Why The Latest Changes To Spin 2 Don't Worry Jared

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slacker.cam
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Re: Why The Latest Changes To Spin 2 Don't Worry Jared

Post by slacker.cam »

jharvey wrote:The issue is that it's predicted to draw on the order of .25 amps to .5 amps under some fairly common built setups. So the regulator needs to drop (18v-5v).5A = 6.5 watts and we have been planning for 1 amp as extra room for growth isn't bad, so it could have to dissipate around 13 watts. With an ambient temp of 110F(43C) and LowZ injector drives in the case (estimated at 9 watts each for 8 cyl's), we are talking of a total case dissipation in the range of 78 watts to 85 watts for something the size of your hand. The internal component temperatures would likely be near the top range of their limits. So the LDO's temp compensation, and abilities to provide a 5V supply vs a 4.8V supply are likely degraded.
I see what you mean now. LowZ injectors really are a pain in the arse :) So are engines with more than 4 cylinders haha. It seems that perhaps it will be more important to design a good heatsinking technique to suck out the 85W of heat generated rather than dicking around with a SMPS though. 85W is a huge amount to be dissipating in that form factor without fan forced cooling, or even any cooling fins. I certainly wouldn't want my ECU being too hot to touch even in a worst case scenario. I guess there's a plethora of ways to engineer around these issues, we just have to pick our battles. Researching a PWM p&h technique that doesn't swamp the rest of the circuit with noise may be a better option given that this is where most of the power dissipation will be coming from. Or just make everyone buy highZ injectors ;-)
jharvey wrote:As a bit of a side note, Marco's first language is Spanish I believe, English is secondary. This is one reason why I'm doing a lot of commenting semi on his part. It takes him longer to type, and his goals are to make PUMA, and less to socialize in the forums. So chatting with me about design details will likely steer PUMA's design even though it's actually being laid out by Marco.
Thanks for your efforts to explain the engineering decisions that are being made by Marcos and yourself. I appreciate you bringing me up to speed. Marcos seems like a top guy. He's certainly put in a lot of effort thus far. His first attempt wasn't bad for a guy who's still at uni. I wouldn't mind giving my own FreeEMS board a shot at some stage. Board design is one of my stronger points of elec design. We'll see if I can maintain motivation for the project as we go forward.
jharvey wrote:As another side note, I have a BS in Electro-Mechanical Engineering. I tend to jump electrical and mechanical bounds on a daily basis. It's common that electrical's will design something, then the mechanicals will make it work. I tend to look at the entire picture a bit more than most typical design builds. It's likely that mechanical issues or obstacle are semi hidden from the electrical designer. In a typical design cycle.
I have a similar qualification - a BE in mechatronics which is split pretty much 50/50 mechanical and electrical engineering. I agree that there's often a lack of communication between the elec and mech sides of a design. At least in my experience. Usually it's because the other team is always telling you can't do something :)

Phew that was a marathon reply...
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Fred
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Re: Why The Latest Changes To Spin 2 Don't Worry Jared

Post by Fred »

Marcos, Jared, you have my total support, don't say otherwise, frankly, it's fucking insulting. Calling me a dictator and describing my moderation actions as "censorship" is equally fucking insulting, and entirely inaccurate. Marcos, as English is not your native tongue, I'll give you the benefit of the doubt, just don't say shit like that to me again, not if you want to remain my friend, anyway. Don't reply to this, either. The only reason Marcos's post didn't get edited, and this is here, is because he grew up speaking Spanish. You've all been warned. Keep it ALL related to the current spin 2 and puma discussions and nothing will be touched. Start commenting on mod actions or this paragraph and I'll crush it with a hammer.
slacker.cam wrote:Just one comment that's related to what Fred had to say the other day about at this stage of the project 'we' should probably be doing whats best for the community rather than what's best for ourselves as what's really needed at this point is engines running on the platform.
As much as I fully agree with this, in practice, over the last few years, I've found that asking or expecting or pressuring people to do such a thing (god forbid!) has not produced any results. Which is why I voiced my opinions in the way that I did. Marcos can develop his solution however he wants it, for his market, and his mil spec, and whatever other requirements that he has, and I can go ahead and produce something more conservative that DOES meet OUR needs, as a group. I have NO problem with him, or you, or jared, or anyone else building any random hardware AT ALL -- I LIKE THE VARIETY. The only things that I control or even want to control in this respect are marketing power and certification power. IE, I can influence a large number of people to obtain or not obtain a design. And I can stamp a design with "this is FreeEMS approved". Nothing else. So carry on! I was, as I said in the first place, just sharing my opinion for those who asked for it. Nothing more or less.

This is not dictatorial, it's freedom, embodied. You're free to design as you please, as am I, and we'll all share our work. The latter is openness embodied. I'm not trying to hide your designs, or stop you doing what you choose, I'm just saying "this is no longer suitable to promote for general use IMO". This paragraph is covered by the same rules the first one is covered by.
slacker.cam wrote:85W is a huge amount to be dissipating in that form factor without fan forced cooling, or even any cooling fins. I certainly wouldn't want my ECU being too hot to touch even in a worst case scenario.
Keep in mind that the worst case scenario involves high duty cycle, and associated very very high manifold, oil, coolant, head, piston, chamber temps too... IE, in any realistic environment, not including the burnout pad or bonneville salt flats, they thing will be dissipating excess heat while at lower RPMs and lower boosts and off the throttle under brakes etc. This IS in a car, not on a test stand. It's *VERY* hard to maintain the full throttle and high RPM necessary to produce high duty cycles in any reasonably high power car. Any car with low z injectors had better be reasonably high power with high flow injectors otherwise resistor packs and high z drivers would be a better choice.

