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 13, 9:53 am
Poster: Richard Hull
On Apr 13, 9:53 am, Richard Hull wrote:
>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.
I am painfully aware of the RF and have posted on it before as well. It does, indeed, seriously interfere with CABLE TV!!!
The amazing thing is that my little, unshielded, hi-res, micro-video camera stares point blank into the viewport and remains stable regardless of pulsing! It sparkles in places as the huge blast of x-radiation discharges the CCD cells at high power, but is otherwise oblivious to the goings on in the fusor. I am stunned as I haven't lost a single pixel to date! RH
>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.
Amen brother! I too have failed to codify logic and reason to weird RF interference problems in my engineering job over the years. What works...works. It is very Yogi Berraesque, but hey, that's life. As he once commented " Progress may have been a good thing once, but it just went on too long"! RH
>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.
I have used pics for years to solve a lot of weird bothers in control situations which I wanted to make autonomous. I have considered pic'ing this setup.