Connector considerations

[AbeFM]

Edge mount with heat sink, for those whining about wasted space:



We're talking about the width of the back end of a DB here. In fact, the space saved off not having the 90* pins might actually offset it, esp if most of one side of the box is taken up with connector (which I assume will be the case).

Quick mental pin count: 6x fuel 6x spark, ground, power = 14 pins for "high power" stuff easy. That makes a DB15 with a DB 37 for IO. I don't have dimensions handy, but it's about the width of a MS or more already with just those side by side.

One last argument for DB's - being narrow top-to-bottom, in a stacked board, each board could have a connector. This is not unimportant.

With an ampseal, what would you do to get signals from the outside work into a board above the computer in the stack?! The whole front face would be taken up. This way, you cut another hole, add a connector.

[jbelanger]

Just to give an idea of the Ampseal size, the picture in the following post show a 23-pin Ampseal on a 3"x5" board: http://www.diyefi.org/forum/viewtopic.p ... 378&p=4051

Jean

[Fred]

As much as I love your heat bus idea, it seems like you'd waste all the end of board realestate on fets instead of connectors when you could just put the fets down each side. the wasted space isn't an issue really, but it could be a nice thing to do for a few to220 devices on one end for the power supply or similar?

Fred.

[Fred]

WT, the key thing here is that no one wants to invest in expensive connectors on an experimental board and experimental device in its entirety. Cheap, quick, semi dirty but done right up front = ftw asap.

Sure, a default board that people buy could have a connector like that, no stress, but you will also need a distributor and as with all businesses, they will design and implement a solution that they feel is best value and a workable solution. B&G go for ampseal with their "i'm too lazy to build it" solutions, so there is some chance its a good choice just based on that. Don't think they are waterproof though. MicroSquirt users have proved otherwise painfully. The seal is touchy and easy to break by having tension on the cables etc.

Fred.

[AbeFM]

Just to give an idea of the Ampseal size, the picture in the following post show a 23-pin Ampseal on a 3"x5" board: http://www.diyefi.org/forum/viewtopic.p ... 378&p=4051

Jean

Thanks for that! I was wondering. 23 pin is a bit low, but let's just look at two of those (46 pin) verses a DB 15 + DB 37 = 52. More fair would be DB 37 + DB 9 but why hamstring myself, plus I think I made a good case for a 15 pin connector.

From your image: 65 pixels from silkscreen keep-out to board edge. 97.5 to the front surface (i.e. inside of case). Width is 266 pixels front face, 192 keep out.

312 pixels for 3" board means: 104 pix/in. So dimensions:
On Board: 0.625" L x 1.846" W
Box Space: 0.3125" "gap" X 2.55" W (this is the "dead space)

With a 1/4" between them, you'd need a box 6" wide (~150 mm) to accommodate these, and would have an 8mm gap between board and case and 16 mm of the entire edge of the board taken up, for 46 pins. Last bit of math I swear: 36 square centimeters from end of all useful board space to edge of case, or about 1.3 pins/cm^2

My beloved DB-37:
9.5 mm case to end of keep out (call it 10 mm), overall width 69.5. Two side by side: 159 mm with same 1/4" gap on all sides. I think you don't need that much gap on these, I don't know about the ampseals so I left a gap.

Keep out:
On Board: 0.138" (3.5mm) L x 2.15" (55mm) W
Box Space: 2.25" (5.8mm) "gap" x 2.74" (69.5mm) W (this is the "dead space")

Same gaps... 6mm dead space gap, but only 3.5 mm of dead board space, for 74 pins (almost all the IO the ecu even has) That's 10mm x 159 mm for a total of 16 cm^2, or 4.625 pins/cm^2.

Interestingly: DB-37: 23 amps/cm^2, ampseal: 22 amps/cm^2 (though it tips further if you only count board space. But overall they are about even. Physics strikes again?)

And those who want it, weatherproof DB37s exist... Nothing I can pretend to care about. What's bugging me is I had one more thing, but I forgot it. So far, my best argument is really a connector per board, which I like. What's the interboard spacing going to be, Fred?

[Fred]

More fair would be DB 37 + DB 9 but why hamstring myself, plus I think I made a good case for a 15 pin connector.

No way in hell should there be a 9 pin DB on that board that isn't serial. It will CAUSE mistakes... I'll veto any board with a non serial db9. 15 on the other hand is an excellent idea, now, do you mean VGA or wide ? VGA wouldn't do the edge solder thing being 3 row, so i guess you mean wide.

What's the interboard spacing going to be, Fred?

Don't ask me, I'm "just" the firmware guy ;-)

Fred.

[jharvey]

Then theres cost, that one you linked to is almost twice the price of a 35 pin AMPSEAL and it has less pins. Theres cheaper CPC connectors but theyre not weather sealed, I dont know of that matters or not for everyone but its a difference.

I'd say yes it matters, it give you choice of low cost vs over built. Personally, I think most cars, ATVs, ect don't need weather sealing. You really only need that if you're doing a boat, submarine, or sum such application.

[AbeFM]

Personally, I think most cars, ATVs, ect don't need weather sealing. You really only need that if you're doing a boat, submarine, or sum such application.

+1



Again, when a final, "production" board is working, it would be time to revisit replacing the modular end of the board from a DB-37 to a footprint supporting ampseals. It shouldn't even be difficult to just have it as an "option".

In the meantime,
1) how does a pair of DB's (one for high power signals, one for signal-signals) sound - with add on boards having their own dedicated connectors
2) If that's setteled enough for our prototype, Fred mentions not wanting power on a DB - though I think it'll work fine. If the DB seems the choice for the prototype, then we could move on to talking about that?
-Abe.

[Fred]

2) If that's setteled enough for our prototype, Fred mentions not wanting power on a DB - though I think it'll work fine. If the DB seems the choice for the prototype, then we could move on to talking about that?

He mentioned it, but he had no solid reasoning behind that... start a new thread discuss how best to use DB perhaps?

My preference would be not to use db37 as they are much less common than other DB sizes and could cause "i thought it was ms compatible pinout" smoking parts problems.

Fred.

[jharvey]

1) how does a pair of DB's (one for high power signals, one for signal-signals) sound - with add on boards having their own dedicated connectors

Also don't forget the theory of using a connector card with two (or more) connectors on it. A DB connector to match the jim stim for testing purposes, then an OEM connector on the other end for the real install. In that case, I don't see a reason why the DB test connector would need to leave a case. So you'd really only need a hole in the case for the OEM connector.

I haven't drawn up a connector card, because I intend to use a harness connector, and I don't know what the pin out for an OEM connector should be. In your case I'd expect a DB on one end, and a OEM Miata on the other end.