This is very important. The PWM freg must be low enough to give the
time necessary turn an injector on and off. This is done in the back
 ground in the Arduino and the MM.

No direct program action is required once it is set up. The longest
the MM will do is 50 msec. As far as I can tell the longest the
Arduino will do is 33.3 msev. Said another way the max time available
for the injector pulse width.

This circuit does the same thing but as long as you want to what
ever you want.

It requires an 8 bit port  for two injectors but as I recall the
same D to A is available in a 4 channel version that will handle 4
injectors.

The fuel injectors will continue to work if it still has power even
though the computer dies.

It requires a 10 HZ oscillator (100 msec injector window) but that
could be done with another 555 or come from a Pin on the MM. The
injector pulse width can be updated ten time a second or less often
at your option.

The 8 bit port sets the pulse width to one part in 256 but once that
 is done this circuit handles the injectors from then on in the back
 ground.

This is a classic example how sometimes it is better to add hardware
 rather than software on low volume computer based products. Software
 cost and programming time becomes the greatest expense.



Paul Lamar

Paul,

The PIC16F1619 has an angular time function.   Part is available in
-40C to +125C range. Under $1.50 single pc.


http://www.microchip.com/pagehandler/en-us/family/8bit/peripherals/coreindependent/angtmr.html

Just amazing what they have in that chip.  I did MPC555 Engine Control,
and set up ignition and fuel events with a TPU (time peripheral
unit).  Took over a month just to figure out the darn TPU!

With the PIC processor, up and running in under an hour.   Just fun.

Quick tip to everyone... if you have a "dry cough" and/or odd chest
pain... do mention to your doctor.  I get to be on the other side of
a Davinci Surgery Robot in a few weeks to get my lung lobe removed
due to cancer.  Never smoked in my life, nothing considered high
risk, but that's life.   Once I have a full pathology report, it may
mean it is time to buy a  new 911 and hit the road for some cool
road trips, but nothing planned yet!

TW


You probably grew up when almost everyone else smoked. Second
hand is supposed to be worse than first hand. Also a lot of other crap
in the air these days. I have been melting snow and it is amazing how
much particulates are in a 20 liter pail. I live in the country with not a
lot of communities or cities west of here. Should be sort of dust free.
I hope all goes well.

Dale Davies


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