[Diy_efi] LM1949 peak-hold driver chip , bank fire 4 injectors?

[Les Dittert]

Thanks Tim,
I guess I'll just make 4 drivers, and for now feed them off the same
pulse.
Do you know if I can substitute a mosfet for the Darlington, perhaps
using the
switching mode of the lm1949.
I wish someone had a little driver pc board with these on there. What
are people
doing to drive modern injectors these days, other than this method?

-Les


-----Original Message-----
From: diy_efi-admin at diy-efi.org [mailto:diy_efi-admin at diy-efi.org] On
Behalf Of Van Setten, Tim @ ACSSD
Sent: Wednesday, September 11, 2002 6:12 AM
To: 'diy_efi at diy-efi.org'
Subject: RE: [Diy_efi] LM1949 peak-hold driver chip , bank fire 4
injectors?


> The national LM1949 is made to drive a transistor to fire an
> injector peak and hold style. Can someone tell me to tell me if 
> it's possible to use this with a bank firing of 4  injectors?
> My concern is the selection of the proper transistor (can it be a
> mosfet)
> and also the overloading of the zenor diode, since it's getting back
> current
>  from 4 injectors instead of one.
> 
	The problem here is that injectors are inductors, and inductors
in parallel don't like to share current.  I know you see setups all the
time and in various wiring diagrams, but the correct way to wire low
impedance or peak-and-hold style injectors in parallel is to put a
resistor is series with each one.  A value of 1 to 2.2 Ohms should
correct this current sharing problem with injectors.

	The LM1949 IC is intended to run only one injector, however, the
current sense resistor can be changed to alter your "Peak" current
level. Hope this helps.....Tim.  

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