[Diy_efi] P/H hammer driver circuits

Greg Hermann bearbvd at mindspring.com
Mon Mar 10 03:39:38 GMT 2003


At 7:25 AM 3/9/03, Mark Bowers & Family wrote:
>> >Delivering a slug of current from a +24V source at
>> >turn on time would sure get the ole' pintle off it's
>> >seat quickly.
>> >
>> >Or, you could build an auxillary +24V (or 36V,
>> >etc)dedicated source with a DC/DC converter, and then
>> >switch the Peak pulse from it, the Hold from +12V.
>> >
>> >Carter
>>
>> This is along the lines of what Bob described to me a few years
>ago--except
>> that he said the peak source was more like 230 Vdc  in the latest
>> generation, with the application time for the "peak" down into the u-sec
>> range !!
>>
>> I would guess the limitation is mechanical--we wouldn't want the pintle to
>> come flying out the other end of the injector, would we ?? :-)
>>
>
> To all,
>
>I would be happy to help design something here for all to practice their
>flamethrowing & sharpshooting. Seriously, I was doodling something on paper
>2 days ago along the lines for the voltage doubling "charge dumper" outlined
>above, but the DC-DC converter then +12V hold sounds better. And maybe, a
>lover voltage hold would be even better, as it would reduce the power
>dissiapted everywhere in the hold state.

THANK YOU, and agreed that a lower--likely adjustable, or, perhaps jumper
selectable hold voltage would be the best deal.
>
>I would ask any comments for specs for this kind of beast, like:
>1) Drive source; the COMS level drive suggested is one possibility
>2) What injector types to drive: just low Z or does there need to be a high
>Z version too?

Might as well make it adaptable to all types of injectors. The more apps
the merrier.

>3) Any adjustability desired for peak current levels or hold current levels?

I would think it might be best to be able to adjust hold current level via
adjusting the hold voltage--jumper selectable sounds NICE now that I think
on it a little bit. Maybe hold voltage choices of .75, 1.0, 1.5, 2, 3, and
8 volts ??

>If so, is there a common external bus structure in use for common EFI
>systems, or are they all proprietary?
>4) Any rise or opening time that is critical or desired?? What are the max
>hold times anticipated in various applications.

15 ms is likely a pretty safe maximum hold time, but it could easily go
longer in apps with high torque at _LOW_ rpm-- Is this really a factor if
hold current is regulated via hold voltage ??? (Think staged turbos, a la
Porsche 959, with full boost/torque up by 1500 rpm !! ) :-)

Would run/check some max ms numbers for you if this is an important design
factor.

Are you thinking of generating the peak and the hold voltages for EACH
drive individually, or doing a power supply that would serve a group of
drivers?? Seems to me that a power board that could be populated (and have
adequate capacity) for up to either four or eight drivers would be a decent
approach. Ability to incorporate the circuit design into an integrated
board, complete with the processor would be nice, as well (less noise).

Using a _TOP_ QUALITY connector(s)  is essential, damn the cost.
>
Don't forget that a circuit to dissipate the fly-back voltage--energy as
QUICKLY as possible (and also safely) when the driver is turned off is
another critical design element in maximizing injector response and dynamic
range.

Would have done this myself long ago if I had the appropriate design
skills, what you are offering is exactly what this list is supposed to be
about !!

Thanks again !!

Greg

>
>Regards,
>Mark B.



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