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 Post subject: Re: A locost EFI
PostPosted: April 30, 2015, 9:24 pm 
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horizenjob wrote:
This is what's called the "rat's nest". In this picture the board is the black work space and has a 5mm grid on it for scale. The reddish boxes represent the pages of the schematic and their parts. I have more work to do but this is a check that is helping me visulaize things.
Yup, now its perfectly clear... :?

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 Post subject: Re: A locost EFI
PostPosted: April 30, 2015, 10:19 pm 
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I am happy to report that my junior scientist was able to measure a resistance of between 1 and 5 megaOhms, all while performing the sound effects of Curly, everyone favorite Stooge. Honestly, I am so proud of her...
Give that young'un a big hug from her Uncle Bubba!!! And tell her I said "Nyuk, nyuk, nyuk!"

Oh, and let me know when that prototype is ready for the brown mustard, diced onions and whole wheat bun test...

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 Post subject: Re: A locost EFI
PostPosted: May 2, 2015, 9:47 am 
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Yup, now its perfectly clear...


It's not a very good picture. I'll make a nicer one when I make more progress.

Chuck wrote:
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time to determine connectors which may end up as a 2x"x" dual row header that can be wired to


So I was shocked when I started looking at these on Digikey that they all seemed to be discontinued items. I was thinking of making in this in two pieces and stacking them, these would have been OK for at least the prototypes. Didn't look for other sources yet, are these just too big for modern boards?

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4 PWM outputs (IAC, Boost, Cam, fuel pump regulation? etc)
4 analog outputs, alternator


I need to go thru and see what the story is on PWM outputs. The coil driver chip can do this, maybe the processor too. Also a transistor to help with this.

I hadn't thought of analog outputs! Well I thought of it for giving the board an ability to calibrate it's analog inputs. Maybe both can be done at the same time. I'm not sure why you mention alternator on that line? Is being the voltage regulator a good idea?

I got the board to compile without errors for the first time last night. :D I'll assign all the stuff on your list and see where that leaves things.

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 Post subject: Re: A locost EFI
PostPosted: May 2, 2015, 12:22 pm 
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I'm not sure why you mention alternator on that line? Is being the voltage regulator a good idea?
Some modern OEM systems control the alternator output based on some algorithms. They use an analog output from the ECU (Body computer?) to feed the field winding of the alternator (I think). I'm just thinking forward..... you could turn back the alternator output when the throttle is open, say, > 75% giving more HP available to the wheels. In any event, if someone is using a donor and wiring harness that uses such an alternator scheme, then whatever method they use would be good to incorporate in your system. I have read where people had to kluge their alternator wiring when they switch to aftermarket ECU's. The DC output could also be achieved with a PWM output feeding a diode, inductor and cap to form the required DC signal.

Similarly, some return-less fuel setups use a pressure sensor and PWM the output driving the fuel pump. I think Ford did (does?) this. In my instance, the '90 RX7 donor used a BH dropping resistor (big hairy) and a bypass relay to produce a 2 speed fuel pump, reducing the load on the pump when at lower demands. This presumably extends the life of the pump. I implemented that with a spare switched output on the MS.

Did I forget to add some stepper motor drivers to the list? OOPS! (drive by wire, Or some other Variable cam timing uses?) It is always good to have the capability and not use it than not have it and need it. Whether 1,2, or 4 outputs are necessary, I'll leave that up to you.

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 Post subject: Re: A locost EFI
PostPosted: May 2, 2015, 12:37 pm 
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rx7locost wrote:
Some modern OEM systems control the alternator output based on some algorithms.

Yes, my 2003 Neon test mule does that.

rx7locost wrote:
They use an analog output from the ECU (Body computer?) to feed the field winding of the alternator (I think)

ECU, not body computer. I am not sure about analog output - in my case it's PWM and hi-side, relatively high-current output.

rx7locost wrote:
drive by wire

Once knock detection and on-board wide band sensor controller is also added to the wish list, it would be safe to say that the chance of one guy pulling this off is not very high.

