PCB layout - JHarvey

[Fred]

thou, mil implies mm :-p get with the game.

Sorry to disagree with you but mil is the unit used on board layouts (even in European software) and it means thousandth of an inch. If you want mm you use mm.

I think you misunderstand. I wasn't saying it was wrong, I know it's used, I was saying it's ambiguous, which it is. thou means only one thing. If you grow up in a metric only society you don't say millimeter, you say mil, and its a common abbreviation. Therefore saying mil is ambiguous and saying thou is explicit and clear. Some of your audience grew up metric only ;-)

(some are also obsessed with being explicit and clear as much as possible...)

Fred.

[jbelanger]

Sorry about the misunderstanding. However, I'm mot sure thou would be clearer but I'm biased because I didn't grow up in a metric only society, I've been using mil in this context for a while and English is not my first language. My point about that last statement is that I'm not sure this abbreviation will be understood by people whose first language is not English.

And I think that the use of mil in the context of board trace size should be readily understood by those who have a minimal experience with the subject but again I'm biased. And while mil might be used in the spoken language (wouldn't know from personal experience), I don't know how widely used it is in the written world since mm is definitely the most common.

I understand the desire to be clear but you don't want to confuse some people to make it clear for others.

Jean

[jharvey]

About KICAD track widths, go to the pull down dimensions --> tracks and via's --> enter a track width, clearance, and mask clearance --> click OK. This should create a new track width in your pull down, hmmm, perhaps it associates the via as well... Not quite sure if it ties both together.

Then you can simply pick it from the pull down list. Probably a good idea to play with it some, I'd like to see if vias are attached to the via sizing or not. I may have small vias on my design, I should double check them. If only I knew how to know what the fab house will produce based on the files I have in hand.

[Fred]

No need to apologise, my attempt at clarifying was itself less than clear (ironically).

Typed, not so sure, spoken, constantly. You are right, but I have minimal PCB experience and that metric education :-) I understood, even if I had to quickly go "25mm, hmm, must mean thou" :-)

Fred.

[AbeFM]

Even with a 1 Ohm injector, I doubt you'd want to let the current go to the maximum possible so it would have to be limited somehow. The most current I've seen for peak & hold injectors was 8A. But I agree that if you want to handle that (and survive the accidental 15A) you definitely want to go more than 25 mil. Using a minimum of 50 mil would be ok with "standard" p&h injectors and 75mil would not be over the board. If you plan on having on-board ignition IGBTs then 100 mil would make sense. (50 mil = 1.27mm, 75 mil = 1.9mm, 100 mil = 2.54mm).

Jean

Well, my logic was that they should never be on all the time - of course, that's assuming everything always works perfectly - probably not the most sound of assumptions.

Well, I'm making them (right now) 62.5, seems like a lot of padding for something which should never seem more than ~5 amps for 1-2ms then get a break.

Or does that logic/conclusion still seem off?

[Fred]

(11:58:17 PM) AbeFM: You can't have mils. It's our word.
(11:58:33 PM) Fred: LOL
(11:58:36 PM) AbeFM: We split up engineering fairly. You get units that make sense, we get all the best words
(11:58:42 PM) Fred: LOL
(11:58:51 PM) AbeFM: also, we can arbitrarily force the rest of the world to do it wrong
(11:58:55 PM) AbeFM: Seems fair
(11:58:57 PM) Fred: :-)

[jbelanger]

I think 62.5 mil should be fine especially if you intend to go with 2oz copper boards. The ones that are likely to push this closer to the limit are those who intend to use LPG or CNG (can't remember which) injectors which are very low impedance injectors. And of course, people who do stupid things.

As you say it's going to be overkill for a lot of setups and most of the time but if your layout allows it then it's good to have it (I think MS doesn't even have traces that big for their injector channels and they have up to 4 low-Z injectors per, but you can draw the conclusion you want from that...).

Jean

[AbeFM]

Ok, well... Thinking about it - the injectors are a ground, which means any current through them then goes back our through ground, so that needs to be the highest current carrying. Especially if two are going at once.

Again, I take solace in the fact the MS has no issues with its smaller traces. Here's what I used:


Board:

and



That's what I'm thinking of using (and thanks to Jean for all the advice!)

[Fred]

Very cool Abe :-)

[jharvey]

Very nice very nice. Well except for the MSII thing

I like that table you posted as well. I'm not familiar with that feature yet. I'm guessing it's part of the auto-router. Perhaps I should inquire if you can elaborate on that a bit.