[chbot] CNC and HC11 crash

[Mark Atherton]

Hi Wallace,

 From what you said it sounds like your setup is now much more 
sensitive to electrical disturbances than it was a few years ago.

Given that the CPU is an HC11, that dates the system to about 
1995-ish vintage, so the power supply is possibly linear, and the 
electrolytic capacitors have had a good chance to dry out. Maybe a 
good start would be to replace all electro caps with brand new, fresh 
off the shelf parts (not new, old stock).

What type of welder do you have ? Charles mentioned large inductive 
loads, back EMF etc. and that was certainly true back-in-the-day, but 
newer TIG and MIG welders are usually based on Switched mode 
technology, and some even have power factor correction. How old is 
the welder, how heavy is it (Iron, or SMPSU ?)

Migration of atoms. Yup, certainly possible with the sub 23nm(?) 
geometries, but HC11 technologies are an order (or two) of magnitude 
larger, and more resilient. My experience is that if it works, then 
it's OK - certainly with SSI and MSI parts (good old HC, and TTL parts).

Carefully placed ferrites (usually only in the signal lead, not 
ground return) may help.

Try and suppress problems at the source, and see if you can find a 
small noise source that makes things lock up -- I used to have a 
mains electric razor without suppression caps, great for tracking 
down noise paths into products.

And the electro caps, as I said, might be a good start.

-mark