#emc | Logs for 2005-12-15

[00:26:39] <robin_sz> meep?
[00:51:34] <operose> meep
[00:53:26] <rayh> Hey
[01:03:20] <CIA-9> 03rayhenry * 10emc2/tcl/tkemc.tcl: disabled calibration and testing menu items until scripts are gone or fixed.
[02:04:25] <Jacky^> g night
[02:04:36] <Jacky^> Jacky^ is now known as Jacky^afk
[02:13:15] <CIA-9> 03cradek * 10emc2/src/hal/drivers/hal_ppmc.c: extend the counter to 32 bits, the emc1 way
[02:31:23] <tfmacz> new here whats up?
[02:32:16] <K`zan> same
[02:33:20] <djb_rh> anyone here need a good deal on a VFD?
[02:33:34] <djb_rh> to use as a phase converter?
[03:29:46] <cradek> IT'S ALIVE
[03:30:37] <fenn> what's up cradek?
[03:30:43] <cradek> my mill moves again
[03:30:53] <fenn> congrats
[03:30:58] <cradek> I found a really great surplus power supply
[03:31:17] <djb_rh> I scored the deal of the century today
[03:31:26] <fenn> a pallet of vfd's?
[03:31:27] <djb_rh> new in the box, with manuals, VFDs
[03:31:29] <djb_rh> yeah
[03:31:33] <djb_rh> basically
[03:31:55] <cradek> wow, holy crap
[03:32:02] <djb_rh> one 10HP
[03:32:06] <djb_rh> couple 7.5's
[03:32:11] <djb_rh> several 5's
[03:32:14] <djb_rh> several 2's
[03:32:23] <djb_rh> all three phase input, so derate accordingly for single phase
[03:32:40] <djb_rh> they're "Benshaw", which I had never heard of, but has a web site with good info
[03:32:50] <djb_rh> the 10HP has card slots for PLC interfaces and such
[03:33:36] <djb_rh> the 7.5's and up were $25 each
[03:33:41] <djb_rh> the rest were $15 each
[03:33:47] <djb_rh> no, the 2HP's were $10 each
[03:33:59] <djb_rh> anyone need any?
[03:34:10] <fenn> you probably shouldn't have told us how much you got them for
[03:34:13] <djb_rh> I'll pass along my deal to folks who will *use* them
[03:34:21] <djb_rh> folks working on EMC, anyway
[03:34:35] <cradek> that's a terrific gesture
[03:34:42] <djb_rh> I'd rather you didn't just resell them, but if anyone needs one...
[03:35:00] <cradek> some of us are working on small (or nonexistent) budgets
[03:35:08] <djb_rh> yeah, many open source hackers are
[03:35:19] <djb_rh> believe me, I've met quite a few
[03:35:20] <djb_rh> :)
[03:35:32] <jepler> I'm just waiting for someone to send me a complete minimill
[03:35:38] <jepler> I'm sure it'll happen any day now
[03:35:47] <fenn> that might be more of a curse than a blessing
[03:35:54] <djb_rh> jepler: what are you going to do with it?
[03:35:59] <djb_rh> CNC it up?
[03:36:09] <jepler> djb_rh: with a cnc minimill I'd probably mill circuit boards mostly
[03:36:14] <djb_rh> ah
[03:36:20] <djb_rh> I got one recently
[03:36:31] <djb_rh> and have the CNC kit from Stirling Steele on order for it
[03:36:36] <jepler> I dunno, though, I might get back to this dxf-to-ngcode converter cradek started two years ago
[03:36:40] <djb_rh> and will likely use it for that purpose
[03:37:10] <djb_rh> that would be nice to have
[03:37:17] <djb_rh> (the dxf converter, I mean)
[03:38:28] <fenn> how do you know which side of the part is the inside with dxf format?
[03:38:38] <fenn> s/part/surface/
[03:38:48] <cradek> dxf polygons or dxf lines?
[03:38:53] <fenn> polygons
[03:39:09] <cradek> there's an implied surface normal from the direction of the triangles/quads
[03:39:30] <cradek> cross product of the vectors from point 1,2 to point 1,3
[03:39:50] <jepler> the dxf file should represent a closed surface, dividing space into two regions. The "inside" is the region that's finite.
[03:40:21] <cradek> ha, that's true too I guess, but maybe not so easy to figure
[03:43:49] <cradek> fenn: with the scheme I described, the surface normals point "out"
[03:44:55] <fenn> cradek: so it depends on the order in which the vertices are listed?
[03:45:12] <cradek> yes
[03:46:10] <fenn> btw know of any .stl viewers for linux?
[03:46:22] <cradek> nope
[03:47:06] <cradek> looks like I wrote a stl-to-dxf convertor, and toolpath (and maybe lots of other things) display dxf
[03:47:21] <cradek> http://timeguy.com/cradek/stl-to-dxf
[03:49:12] <fenn> seems like a dxf to stl converter might be more useful
[03:49:14] <fenn> shrug
[03:49:36] <jepler> what produces or consumes stl?
