#robotics Logs

Jan 26 2015

03:22 mrdata perhaps like an arduino and motor shield
03:24 mrdata https://www.adafruit.com/categories
03:26 mrdata https://www.adafruit.com/product/749
03:36 joga if you have kids, maybe lego mindstorms ev3 might be worth checking out... it runs linux, does wifi etc and you can build the chassis from lego parts (which is, of course, fun). it's a rather expensive kit though
03:52 Trudko joga: i am only kid in my family :D
03:56 Trudko mrdata: ok will check it
08:07 A4K Hello all, just dropped by to let you guys know of this free introductory robotics online course: http://www.petercorke.com/MOOCs.html Very good lecturer teaching it.
08:10 deshipu matlab :(
08:11 A4K I think you can use R if you like
08:12 A4K Plus the concepts are what's important
08:16 deshipu not if all the examples you get are in matlab
08:16 deshipu and they require some proprietary matlab plugins
08:16 deshipu but yeah, better than nothing
08:17 deshipu it's great that there are such courses
08:17 deshipu I'm just a little sad that they depend on proprietary software so much
08:20 A4K It uses the Toolkit from the textbook Robotics Vision and Control, which is not proprietary. You can also use the R port of the toolkit, although I haven't tried it.
08:23 deshipu ok, sorry, I made an assumption based on the underactuated robotics course
08:23 deshipu also on edx and with matlab
17:01 dpy hi guys
17:02 dpy Would this be an okay stepper motor for a Proxxon MF70 CNC conversion with L298 chopper drivers: http://www.ebay.com/itm/131002793272
17:04 Tom_itx a little small for a cnc
17:04 dpy To be clear, I don't need super powerful or high speed. The MF70 is only a small machine with a small delrin nut on its axis anyway
17:05 dpy Tom_itx: I've read of succesful conversion using 4800g.cm NEMA17
17:05 dpy what confuses me is the seemingly low current of 0.4
17:05 dpy I also see stepper motors of 2.5A for a similar holding torque
17:06 Tom_itx http://www.aliexpress.com/store/product/5pcs-NEMA17-78-Oz-in-CNC-stepper-motor-stepping-motor-1-8A/704350_554160664.html
17:06 Tom_itx those are quite popular with reprappers
17:09 dpy -sigh- I try to stay away anything alibaba/aliexpress
17:09 dpy very insecure site
17:09 dpy with fake verisign logos all over
17:10 dpy anyway, is there a catch somewhere
17:10 dpy with the 0.4A ?
17:10 dpy or should I look at the power consumption?
17:11 dpy 2.5A * 2.8V versus 0.4A * 12V ?
17:13 Triffid_Hunter dpy: get the 2.8v ones if your driver has current control. get the 12v ones if you don't care about your motors hemorrhaging torque at speed and don't want current control
17:15 dpy I don't have a deal on the 2.8V ones unfortunately, I was just comparing against some keling stepper motors
17:16 dpy I intend to use some old reprap 1.2 drivers
17:17 dpy with the L298/L297 combo
17:18 Triffid_Hunter dpy: for nema17 size it's hard to beat rattm motors.. j1s I find a link
17:18 Triffid_Hunter oh, tom already linked them
17:18 Triffid_Hunter they're on ebay too if you don't like aliexpress
17:19 dpy I found this: http://www.ebay.com/itm/141529522276
17:19 dpy are those the same?
17:19 dpy same no.
17:19 jacknone What kind of project are you guys talking about if you don't mind me asking?
17:19 Triffid_Hunter dpy: yep that's the one
17:19 Tom_itx dpy, those are the best anyone has found so far
17:20 dpy okay
17:20 dpy then I'm gonna go for these
17:21 Tom_itx they're cheaper at alibaba
17:21 dpy yes,everything is cheaper at ali
17:22 Tom_itx by ~40 bucks
17:22 Tom_itx 30ish
17:22 Triffid_Hunter hm, http://www.ebay.com/usr/rattmmotor looks like rattm's official ebay outlet
17:23 Triffid_Hunter they've got bugger all sales though, very strange
17:24 dpy these are even more powerful: http://www.ebay.com/itm//251808527074
17:24 dpy but may be overkill for MF70?
17:25 Tom_itx http://www.ebay.com/itm/Nema17-Stepper-motor-60mm-95-Oz-in-1-8A-CNC-stepper-motor-Military-motor-/251808527074?pt=LH_DefaultDomain_0&hash=item3aa0f532e2
17:25 Tom_itx that looks like a double stack nema17
17:25 Triffid_Hunter the 17HS8401 is double stack, that one's triple stack
17:25 Tom_itx oh
17:26 Triffid_Hunter dpy: oh yikes, check the winding resistance.. 22Ω
17:26 dpy That's bad?