You have to keep in mind that the person who is setting up the car will have to make choices about injectors and resistors and external driver boxes and so on and so forth. Don't assume that they'll make a dumb setup choice. Don't assume that they'll make a smart one, either, I guess, but it isn't necessarily necessary to pander to idiots bad choices. FWIW...

BTW, Cam, GREAT posts!

Fred.
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Re: Why The Latest Changes To Spin 2 Don't Worry Jared

Post by Fred »

Oh, and I forgot, the current numbers that you're talking about for 5V draw are TOTALLY unrealistic. And, as Cam said, even if it is as bad as you say, they pale into insignificance when compared with the TOTALLY unrealistic P&H power dissipation numbers anyway.

I also forgot to point out that I setup a friends car with P&H using Jean's board a month or two back, and I couldn't feel ANY warmth in the enclosure that I mounted the setup in. None. Nothing. Nada. At higher duties, or with more extreme lowness of z, sure, it would have got warm, but nothing obscene.

It's very tempting to get into the habit of choosing the extremes as design parameters, but in the real world, this is very rarely done, and not just to save costs, but because of the other compromises that it causes. This thread illustrates that well, both from the vibration/mil spec point of view, and the heat/regulator point of view. Again, though, I don't mind what you do, if I don't like it, I'll do something else.

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Re: Why The Latest Changes To Spin 2 Don't Worry Jared

Post by jharvey »

Fred wrote:I also forgot to point out that I setup a friends car with P&H using Jean's board a month or two back
Are there pictures, videos, or other documents that allow us to see how this is setup? For example, Jeans board is remote, so it makes sense the FreeEMS board (or what ever drive board) is cold.
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Re: Why The Latest Changes To Spin 2 Don't Worry Jared

Post by Fred »

I have some pics that I will upload later along with all of the FreeEMS ones, but you've misunderstood. The remote P&H box was stone cold, I wasn't talking about the ms2 box that was controlling it with logic level signals...
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Re: Why The Latest Changes To Spin 2 Don't Worry Jared

Post by nitrousnrg »

A small comment:
The board by default is going to have high Z, using an SMD transistor. If I make boards for argentina, they must be assembled here (because of customs restrictions)

The case is probably going to be the Cinch one, its hard to find an appropriate case, or at least expensive. I think its better to put some extra work in the PCB if it loosens your restrictions in the case :-)

Wow, sounds like quite an impressive outfit. I don't think we have anywhere near as cost effective or that provides the range of services here in NZ
Yep, in china the assembly cost for 1 was around $80, and it drops a lot depending on quantity.
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Re: Why The Latest Changes To Spin 2 Don't Worry Jared

Post by Fred »

Somewhere above it was stated that the SMD drivers for fuel where high Z only and, I think, that the to220 were to be retained as well for P&H resistive use (or perhaps it was just implied, intentionally or not). However more recently I read somewhere that they were to be used in PWM mode. If that is true, which this implies, then all of my original comments stand. Please understand that it's not a criticism of the design or process, rather just an indication that it is not where I expected or wanted it to go. Perhaps start another thread to discuss development of this new style of output configuration? It probably deserves one.
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Re: Why The Latest Changes To Spin 2 Don't Worry Jared

Post by MotoFab »

Fred wrote:However more recently I read somewhere that they were to be used in PWM mode. If that is true, which this implies, then all of my original comments stand. Please understand that it's not a criticism of the design or process, rather just an indication that it is not where I expected or wanted it to go.
That looks like an mbed.com board running the show. I can't see any reason to not operate the drivers in PWM mode. Code is often more important than hardware for dealing with the electrical environment. Nice one Marcos!

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Re: Why The Latest Changes To Spin 2 Don't Worry Jared

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MotoFab wrote:I can't see any reason to not operate the drivers in PWM mode.
There is none, in a long term well developed design. However the traces and routing and noise control mechanisms MUST be right, and it's difficult to achieve that on a first cut. Hence it's not conservative enough for me at this time, which is the subject of this thread.
Code is often more important than hardware for dealing with the electrical environment.
Both need to be right, however even the best code can't deal with a bad signal, shit in, shit out. It's a fundamental rule...
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Re: Why The Latest Changes To Spin 2 Don't Worry Jared

Post by MotoFab »

Fred wrote:There is none, in a long term well developed design. However the traces and routing and noise control mechanisms MUST be right, and it's difficult to achieve that on a first cut. Hence it's not conservative enough for me at this time, which is the subject of this thread.
Of course they have to be right. From Marcos' video, it doesn't take all that much care. Power and I/O are out on the end of 150mm leads, and it works.

(Regarding the thread subject, this is the 'Why [PWM] doesn't worry Jared' thread. Isn't there another thread for what worries you?)
Both need to be right, however even the best code can't deal with a bad signal
If code isn't written to deal with a bad signal, then it really can't be called the best code can it?

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