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 Post subject: Re: A locost EFI
PostPosted: May 8, 2015, 2:57 pm 
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Once knock detection and on-board wide band sensor controller is also added to the wish list, it would be safe to say that the chance of one guy pulling this off is not very high.


You're just not an optimist! :rofl: Seriously, I don't expect this to be a one man project. Knock detection would be hard without a dyno for each engine. Also spare engines! Wide band is cheap on the aftermarket already, but with an open project like this anyone can work on these things. There is example code provided for the knock detection by the chip manufacturer...

I've figured out how to make pdf's of the schematics, so you can expect to see them soon. I need to pick a copyright license and it's daunting. It seems the choices for hardware are more limited and untested and etc.

I need a name for this unit, does anyone have a cute idea? Bang box, as in "Suck, Squeeze, Bang, Blow" might work. Open to suggestions...

Right now I'm working on some stuff for the power to the unit. Still worrying about: reverse battery, alternator load dump, cold cranking and the inrush current when it gets turned on.

Of these the reverse battery seems a problem. Lot's of the parts that are being used have protection against this, I think it's part of automotive standards. More careful reading shows though that some of the parts are protected simply because they turn on! I think that might include the coil drivers, but I have to check again. So there is a lot of stuff to protect. Maybe just a really big diode shared among the coil grounds would work.

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 Post subject: Re: A locost EFI
PostPosted: May 10, 2015, 11:29 am 
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I'm working towards being able to post the whole schematics, but for the moment it's easier to post a piece.

Originally I used a large TVS diode for protection against load dumps (voltage spike caused by alternator) and also diodes to protect against reverse battery connection and to isolate the CPU power from other parts of the system. Now I'm thinking the circuit I dreamed up here will do the same thing and also allow for a small ramp up (soft start) of power to the board as opposed to the battery which can provide a lot of current instantly.

The soft start would help the input capacitors a bit. I would like to use some large tantalum caps because I think they have a longer lifetime than the more typical aluminum electrolytic ones. From what I've read the tantalum are pretty good but occasionally explode :rofl:, using the polymer version helps, but I think also have a soft start would help too.

In the circuit I am using a smart dual MOSFET IC. The idea is that one MOSFET is connecting the board's ground to the car and the other MOSFET disconnects the first if the voltage goes above some amount, say 20V. If the board is connected with reverse power, the MOSFET will not be turned on providing protection. At the moment this is just for the CPU stuff, but I guess I could use larger MOSFETs and protect the coil drivers too.

If anyone has opinions, please chime in!


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C9_ECU_Battery.jpg
C9_ECU_Battery.jpg [ 250.06 KiB | Viewed 2781 times ]

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 Post subject: Re: A locost EFI
PostPosted: May 11, 2015, 1:15 pm 
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Before anyone wastes too much time on this it seems on further inspection that the MOSFET in the drawing is not appropriate for this. It's a smart unit and somewhere down in it's tiny little brain it seems like it has opinions about this type of thing. A more normal unit might work better, but I think I will have to count electrons and do some basic math to see if this idea works out.

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 Post subject: Re: A locost EFI
PostPosted: June 1, 2015, 2:02 pm 
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Well time flies...

There have been a lot of late nights, slogging and I am not ashamed to admit actual groveling in the pursuit of this porject. I have had to learn some different tools for the actual circuit board design and also read up on tons of stuff.

The work is now being done using the KiCad tool which is open source and available for Windows, OSX and Linux. I have an early take of the schematics and have been able to use them to provide information for the actual circuit board layout. With that I have been able to place all the parts on a 75mm x 125 mm ( 3" x 5" ) board outline and fix the orientation of the parts and the assignment of the pins on connectors to work well together.

At the moment this ECU is organized as a general purpose CPU board which takes a partner board on top of it that has the parts to actually drive the fuel injectors, ignition coils and other functions.

So here's apicture. It doesn't show much really. Now I need to drive the tool to actually put in the real copper traces for connections. There are still a very small number of missing parts. I also don't really have a strong handle on dealing with protection from alternator "load dumps". I do thank team Slotus for providing early test information on this subject. It seems batteries really do become disconnected while a car is running. This can cause a huge power surge and the Ford unit in that car seems to have handled it, or maybe the alternator did.


