[Diy_efi] New MegaWideband schematic

[Perry Harrington]

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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