[03:49:39] <cradek> that's just as easy to write
[03:49:57] <fenn> i mean, somewhere you are going to have to figure out the surface normal direction
[03:50:10] <cradek> I told you how ... it's trivial
[04:00:35] <Jymmm> what app is .STL ?
[04:01:28] <SWPadnos_> stereolithography files
[04:01:37] <SWPadnos_> just about any 3D CAD app
[04:02:03] <Jymmm> .DOC is M$ Word, .STL is ___________________
[04:03:31] <SWPadnos_> .STL is the industry-standard format for stereolithography files
[04:03:34] <SWPadnos_> it's like DXF
[04:03:41] <fenn> but there's actually a spec
[04:03:41] <SWPadnos_> (only actually pretty standard)
[04:03:50] <fenn> dxf is just "whatever loads into autocad"
[04:03:59] <SWPadnos_> yeax
[04:03:59] <SWPadnos_> yeah
[04:04:00] <Jymmm> DXF is AutoCad
[04:04:14] <SWPadnos_> DXF is "Data eXchange Format", not AutoCad
[04:04:25] <SWPadnos_> though they may have been the originators of the format
[04:04:30] <fenn> Jymmm: it's like .html, but for 3d graphics
[04:04:38] <SWPadnos_> 3d solids, actually
[04:04:43] <fenn> yeah
[04:04:48] <fenn> no texture information or anything
[04:05:35] <SWPadnos_> it's basically a surface with a mesh of triangles representing some CAD model to some accuracy
[04:55:08] <fenn> would it be hard to hack AXIS to work in standalone mode? as a general purpose g-code viewer/verifier
[05:36:12] <SWPadnos_> fenn: probably, since AXIS doesn't actually interpret the G-code, it leaves that to emc
[05:36:45] <SWPadnos_> though it's probably possible to make a standalone G-code and canonical command interpreter
[05:36:48] <SWPadnos_> see ya
[05:36:51] <SWPadnos_> SWPadnos_ is now known as SWP_Away
[05:36:54] <fenn> heh
[05:37:09] <SWP_Away> (tricky - wasn't that? :) )
[05:37:16] <fenn> no time for rebuttal
[05:37:22] <SWP_Away> exactly!
[05:37:24] <SWP_Away> bye
[05:38:24] <SWP_Away> of course, cradek and jepler are the ones to ask, but AFAIK, AXIS basically sends teh program to emc, and pipes the output of the interpreter into axis instead of the TP (or something similar to that)
[05:39:11] <CIA-9> 03paul_c * 10emc2-auto/wiki/ (12 files in 9 dirs): "Auto update wiki from a cron job. Thu Dec 15 05:30:01 GMT 2005 "
[05:39:12] <CIA-9> 03petev * 10emc2/configs/m5i20/ (m5i20.ini m5i20.var m5i20.tbl): Initial revision.
[05:40:35] <CIA-9> 03petev * 10emc2/configs/m5i20/ (m5i20_io.hal m5i20_motion.hal): Updated to latest pin names, etc..
[05:41:58] <CIA-9> 03petev * 10emc2/configs/motenc/ (motenc.var motenc.ini motenc.tbl): Initial revision.
[05:43:31] <CIA-9> 03petev * 10emc2/configs/motenc/ (motenc_io.hal motenc_motion.hal): Updated to latest pin names, etc..
[06:22:08] <LawrenceG> hi Ted
[06:22:17] <tfmacz> Hi lawrence
[12:22:03] <Jacky^afk> hi rayh
[12:22:09] <Jacky^afk> Jacky^afk is now known as Jacky^
[12:22:21] <rayh> hello Jacky^
[12:26:07] <operose> hi
[12:26:28] <Jacky^> morning operose :)
[12:26:37] <operose> how's it going today?
[12:27:09] <Jacky^> im reading the news.. :)
[12:27:13] <operose> cool
[12:27:17] <operose> I'm a bit late for work
[12:27:18] <operose> just got here
[12:27:40] <Jacky^> good ;)
[12:28:15] <operose> oh, you know tonight the moon will be at it's highest point for the next 18 years
[12:28:38] <Jacky^> ah, nice
[12:28:42] <operose> have to share that with everyone
[12:29:19] <Jacky^> can you observe it ?
[12:29:26] <Jacky^> how ?
[12:29:26] <operose> after this week, once I'm back to regular working hours (rather than 60 a week)
[12:29:30] <operose> dunno
[12:29:38] <operose> but I'm gonna put together an emc box
[12:29:45] <operose> and get some motors
[12:29:45] <Jacky^> hehe
[12:29:54] <Jacky^> :P
[12:30:06] <operose> don't have any tools to control yet
[12:30:11] <operose> but I wanna play around
[12:30:12] <operose> hehe
[12:30:34] <fenn> you can watch the motors spin on the table.. it's more fun than you would expect
[12:31:04] <operose> yeah
[12:31:06] <operose> that's the plan
[12:31:08] <operose> :D
[12:31:16] <Jacky^> id like to stress it in avery way :P
[12:31:33] <Jacky^> too see how it work
[12:31:56] <Jacky^> there's some cool gcode file test in emc
[12:32:12] <fenn> the penguin?
