Letting go of the "MegaSquirt mindset" (hardware)

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Fred
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Re: Letting go of the "MegaSquirt mindset" (hardware)

Post by Fred »

It's ironic/fitting that you put that post in this thread :-)

In MS land you buy a board and it is the only one, there is no real choice, someone else decided what would and wouldn't be on it, and which components you would have to use. That is not the case here.

When I push for through hole, I push for a simple initial version for normal enthusiasts to build. My mate Cam already has plans for a fully DIY SMD board for us. Being open, once the firmware gets up and running and gains some recognition it's almost certain that multiple people will design boards and share those designs. I hope they all do it by posting first and discussing it openly, but some won't do that and will just post up one day "look what I made". At that point, you will have a 1000 choices of main board to use and a thread that gives the pros/cons of each one etc and perhaps endorses some as "standard".

For a start though we want something simple, tried, and true. Through hole fits the bill for that IMO. You certainly won't be stuck with that down the road.

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Re: Letting go of the "MegaSquirt mindset" (hardware)

Post by AbeFM »

Well put. I worry about a lot of versions running off in different directions, and I am pretty convinced that a rigid design is the reason for the success of the B&G line. That said, sucsessful or not, it's not what we're looking for. :-)

Are you so sure that SMD is the project killer you're making it out to be?

I've now worked with several people on their MS's, mostly miatas, but not only.... And, I've found the people who have enough understanding to know what a wire is and what a diode is, would just buckle down and do SMD parts if it were better. The number of capable people who would let SMD stop them is quite small. In my opinion.
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Re: Letting go of the "MegaSquirt mindset" (hardware)

Post by Fred »

8InchesFlacid wrote:Well put. I worry about a lot of versions running off in different directions, and I am pretty convinced that a rigid design is the reason for the success of the B&G line. That said, sucsessful or not, it's not what we're looking for. :-)
Yeah, it's not ideal, but you hit the nail on the head, we aren't looking for a closed hardware setup, we want one that will evolve. Reality is that if someone designs something actually *good* people will flock to it and no one will want to do an alternative of the same size/style that has no real advantage. Something smd, something small, something rugged, something simple are likely to be options, but how many of each there are, who knows or cares. The rubbish ones will soon filter out...
Are you so sure that SMD is the project killer you're making it out to be?
When/Where did I say that? I like it. But, for initial versions I don't want to have to use it. Burning up stuff is a lot easier when you can replace a single through hole part. Additionally, through hole = heat sink for to220 stuff. My personal preference for an initial board only. If no one wants to design such a board with/for me/us I will step up and do a mediocre job myself :-) No pressure.

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Re: Letting go of the "MegaSquirt mindset" (hardware)

Post by davebmw »

Hi Guys,

I work for a CEM here in the UK TT Electronics and I personally would like to see a 50/50 split of SMT and PIH.
The majority of the components ideally should be surface mount and the large power devices should be TO220 or TO3P tabbed packages bolted or preferably clipped vertically to a heat-sink block. This not only saves space but saves on fried PCB's should the worst happen. After all this is a largely an experimental project and surface mounted Mosfets overheating will knacker a PCB and you are back to square 1. Not to mention the un-nescesarily complex design process required for integrating heat-sinking.

I would personally hate the idea of stacking PCB's on headers, we have a product under my wing at work that uses 3 PCB's stacked on 0.1" IDC headers there are always problems with this product mainly because of the stacking header design but also because of the debug constraints caused by in-accessibility.

Careful selection of SMT devices would be a low cost option as these parts are a cheaper alternative to PIH due to mass production savings. also the more holes you have to drill the more the PCB will cost.
An ideal PCB size to aim for would be eurocard as its the most common and therefore cheapest to buy from PCB Pool or similar especially if we all pile in and get a batch made up out of a panel we should get a really good deal.

SMT soldering need not be that scary at home as long as you avoid:
0402 devices, Lead free solder, messy workstations, stiff breezes, and booze the night before.
and have the basics:
a good soldering iron with a selection of pointed tips, i use Weller 80W pro soldering station as a personal preference but metcal and oki are superb also. some savbit tip tinner is essential along with a damp sponge. get some 60/40 lead tin solder, lead free is absolute crap it has a design life of 2 to 5 years and requires twice as much flux solids which makes for a really mucky PCBA. not to mention that if military customers frown upon it then it must be Crap.

A hot air pencil would be a serious benefit, nothing except a correctly profiled reflow oven gets perfect shiny fillets quite like it. I have access to the SMD stations at work but they are £230 upwards to around £1200, so i use a weller pyropen at home, these work great and the cheaper £20 maplins jobbies are great value for money. HAP also make removing SMT discretes very quick and easy.
and last but not least....
Some liquid rework flux in a dispenser pen, I use NR205 at work so i have a ready supply of it! smells nice like pear drops too!
This is fantastic stuff i will take some shots of SMT fillets with and without NR205 the difference is night and day, seriously.
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Re: Letting go of the "MegaSquirt mindset" (hardware)

Post by GrowlingandBiffo »

Eurocard is a standard format, not a size per sec.

http://en.wikipedia.org/wiki/Eurocard_%28PCB%29

You should always use lead free products as lead is banned and for very good reasons...
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Re: Letting go of the "MegaSquirt mindset" (hardware)

Post by Fred »

GrowlingandBiffo wrote:You should always use lead free products as lead is banned and for very good reasons...
With all due respect, lead free stuff can get f@#$ed. There is a reason medical and military stuff doesn't use it :-) I agree with the post above in most ways, but I think this is the wrong thread for it. I might try to find the right thread and shift these three at some point.
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Re: Letting go of the "MegaSquirt mindset" (hardware)

Post by GrowlingandBiffo »

Medical stuff do not use lead..(UK&US)

As regards military stuff it is being phased out...

Like the UK smoking ban it all comes under the jurisdiction of the Health & Safety Executive...
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Re: Letting go of the "MegaSquirt mindset" (hardware)

Post by Fred »

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Re: Letting go of the "MegaSquirt mindset" (hardware)

Post by GrowlingandBiffo »

In the real world if you submit a Medical PCB that is non RoHS compliant it will not be accepted unless have applied for an exemption.
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Re: Letting go of the "MegaSquirt mindset" (hardware)

Post by Fred »

The PCB in the ghetto blaster on the window sill at the hospital doesn't count as medical you know ;-) I'd be unhappy if my fake heart was running on lead free stuff :-(
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