Comments on The Art of Engineering: Light and heavy symbols

I agree that symbols should be light. Attributes f...

2008-11-12T10:56:00.000+02:00

I agree that symbols should be light. Attributes for each component should be stored in a database, along with a reference to a symbol. If you draw a schematic for a PCB design you should preferably not place symbols (really!) but a component from the database. The correct symbol with attributes would then be in the design with just one action.

From my experience with Mentor-DxDatabook and Cadence-Capture-CIS as both designer and component-library/database maintainer I believe this is the way to go for any design team that involves more than one person or more than one design. The advantages are numerous.

For gEDA both gschem and gattrib should be database aware for this to work properly. This is an absolute requirement for any schematic capture program to function in a company that does multiple designs.

A ha! Good point Duncan, one I had not thought of....

2008-10-21T13:07:00.000+02:00

A ha! Good point Duncan, one I had not thought of. So if you have people who are meticulous when they link up the part name (I'm assuming one specific enough to give all the pinout information and such), then you'll be in good shape. Excellent point!

~Chris

Hi Chris,All the necessary information is still st...

2008-10-20T14:08:00.000+02:00

Hi Chris,

All the necessary information is still stored in your schematic, just not in your library. The schematic has detailed part info and so on, but the library does not (attributes are added to the schematic after placing the symbol from the library).

The symbol library just has an opamp symbol (with the correct pin-out), then the part number (and any other attributes) are added to the schematic. The schematic persists over time, and the new engineer should still know what is going on.

Hi Duncan,Even though I understand the rigors of m...

2008-10-20T13:58:00.000+02:00

Hi Duncan,

Even though I understand the rigors of maintaining a heavy symbol library, I am in favor of it. The main reason is longevity of projects. I'd like to think that if I design a product that it will still be alive and well 10 years later. If a young engineer comes in and looks at my schematic and sees that I need an op amp and thinks "oh, well I'm sure a LM741 will work fine here. It's just an op amp, right?" In fact, the node the op amp is on was very sensitive and required pA of bias current and mV of offset voltage. Not only that, the young engineer also gets the part in house and realizes they have the wrong part size AND pin layout. So while I understand your argument for speed and simplicity of maintaining a library, I think designing for long term projects might convince you otherwise. Good post and one I enjoy talking about!

Chris