On Tuesday, November 08, 2011 11:57:11 AM Dave did opine: > On 11/8/2011 6:56 AM, andy pugh wrote: > > On 8 November 2011 11:16, James Louis<[email protected]> wrote: > >> Good morning all, > >> There is an ad running in Digital Machinist magazine for an RC speed > >> control of a brushless motor with ESC. If interested go to > >> www.logicnc.com It gives EMC2 a way to control spindle speed from > >> the parallel port. I haven't used one yet though. > > > > It isn't strictly necessary. As the RC pulse protocol is a 1 - 2mS > > pulse every 20mS the standard EMC2 PWM function can be used, but gives > > fairly poor resolution. (20 discrete steps with a 25,000nS base > > thread). > > 1-2 ms in 20ms ... I've read that before. So the min pulse width is > 1 ms and the max is 2ms.. in a 20ms time slot? > > Seems like a waste to only use up to 2ms of the 20 ms time slot... >From my experience, they work essentially as a sample hold, integrating the charge during the pulse, then hold & drive the motor which ever direction balances the bridge during the hold/rest period. I believe the 20ms is the alloted time to reset the integrator so it restarts at a consistent state. We had one mcu based controller that used the 1-2 millisecond signal, but had about a 500ms cycle rate, worked just fine. OTOH, putting a 1 khz square wave in didn't seem to get usable operation for testing on the bench, it just stayed where it was at for the most part, so the cycle time can be too short.
Quick enough (just barely) for model airplane RC usage, but IMO not nearly fast enough for accurate machining at industrial speeds if scaled up 1000x and used to drive the tables. > Dave > > ------------------------------------------------------------------------ > ------ RSA(R) Conference 2012 > Save $700 by Nov 18 > Register now > http://p.sf.net/sfu/rsa-sfdev2dev1 > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users 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) My web page: <http://coyoteden.dyndns-free.com:85/gene> I guess I've been wrong all my life, but so have billions of other people... Certainty is just an emotion. -- Hal Clement ------------------------------------------------------------------------------ RSA(R) Conference 2012 Save $700 by Nov 18 Register now http://p.sf.net/sfu/rsa-sfdev2dev1 _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
