#emc | Logs for 2009-08-12

[01:29:50] <tom1> tom1 is now known as tom3p
[06:26:22] <micges_work> good morning
[07:58:29] <micges_work1> micges_work1 is now known as micges_work
[09:20:49] <piasdom> g'mornin all
[09:23:30] <micges_work> morning
[16:04:58] <tom1> tom1 is now known as tom3p
[16:28:50] <tom3p> BJT-Work: I read you had success in removing the 'comp for your THC. congrats! any docs? (just checked the support forum and didnt see updates)
[16:29:52] <BJT-Work> tom3p: not sure what your asking
[16:31:25] <tom3p> hi, can you remove the comp without jerk?
[16:31:25] <tom3p> iirc you had a sudden motion when the comp was removed, and stuff on the cha tline said you had resolved that
[16:32:39] <tom3p> maybe.. 'comp' is not your term, your notes use 'correction'
[16:32:40] <BJT-Work> oh you mean and + or - compensation
[16:32:48] <BJT-Work> yes correction
[16:32:55] <BJT-Work> that part works fine now
[16:33:07] <BJT-Work> in fact I have 98% of working now
[16:33:33] <tom3p> for the thc head, a value added to the axis.2.motor-pos-cmd
[16:33:54] <BJT-Work> I've changed it a bit to take either +/- inputs or the freq from the Mesa THC
[16:34:01] <BJT-Work> yes
[16:34:13] <tom3p> cool, plz let us know how
[16:34:33] <tom3p> thx
[16:34:39] <BJT-Work> I need to complete it and commit it
[16:34:54] <BJT-Work> I could have used it this morning cutting out some parts for work
[16:38:13] <BJT-Work> * BJT-Work goes back to PLC programming :)
[17:58:48] <jepler> wow, there are LDO linear regulators with dropout voltages like .04V @ 150mA
[18:39:05] <jymm> LDO?
[18:39:20] <archivist> low drop out
[18:39:56] <jymm> Like if the supply voltage goes below a certain point?
[18:40:16] <archivist> yes
[18:40:27] <jymm> touchy
[18:40:39] <archivist> .04 is seriously low
[18:40:56] <jymm> less that the voltage drop across a diode
[18:41:04] <jymm> (.07)
[18:41:09] <archivist> yup
[18:41:21] <jymm> kinda creepy
[18:41:23] <archivist> .7 for a silicon diode
[18:41:37] <archivist> .2 for germanium
[18:41:55] <jymm> err .7 I meant, always mucj that up
[18:41:59] <jymm> muck
[18:44:44] <archivist> odd diode type out is schottky diode
[18:44:52] <EbiDK> EbiDK is now known as EbiDK|AWAY
[18:48:51] <jymm> It's nice being able to stream radio on the lan
[18:49:47] <jymm> well, cable radio stations that is
[18:50:09] <jymm> I dont think braodcast radio are transmitting in digital
[19:13:09] <geo01005> mikegg, did you figure out your servo issue?
[19:55:36] <mikegg> yes and no
[19:55:48] <mikegg> fixed the PDM/PWM stuff
[19:56:17] <mikegg> took out some hackery that I did to enable/disable the amps
[19:56:42] <mikegg> the audible noise is just about totally gone
[19:56:49] <mikegg> you can still see it in the scope though
[19:57:36] <mikegg> I think it might be a ground loop issue. i dunno
[19:58:09] <mikegg> we hired an EE. starts next week. I'm hoping he can help
[20:24:54] <PCW> mikegg: Is the noise synchronized to rotor position? (a really slow move may allow you to observe this)
[20:24:56] <PCW> In brushless motors this may be related to commutation. If so you may be able to improve it
[20:24:58] <PCW> by tuning the current loop in the drives
[20:31:16] <PCW> Also free running the motors with battery connected to the velocity input could determine
[20:31:18] <PCW> if the noise is commutation/cogging noise or some kind of ground loop noise.
[20:31:20] <PCW> (you may need to divide the battery voltage down with a pair of resistors to get a reasonable speed)
[21:57:04] <tom3p> PCW: good idea , i always use a battery box to test drive systems with Vcmd. didnt think to use it to debug noise issues tho.
[22:13:57] <tom3p> btw 2 nine volt batteries and a pot make a nice +/-9V servo tester
[22:18:12] <robh_> here we go guys, what to do with all that old PC stuff laying around http://www.youtube.com/watch?v=Ht96HJ01SE4&feature=channel_page
[22:20:21] <archivist> grmbl....I need a sound card
[22:42:40] <fenn> the daisy demo with EMC puts that to shame
[22:45:18] <archivist> I think that only has 4 voices it needs another :)
[22:58:34] <PCW> tom3p: yah, batteries are pretty much noise/groundloop free