[Diy_efi] schematic critique

[Toyota Supra]

hey mark!

you should be able to email to this email address

turbosupramk3 at hotmail.com , it can receive up to a meg if i remember 
correctly.

thanks for taking the time out, i was just about to give up, as i built the 
other circuit, and it does not work

tty soon!

-j







From: "Mark Bowers & Family" <mbalntel at cfw.com>
>Reply-To: List for general do-it-yourself EFI talk <diy_efi at diy-efi.org>
>To: "List for general do-it-yourself EFI talk" <diy_efi at diy-efi.org>
>Subject: Re: [Diy_efi] schematic critique
>Date: Fri, 21 Feb 2003 23:39:59 -0500
>
>J,
>
>I have finally gotten around to the schematic, drew it by hand, and have
>scanned it for you, into a 750k .jpeg file; it a bit fuzzy, but readable.
>Let me know where I can email this, and you can put it in your schematic SW
>and post.
>
>Items to note about this circuit:
>1) Includes an input buffer resistor on the 12v supply to the 7808; this
>prevents the input filter cap from trying to filter out all the noise on 
>the
>car's 12v system, which will dry out the cap in short order and make it
>useless
>2) Adds filtering on the line from the fuel level sender, plus a slow time
>constant (several seconds) to smooth out any "wiggling" of the sender
>output. The noise filter is important as you will ground the sender near 
>the
>tank, and the gound for the control circuit may be in a different location
>in the car. If so, you will need a noise filter.
>3) Feeds the fuel sender from the 8v bus; this will be a MUCH more stable
>circuit, rather than feeding the sender form the car's 12v syste, If you 
>use
>the 12v system to feed the sender, without running cvia the dash units
>regulator, the switching point of the circuit will vary widely as the car's
>12v system voltage varies. (Hence why the put soem soret of regualtor in 
>the
>dash!)
>4) Implements the hystersis you wanted of approx 0.1v; you can increase 
>this
>by DECREASING the 220k feedback resistor, within reason
>5) Uses a simple NPN output driver
>
>Things to note:
>a) Assumes that the fuel sender will present about 55 k ohms resistance at
>the point that you want the pump switched off; this can be changed by
>varying the pot connected to pin 5.
>b) The output drive transistor can support about 100mA max current, and
>still be saturated. (Which means it will turned on hard, and there will not
>be much heating in the transistor.) This means your relay coil resistance
>needs to be about 1200 to 1500 ohms. It is important that you measure this.
>If it is much lower, then the FET driver circuit that was espoused by one
>fellow should be used.
>c) Assumes that the fuel guage will NOT be connected to the sender; this is
>important.
>
>I took a quick look at the schematic 7 and I can't see it working at first
>glance; I lost the link so I can't look at it more..
>
>  And, my apologies for the long time to work on this; gotta work for a
>livin' !
>
>Regards,
>Mark B.
>
>
>
>
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