Extra Inector Controller project

[Martin Easterbrook]

HI Jeff

>From memory the Cherry CS452 is a linear device, it gives you the peak and 
hold current (for low impedance injectors) by dropping the appropriate 
voltage internally.  You get a smooth current trace, but the device gets 
quite hot.  It works quite well though, if you can put up with the power 
dissipation.

The 584 is a switch mode device and is quite energy efficient.  You set 
whatever peak and hold currents you want (within reason) whereas the cherry 
chip has fixed settings (one has 2.4A/0.6, another has 4A/1A).  The L584 
can also be set up to have a peak sustaining time (ie current goes to the 
peak setting, stays there for a defined period of time, then switches to 
the hold setting).
This feature may be useful if you intend to run at high pressures. In some 
applications you will find that the peak current is reached before the 
injector has fully opened, so the peak sustain can be used to ensure that 
the injector opens fully before switching to the hold.
Martin

mailto:martin.easterbrook at virgin.net

-----Original Message-----
From:	Jeff Smith [SMTP:bureau13 at mediaone.net]
Sent:	09 May 1999 06:49
To:	diy_efi
Subject:	Extra Inector Controller project

Hi all,

I know then subject of "EICs" has been covered, as I've scanned through
the archives already and found a lot of good info. I do have a couple of
questions regarding this, however. First of all, I have seen a lot of
mention of the Cherry or Motorola drivers (they appear to be identical)
and the National LM1949, however ST Micro makes something called an L584
that also looks interesting (more like the 1949 than the Cherry parts,
it requires an external Darlington to turn the injectors on and off).
Has anyone had any experience with this part?  Other than the
requirement of external parts, what are the pros and cons that have been
found with any of these parts relative to the others?

My second question has more to do with the timing of the injector
pulses. I will most likely be using the ignition coil as the interrupt
used to fire the injectors, but is there a more appropriate time to do
it? Is there a delay that I should wait after the coil fires, or is
there some other interrupt, which would provide a more optimal firing
time?

TIA,

jds