[12:32:32] <Jacky^> if I remember well 3D test
[12:33:06] <Jacky^> may written by rayh , cant remeber now..
[12:34:31] <operose> cool
[12:35:00] <Jacky^> operose already tried the backplot feature ?
[12:35:08] <Jacky^> its another nice thing :)
[12:36:11] <operose> I haven't had a chance to play with it really at all
[12:36:16] <operose> been reading documentation
[12:36:21] <operose> while at work
[12:36:38] <operose> but lately it's been wake up, go to work, come home, go to sleep, wake up, go to work.. etc
[12:36:52] <Jacky^> :-)
[12:38:40] <operose> is there any chance this would work with freebsd or netbsd?
[12:38:46] <operose> maybe with linux emulation or something
[12:39:49] <Jacky^> I think all is possible ..
[12:39:59] <operose> hehe
[12:40:03] <operose> has it been attempted?
[12:40:26] <Jacky^> but how many time and work could it required ?
[12:40:43] <Jacky^> note sure about the advantages youll take
[12:41:12] <Jacky^> im interesting in embedded linux system
[12:41:17] <operose> advantages for me would be that I already have a bunch of netbsd/freebsd machines I wouldn't have to reinstall on
[12:41:23] <Jacky^> ive a small handheld pc ..
[12:41:35] <operose> yeah I'm rather interested in playing with embedded netbsd
[12:42:00] <Jacky^> realtime ?
[12:42:59] <Jacky^> I found my handheld required a lot of hacking to work with emc
[12:43:26] <Jacky^> patch on kernel, cross compiling, drivers ..
[12:43:49] <Jacky^> hw adapters and more
[12:43:59] <Jacky^> i done the idea for now
[12:45:15] <rayh> I confess I wrote 3D test
[12:45:27] <Jacky^> hehe
[12:45:40] <rayh> I needed something to see if I had the axes reversed in the display.
[12:46:24] <Jacky^> cool code ;-)
[12:47:51] <rayh> operose: You anywhere near antwerpen?
[12:48:01] <operose> antwerp, I am close to
[12:48:03] <operose> in NY
[12:48:14] <operose> not sure what antwerpen is
[12:48:58] <rayh> I saw the .be on your addy
[12:49:02] <operose> ah
[12:49:12] <operose> there was a company giving away .be domains a while ago
[12:49:16] <operose> dunno if they still are
[12:49:23] <rayh> oh I see.
[12:50:34] <operose> grabbing tarball now
[12:50:38] <rayh> Long ago there was an attempt to run emc with freebsd
[12:51:10] <operose> who are the mages that tackled such a beast and where must I adventure to to find them?
[12:51:33] <rayh> the emc2 stuff sifted out anything but linux.
[12:51:48] <operose> ah
[12:54:07] <rayh> First task would be to find adeos and rtai for bsd.
[12:56:17] <operose> if it's too much work, honestly, I'll use linux
[12:56:19] <operose> :P
[12:56:37] <operose> interested in getting it working sooner, rather than later
[12:56:48] <operose> it takes me so long to finish a project, the last thing I need to do is port emc to freebsd
[13:02:45] <rayh> yep.
[13:15:19] <cradek> operose: I briefly looked into realtime freebsd but it looks like there isn't one and there's very little interest.
[13:15:44] <rayh> morning chris
[13:16:22] <cradek> hello
[13:16:28] <cradek> did you ever get your ppmc working again?
[14:15:01] <les_w> morning
[14:15:24] <les_w> it's a wonder I still have power here...ice storm in progress
[14:15:26] <jepler> hi les
[14:15:39] <les_w> hi jeff
[14:15:53] <les_w> morning ray
[14:16:07] <cradek> hi all
[14:16:10] <rayh> Hi l;es
[14:16:14] <rayh> oops
[14:16:23] <les_w> haha
[14:16:38] <cradek> good morning johnboy
[14:16:44] <Jacky^> morning folks
[14:16:59] <jepler> morning Jacky^
[14:22:05] <fenn> hey les: math question
[14:22:48] <fenn> if you represent a set of boundaries as a space, does it make sense for a rectangular space to have rotational boundaries?
