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Regarding the old PC with serial port - can you not get a
USB-Serial (Rs232) dongle from your local Radio Shack - that is what I had to do
because I also need the D sub 9 type connector.
One thing my precepitions is that your are
starting to get close to violating the old Keep it Simple Stupid
principle. The more components, the more redundancy, the more things that
could go wrong with the systems and there perhaps unintended interaction.
Not saying there should not be any redundancy - that is why I fly with the
EC after my HALTECH system went belly up (fortunately on the
ground). But, you gotta know where to draw the line.
Another factor is that unless these systems are
automatic, you will find your time (and attention span) somewhat limited when
things start to go wrong (don't ask me how I know).
But, thinking out the failure modes before you fly is
certainly a good thing to do.
Ed
Sent: Wednesday, May 18, 2011 6:02 PM
Subject: [FlyRotary] Re: Reliably starting
On 05/18/2011 05:21 PM, josrph berki wrote:
Ernest,
Will you be running Megasquirt for flight or is
it a gound development tool? Do you have any words of wisdom for someone
contemplating Megasquirt? I would really like to see an electronic
analog injection / ignition system developed. Software that controls the
engine scares me. Thanks for any
help.
Analog injection/ignition systems scare
me. Well...not really. All software systems are analog
underneath.
I will be flying with the MegaSquirt, but I can throw it a
lot further than I trust it. But, that is ok. The goal is do design
the system so that it fails gracefully. The MS gives an incredible amount
of flexibility and configuration control. It is REALLY nice to have.
So I take the benefits, but have backup(s).
If the MS quits on me
for some reason one day, I have a 3/16" line plumbed to the throttle body with a
needle valve sitting next to me in the cockpit. I've already verified that
on the ground, with gas barely covering the bottom of the tank, I get flow to
the throttle body. I'd probably never be able to get the engine started
with this setup using the starter, but with the wind still spinning the prop I
will be able to slowly open the valve till I can maintain altitude. Then I
can make for the longest runway I can find.
That's good for fuel, but
what about spark? I'm having the MegaSquirt control EDIS ignition control
modules. The EDIS handles all the VR pickup, dwell and other such
details. These things have proven to be very solid performers during a
decade of use. All MS is doing is getting a tach signal from the EDIS, and
sending back a signal to control advance. Two wire interface. If the
EDIS looses communication with the MS, it falls back to its limp-home mode which
is 10*BTDC. I shifted the VR so that I actually get 25*. But, that
just shifts the critical failure from the MS to the EDIS. I don't have it
wired up yet, but eventually I will have two EDIS modules running, one on
Leading and one on Trailing. The second will have its own power source,
driven by the distributor shaft.
Sure, power will degraded if all
I have is the trailing plugs and I'm dumping fuel into the throttle body instead
of a proper spray, but it isn't meant to be a normal mode of operation. It
is meant to get me past the crash site. I don't have to be scared of the
software, because I'm not hanging my life on it.
The only other advice I
have is buy one of the MS3s. They have a USB interface, and can datalog
directly to a flash card. I'm stuck with an MS2 for now. Because of
that, I have to use a 15yr old laptop, because it is the only one I have that
has a serial port.
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