[Diy_efi] Re: injector current-feedback driver
Sid.Young at qml.com.au
Sid.Young at qml.com.au
Mon Mar 3 10:51:49 GMT 2003
Hi,
Do you have a circuit with actual values on it ?
Sid
-----Original Message-----
From: Marcell Gal [mailto:cell at x-dsl.hu]
Sent: Monday, 3 March 2003 8:49 PM
To: List for general do-it-yourself EFI talk
Subject: [Diy_efi] Re: injector current-feedback driver
Hi Mark,
> The Qfeedback needs to be a PNP transistor to work with the Rcurrent
> connected as shown.
> The Schottky diode is not connected in the right place
yes, you are absolutely right. I fixed those typos. It must have
been very late last night ;-)
http://x-dsl.hu/genboard/injector/
> that could be made better, and the dependence of frequency on a lot of
> variables in the circuit components would make this circuit pretty hard to
> predict in exactly how it would perform,
the inductance and supply voltage determines di/dt
through the injector. Rhisteresis/R2 determines
the histeresis voltage. This together determines frequency.
Is it that bad or unpredictable? Or are you afraid of
the temperature dependance of Qfeedback?
>> Can 4 paralleled HC7404 inverters drive an injector driving
>> NPN transistor?
> ..
> the injector, then 4 paralleled gates do not have nearly enough output to
> drive Q1 as shown. (I assume you want to saturate Q1, and use the pulsing
> feature to provide the current limiting.)
yes, your assumption is correct.
> Since FET's do not need actual
> current to keep them on, they are easier to drive with logic gates; that
> would be a better choice for this design.
What if Q1 is a darlington?
What FET do you recommend for max 6A? Do I need a FET-drive
than (like megasquirt) or 5 Volt HC output is fine for
driving FET gate?
thanx:
Marcell
Maybe one other change would be right:
To connect Rhisteresis directly to Qfeedback base,
but the common point of R2 and C2 via a resistor.
That way C2 could not unwantedly slow the positive
feedback effect of Rhisteresis...
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