[14:23:59] <fenn> for instance i have a 6d vector describing the position and orientation of an object, and i dont want it to go further than <x> units in such and such axis
[14:24:07] <Jacky^> news fro EU: http://www.europarl.eu.int/news/expert/infopress_page/019-3536-348-12-50-902-20051206IPR03225-14-12-2005-2005--false/default_en.htm
[14:24:44] <fenn> oh wonderful
[14:25:03] <fenn> only for “specified forms” of serious criminal offences
[14:25:31] <fenn> i bet that will last precisely 0.2 seconds
[14:25:36] <Jacky^> we can send away logger_aj
[14:25:38] <Jacky^> hehe
[14:26:52] <fenn> haha they dont even pay for it either
[14:27:00] <Jacky^> :)
[14:29:52] <les_w> sorry fenn was away
[14:30:03] <les_w> may vanish any second...ice storm
[14:30:59] <les_w> fenn, sounds like possibly a job for quaternions
[14:31:36] <les_w> They are unique in that they require only 4 numbers, and they don't suffer from gimbal lock.
[14:33:16] <rayh> rayh is now known as rayh_away
[14:34:33] <fenn> crappity crap.. ij=k, but ji=-k
[14:35:02] <les_w> haha yeah non commutative
[14:35:33] <fenn> you can create a space from quaternions?
[14:36:17] <les_w> transforn them...I'm no expert though. I generally use vectors, but they DO gimbal lock
[14:36:27] <les_w> lots of stuff on the web
[14:36:50] <les_w> you read it and tell me and then we'll both know
[14:37:08] <fenn> i dunno.. complex matrices.. not my cup of tea
[14:37:31] <les_w> I did em in school a lot...
[14:37:37] <les_w> ahem 25 years ago
[14:37:56] <fenn> how does a vector's gimbal lock manifest itself?
[14:38:05] <fenn> not enough resolution?
[14:38:29] <fenn> division by zero?
[14:38:39] <les_w> well, certain orientations lose a degree of fredom
[14:38:48] <les_w> let me give an example...
[14:39:05] <les_w> latitude and longitude
[14:39:24] <les_w> say you were traveling near the north pole
[14:39:35] <les_w> and want to know lat long
[14:40:15] <les_w> as you get close to the pole any small movement makes big changes in longitude
[14:40:29] <les_w> more and more sensitive the closer you get
[14:40:52] <les_w> right at the pole longitude basically has no meaning
[14:40:58] <les_w> makes math blow up
[14:41:11] <les_w> that is classic gimbal lock
[14:41:34] <rayh_away> Till was talking about applying quaternions to the emc a couple years back.
[14:42:04] <les_w> they are used a lot in 3d graphics I guess
[14:42:14] <les_w> computationally efficient
[14:42:27] <fenn> really.. i thought people used transformation matrices
[14:42:43] <les_w> but that lack of gimbal lock is the main reason for using them instead od matrices
[14:43:57] <jepler> OpenGL certainly uses transformation matrices everywhere, no quaternions in sight
[14:44:07] <les_w> People usually think of the movie apollo 13 when gimbal lock is mentioned , huh
[14:45:07] <les_w> Apollo used a 3 gimbal gyro to save weight
[14:45:20] <les_w> so certain poses were not allowed
[14:45:26] <fenn> they are both the same type of singularity.. it makes sense to call it the same name
[14:45:41] <les_w> if they wanted to pitch they had to roll first
[14:46:53] <les_w> I'd have to read up on it some though....I know openGL does not use them
[14:47:13] <fenn> jepler: you can represent a quaternion with a complex matrix
[14:47:41] <fenn> or a 4x4 matrix
[14:52:35] <fenn> another dumb question: inertia is described by the mass term in f=ma right?
[14:53:11] <fenn> but rotational inertia is described by J in t=ja
[14:54:00] <fenn> so how do you convert rotational inertia (N*m^2) to kg?
[14:54:06] <les_w> j is polar moment of inertia
[14:54:27] <les_w> torque= j* angular acceleraTION
[14:54:29] <les_w> OOPS
[14:54:46] <les_w> shift key sticks.
[14:56:33] <fenn> still there les?
[14:56:54] <les_w> We (machine designers) usually use mechanical impedance for such things
[14:57:21] <les_w> It's a complex number...in MKS units are newton *sec/meter
[14:57:30] <fenn> right.. i'm trying to subtract the "apparent mass" caused by the inertia of the motor
[14:57:38] <fenn> er, add not subtract
[14:57:39] <les_w> laplace transform of force/velocity
[14:57:41] <Jacky^> * Jacky^ confused :/
[14:58:36] <les_w> motioneering does that automatically saves a lot of calcs...
[14:58:39] <Jacky^> :D
[14:59:37] <les_w> for example in my machine x axis motor rotor inertia has the same apparent mass as the 500 kg gantry!
[14:59:46] <fenn> i believe it
[14:59:51] <Jacky^> les_w: thats very cool app
[14:59:59] <les_w> yes very handy
[15:00:02] <fenn> but how do i get that number if i'm calculating by hand?