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C9_ECU_cpupcb_early2.jpg
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 Post subject: Re: A locost EFI
PostPosted: June 1, 2015, 2:07 pm 
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horizenjob wrote:
work is now being done using the KiCad


That's good news!

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 Post subject: Re: A locost EFI
PostPosted: June 1, 2015, 4:35 pm 
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I'm to a point where I could start to use some input. So I'll start a thread on the Rusefi site....

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 Post subject: Re: A locost EFI
PostPosted: June 1, 2015, 8:38 pm 
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is it possible that having the headlights on when running would be a suitable dump.

perhaps a system like the one used in battery cutoff switches that kills the field windings in the altenator could be used, or just a relay, held closed by the battery that would open if the battery were lost, dropping the field.

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 Post subject: Re: A locost EFI
PostPosted: September 21, 2015, 12:22 am 
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So, way behind on updates on this! Still getting better at doing layout of the components and the connections between them. Sometimes I see a way to save some space and spend some hours rearranging a few little things and then adjust everything and realize I only moved an integrated circuit maybe 2 millimeters.

The CPU part of the ECU project is well enough along now that I am getting quotes for it's fabrication and assembly. That's exciting. It was slowed somewhat because my phone line was taken out the other day by lighting.The first step will be to have several boards fabricated which means made but with no parts assembled on them. Then I get to use an ohmeter and check every trace, via and pad for proper connection.

I am also now doing the basic work for the coil and injector driver board which plugs on top of this board. That's to make sure the two will be able to work with each other.

I found a couple of mistakes this week and fixed them. I added two Analog channels that connect to the driver board. To start they will be connected to monitor the fuel injectors. In theory you can measure the dead time of the injectors or see if they are operating properly. It may also be fun to be able to monitor the coils, so I'll try to see if that's possible.

My current plan is to offer what's needed for most straight forward needs on a 4, 6 or 8 cylinder motor. Then for a fancy setup it should serve all the critical needs and then be able to connect to another identical CPU board with the CAN bus which could provide the rest.

The CPU itself has protection on these inputs but for the moment I am including extra protection. There are TVS diodes wheret he signals enter the box, in front of the filters. Then there are Schottky diodes after the filters. These diodes protect the unit from static electricity and also shorts of the sensor wires to the battery voltage. Actually I think you could use a welder on the wires or plug them into a wall outlet and the unit would survive, not a 240V outlet though so do exercise some caution.

The extra protection costs about $3 and might also take up as much space on the board as another 2-4 analog inputs. Does that sound like a good tradeoff?

I may still be able to find enough room for some more analog inputs or digital inputs. What do you guys think?

RIght now we have:

Variable reluctance:
- 4 differential inputs

8 external analog inputs:
- throttle position
- manifold pressure
- air temperature
- water temperature
- fuel pressure ( sometimes? )

for tuning
- 1 or 2 oxygen sensor

driver entertainment
- oil pressure
- oil temperature

internal
- voltage

digital inputs
- 2 available

On the partner board,
digital outputs ?
- 8 floating mosfets, 1A
- ? higher current outputs ( low side? )

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 Post subject: Re: A locost EFI
PostPosted: September 21, 2015, 8:33 am 
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All I can say is let me know when I need to build a test stand for the BMW engine.
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 Post subject: Re: A locost EFI
PostPosted: September 21, 2015, 4:42 pm 
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Well, it's at least time to start thinking about building the stand. Maybe clear a little lab bench space to play with the board before you install it.

Today I talked to the fab and assembly house and the the discussion went well. They seemed super easy to work with. Even though their big machine places 40,000 parts on boards an hour, they have smaller ones and are happy to deal with someone just building 2-3 boards for testing.

Paul would you like or have the time to look at my schematics and board files? I am doing the work in Kicad which is a free open source tool. It runs on Windows, Linux and Macs. I'm mostly using a MAC.

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