On Monday 24 March 2008, Ormund Williams wrote: >On Mon, 2008-03-24 at 17:20 -0700, Peter C. Wallace wrote: >> We used 10K input resistor to protect comparator and 510K positive >> feedback resistor on our little adapter board. This gives a sensitivity of >> ~100 mV. Might be possible to improve this a little with >> experimentation... > >Thanks for the tip. I was going to setup a test to see what the output >voltage range was. > You might also want to put a paralleled pair of small signal diodes, one facing each direction to absorb the overvoltage when the wheel is given a good spin. Put them on the comparator inputs so the current will be limited by the 10k's. Half a meg seems like too much feedback too. 5 megs would then give ~10 mv sensitivity, and much of the step loss at start/stop would go away. However, be sure the diodes, if in glass, are in the dark as they are also photocells that can do a great job of picking up the common ballasted flourescent light, which has a huge 120 hz flicker.
I like this idea for a jog wheel a heck of a lot better than trying to use the old vcr editor controls I have laying there, waiting till I find my round tuit I haven't seen in years. I assume we are talking abut the steppers that drove the head carriage through a strip of about 1 mill stainless steel ribbon about 1/4" wide, or the same size motor but with a long shaft with a spring wire for a half nut? The little ones like in the 3.5" disks aren't ball bearing, and with their 1/8 worm shaft, would not be too rugged a part for shop floor use. The motor I'm thinking of, and I have several in old tandon 5.25 drives and the motor is about 1.75" square by an inch and a half long not counting the shaft. Those are well built. -- Cheers, Gene "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) Nice guys don't finish nice. ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
