Using PC HW (& Ignition timing reference points)

[tom cloud]

I received this response:

>Hi Tom.
>
>On Tue, 8 Oct 1996, you wrote:
>> Y'know, I've been reading with the greatest of anticipatory delight
>> the posts on various efi schemes.  But ... one thing keeps coming to
>> my muddled mind (I've got old-timers disease).
>
>Ditto.
>
>> a programmable up/down counter driven by a clock to produce the injector
>> pulse.  The counter was loaded with a number that corresponded to how
>> long the injector stayed open, and was triggered by RPM.  If that
>> were used by a computer controlled system, that number would only be
>> changed when the injector timing needed changing (and some filtering
>> could spare lots of unnecessary changes due to slight variations).
>> 
>> A similar system could be devised for ignition timing.  Let a PLL take
>> a few timing points from the crank or cam and produce any degree (pun)
>> of resolution desired.  Load a counter with the advance desired and let
>> that peripheral circuit control the timing.  Only change the advance
>> when needed.
>
>That's more like what I had envisioned also. The list majority seems to
>be dead set that a Motorola CPU is the way to go, but I'm much in favor
>of simple stupid hardware solution which is tweaked by a computer (PC?).
>I'm preparing to buy a Data Acquistion & Control board (for research
>and prototyping mainly) any day now. The other half of the design would
>be similar to the system your friend designed but I don't know enough
>about PLCs, PLLs (?), and PICs to make a good decision about which would
>be better for that application. Can you give me any more insight
>about the hardware he used to drive the injectors?
>
>BTW--I'd be glad to share my experiences/ideas offline until I get
>something going. Many of the DIY_EFI Motorola guys are working on real
>projects and I'm not going to interject my stupidity until I feel better
>about proving my thoughts with a running motor. Could be the wrong
>attitude, but then again...I'm just tinkering with very little time
>and even less money.
>
>Thanks,

to which I respondeth backeth:

I think your thoughts would be very beneficial to the group -- I
wish you'd re-post this to diy_efi.  There's many on the list that
feel just like you, and discussion can't occur if people don't do
it or do it out of the group.  I think what you've said is very
relevant and would be of interest to the majority -- not the minority.

[Actually, I'm gonna post it -- just won't use your name, okay?]

As far as what my friend used?  Dunno.  I can ask him again, but he's
moved on and has forgotten.  He says that there are drivers available,
but seems t'me a simple BJT or MOS transistor is adequate.  Now, if
you're trying to pulse the injector hard (with a 'high' current) and
then holding it on with a lower current, that might take a little
more thought (though, a capacitor can deliver the pulse).

So, I'm green too.  Maybe know more than some about a few things and
definitely know less about others.  Flame on the person that makes you
feel bad 'cause you ask a 'dumb' question.

Time honored 'dumb' question:
"Why is the sky blue?"
answer: Clearly that's a two part question. ... "Why?" Well, we'd all
like to know that. And "Is the sky blue". Yes.

Tom Cloud <cloud at peaches.ph.utexas>