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To: BillHoo who wrote (16940)	8/19/1998 11:23:00 PM
From: WebDrone	Respond to of 213177

**OT Discussion of Stepper Motor Drivers. Bill, we swapped the original Adaptec scsi with a newer adaptec scsi, as recommended by the company. The Bios could well be a little messed up, but our very large tech support group only has a few people willing to rip in to the bios of a brand new dell workstation! Here is what I think the problem is- a numerical rounding error in calculating the position of the stepper motors. This could be a numerical oddity between Windows, NT, or porting 16 to 32bits... I dunno how they did it, but... it could be a bad pin somewhere, too. I can scan fine at certain resolutions. As I increase the resolution by small increments, a buzzing noise starts. Keep incrementing, the noise gets louder, eventually the scan becomes useless due to the damn scanner is shaking so hard the CCD is vibrating more than a pixel, and the puppy sounds like it's going to self destruct. Fine with me, it's under waranty. Keep increasing the resolution, it starts to quiet down, until a new acceptable resolution is found. If you keep increasing the noise will increase, repeating the cycle. What I am describing is the beat pattern between two numbers of different ring modulus-- the interpolation of the stepper motor was messed up, and since it scans at 72, 150, 300 and 600 dpi... Why would a webdrone scan at 200dpi? Well, I know sampling theory, and I had my reasons. When I did- BUZZZZZZ! There are a lot of ways to get this-- I first saw it on a medical scanner, when we ported from 16bit to 32 bit. The discontinuos rounding error we created caused the stepper to mis-cog at certain speeds that were not halves or quarters or eighths... This was hauling a 200 pound C-arm down a table, and THAT was a hell of a loud buzz! Same behavior, though. Lesson- stick to something closse to a multiple of 600/(2^n) where n is an integer! Now, why did this take me 3 months, using top of the line gear, only to give up and move to another bureau? By the way, my new IT support guy is blind, so he is allowed to use Win95. His scanner works. He is also competent to mess with BIOS. That's what I needed to get a working scanner- a dedicated support person running a different OS than NT4.0 He really likes my artwork, since I compress the SNOT out of it! He appreciates that it downloads faster than greased lightning. (design for GIF!) Back on topic- anyone like $40 for Friday? Amazing how many stocks move to the strike price. Manipulation? Why, that would be as SHOCKING as a dishonest politician! Web