Here's what I was thinking of: http://www.protoplant.com/stepperature That page has links to the circuit, board, and code.
It looks very well finished, and I have little doubt that it works, but it includes this note: "Stepperature is not a position encoder. Because of the small analog signal used to generate the signal it will miss some steps if turned extremely slowly." Also, he uses a 0.9 degree motor to get 100 steps/rev. "Yeah, I seem to have miss-laid my round tuit too as the years go by. In fact I haven't seen it since we moved from Rapid City in '71." Who warned you? I was there in '72. On Tue, Aug 26, 2014 at 8:53 AM, Gene Heskett <[email protected]> wrote: > On Tuesday 26 August 2014 06:43:28 Erik Christiansen did opine > And Gene did reply: > > On 26.08.14 05:13, Gene Heskett wrote: > > > I have a box in the basement with 4 ea small steppers designed to run > > > from a 24 volt supply, and a bunch of comparators to convert the > > > induced voltages into an A/B signal, was going to use them as jog > > > wheels, but the one time I tried to setup a test to see if the idea > > > had merit, I found that by the time I had added enough hysteresis to > > > the comparators, the minimum speed at which a reliable signal could > > > be obtained was faster than I had envisioned for fine control. > > > Doable, yes, practical for the job, no. > > > > Adding a bit of DC excitation appears to be the secret. About a > > fortnight ago I stumbled across a hardcopy I'd made from out there on > > the web somewhere, showing a 680 ohm resistor from each coil end to +5v > > or ground, and a LM339 comparator picking off the coil emf, IIRC. > > Unexcited, the generated emf was dismal (as you've confirmed), but > > leapt to hundreds of millivolts (i.e. heaps) with the coils lightly > > energized. Cogging (detent action) increases a bit, giving improved > > jog wheel action, according to the author. > > > With the 24 volt rated motor, I was getting volts per felt cog. But it > was ringing like a bell at the comparators output. It may not have > effected the usual flip flop based direction detector as it was only one > or the other line. > > ISTR seeing that link, someplace in time back up the log, and thought at > the time that whoever drew the drawing was perhaps not as well versed in > electronics as I have been after about 65 years of this. I don't recall > that I bookmarked the page, so if you can supply that URL, I'd be glad to > look at it and comment again. > > IIRC: The effect of the 680 ohm resistor was more than likely just getting > the comparator inputs off the supply rails far enough to good performance, > the LM339 I was using needed its inputs pulled away from the rails a few > hundred millivolts unless it was powered bipolar. > > One generally would do that, and I did, by putting in a bias network to > split the supply voltage in the center, and a resistor from that divider > then was connected to one end of each motor coil just to supply the bias > to do that. By choosing which side of the comparator gets the bias r > connected, then the other side gets a much larger r connected as feedback, > the really low level noises are suppressed below the trigger point. This > occurs due to the windings r causing a few microvolts of diffs between the > inputs when at rest effectively locking the comparator output to the last > state. > > It will of course oscillate if you get that wrong. > > I was at the time, trying to use some of the shacks single sided perf > board for a breadboard, but that stuff is so cheap it may fall apart the > first time a 275C iron tip hits it. This sort of thing should be worked > out using that white plugin breadboard, then made into something useful in > eagle, but I never did buy me one of those plugin solderless boards. I > always considered them to be a bit pricy... > > > Due to a lacking round tuit, I haven't yet gone as far as you Gene, > > to make one up for storing in a drawer for later. > > Yeah, I seem to have miss-laid my round tuit too as the years go by. In > fact I haven't seen it since we moved from Rapid City in '71. I've been > threatening to make some more out of much sturdier alu as that one was a > hot stamped maple coin about the size of a silver dollar. I miss it too. > But in all this time I have not come across any artwork I could run thru > potrace to use to make it, and my artistic ability usually got me a D in > grade school. > > > (Came back a couple > > of hours ago, from a fortnight on the farm. The fences are whole again, > > with no more trees through 'em, and I have another load of firewood to > > get me through what's left of winter. Three local council workers > > turned up on one say, to clean up the heavily wooded lane which runs > > along one boundary, and dropped another tree through the fence. Still, > > I can't complain that we pay our rates, and I never see them way out > > there.) > > These guys can't lay a tree where it doesn't hurt anything? Sounds like a > good teaching moment to me. I've made more than 1 6-pack of suds betting > on where the tree was going to fall. I don't make those bets in a high > wind of course. ;-) > > Making up a heat sink yesterday to put on one of Jon's pwm driven servo > amps I am going to use for the spindle driver on my 7x12, I found I cannot > locally buy a 4-40 screw in any length, so I think I'll re-seat it on the > mill table and drop a 2 flute 1/4" mill into it to get it down to where > the 1/2"ers I have will do. This mornings project I guess since I'm > cooling my jets till the mailman drops a box with the amp hidden in it on > the patio chair beside the front door. I went online & bought some 1.25" > socket head versions, but those are in MN & won't materialize till next > week. I hate waiting for pissy-assed little things like 4 screws I can't > buy locally... > > Then, talking about round tuit's, I just heard some very uncharacteristic > exclamations from the better half, emanating from the general vicinity of > the kitchen sink, she had pulled open the lower door to extract a spray > bottle from a small tub sitting under the garbage disposal, and found the > tub 1/2 full of dirty water. Seems the disposal's shaft seal in the > bottom of its grinder has gone away. Disposal sounds normal. So, saddle > up and go get a new one is the days project. Damn! OTOH, thats the 3rd > one I've put in in the nearly 25 years I've been here. And even with a 5 > year warranty, if I could find it, it has to be 2-3 years out of warranty. > > The advantages of ones "Golden Years", but the only gold is in the > porcelain bowl in the middle of the house. :) > > Thanks Erik. > > Cheers, Gene Heskett > -- > "There are four boxes to be used in defense of liberty: > soap, ballot, jury, and ammo. Please use in that order." > -Ed Howdershelt (Author) > Genes Web page <http://geneslinuxbox.net:6309/gene> > US V Castleman, SCOTUS, Mar 2014 is grounds for Impeaching SCOTUS > > > ------------------------------------------------------------------------------ > Slashdot TV. > Video for Nerds. Stuff that matters. > http://tv.slashdot.org/ > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users > -- ---------------------------------------------- Gary A. Crowell Sr., P.E. <http://www.nspe.org/>, CID+ <http://dc.ipc.org/html/default.htm> Linkedin <http://www.linkedin.com/in/garyacrowellsr> Elance <http://www.linkedin.com/redirect?url=http%3A%2F%2Fgaryacrowellsr%2Eelance%2Ecom&urlhash=kJm9> KE7FIZ <http://www.arrl.org> Things <http://www.thingiverse.com/garyacrowellsr/designs> RocketryCNC <https://www.etsy.com/shop/RocketryCNC?ref=l2-shopheader-name> ------------------------------------------------------------------------------ Slashdot TV. Video for Nerds. Stuff that matters. http://tv.slashdot.org/ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
