In robotics, DC motors are always the hardest to control at the slowest speeds. The root of the problem applies to model trains too. The coefficient of friction is different for static friction than for moving friction. So the sleeve bearing in a motor takes a certain torque to break free, then after it is moving requires less torque to continue moving. Because of the difference in frictions it always takes more current to start a motor than to keep it moving.
I think the point of the pluses is to vibrate the motor and get it moving, and then the DC superimposed on the pulses is what keeps it moving. A better way is to use an aggressively tuned PID loop so that we start the motor with a large current then a millisecond later before it has moved 2 degrees we reduce the current. But a PID loop controller would have cost as much as a small car back then. I'd say this thing was a vibrator with a DC component and not PWM control. On Sun, Apr 10, 2022 at 4:20 PM John Figie <zephyr9...@gmail.com> wrote: > I remember a similar model railroad throttle for DC trains published in > Model Railroader Magazine called the TAT IV. I was just a kid and tried > building one. Back then you could make thing for less than what they cost > assembled. My first build was a total failure. A second attempt using a kit > that becam available also failed as the electrolytic capacitors exploded > because I put them in backwards. I never got it running because my > electronics knowledge was lacking, I had only a simple voltmeter and no > idea on how to troubleshoot it. Later I went to engineering school and by > the time I graduated I moved on to other projects. The TAT IV used the same > idea of mixing DC with pulses. The theory was that the pulses would provide > smoother starting and the transition to pure DC would be quieter once the > train was moving. > > On Sun, Apr 10, 2022, 11:53 AM John Dammeyer <jo...@autoartisans.com> > wrote: > > > In keeping with the off topic theme and since you mentioned CD > ignition... > > http://www.autoartisans.com/images/igf200.jpg > > This one is CD ignition (with that 350V step up) for one coil per > cylinder > > and multi-point sequential fuel injection for Honda VTEC 1500CC engines > > used in homebuilt aircraft and hovercraft. > > > > But I had fun last night after reconditioning all the filter caps since > > they hadn't been powered since about 1991. > > http://www.autoartisans.com/S100/Hydra-80186-Inside.jpg > > and then put the power supply back together, verified power was good > > before I plugged in the motherboard and SASI/Floppy disk controller. > > http://www.autoartisans.com/S100/Hydra-80186-DriveB.jpg > > > > Might just have to write a utility that reads and rewrites each sector on > > the hard drive. > > > > Don't think something like LCNC would run on something like this. > > John > > > > > -----Original Message----- > > > From: dave engvall [mailto:dengv...@charter.net] > > > Sent: April-10-22 9:23 AM > > > To: emc-users@lists.sourceforge.net > > > Subject: Re: [Emc-users] Controlling DC motors. > > > > > > Clearly OT! > > > Indeed electronics have�� come a long ways since then. > > > I still have my Dad's 200 w-sec strobe. Oil filled caps from Edmund > > > Salvage dumped to the flash tube with a thrytron. Later vintage an > > > electronic ignition, nice toroid 6 v to 400 v converter and a decent > SCR > > > for my�� PV544 (pregnant roller skate). Got me a gain of about 1.5 > > > mi/gal averaged over a year. .... and a constant current supply ... > that > > > drove a 1:2 step up transformer to light 5 to 32 orchard heaters ( eg. > 1 > > > row ) a single person could light up a whole orchard in a few minutes, > > > either propane or fuel oil. I think that project only lasted a few > > > years. pulsed 220 drifting avout an orchard was just too dangerous. > > > Finally came the switch to sprinklers and orchard fans. .... > > > and then grey smog� in the morning went away. No the old days were not > > > necessarily the good old days. > > > > > > Dave > > > > > > On 4/10/22 8:31 AM, Mark Johnsen wrote: > > > > That brings back memories. The fun of being at Grandma and Grandpa's > > was > > > > the Popular Mechanics and Popular Science magazines I could page thru > > when > > > > visiting. > > > > > > > > I remember all the pages in the back of the magazine where people > were > > > > trying to sell things, I always wanted a VW Bug replica car > conversion > > to a > > > > porsche or some old cool MB. Those pages are like today's internet > > > > advertisements, only the pages didn't do much tracking of your > > 'reading' > > > > history. > > > > > > > > Mark > > > > > > > > On Sun, Apr 10, 2022 at 4:55 AM Mark <wendt.m...@gmail.com> wrote: > > > > > > > >> Beat me to it. I was just about to say the exact same thing. > > > >> > > > >> What comes around goes around. > > > >> > > > >> Mark > > > >> > > > >> On 4/10/22 05:28, Gregg Eshelman via Emc-users wrote: > > > >>> In other words the person who designed that created a pulse width > > > >> modulation motor controller without calling it that. > > > >>> > > > >>> On Saturday, April 9, 2022, 08:18:17 PM MDT, John Dammeyer < > > > >> jo...@autoartisans.com> wrote: > > > >>> > > > >>> Really nothing to do with LCNC or even automation. > > > >>> > > > >>> I've been cleaning out old shelves and I have piles of Popular > > > >> Electronics Magazines. This one from December 1965 (yes, almost 57 > > years > > > >> old) has an article on how to improve model trains so they start > > slowly or > > > >> crawl rather than lurching forward requiring backing off the speed > > control. > > > >>> They call it pulse power. Using only transistors and diodes the > > article > > > >> describes a method of creating narrow pulses superimposed on a > > varying DC > > > >> voltage. One knob controls the width of the 12V pulses and the > other > > the > > > >> amplitude of the DC mixed with the pulses. The pulses are 60Hz. > > > >>> Now we just buy stuff like that for way less than what the > > transistors > > > >> would cost. Things have come a long way. > > > >>> Just thought I'd share. > > > >>> John > > > >> > > > >> _______________________________________________ > > > >> Emc-users mailing list > > > >> Emc-users@lists.sourceforge.net > > > >> https://lists.sourceforge.net/lists/listinfo/emc-users > > > >> > > > > _______________________________________________ > > > > Emc-users mailing list > > > > Emc-users@lists.sourceforge.net > > > > https://lists.sourceforge.net/lists/listinfo/emc-users > > > > > > > > > > > > _______________________________________________ > > > Emc-users mailing list > > > Emc-users@lists.sourceforge.net > > > https://lists.sourceforge.net/lists/listinfo/emc-users > > > > > > > > _______________________________________________ > > Emc-users mailing list > > Emc-users@lists.sourceforge.net > > https://lists.sourceforge.net/lists/listinfo/emc-users > > > > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > -- Chris Albertson Redondo Beach, California _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
