[Diy_efi] New MegaWideband schematic

[Jorgen Karlsson]

Hi,

Did I miss something?

I took a look at the schematic and I can't find any current regulation
(other then R12, but that will not regulate current very well) or current
sensing for the Ip current. I can't see how it will work without it.

If we want to keep a minimum part count we can measure the voltage drop over
R12 and take an average. An analog filter could be simpler but that would
add parts.

If you are interested I can mail you my latest digital WB controller
circuit, it will need a sanity check anyway. It should work and it includes
temperature sensing on the sense cell to be able to use a Bosch sensor. It's
operation is quite different from yours as it use a regulated ip current.
Feel free to rip what you want from it.

Jorgen





> -----Original Message-----
> From: diy_efi-admin at diy-efi.org [mailto:diy_efi-admin at diy-efi.org]On
> Behalf Of Perry Harrington
> Sent: Wednesday, July 17, 2002 3:25 AM
> To: diy_efi at diy-efi.org
> Subject: [Diy_efi] New MegaWideband schematic
>
>
> Hello,
>
> I have updated the MWBO2 schematic to reflect the changes I have
> discussed with
> people over the last week.
>
> The schematic is:
>
> http://www.dainst.com/info/circuits/megawideband/MegaWideband_02.pdf
>
> The changes are:
>
> Redesigned the Heater driver.  It now uses battery voltage
> directly, with a
> voltage divider to determine what battery voltage is.
>
> The current sense resistor has been moved to the ground leg of the FET.
>
> The Ip enable has been redesigned.  The ground is driven via an
> LM324.  The
> input of the 324 is a 1k voltage divider with the high pole driven off the
> Ip ENB pin on the MCU.  This prevents the IP pump from operating
> unless the
> pin is driven by the MCU.  During reset the pin is HiZ, after
> reset it's low.
>
> The Vs input to the CPU is now buffered via an LM324.
>
> The reset and filtering portion of the schematic has been cleaned
> up.  The RST
> pullup resistor is gone now; the DS1233 has an internal 6.2k
> pullup resistor.
>
> A note:  If high baud rates are desired with the MCU, a
> 14.7456Mhz oscillator
> should be used.  This allows up to 115200 with 0% error in the
> baud clock.  The
> error is too high with a 16Mhz to permit 115200, thus only 57600
> is attainable.
>
> --Perry
>
> --
> Perry Harrington			Data Acquisition &
> Instrumentation, Inc
> perry at dainst dot com
http://www.dainst.com/

Those who would give up essential liberty to purchase a little temporary
safety
deserve neither liberty or safety. Nor, are they likely to end up with
either.
                             -- Benjamin Franklin

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