We draw a schematic to define the connections that are going to be made on the PCB layout, and so we sometimes get lost in that purpose, forgetting that when everything is done there are good odds that someone else is going to have to reference what
We draw a schematic to define the connections that are going to be made on the PCB layout, and so we sometimes get lost in that purpose, forgetting that when everything is done there are good odds that someone else is going to have to reference what we’ve drawn and decipher it. We understand it, and it works well enough to get the netlist created for the routing, but can someone else look at it to do troubleshooting or understand the functional intent of the design? It’s important that we follow conventions that will ensure clear communication.
Take for instance this circuit:
It works. The netlist is created and I can route it on a PCB. But if you wanted to figure out what it was, you’d have to do some deciphering. Here’s the same circuit, drawn in a more conventional manner:
One look and you’ll realize it’s a common emitter amplifier.
So what are some common rules for a schematic design that we should all follow? If you are just starting to get into designing circuit boards to jump on the IOT craze, then you may not know/remember all of these.
Schematics should read left to right, top to bottom
It should read like a book. Inputs go on the left, outputs on the right, and the signal flows left to right. If you reach the end of the page and need to go to a new row, don’t make the next row flow right to left. Bring the wires from the first row all the way back to the left side of the page to start a new row. If you don’t like how that looks, then use ports or net name to tie the netlist together without the visual of the long wire.
Clean up the text around your symbols
Sometimes the schematic gets crowded and we end up with a lot of text in a small area. Make sure all of the text is oriented the same way, you can easily tell which symbol for which it is providing information, and you don’t have wires or symbol lines running through the text. How easy is this to read?
Answer: not very.
Name your nets, and group related signals together
SOLIDWORKS PCB will name your nets for you if you don’t apply your own names, so that it can generate a netlist, but you won’t see those names except when routing. However, if you give them your own (meaningful) names, it will be a lot easier to understand your design intent. Here is a page of ANSI/IEEE recommended net name abbreviations.
Also, we have the ab