[15:00:14] <Jacky^> id like to see in the next future some similar app open source :P
[15:00:19] <les_w> oh gosh let's see
[15:00:31] <les_w> you need reduction ratios and stuff
[15:00:33] <Jacky^> would be very nice
[15:00:42] <fenn> so let's say a 5mm pitch ballscrew
[15:00:56] <les_w> ok
[15:00:56] <fenn> and a 1:4 gear ratio
[15:01:17] <les_w> coffee...coffee
[15:01:55] <les_w> ok. first establish the relationship between angular position and linear position
[15:02:36] <operose> yeah coffee
[15:02:41] <operose> I jsut drank a cup really really fast
[15:03:56] <les_w> so x=( angle/2*PI) *5mm/4
[15:04:11] <fenn> x = .25*rev*5mm damn
[15:04:26] <les_w> yeah
[15:04:31] <fenn> i was trying to balance units.. but angle has no units
[15:04:41] <les_w> radians fenn
[15:04:45] <operose> you guys are crazy smart
[15:04:55] <les_w> haha
[15:04:55] <fenn> well, radians is dimensionless is the better way to say it
[15:05:15] <les_w> nah...but spent a few years in engineering school
[15:05:41] <fenn> no thanks to the american education system here
[15:05:42] <jontow> this channel is an engineering school in itself ;)
[15:05:47] <operose> no doubt
[15:06:00] <les_w> anyway you can start taking derivatives...
[15:06:17] <operose> I've got my mind completely made up to go get a 2 year mech. engineering degree
[15:06:25] <fenn> to get velocity?
[15:06:27] <operose> s/completely/almost completely
[15:06:35] <les_w> 2 year?
[15:06:40] <operose> ya
[15:06:55] <operose> to start
[15:07:08] <Jacky^> to start learn ? O_O
[15:07:13] <operose> no
[15:07:16] <Jacky^> :D
[15:07:16] <operose> to get a degree
[15:07:20] <operose> don't need college to learn
[15:07:21] <operose> just for the paper
[15:07:36] <Jacky^> kidding.. :P
[15:07:57] <les_w> I liked school.
[15:07:59] <les_w> a lot.
[15:08:20] <jontow> i think mechanical engineering would be much more fun than computer science, thats for sure
[15:08:23] <Jacky^> les_w: right, all depend on teachers
[15:08:28] <jontow> i've always considered the idea
[15:08:32] <fenn> dx/dt = .25*5mm*(da/dt)
[15:09:18] <operose> time for "brunch" as my boss puts it
[15:09:18] <fenn> hmm been a decade or so since calculus
[15:09:43] <les_w> let me get pencil and paper
[15:10:58] <Jacky^> les_w: the wierd thing, I was reading today in the it news, only 25% of students who finished theyr school dream to do the work for what they have studied
[15:11:16] <Jacky^> http://www.repubblica.it/2005/j/sezioni/scuola_e_universita/servizi/giovanilavoro/almalaurea/almalaurea.html
[15:11:21] <fenn> yeah because school beats the life out of you
[15:11:23] <Jacky^> sorry .. is Ialian
[15:11:45] <Jacky^> italian*
[15:12:23] <Jacky^> so, the school sometime fail :(
[15:12:37] <Jacky^> in 50 % of cases
[15:12:40] <Jacky^> or more..
[15:14:20] <Jacky^> ah, les_w
[15:14:29] <Jacky^> another strange thing
[15:14:33] <fenn> ok how about this: dx/dt = .25*5mm*(da^0/dt) == 1.25mm/dt
[15:14:43] <les_w> ok, now you have a relationship between angular accel and linear accel after 2 derivatives
[15:14:49] <Jacky^> in some UK school are experimenting to pay students to learn
[15:15:12] <Jacky^> they say are getting good results
[15:15:14] <Jacky^> :)
[15:16:06] <fenn> dx/dt^2 = 1.25mm^0/dt^2 == 1/dt^2 ??
[15:16:07] <les_w> you can plug into f=M*d^2x/dt^2 ant T=J*d^theta/dt^2
[15:16:10] <les_w> phone
[15:16:46] <Jacky^> fenn: ugh ! whats that ? -> les_w> you can plug into f=M*d^2x/dt^2 ant
[15:16:46] <Jacky^> T=J*d^theta/dt^2
[15:17:10] <fenn> Jacky^: that's the shortcut they tell you after you do the hard work
[15:18:09] <Jacky^> hehe
[15:18:14] <Jacky^> :/
[15:19:22] <fenn> * fenn looks scornfully at his units program.
[15:21:48] <Jacky^> Im really thinking at open source ver. of mootionengineer ..
[15:21:53] <Jacky^> or similar app
[15:22:19] <Jacky^> the formules should be free
[15:22:33] <Jacky^> the problem could be motors data
[15:23:02] <Jacky^> database
[15:23:29] <fenn> Jacky^: it should be easy enough then without the database.. get writin' code!
[15:24:40] <Jacky^> really, les_w could help in calculations functions
[15:24:58] <Jacky^> it could be a nice app for emc
[15:25:16] <fenn> well, with the units command there's not a whole lot left to do but this particular bit of calculus
[15:26:06] <fenn> unless you're doing a robot arm or something
[15:28:11] <Jacky^> robot arm move in 3 dimensional space, it should not hard to implement routines for that
[15:28:18] <Jacky^> just a lot of math
[15:28:45] <Jacky^> a guy some day ago pasted an interesting url about 3d space..
