Streets are supposed to be divided into fairly uniform blocks that have the appearance of a grid. Your GPS is supposed to be able to navigate this gridded structure to get you where you want to go. It would seem like a great system, except when it doesn’t work. At least that was the message I got when my navigator turned me into the entrance of a military base, and the guard approached my car with his weapon at the ready.
Grids are supposed to help you, and not force you into situations where you have to smile brightly while you hastily reverse back out of checkpoint bravo. I have no idea what went wrong with my GPS that day, but when I have problems with my PCB schematic capture system, it sometimes is because I didn’t set the grid properly. Here are some ideas that might help you to get more productivity out of your design tools by choosing schematic grid sizes that will steer you in the right direction.
What are the Different Schematic Grid Options that You Can Choose From?
Grids are an essential part of designing a circuit board. On the layout side, your PCB design grids can assist you in how you place component footprints on the board, route traces, and move text around. Over on the schematic side, it is much the same. Your grids will help you to neatly organize and place your symbols, draw nets, and add or edit text. To accomplish this, most schematic capture systems will give you some options for working with your grids.
Typically these options will be available in a display menu for the schematic. You can toggle the visibility of the grid on and off, as well as set up the style of the grid such as dots or lines. Depending on the system, you may also enable or disable snapping to the grid, or set up other grid functions such as units, page sizes, and even sheet borders and title blocks. Schematic capture systems will also give you the ability to change these values independently between editing symbols, or editing schematic pages.
Schematic grids do differ from layout grids though in that the grid the component pins land on has to remain locked during the design. This will prevent the pins from behaving erratically on a schematic page if the grid values were changed after some of the components were placed. You can usually set up the pin grid spacing however when you first open a new schematic sheet, but after that, those values will be locked in. You can also change how you can work with that grid by changing the display of its spacing. This will allow you to alter the display of the grid on a schematic sheet in multiples of the grid without actually changing the pin spacing.
The grid display menu in a schematic capture tool
Considerations when Choosing Schematic Grid Sizes
As we said above, you can change the value of the pin grid spacing when you first open a new schematic sheet, but you should give this careful consideration before doing it. Changing the pin spacing will change the scale of the part on the sheet, and you want to make sure that all library symbols will display normally on the page. There have been many instances where someone will create a symbol at one grid value, and then that part is scaled incorrectly on the schematic sheet because it is using a different pin to pin spacing. Also, you may end up making a lot of extra work for yourself that isn’t required. Most schematic capture systems come with a default pin spacing setting that will do the job quite adequately.
There are times though where changing the pin to pin grid spacing can be beneficial. If your design has a lot of small components on it and you want to conserve space on the schematic sheet, you can change to a smaller pin grid spacing. For instance, by changing the spacing from a default setting of 0.10 inches to 0.010, you will scale your components back to 10% of their original size. Just remember though that a change like this has to happen before you start working on that sheet, and it will have to stay that way throughout the life of the design.
The ability to customize how your grid displays will greatly help you with designs like this
More Design Tool Versatility Gives You More Design Productivity
To get this level of control over the design grids that you will use in your schematic capture system, you need to use PCB design tools that are both powerful and versatile. In addition to having a schematic capture tool with full features, you also need to consider tools that will work hand-in-hand with libraries, simulation tools, and of course PCB layout tools. The features that your design system has, the more that you will be able to configure it to do the job the way that you need it to.
The PCB design tools that you are looking for to give you this technological edge are already on the market and available to you today. One of the best PCB design systems that has all of the features and capabilities that we’ve explored here is from Cadence. OrCAD PCB Designer has the advanced tools and functionality to not only give you the control over design features like schematic page grids, but much more as well. With OrCAD you will have access to PSpice, one of the industry’s leading simulation tools, as well as different library, layout, and analysis tools.
If you’re looking to learn more about how Cadence has the solution for you, talk to us and our team of experts.
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