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Potential Bulk Buy for FreeEMS first edition PCB 
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gearhead wrote:
My guess is that with a proper grounding and power scheme, this will become a non-issue.

Could be right, but dodgy grounding and power isn't the only reason people get noise issues with MS. CDI *can* be really bad, as can various other things like starter motors etc. I also have an optical digital input for my second trigger and had zero issues with it without a filter, but that doesn't mean we shouldn't do something for it.

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Tue Aug 26, 2008 3:22 pm
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How is 4-6 sense resistors going to take up serious board space? It's really just a resistor (or, maybe there are already resistors in the drive circuit) and you run a line to an ADC (maybe through a protection resistor?)

I don't think we need it, but I like it, and I couldn't think it could take up much space. If it doesn't make it in, I won't much care.


Tue Aug 26, 2008 10:43 pm
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QFP80 - Contributor

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Why is it dependent on price?


Thu Sep 18, 2008 8:22 am
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if it wasn't dependant on price, I'd have as many Motecs or better. basicaly what I can afford, given the features, timing, Bill of materials ect.

If it is everything I want, which it sounds like, for under 300 TOTAL for each unit, (obviously much less for bare pcbs) then I want one for each of my projects. So I'd rather bulk buy my pcbs now and hopefully get alittle break as that seemed to be the single most expensive part of MS. Which pcbs done in bulk, even when as complicated as the MSv3 can be much cheaper than they are.

I hope I am making sense... I am alittle ill at the moment and it effects my thoughts.


Thu Sep 18, 2008 5:43 pm
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Makes perfect sense to me :-)

You have to be careful to compare like to like though. EG, ms2 chip/card is about 90 us, this cpu thumps that one, but only has a 2 layer board, is low temp, and is 125 us. It is a MUCH better chip though. The closest comparison to it will be the MS3. It should thump VEMS. If you compare with MS3 and VEMS it will look like peanuts. I think it could be as low as 300us total, but it will really depend on how much of the optional stuff you intend to solder on. if you cut back to a pair of fuel and pair of ignition drivers it could come in under 300, if you have a 6 cyl with sequential the fets and igbts will add up alone, then all the other bits on top of that. One thing is for sure, it will be as cheap as humanly possible for what you get ;-)

Apples for apples :-)

When you acknowledge this post I'll move the last two posts and mine and further OT ones to the other thread where the comments belong.

Cheers,

Fred.

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Thu Sep 18, 2008 8:45 pm
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I migrated this part of this thread from the PCB layout. So here I continue.

When we purchase, I think we are best off getting say 5 boards, then once a basic check has been done, get the rest. One item I'm concerned with, but is probably OK, is that the PDF'ed layout shows the wire connection via's as very small holes. However, KICAD shows them as large holes. I suspect the drill file will correct this, and that the copper layer is left with a small hole. But there is a chance we might get smaller holes than we expect. So I think we should by 5, then the remaining. That way we don't have several people drilling out via's or what have you.

This will delay some early alpha or beta testing slightly, perhaps a couple days, but will increase the chances that they can use the boards. Perhaps increasing number of people with successfull beta test's.


Fri Sep 19, 2008 5:43 pm
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You could always just email the files to a supplier and ask them what size the vias appear to them to be and how to check :indiff:

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Fri Sep 19, 2008 6:01 pm
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You can use a Gerber file viewer to make sure that the files and the board are ok independently of Kicad. Here's a free viewer: http://www.pentalogix.com/Download/download.html.

Jean


Fri Sep 19, 2008 6:28 pm
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Yup you can, and it seems like stuff still pops up. You never seem to know what, or where.

In a past life, a fellow engineer predicted a trace size for a specific resistance as a current sense resistor, and added some trim ability to compensate for expected copper variations, ect. I got a chance to have say in it before it was sent out, and I gave a thumbs up. It was a very nice design. For some reason the copper came thicker then expected, and the resistance was about half the expected. It was just one of those things that popped up.

However, I plan on being in on the first buy, so it really doesn't matter to me. I'm mostly concerned for the other folks out there. Do what you want.


Sat Sep 20, 2008 3:09 am
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If the work is sent out to a decent PCB House, they will ensure that the designer has not made any silly mistakes, and will double check and clarify all areas.

Conversely if you go to the cheapest, they will subscribe to the retail idiom. "The customer is always right".

With the safe expression "that's what you said you wanted".

This applies to all engineering operations whe stuff is subcontracted out.

Smart operators use the same supplier, and try to build up a relationship, as they soon realise it is really a partnership.


Sat Sep 20, 2008 9:54 am
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