[Diy_efi] Measuring Pulse Width/Duty Cycle of an Injector?

[Steve Ravet]

> -----Original Message-----
> From: diy_efi-bounces at diy-efi.org 
> [mailto:diy_efi-bounces at diy-efi.org] On Behalf Of Marcello A. Belloli
> Sent: Saturday, May 21, 2005 10:31 PM
> To: diy_efi at diy-efi.org
> Subject: [Diy_efi] Measuring Pulse Width/Duty Cycle of an Injector?
> 
> Hello Everyone,
>      I'm still working on a datalogger project.  Been doing a 
> lot of the
> software while I've been on vacation in Thailand. I'm still on
> vacation, but can't keep my mind off of this project.  I'm using a
> PIC18F452 as the Micro behind my datalogger.  I've got just about
> everything working.  The one place I'm having problem is the
> understanding of how to read pulse width of a fuel injector.
>      Is there a way of looking at all types of injectors, 
> that will allow
> for an accurate account of timing?  I've been looking at two type of

For the pulse width meter I built (see the diy-efi.org projects page) I
used an opto-isolator to both insulate the measuring circuit from the
injector circuit, and make it able to hook up across the injector no
matter which side of the injector is driven, or what the voltage
waveform looks like.  This particular opto-isolator has 2 diodes in
parallel, so the polarity of how it's connected doesn't matter -- if the
injector fires, then one of the diodes will light up and complete the
circuit. 

> injector firing.  Low resistance injectors, which use a driver that
> duty cycles the injectors after the main firing to keep the current
> within limits.  And Higher resistance ones where the resistance alone
> keeps the current down.  Now how do you look at firing time of an
> injector when the driver starts to duty cycle it after 1.2ms?

I haven't see all driver circuits out there but I think most of them
don't duty cycle the injector, they just reduce the voltage applied to
the injector.

--steve