[Diy_efi] EFI system data

[Lasse Langwadt Christensen]

how about ...
 
          + 
          |
          R              +--->
          |  __          |
     -------|  \       |/  
          | | & |------|  
          +-|__/       |\  
          |              |
           \|____________|
           /|     |      |
          |       C      R
         _|_     _|_    _|_ 


not programmble, not P/H but fixed current but atleast it's simple ...

-Lasse

steve ravet wrote:
> 
> The 20KHz during the on period is to provide current limiting for a
> peak/hold injector?  It seems like you could do something clever with a
> 555 or two on each injector output.  Like have the injector output from
> the MCU enable a 20 KHz 555 PWM circuit, where the 555 PWM ratio is
> controlled by a decaying RC circuit.  Or a sawtooth output from a second
> 555.  Or something like that.  You don't want to do that in software
> (but you already knew that).
> 
> --steve
> 
> Kent Martin wrote:
> >
> > The MCU does have pwm output but I'm superimposing a 20Khz square on top of
> > the injector
> > on period. To do this I must have an interrupt at each toggle of the output
> > or use another timer to
> > stop the 20Khz timer. This would require two timers for each injector and
> > this is not desirable
> > as it has only 11 timers, and I need a few others as well. |A ballast
> > resistor I would have thought would
> > give a slower opening time and more non linearity of  volume with open time,
> > plus it's a bit low
> > tech for me.
> >
> > Kent.
> >
> > ----- Original Message -----
> > From: <bill.shurvinton at nokia.com>
> > To: <diy_efi at diy-efi.org>
> > Sent: Wednesday, July 24, 2002 8:37 PM
> > Subject: RE: [Diy_efi] EFI system data
> >
> > www.bgsoflex.com/megasquirt.html
> >
> > Chose an MCU with PWM outputs, much easier. OR use the tried and trusted
> > ballast resistor method. I have yet to see measured data to show that this
> > is any worse than a true peak and hold driver or PWM system. The inference
> > being that, for OEMs the circuitry of a P&H driver was cheaper than a bank
> > of big power resisitors.
> >
> > Bill
> >
> > -----Original Message-----
> > From: ext Kent Martin [mailto:kentmartin at froggy.com.au]
> > Sent: 24 July 2002 08:03
> > To: diy_efi at diy-efi.org
> > Subject: Re: [Diy_efi] EFI system data
> >
> > What's an MS style PWM?
> > I'm using a micro to generate the PWM.
> > I may run into trouble generating 10-15% duty because
> > of processor load, will 50% kill the injector.
> > Kent.
> > ----- Original Message -----
> > From: <bill.shurvinton at nokia.com>
> > To: <diy_efi at diy-efi.org>
> > Sent: Tuesday, July 23, 2002 10:39 PM
> > Subject: RE: [Diy_efi] EFI system data
> >
> > -----Original Message-----
> > From: ext Bruce [mailto:nacelp at bright.net]
> > Sent: 23 July 1995 13:02
> > To: diy_efi at diy-efi.org
> > Subject: Re: [Diy_efi] EFI system data
> >
> > ----- Original Message -----
> > From: "Kent Martin" <kentmartin at froggy.com.au>
> > <SNIP>
> >
> > If you are using a MS style PWM to provide the hold current then start at
> > 1Amp per injector, which is 10-15% duty cycle for a 2Ohm injector. Adjust
> > till it works. Once you are tuned in, it may be worth backing off a little
> > until you reach a minimum reliable hold current.
> >
> > Bill
> >
> > > What is the duty cycle required to keep the average injector open
> > (assuming
> > > a 20 Khz frequency)?
> >
> > 20KHz?  Your not goin find and injector to operate at that speed.
> > Bruce
> > >
> > > Kent.
> >
> > _______________________________________________
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> >
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> 
> --
> Steve Ravet
> steve.ravet at arm.com
> ARM,Inc.
> www.arm.com
> 
> _______________________________________________
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-- 
// Lasse Langwadt Christensen
// Aalborg, Danmark


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