All you guys in Oz & Nz got to get a Jan 14 back issue as there is
an article on how to build an EFI with a low cost Arduino micro
computer. This will be a good education in EFI's. I ordered a copy
for me shipped to the US for $15 Oz
Silicon Chip mag is a great Oz publication for buying and learning
electronics.
http://siliconchip.com.au/
What works on one cylinder works on one rotor. It's cheap enough to
dup it for the second rotor.
Don't mess around. They will be sold out of Jan back issues shortly.
Paul Lamar
I strongly recommend Arduino kit. I made some by Ebay's chinese
circuit. mostly charging battery and drill and soldering. but as
going study harder. most circuit already on Ebay or any hardware
store. only left thing is controller.
Arduino is very very cheap and most of all it's programming language
and IDE is most valuable. just plug in via USB and install IDE(
programming software) you can programming micro computer . and there
is already so many example at IDE, ( IDE is just same as word
processor, it's programmer's word processor ) there is so many
tutorial about this.. I just pick this. but you can search all about
it.
http://www.youtube.com/watch?v=E6KwXYmMiak
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http://www.youtube.com/watch?v=E6KwXYmMiak
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http://www.youtube.com/watch?v=E6KwXYmMiak
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http://www.youtube.com/watch?v=E6KwXYmMiak
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http://www.youtube.com/watch?v=E6KwXYmMiak
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http://www.youtube.com/watch?v=E6KwXYmMiak
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http://www.youtube.com/watch?v=E6KwXYmMiak
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http://www.youtube.com/watch?v=E6KwXYmMiak
making 3D printer or CNC also very easy. there is already part and
firmware there. and we can use this as almost everything. we can use
it monitoring voltage at sensor so on.
http://www.youtube.com/watch?v=85LvW1QDLLw
http://www.youtube.com/watch?v=gDFeXYWxQ_Y
IT's key is easy to programming. that's the key and there is already
many tutorials and datas. I recommend it as software engineer
expert.
P_Bear.
Using the Arduino IDE has some drawbacks- as you add more
digitalWrite commands and digitalRead commands, it slows down
considerably. The problem isn't the chip, its the Arduino IDE. The
Arduino.h file that includes the functions that allow the
digitalWrite, digitalRead, analogWrite and analogRead functions
require the compiler to write a lot of non-optimized code. For
example, to enable digitalWrite on pin A1, the compiler has to write
8 separate lines of code- one for each bit for each of the available
pins. Same for the other commands. This ends up taking a lot of the
processor power for unnecessary commands.
The only way to make the Arduino work for an EFI would be to write
the code in C or C++ and manage the bits individually. While the
Arduino IDE is simple enough for beginners, it is not suitable for a
really high end high speed critical system.
There is another board made by Texas Instruments called Hercules that
is much more suitable for an EFI- it has a built in watchdog timer as
well as built in self monitoring provisions. The board is marketed
for "safety critical" applications, which an aircraft EFI would be.
I wrote the code for an Arduino Mega 2560 that monitored the
potentiometers for 4 linear actuators, would read the pots and
control the pwm for 6 channels of LED lights, it read the temps
inside and out and monitored the output of an electric heater for
safety purposes. The system ran slowly enough that it would miss the
stop points for the actuators causing the actuator to "hunt" for a
bit before stopping at its intended location. Once I identified the
problem, I was able to use a different IDE to write the code at the
bit level and make it work. The problem turned out to be the time
required for the system to read and write to all the pins, and the
time lost to the ADC.
If you want to see for yourself, the Arduino code for a lawnmower EFI
system is on the internet, as well as a Youtube video. Download the
code into the Arduino IDE, then compile it into assembly. As you go
through the code you will see what I mean.
I have been working on and testing bits and pieces of a similar
system for a while now and my conclusions are that the best system
would be built on the Freescale S912 series chip or an ARM 7 or 9.
The freescale chip has a second chip on the board known as Xgate that
has a singular purpose- to read sensors and gather information. This
frees up the main processor which is many times faster than the Atmel
in the Arduino to do nothing but calculate and bit bang the injectors
and other necessary items for the EFI.
Kevin Alderman
Kevin what about multiple Arduinos one for each injector and one for
the display? The Motec is $3000.
If you want a real powerful ARM I have just the board for you :) You
can have it for what I paid for it in a day or so. About $200 I
just don't have time to work on it. I am focused like a laser on the
ignition :)
http://www.mikroe.com/
Paul Lamar
Its not so much the Arduino, it is the Arduino IDE. The arduino guys
went to a lot of trouble to make an IDE that was easy to use, but
this has drawbacks. When you call digitalWrite, the compiler
literally has to write 10 to 12 lines of code to make that work- and
it does it for each pin. How it works in a nutshell and kind of
generally. If you look at the Mega pinout for the chip itself, you
will see things like PA0, PB1, etc. The actual layout goes like PA0
through PA7, PB0 thorugh PB7, etc. Each pin is part of a group of 8
bits 0 - 7. What the compiler does when you call digitalWrite(A8), it
will use the IDE header file to find A*, which is PC0. It will have
to write to that bit, while not changing any of the other PC bits- so
it will call the code PORTC_0 0b = 10000000, where port PC0, aka A8
is given a bit of 1, and the others are given a 0. This sets that
particular pin to high, and the others to low. Now, you might not
want A9 to be low, so it will stick another line under it that looks
like PORTC_1 0b != 00111111, which will in effect invert the other
bits to the opposite of what they are. So, since somewhere in the
program A9 is HIGH, the program has to flip bit one and 2 of port C
to high and then flip the remainder to LOW, and keep checking each
bit and comparing to what the program needed before it got here. This
takes up a lot of processor time and makes it slow if you have any
complexity at all.