[15:28:50] <Jacky^> searching ..
[15:29:10] <fenn> yeah, right, tell me when you're done writing a robot arm trajectory planner
[15:29:50] <Jacky^> :)
[15:30:09] <Jacky^> can you wait 3-4k years ?
[15:30:11] <Jacky^> :D
[15:30:13] <Jacky^> hehe
[15:33:11] <operose> oh I'll get right on that
[15:33:14] <operose> ok done
[15:33:28] <Jacky^> ah, operose was you , right
[15:33:53] <operose> I need to get readin' the wiki
[15:33:53] <fenn> thanks operose, i knew it was easy after all
[15:33:58] <operose> yeah it was really easy
[15:34:01] <operose> only like 5 lines
[15:34:02] <operose> :O
[15:34:58] <operose> what's the best supported controller right now with EMC?
[15:35:05] <operose> I think it's called a controller
[15:35:11] <operose> yeah
[15:35:30] <operose> servotogo xylotex or pico systems it looks like by the wiki?
[15:35:49] <fenn> eh, depends how much money you want to spend
[15:36:04] <operose> what if I don't want to spend a lot? :D
[15:36:04] <les_w> power is bumping...had phone call about trees falling from ice
[15:36:17] <les_w> fenn let me get you a link with all the calcs
[15:36:27] <les_w> easier than deriving them here
[15:36:40] <les_w> also irc text is real bad for doing math
[15:36:43] <fenn> operose: get a hobbycnc board.. it's like $75 and has the amps built in
[15:36:55] <fenn> les_w: actually i find it to be easier to read than standard math notation
[15:37:05] <operose> cool the xylotex is pretty cheap
[15:37:10] <operose> nice
[15:37:12] <operose> hobbycnc you say
[15:37:22] <fenn> shrug
[15:37:45] <fenn> you can spend upwards of a zillion dollars on "the best" driver electronics
[15:37:47] <operose> yeah
[15:37:52] <operose> no point in me doing that though
[15:37:54] <operose> just playing for now
[15:38:02] <fenn> hobbycnc is probably the minimal, which is more than enough for your first system
[15:38:08] <operose> cool
[15:38:19] <fenn> you do have to solder it together though
[15:38:26] <operose> yeah that's fine
[15:38:42] <Jacky^> operose: what are you intersting in ? milling , drilling , wood, steel ?
[15:38:49] <fenn> oh and you still have to get a power supply
[15:39:05] <operose> well, honestly, I don't have any machine tools whatsoever right now
[15:39:21] <operose> but I'd probably put together a little mini-mill if I could get the CNC stuff working
[15:39:36] <operose> got some random projects in mind
[15:39:46] <les_w> http://www.techno-isel.com/Tic/H834/HTML/H834P009.html
[15:39:51] <les_w> some calcs here...
[15:40:00] <Jacky^> oh, I dont think you need to spend a lot of money then
[15:40:17] <operose> what are the tolerances this will work to?
[15:40:31] <operose> I'd like +/- 0.002" at least?
[15:40:40] <Jacky^> you can take a lot of advantages learning to hack a cheap machine before
[15:40:44] <operose> I guess that depends on the machine though
[15:41:43] <Jacky^> les_w: go on :)
[15:42:09] <les_w> most calcs we want are on that link I think
[15:42:29] <les_w> and the other pages of the site
[15:42:54] <Jacky^> * Jacky^ bookmarking
[15:47:40] <Jacky^> fenn: sorry for the break, go on
[15:49:22] <fenn> so i should end up with something like.. (kg*m^2)/((m/s)/(2rev/s))^2 = kg
[15:49:25] <Jacky^> les_w: great website
[15:56:16] <operose> would it be an alright idea to get a package from hobbycnc with controller and steppers for $235 or could I get the steppers cheaper somewhere else like ebay?
[15:57:35] <les_w> lintechmotion.com/pdffiles/MotorSizing-02-01-2002.pdf
[15:57:45] <les_w> calcs are there too fenn
[15:58:01] <operose> nevermind that question
[15:58:05] <operose> always looking for the easy answer
[15:58:07] <operose> I'll search around
[15:59:16] <fenn> just make sure your steppers are compatible with the driver
[15:59:32] <fenn> and that they still work
[15:59:52] <fenn> demagnetized motor looks fine on the outside but won't do anything (or do it poorly)
[15:59:58] <operose> :/
[16:03:06] <delacroix2> hi
[16:03:26] <operose> so in other words, maybe shy away from motors on ebay unless there is a good guarantee and good feedback etc.. like usual
[16:04:33] <fenn> well, if the person doesn't know what it is, they probably don't know where it came from either
[16:04:57] <operose> right
[16:08:00] <delacroix2> out of interest, has anyone here managed to build adeos patches into a recent kernel version?
