How do I reduce ignition noise. (HELP!!)

[Walter Petermann]

Chris Vandrachek wrote:
> 
> To all in EFT land:
>         I have recently designed and built a simple EFT system based on a
> Mot. HC12.  All has gone well until now.  I can't keep the MCU from
> reseting whenever the ignition fires.  I am only a sophomore EE student so
> I don't exactly know where to start.
> 
> Here is a quick outline:
>         -The MCU is physically isolated from the coil etc (5ft), but they
>         share the same battery.
>         -I'm using a standard points ignition...I'd do a electronic, but I
>         have to be done by this Friday.
>         -The MCU supply is regulated with only a LM2935 (an automotive
>         specific device).  Only a .1 cap on the inputs.
>         -It seems that reset occurs most whenever a open arc is present,
>         arcing in distributor cap included.
>         -The problem is independent of my triggering pulse (from
>         coil)...so I'm guessing it is due to voltage spikes/drops or it is
>         "in the air" (EMF?).
> 
> I don't know what to do and I gotta have the done by Friday for a design
> competition.  Any advice would be greatly appreciated!!!
>         Thanks,
>           Chris Vondrachek
>           EE student, University of Portland
>           chrisv at egr.up.edu

Chris,
 one more thought:
 Are you sure that it's not a software problem? When the
coil fires are  you branching and possibly overwriting some
data with the stack?

 Walter