If you learned C or C++, you would be able to call each port (pin)
with an individual bit, and not bother the rest unless you needed to.
This is called bit banging- changing a single bit high or low to turn
something on or off repeatedly.
There are other issues, but the problems are mostly related to the
Arduino IDE and its inefficient compilation so that people don't have
to learn C. And stay away from the delay function if you can- it
literally stops the program. I use delay only if I want to stop the
program- like if I want to move the actuator with a button press. The
chip will read the button press so fast that no matter how fast you
are, it will read multiple presses. So, if the button is pressed, I
use delay for 20ms do "debounce" it. I also use code that says if the
associated pin is HIGH for more than once in a period- 200 ms works
well- then it reads as one press. I also successfully used code that
said that until the flaps were at position 1, you cant select
position 2, which prevents one long press giving full flaps at the
turn from base to final when I only want one notch of flaps.
This is actually used to control the flaps in my Wheeler (along with
the lights, etc.) One press lowers the flaps to 10 degrees, but only
if the airspeed is lower than 110 knots. 20 degrees if airspeed is
less than 90. 30 degrees if airspeed is less than 80. In the event of
a go around, i.e. full throttle, and airspeed above the limits, the
flaps come up one notch at a time. Trying to make my plane idiot
proof. It works quite well at this point, and is built on an Arduino
Mega 2560. I can also disable the automatic flap part and manually
control the actuator with a single switch on the panel. I like
backups.
I dont like the idea of a 2 inch hole in my firewall where noise and
exhaust can come in, so I opted for an electric heater. I use a
digital temp probe that will shut off power to the heater if the
output temp exceeds 120 degrees, which means the fan has stopped. You
can use this approach to monitor basically anything in the aircraft.
However- displaying the information drastically slows down the
processor. If I wanted to use the Mega to monitor and display a lot
of parameters, I would use a board just for the flaps, and another
board for the other so that the displayed info doesnt slow it down
too much.
One more thing that significantly slows down the arduino is
serial.Print. speed killer.
If you want to see it first hand, get an LCD shield. The lcd.print
is faster than serial.Print. Load some code in, and watch the update
speed of the lcd. 3 or 4 serial.Print lines and you will be able to
see the blink of the lcd update, indicating a slow down of the
processor.
For critical systems, I would opt for an RTOS, real time operating
system. Basically this OS gives a time and priority to each function
or almost line of code. If a sensor is having an issue, the program
wont get stuck there but use a default value and skip it after a
programmed amount of time. This approach is used in fly by wire and
FADEC systems.
Now to finally answer the question- yes you could use multiple
boards like one for spark, one for fuel etc. But you would lose the
ability to fine tune the whole system at one time. I did test using
one board for the strobes, one for flaps, etc. and it works. Some of
the 16mhz tiny pro boards are on ebay for like $3, and these work
well for little programs.
Kevin Alderman
I got it Kevin.
What about my ARM board? Mikroe is a great outfit. They do
everything they say they are going to do.
You want real time check out my SuperKim I built in 1975 :)
Paul Lamar
Opss a 5 meg file made it into that last message. Sorry.
You are right Kevin. Delay loops are dumb. The QB DOS IDE has an on
time hardware interrupt.
How about one Arduino for two injectors. Rotor one and rotor two.
They could load the common mixture map from USB drives on boot up.
Paul Lamar
Assuming that you didn't need or want sequential injection, I guess
you could just PWM the injectors based on a mixture map. If you fired
both injectors from the same pin/ variable combo that should work.
The ignition would be a little more difficult, but with the CD
ignition even that wouldn't be a huge issue. You could even code in
ignition timing advance for the CD ignition with multiple HE sensors-
read the time between 1 and 2, calculate x, and fire x ms after 3. No
dwell to mess with. Could code in a pot for manual mixture
adjustment. I would use duplicate boards to add redundancy, and it
should work.
Kevin Alderman
My new Lamar Ignition does not need or use a computer.
It fires when it is told to fire by the crank angle sensor (CAS) within
a few microseconds.
It uses way less current than smart coils like the LS1 and RX8 coils.
That means the engine will stay running longer in the event of an
electrical failure (with a carb).
It fires multiple times up to 11,000 RPM unlike a cap discharge system.
It can fire at 20 BTDC, 10 BTDC, TDC, 10 ATDC, 20 ATDC and so on up to
160 degrees
of e-shaft rotation.
Paul Lamar
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