17:26 Triffid_Hunter so you'll need 40v to push its rated current when it's sitting still, and quite a bit more when it's spinning
17:26 dpy I found these again: http://www.ebay.com/itm//251808521844
17:27 dpy 16USD free shipping
17:27 Triffid_Hunter dpy: yep, direct from rattm
17:28 dpy ok
17:28 Triffid_Hunter dpy: get some http://www.panucatt.com/product_p/sd8825.htm or similar to go with it if you find the L298 shopper is too crunchy
17:28 dpy then I just buy these
17:28 Triffid_Hunter dpy: do your L298 drivers have proper current control, or just PWM
17:28 Triffid_Hunter ?
17:28 dpy I don't know
17:28 Tom_itx get couplers with em
17:28 dpy it's the reprap 2gen electronics
17:29 Triffid_Hunter dpy: best find out, you need a proper current controlled driver for those motors.. there's a reason ramps and similar left reprap gen2 electronics in the dust ;)
17:29 dpy Triffid_Hunter: yes, but I first want something working
17:30 dpy then I can improve on that
17:30 Triffid_Hunter dpy: "One interesting feature of the L297 is its current sensing and 'chopping' abilities. The L297 will sense the amount of current flowing through the coils, and will 'chop' the signal to the L298 so that the average current flowing is the desired amount" - http://reprap.org/wiki/Stepper_Motor_Driver_1.2
17:30 dpy rather than spend $$$$ and have nothing working
17:30 Tom_itx the ramps is current controlled?
17:30 dpy I have these lying around anyway now
17:30 Tom_itx set with a pot?
17:30 Triffid_Hunter Tom_itx: ramps itself, no. the drivers we plug into it are all microstepping current-mode drivers
17:30 dpy yes it has a precision pot
17:30 Tom_itx the newer drivers or the older ones or both?
17:31 Tom_itx i forget the pn's
17:31 Triffid_Hunter Tom_itx: all of them
17:31 Tom_itx k
17:31 dpy I have these: http://reprap.org/wiki/Stepper_Motor_Driver_1.2
17:31 Tom_itx aren't they allegro parts?
17:31 dpy exact match
17:31 dpy so it's 2007 electronics, yes
17:31 Triffid_Hunter Tom_itx: yes. first we used the A4982, but it had a few issues and was later replaced with the A4988. The DRV8825 is a more recent contender
17:31 dpy but hopefully enough to get it to work
17:32 dpy then I can order some newer electronics to improve the setup a bit, if needed
17:32 Tom_itx i don't keep up up with them, i'm using geckos on my cnc
17:32 Triffid_Hunter dpy: those panucatt DRV8825 breakouts are nice, you can actually mount a heatsink to the board in a way that's useful
17:33 dpy Triffid_Hunter: I did look at the electronics, also much more compact
17:33 Triffid_Hunter dpy: sure, L298 is ancient, still uses BJTs I think whereas all the modern chips use power mosfets and have the current control built in
17:33 Triffid_Hunter so they dissipate a lot less heat, and can be massively smaller for the same current
17:33 dpy But like I said, I have my mind set on first trying it with the old stepper drivers I have lying around...
17:34 Triffid_Hunter dpy: well they do have current control so they should work fine
17:34 dpy ok, cool
17:34 dpy hey guys, thanks a lot for the pointers
17:35 dpy I'm now much more confident in buying the better steppers
17:35 dpy and even cheaper as well!
17:35 Triffid_Hunter dpy: you're welcome, learned lots from doing repraps :)
17:36 Tom_itx http://tom-itx.no-ip.biz:81/~webpage/motors/hb4.jpg
17:36 Tom_itx i've got several of those laying around
17:36 Tom_itx LMD18200
17:36 Tom_itx old
17:43 dpy Ok, I ordered one of the RATTM motors
17:43 dpy on ebay
17:43 Triffid_Hunter just one? usually need a few for CNC conversion :P
17:44 dpy yes, whenever it's marked as sent, I'll order the next
17:44 dpy They should be sent separately (no problems with customs)
21:06 anonnumberanon is there a better kind than those? maybe with different strengths? http://www.amazon.com/Spring-Clamps-Muslin-Woodworking-Professionals/dp/B00LD5ALTQ/ref=sr_1_1?ie=UTF8&qid=1422326541&sr=8-1&keywords=Plastic+Spring+Clamp
21:10 Tom_itx http://www.amazon.com/TEKTON-3911-6-Inch-Steel-Spring/dp/B000NPPAXY/ref=sr_1_6?ie=UTF8&qid=1422326971&sr=8-6&keywords=steel+A+clamp
21:26 DagoRed .shrink
21:26 makepi DagoRed: http://goo.gl/oZiJ61