to get what I believe is common-sense crossprobing (backed up by the crossprobing of other ECAD programs I've used). Hopefully Cadence will address the myriad of crossprobe shortcomings in the future.

How to make a PCB in KiCad without a schematic is a repeated request on this forum. KiCad is very much geared into having netlist information extracted from the schematic, and working around that is probably more of a nuisance then a shortcut.

A wonderful tool for reverse engineering a PCB would be to make photographs of an existing PCB and then load (and scale) those photographs in Pcbnew, but that is unfortunately not supported (yet). There is a nice writeup on the closest you can currently get, which you can find via:
=reverse+engineering+with+KiCad
Which gets you here:

I spend more time than I probably should reverse engineering circuit boards, so I figured I would write up a page on how I do it. This only applies to two sided PCBs, and requires some time of imaging device,

Conclusion:
I experimented now for the first time in my life with this method and it works quite well. Creating the netlist inside Pcbnew is quite easy and intuitive and you get all the benefits that come with a netlist. Some of these are:

But my hand (writing/drawing) is pretty bad and if the sketch gets at all complicated I need to then resort to KiCad or other computer interface which gives me straight lines and is more easily edited.

If this command does what I expect I would like to vary the pin position from pcb for example of an MCU or fpga to make the layout cleaner without having to change from schematic, which requires having both windows open and generates confusion on the order just some labels to move.

I tried to do some experiments:
1st change in value and it works.
2nd change net name and it works.
3rd I inverted the net on 2 pads of a connector and in the eschema comes
the same label is shown on both pins. See photos

Refdes changes do not happen without user interaction. Even while using update from schematic. If the process finds you do not have a fully annotated schematic then it will open the annotation dialog. At this point you can stop. The same is also the case if you go via the export netlist dialog! It also opens the annotation dialog if it needs to.

And be aware that there is no back annotation. So if you change a refdes on the board then it will not change in eeschema by going through this. It will change back the one on the board to what it was in eeschema.

If you however have for example R1 and R2 placed but discover that the position of R1 would better fit for the connections of R2 then you can change the refdes in pcbnew. However on update you will need to tell kicad that it shall use the refdes for reconnecting the schematic to the layout. See Update PCB from Schematic's match methods (current nightly might have different names for the options but the underlying behavior is the same)

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