Mike was having trouble with his computer. He was getting very
 discouraged. It would dump the B computer fuel map.

 Is a voltage drop causing computer problem?
 This is more likely to occur if your batteries are in
 the back of the airplane. I would run heavy
 wires for the starting and alternator  functions
 and a separate smaller wire directly from the battery for the
main bus. The reason is the battery acts as a giant capacitor so
starting and alternator glitches are less noticed on the main buss.

 Here is a sketch of his wiring design that Mike drew and that I
 have edited a bit.

 The other possibility is the computer is not sensing a power
down situation and not cleaning up what it is doing in software.
A way of doing that is add a small 5 volt rechargeable
battery that keeps power on the computer long enough to clean
itself up.

 This can mostly be done in software if one analog to digital converter
 is dedicated to monitoring the raw 12 volt supply. If the
voltage drops below say 9 volts the computer starts cleaning up
the software for shut down. Kind of like old Windows where you
had to tell it to shut down and Windows would clean it self up
before actually shutting down.

 The 5 volt regulator feeding the computer usually has a very large
 capacitor that can keep 5 volt power on the computer long
 enough to clean it self up. This capacitor can serve as
 the small five volt battery.

 Paul Lamar

Voltage spikes (possibly through grounding scheme) is a more likely
candidate.

I had one case where ground bounce caused this kind of problem and I
couldn't talk the builder through corrective measures (did not speak
english well).   Ended up having to add a number of filters & such to
the EC2.  The ones I can remember are:

Added a spike clamping diode  (1n4004) across the coil of the
injector relay. Added a .01uf  capacitor to PCB ground to the Master
Clear pin on both controller chips. Added .1 uf capacitor between
ground & the air temp sensor connector pin.

Didn't hear of any more map table corruption problems after that so I
assume it helped.

Other than bugs in the code, the ONLY way corruption problems can occur
is through  large voltage spikes (usually through ground).   There
is an elaborate software procedure needed to do any alteration to
EEPROM where the table is stored.  The other way to erase it is
through program voltage (+12 v) being applied between ground and
master clear pin.  That is the reason for the filter added on that
pin.  It would be better to eliminate the root cause because there
are other possible side effects of ground noise.

Tracy

Can you do this on Mike's early computer if I send it back?
I added vibration isolators with braided case grounds to the
mounting arrangement.

It appears to be well grounded to the air frame both before and
after. Also the 6-32 ground bolt on the computer has at least 4
wires going to it. Maybe more.

Paul Lamar


Hi Paul,

ALL coils require clamping diodes across them. When they de-energize they act
like an ignition coil and put out a short higher voltage that can damage
electronics. Note the 0V contacter has one. The K1A and K2A do not show diodes
across them. A note on relays like for fuel pump, lights etc; there are some
available with diodes in them.

Dale Davies