Fusion Message Board

In this space, visitors are invited to post any comments, questions, or skeptical observations about Philo T. Farnsworth's contributions to the field of Nuclear Fusion research.

Subject: Re: Computer control
Date: Apr 12, 5:44 pm
Poster: Scott Stephens

On Apr 12, 5:44 pm, Scott Stephens wrote:

>One last problem. This is really hairy too. The rarely shut off restart EMP pulse of a system working at optimum in glow mode near 2 microns is so fearsome that it will shut off the low voltage instrumentation Lambda supply and has destroyed its read out!

Do you have an RF detector? If you leave a radio running you might notice your fusor is generating EMI, possibly in the vhf-microwave, and radiating it throught its wiring, unless the fusor is filtered at the feedthroughs. I would think those vacuum feedthroughs would be great filtering caps, but RF still might radiate through the viewport.

>It also advances the HP counter by several thousand counts. Other bothers exist, but I figure this may not a radiated signal, but could actually be ground bounce!

I worked on a scanning acoustic microscope that use kilowatt steppers to sling around a transducer sensitive to pico-watts. Its can be maddening trying to keep out EMI. Sometimes cables were best grounded, other times floating.

I think tutorials and app notes on EMI, instrument and rack grounding are available from vendors like Intel and others on the web.

>Can you imagine a poor CPU in this environment with all those lines headed into it. Yeah even opto-isolated, I might not cook anything, but it would likely be a "reset city" moment on the CPU buss.

There is a lot you can do, if you write the code yourself. I love PIC's. They are pretty EMI robust, have a watchdog timer to reset them (unless you go into SCR latchup, which shouldn't happen if the ports are protected). Software tricks like state-machine design with checkpoints, interleaved jump-to-init, and redundant variables can also mean your system comes back up and keeps working after a hit. I wouldn't dream of using a PC.

>Variacs moving to the moon, vac valves opening wide or shuting down.............I have seen such things occur in my robotics days.

I have a list somewhere of EMI faults. My favorites are the San Fransico ATM that spit out money when the cable car drove by, the animatronic robots that had Gran-mal siezures when the neighboring arc welders lit, and from my own youth, when my accomplices and I would skate over carpet to the tank-battle game with coins and shock it for free games :-)

That game was OOS an awfull lot!