[Diy_efi] P/H hammer driver circuits

[Bevan Weiss]

I think it's a little hard to regulate current via regulating the voltage
source.
Perhaps using a current chopper that drives into a large capacitor would be
the best solution.  It would also allow a MOSFET to operate in the most
desired region, just 'ON' or 'OFF'.
It would have to be a pretty large capacitor though.  Such that the current
drawn from it (by the injectors) doesn't reduce the voltage on the cap too
quickly.
Then it would be a simple comparator with a variable reference voltage (and
certain hysterisis for stability).  The comparator would either turn 'ON' or
'OFF' the MOSFET.

----- Original Message -----
From: "Greg Hermann" <bearbvd at mindspring.com>
To: "List for general do-it-yourself EFI talk" <diy_efi at diy-efi.org>
Sent: Monday, March 10, 2003 4:45 PM
Subject: Re: [Diy_efi] P/H hammer driver circuits


> 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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