On Tuesday 04 February 2003 03:38 pm, you wrote: > michael brown wrote: > > That's pretty neat, I'll have to try that. I'm guessing that the > > advantage is reduced current consumption and the fact that the > > comparator is being operated at it's most accurate point. Does > > that sound right? > > Yes to reduced current consumption, although I still show a 10K pot, > which will consume 0.5 mA all by itself. It's important that the > source impedance be low with respect to the wiper series resistor, or > you'll get some nonlinearities. You could go with a higher-value pot > and correct the nonlinearities in software if they get too large, > since they're quite predicatable. Good things to know, thank you. ;-) > It isn't so much that the comparator is operating at its "most > accurate" point, but simply that it's operating at a single point. Yes, of course, I realize how dumb that sounded after sending it. <:-) > This eliminates all common-mode range issues. Another good thing to know. ;-) My next trick is to hook up one of these L-293D bridges to my PIC and=20 get it manipulate the little stepper motor in a GM throttle body's idle=20 air control valve (IAC). This is so some guys on the MegaSquirt list=20 (including myself eventually) will be able to set a normal and fast=20 idle preset, or to simply adjust the idle speed manually by twisting=20 the pot. I've run stepper motors before, but they have all been unipolar so I=20 didn't need any kind of bridge. Other than that, I don't anticipate=20 much difference in controlling this one. The software should be pretty=20 much the same. I really enjoy tinkering with these things for real, as I feel that I=20 learn much more than I would by playing with some simulator. A=20 simulator wouldn't bring to light the most interesting "real world"=20 aspects (to me anyway) of my insignificant experiments. michael -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listserv@mitvma.mit.edu with SET PICList DIGEST in the body