History is full of dreamers and inventors who created innovative technology out of practically nothing. Take the Wright brothers, for example. When presented with the problem of not finding an internal combustion gasoline engine that met their airplane’s power and weight requirements, they went and built one themselves. Since there isn’t a complete set of plans for that engine available to us today, historians have had to guess from pictures and descriptions for the details of how it was configured. It could have been designed on an old envelope for all anyone knows.
Designing on paper certainly has a nostalgic charm, and many of us learned circuit design using simple drafting tools. However, circuit board design has become more complex since the good old days of using a drafting board. If you are still using pen and paper, you miss out on some beneficial functionality available in even the most simple schematic drawing software tools. Let’s compare pen and paper schematics with CAD schematic capture systems and see some of these differences.
So What if My Schematic is Drawn on a Napkin? What’s the Big Deal?
There is only one advantage of using pen and paper to draw an electronic schematic; it is quick and easy. Other than that, though, you start running into a plethora of problems with hand-drawn schematics. For example:
- Size restrictions: Most people run out of room very quickly when drawing on a piece of paper.
- Messy editing: To make any change, you have to either erase or block out your work.
- Now, where did I put it?: It can be so easy to misplace a document, especially one hastily drawn up on the back of an envelope.
- Ketchup stains can easily be mistaken for power connections: No further explanation is needed for this.
Let’s face it, drawing up some circuitry on a napkin may be a great way to hash out some ideas at lunch, but it shouldn’t be our primary method of capturing PCB schematics. Here are some other hand-drawn schematic problems that should be considered before you dip your pen in the old inkwell:
- Schematic symbols: Are often drawn from memory or using a template, resulting in incorrect pin configurations and other drafting errors.
- Part numbers: This information and other critical data are often left out of hand-drawn schematics, which invites additional errors down the road.
- BOM checking: Without an automated method of collecting and collating component information, verifying the parts list to current supply chain resources is challenging.
- Design rule checking: Obviously, a hand-drawn schematic can not be run through an automated DRC system, which only increases the possibility of errors.
- Database management: Paper schematics can’t be stored using modern product data management systems (PDMs), nor can they easily be reused. Schematic storage requires large flat file document storage systems that take up a lot of space.
- Legibility: Depending on the medium used and the skill of those drafting, a paper schematic can be difficult to read and understand.
A schematic has to synchronize with a PCB layout database. Whether it interfaces directly or a netlist is extracted from the schematic to import into the layout system, the design still requires a CAD schematic. Yes, a paper schematic can be recreated in a CAD system, but why draw it twice when you can capture it electronically. Next, we’ll look at some of the advantages that you will enjoy using a schematic capture CAD system.
The Advantages to Using Even a Simple Schematic Drawing Software System
The capabilities of a PCB design system, and specifically those belonging to a schematic capture CAD tool, will give you the following benefits:
CAD libraries
With the ability to create, check, and save verified library parts, you no longer have to worry about questionable hand-drawn parts. There are also third-party library services that can provide you with PCB components making your job easier. These symbols will be drawn at the correct size and shape and include all the necessary pin information, properties, and attributes. These parts often include schematic simulation models, PCB footprints, and 3D STEP models to complete your PCB design library.
Consistency
Using even simple schematic drawing software will give your schematics a consistent look that is difficult to achieve with hand-drawn documentation. CAD schematics can all be created at the same size and scale and include denoted company information, part numbers, and other crucial data.
Speed
Typically, and with some practice, placing symbols and wiring them is faster in a CAD system than drawing them by hand. But even if it wasn’t, the real time-consuming portion of schematic capture is editing and organizing the document as you go. Here is where you will truly enjoy the benefits of a schematic capture CAD system:
- No more erasers, white-out, or crossing out mistakes with a big red “X.”
- Deleting symbols and parts is as easy as; “select – delete.”
- Moving parts and wires around are simple and can be done individually or in groups.
- Adding parts to existing circuits is simple, and in some cases, the CAD tools will merge parts in line with existing circuitry as needed.
Features, functionality, and advanced capabilities galore!
Take a look at some of the new tools that will be at your disposal with a schematic capture CAD system:
- Online and batch mode design rule checking
- Easy part updates and replacements
- Bulk selection of parts, wires, text, etc., for editing
- Automatic assignment of reference designators
- Forward synchronization with the layout database is easy
- Backward annotation takes layout changes and automatically incorporates them into the schematic
- And lastly, if you still want paper – print it out!
If You’ve Got More Questions, Here’s Who to Ask
Using a schematic capture CAD system will help you avoid costly errors, speed up your design cycles, and provide you with convenient functions and features to increase your engineering efficiency. PCB contract manufacturers like VSE have been using various schematic capture programs for decades in their design flows and can help you select the right CAD system for your designs. It’s time to leave the napkins at the restaurant and create your schematics in a CAD system where they belong.