[16:11:33] <cradek> delacroix2: I think most people are using the latest BDI version which uses kernel 2.6.12
[16:15:59] <les_w> did you get the equation for equvalent mass fenn?
[16:16:31] <fenn> eh, kinda
[16:16:40] <les_w> j=m*(lead/2*PI)^2
[16:17:02] <les_w> woops sloppy notation
[16:17:21] <fenn> m?
[16:17:24] <les_w> paren around 2* PI
[16:17:31] <les_w> m=mass
[16:17:52] <les_w> equivalent mass
[16:18:52] <les_w> you can solve for m as well
[16:18:56] <fenn> right
[16:19:18] <fenn> still not sure how the 2pi got in there
[16:19:28] <les_w> plug in j and lead and you will get the equivalent mass
[16:19:31] <jtr_away> delacroix2: if I read the wiki right, the kerner 2.6.12 is using magma, 2.6.10 used adeos.
[16:20:15] <delacroix2> magma is a verson of rtai, adeos is the kernel patch to make rtai work right
[16:20:15] <delacroix2> ?
[16:20:23] <delacroix2> am i getting confused here?
[16:20:25] <les_w> lead is movement per 2PI radians that's why
[16:20:26] <jtr_away> delacroix2: see http://wiki.linuxcnc.org/cgi-bin/emcinfo.pl/emcinfo.pl?BDI-4_Compile_EMC2
[16:20:44] <delacroix2> have read that
[16:20:50] <fenn> ah so j has a radians in it also
[16:21:13] <delacroix2> have followed it, and couldnt get the patches to apply right, im guessing i was using a wrong combo of kernel and patch version
[16:21:22] <cradek> delacroix2: I'm in the dark just as much as you
[16:21:34] <cradek> delacroix2: the rtai documentation is not good.
[16:22:02] <cradek> delacroix2: few here build their own RT kernel, and the ones that do tend to use older stuff (I use rtlinux on a 2.4 kernel)
[16:22:36] <fenn> delacroix: you were having problems with applying the patch or with building it after you patched it?
[16:23:12] <delacroix2> i can apply the patch, but i dont get a tickbox in make xconfig for adeos, also the kernel built doesnt have the adeos hooks
[16:23:25] <delacroix2> although the patch appears to apply fine
[16:23:26] <jtr_away> ah, ok, I'm learning here. Sent the ref so you could see where I got it from.
[16:25:22] <delacroix2> i have tried to get rtai working before, and the wiki is wrong in a couple of places, my real problem is that i cant find any release notes for adeos, anyone know if they have a webpage?
[16:27:26] <cradek> delacroix2: if you figure this mess out, please let us know (maybe add a page to the emc wiki)
[16:27:41] <delacroix2> cradek: will do
[16:27:52] <delacroix2> might try the rtai mailing lists
[16:30:33] <fenn> delacroix: try a make distclean? (wild guess)
[16:30:38] <les_w> fenn: oh have to put a square of reduction ratio in there too
[16:30:55] <les_w> or just dive lead by reduction ratio
[16:31:01] <les_w> divide
[16:32:01] <les_w> so equvalent mass is 16 times bigger than direct drive with your 4:1 reduction...
[16:32:11] <fenn> yow
[16:32:22] <les_w> (armature mass that is)
[16:32:47] <fenn> that ends up as 1600 kg apparent mass
[16:32:51] <les_w> yeah...gotta watch those grear reductions...square term...gets big fast
[16:33:50] <les_w> but fear not...
[16:33:53] <les_w> www.ecst.csuchico.edu/~repanich/Technical_Tools/ The%20Myth%20of%20Inertia%20Matching.pdf
[16:34:00] <les_w> for your reading pleasure
[16:34:14] <SWP_Away> SWP_Away is now known as SWPadnos_
[16:36:14] <fenn> i dont really know what inertia matching means.. i was just going to see how quickly it could accelerate a mass to top speed
[16:36:33] <fenn> i'll read it though, so i'll know
[16:36:38] <les_w> you don't have to precisely match motor and load inertia
[16:36:58] <les_w> but if motor/load is huge like in your example...
[16:37:10] <les_w> it swamps everything else
[16:37:54] <les_w> so the motor J is the limiting factor in how fast you can accel
[16:39:10] <les_w> steppers are not known for good torque to inertia ratios
[16:39:23] <les_w> otherwise known as angular acceleration
[16:39:58] <les_w> units= radians/sec^2
[16:40:53] <fenn> if you know the rotor inertia, you can figure out the torque curve pretty easily right?
[16:41:01] <fenn> with servos
[16:46:08] <les_w> it's independent
[16:46:36] <SWPadnos_> if you know the torque and inertia, you can figure out the accel curve ;)
[16:46:36] <les_w> but angular accels of 10-20,000 radins/sec^2 are common in servos
[16:46:58] <les_w> some are as high as 100,000
[16:47:11] <les_w> talk about winding up fast...
