I just ordered a maximite kit. I'm going to see if I can make this
work instead of buying the GRT EIS. By adding the maximite rs232
serial port chip, I should be able to send the same commands to
display on the GRT HXr glass EFIS display. At the same time, the HXr
has video in, so I'll be able to see my own display, and see the HXr
display onscreen.
Fuel flow will be the only real calculation based on the injectors
opening/closing (cycle rate), the rest is simply reading the gauges
and sending the value out to the screen/serial port. Should be
pretty straight forward.
Stay tuned.....
Paul, I'm not sure if you are focusing on EIS or the ignition
controller with this chip, but I'm going to start with the EIS. I'm
sure we will talk off-line and share our ideas and code. Open Source
always wins !
- Matt Boiteau
Great Matt. Don't be afraid of asking any question no matter how dumb
it might seem :)
All three can be done at the same time with the Maximite. Ignition
trigger, EFI and EFIS. For EFIS all you do is say "PRINT' and the
data magically appears on the EFIS screen :) Send a 15 usec wide 12
volt pulse to the Lamar Inst. cd system and you get a spark. Best to
use MC4424 for this as it requires a bit of current to keep down RF
noise pulse from false triggering. Each MC4424 will fire two CD
systems.
BTW these are the greatest MOSFET drivers I have found so far for
the injector MOSFETs. Each one will drive two MOSFETS. Very easy and
simple to use. Put a series 1K resister between the chip outputs and
the driver input pins.
Just about any TO-202 MOSFET will work for the injectors.
The IRFB8721 are about a buck and a quarter each from DigiKey.
Paul Lamar
Something to note- for the fuel pressure and oil pressure sensors
(and maybe others depending on the particular sensor) they need a 5v
excitation source. The EIS has this internally sent to the OP, not
the FP. The solution is easy- a 7805 regulator chip with a resistor.
The info (other than the 7805 part) is in the EIS installation
information.
no V will result in no reading.
Kevin Alderman
Kevin Alderman A&P, GROL, ASEL Comm/Inst
I would recommend a separate 7805 for these. If you feed the sensor from
the chip pin and the sensor fails and creates a dead short, it will
overload the on chip outputs and quite possibly shut down the chip. Better
to have no pressure reading instead of a malfunctioning chip.
I keep saying it, and here I go again. More time and effort will go into
making sure the EFI keeps going than will go into making it go. I really
hate "what if" statements and scenarios, but in the world of coding this is
a staple. After you get it working, you have to go over every bad scenario
that you can think of whether you think it is possible or not and ascertain
the impact on the continued operation of the system. Never ever forget that
if this system fails for any reason, your life is at risk. The Megasquirt
II code is over 6000 lines long. Do you really think that that much code
can be replaced by a few lines of Basic?
Download the MSII code, it is available and open source. Go through it and
if you can follow it see what it is doing. They try to handle almost every
circumstance, mixture possibility, timing possibility, etc.
Computers by their nature only do what they are told. If something comes up
that is not in the code, it will just stop [?] and be like this guy.
There will be more code to handle errors and error checking than will be
used to make the injectors and plugs fire.
Kevin Alderman
Kevin Alderman
A&P, GROL, ASEL
Comm/Inst
Are you talking about the asm version or the C version of MegaSquirt?
There is only one program in the Mega Squirt and Tracy's computer.
The Maximite can have dozens of programs any one of which can be
loaded and run in seconds.. One for every possible sensor
failure scenario including having all the sensors fail.
A fuel injection engine will run with a gravity feed of fuel dribbling
through
a small hole in the intake manifold. Klause tested it with his O-200. It
works.
The Wright Brothers dribbled fuel on to a hot intake manifold
controlled by a manual pet cock.
The Maximite system is a whole new frame of reference. Until one
tries it it hard to understand what the Maximite system really is.
You actually have time to write a short new program and run it with
the engine stopped and while you are gliding to an emergency landing.
It is an interpreter and not a compiler.
It is also cheap enough at $50 to have two or three.
You could have one per injector with redundant CAS and $10 manifold
pressure sensors.
Paul Lamar
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