topic Re: Multiple Trace Widths, Same Node in EAGLE Forum

Multiple Trace Widths, Same Node

airpanther — Fri, 24 Feb 2023 04:45:01 GMT

Hello all,

I have 8 outputs (lamps) in parallel and each is ~ 120ma. Rather than having super thick traces go to every output, I want to use smaller traces for each output, leading to a thicker trace where they all come together. Is this possible to have multiple trace widths on the same node/net?

In another situation, I have a TSSOP IC which requires very small traces, but my ground trace needs to be sized for the total current. Again, if I can have a thicker ground 'bus' to tie all the individual grounds together, that seems ideal.

Any suggestions?

Thanks,

Robert

Re: Multiple Trace Widths, Same Node

one-of-the-robs — Fri, 24 Feb 2023 07:59:41 GMT

It's all possible if you route (parts of) the board by hand. It's a bit harder with the autorouter!

BTW 120mA isn't a lot - even all eight makes only 1A, which only needs a 12mil trace, according to the usual suspects.

Re: Multiple Trace Widths, Same Node

airpanther — Fri, 24 Feb 2023 15:08:50 GMT

Thank you very much for your response. For some reason, whenever I try to route by hand and change the Trace width, the width doesn't change. I've tried the settings at the top of the screen, and I've tried the CHANGE command, but the trace always stays the size defined by the NET. If I draw the trace THEN use the CHANGE command, that seems to work, but surely there is a better way. Sounds like I'm doing something wrong?

Good point... 1A doesn't really require thick traces, but then I have a master board where multiple boards come together, and the total current can reach +4 Amps. So the individual 12mil traces are great, but then need to branch into a thicker trace that can handle 4+ amps on the same net.

Re: Multiple Trace Widths, Same Node

one-of-the-robs — Fri, 24 Feb 2023 18:25:51 GMT

If you have defined the net in a class that specifies a minimum of, say, 20mil width, then Eagle will be reluctant to route it at 12mil. The other way round, though, should be no problem.