[16:47:45] <fenn> i dont want the accel curve, i want the torque curve! *wah*
[16:48:04] <les_w> servo?
[16:48:25] <fenn> more precisely i want the current to torque ratio
[16:48:34] <les_w> oh
[16:48:42] <les_w> ok just a motor spec
[16:48:47] <fenn> so that when i command a particular current i know how much torque is coming out
[16:48:49] <SWPadnos_> that should be given by the manufacturer
[16:49:05] <les_w> and torque curve is a constant with most
[16:49:09] <les_w> straight line
[16:49:14] <fenn> well, what if i dont have a spec?
[16:49:17] <SWPadnos_> hence the term "torque constant"
[16:49:39] <les_w> no spec? well you are SOL ;)
[16:49:45] <SWPadnos_> apparently, you can calculate the torque constant from the voltage constant
[16:50:06] <les_w> you can measure it with a weight or fish scale easily
[16:50:21] <SWPadnos_> but I'm skeptical, and I also don't have the conversion constant
[16:50:33] <fenn> les_w: duh why didn i think of that
[16:50:43] <SWPadnos_> too easy :)
[16:50:48] <les_w> yeah, torque from voltage constant needs some assumptions
[16:51:02] <les_w> string, weight, power supply
[16:51:04] <les_w> easy
[16:51:05] <SWPadnos_> yeah - like max voltage == voltage at max speed
[16:51:22] <SWPadnos_> which isn't true for my motors, for example
[16:51:32] <les_w> right
[16:51:41] <les_w> little matter of IR
[16:52:39] <les_w> fenn do you have a power supply?
[16:53:00] <les_w> capable of constant current?
[16:53:13] <fenn> hmmm no
[16:53:24] <les_w> if not you can simulate it with a voltage source and series resistor
[16:53:47] <les_w> resistor value at least 10 times winding resistance
[16:54:02] <les_w> (if you have dc motors)
[16:56:05] <fenn> this is great.. you can get force feedback with just an encoder and a current loop
[16:56:46] <SWPadnos_> that depends on the speed, no?
[16:57:18] <fenn> why? torque is constant with motor rpm (you said)
[16:57:32] <fenn> er, les said
[16:57:59] <SWPadnos_> you can get torque with just a current loop
[16:58:18] <fenn> yes but not feedback
[16:58:20] <SWPadnos_> so you dont even need the encoder to get force
[16:58:43] <fenn> that's in the drive electronics
[16:59:01] <fenn> i'm using a very very simple current loop
[16:59:16] <fenn> comparator and a dac
[16:59:19] <SWPadnos_> sure - the drive monitors current, so it "knows" force
[17:00:40] <les_w> just create a known torque with a pulley, mass and string
[17:01:04] <les_w> torque= pulley radius* mass*g
[17:01:20] <les_w> cank in just enough current to lift it
[17:01:25] <les_w> and divide!
[17:01:47] <jtr_away> question - could you get the torque constant by letting the weight fall with an ammeter across the motor leads?
[17:02:05] <jtr_away> no external power supply?
[17:02:12] <les_w> hmm
[17:02:22] <SWPadnos_> I don't think so - the current would depend on the speed and the external load
[17:02:44] <fenn> you can measure the speed with an encoder though
[17:02:50] <les_w> yes you could. You would have to put a load on the motor and time the drop
[17:03:01] <les_w> a little sensitive to friction though
[17:03:02] <SWPadnos_> you'd have to measure pretty accurately how much slower the weight drops, so you'd need a good timer rather than a power supply
[17:03:32] <les_w> yeah
[17:04:05] <fenn> jtr_away: your servo driver should work as a constant power supply
[17:04:20] <les_w> car battery and 100 ohm resistor is cheaper...
[17:05:20] <les_w> 126 MA current source! (kinda)
[17:05:52] <SWPadnos_> and you don't even have to take it out of the car! ;)
[17:05:57] <les_w> haha
[17:06:27] <jtr_away> no machine yet, no drivers - just hanging around trying to get an education and some mental exercise.
[17:06:50] <les_w> only need a 2 watt resistor or so...
[17:06:56] <fenn> jtr_away: just start asking about motor drive electronics.. plenty of mental exercise there
[17:07:15] <fenn> especially microcontroller programming.. that's a good one
[17:08:27] <jtr_away> Been doing embedded programming for years, just not with a normal language.
[17:09:21] <jtr_away> Done some assembly, c, RATFOR. Built a test executive to test a lamp controller I designed.
[17:09:35] <les_w> oopsie
[17:10:55] <SWPadnos_> AVR RULEZ!!!
[17:11:19] <jtr_away> few years ago, built an analog speed controller for the motor on a cassette deck
[17:11:37] <jtr_away> had to recover a tape made with dying batteries.
[17:11:51] <SWPadnos_> follow the bais ...
[17:11:54] <SWPadnos_> bias
[17:14:04] <les_w> yeah bias actually records