#robotics Logs

Apr 10 2015

17:45 superkuh http://oceanexplorer.noaa.gov/okeanos/media/exstream/exstream.html - watch a robot arm repeatedly failing 2000m under the atlantic ocean in real time.
17:48 chris_99 all i see is blue heh
17:48 superkuh They just moved it out of the way.
17:48 superkuh "It's not going to work."
17:49 superkuh Oh well.
17:49 chris_99 ah darn
17:49 superkuh It was a very pretty arm. It just kept freezing and let the hand go limp. So they can't use it for holding tools, etc.
17:54 superkuh Different robotic arm on now.
19:15 Anniepoo 8cD any dive that ends up with the ROV on the deck is a good dive
20:53 rue_shop3 "whats tommorow?" "DEAR GOD!!! __TOMMOROW__ is the day after today! didn't anyone tell you about it!?"
22:27 peepsalot any recommended resources for learning kinematics?
22:28 Jak_o_Shadows Forward? Or reversed?
22:30 peepsalot i guess i'm thinking more of like a catalogue of mechanisms, maybe kinematics is the wrong word
22:33 peepsalot do they teach that sort of stuff to mechanical engineers?
22:33 Jak_o_Shadows Nope
22:34 Jak_o_Shadows Basic dynamics is taught: a few different coordinate systems, and calculus for going from accelration to velocity to displacement, etc
22:37 Triffid_Hunter peepsalot: 3d computer graphics should give you a good foundation for kinematics
22:39 orlock my first own-designed component is on the printer currently
22:39 Jak_o_Shadows I should be finding my thermistors!
23:07 rue_shop3 wow, I just had the heater lock on-ish at the start of a print
23:08 rue_shop3 the fet was getting hot, but with my driver thats impossable
23:08 Jak_o_Shadows I just found "a" thermistor
23:08 Jak_o_Shadows it'll do
23:08 orlock rue_shop3: just took my first self-designed part off the printer
23:08 rue_shop3 SWEET!
23:08 orlock X and Y and .26mm too wide
23:09 orlock my parts always seem to come out a fraction of a mm too wide
23:09 Jak_o_Shadows what is it?
23:09 orlock i've already reduced preimiter extrusion
23:09 peepsalot Triffid_Hunter, i've a bit of 3d graphics experience :)
23:10 peepsalot not much physcs based though
23:10 jason__ Im guessing he means the linear algebra involved
23:10 rue_shop3 this is a 140A fet driving a non-inductive 3A load at 12V, with full gate driving
23:11 rue_shop3 why is this thing even warm
23:11 rue_shop3 orlock, can I get you to print a calibration object I made?
23:11 orlock Jak_o_Shadows: a mounting bracket to go on top of my equatorial head
23:11 orlock rue_shop3: sure
23:11 rue_shop3 ok, 1 min...
23:12 rue_shop3 I cant see your printer on the network... jk ;)
23:13 orlock yeah i need to give it a hostname
23:13 rue_shop3 whats its netbios name?
23:13 rue_shop3 :)
23:13 rue_shop3 uploading...
23:13 Triffid_Hunter rue_shop3: what
23:13 rue_shop3 dont take this off the bed when its printed...
23:13 Triffid_Hunter 's the Rds(on)?
23:14 orlock 2001:44b8:41dc:c900:3920:8fa2:4462:fa01
23:14 rue_shop3 oh noes! ipv6!
23:15 rue_shop3 http://ruemohr.org/%7Eircjunk/tutorials/mech/testsquare.stl
23:15 rue_shop3 orlock, print that, dont take it off the bed
23:15 rue_shop3 have calipers?
23:15 rue_shop3 Triffid_Hunter, .0005 ohms or so
23:15 rue_shop3 its an IRF1440
23:17 rue_shop3 oh wait, I used an irfz44
23:17 rue_shop3 its still a 40A fet...
23:17 rue_shop3 orlock, the distance from the inside of one edge, to the outside of the opposite edge should be 10cm
23:18 orlock no brim?
23:18 rue_shop3 thats regardless of the actual print trace width
23:18 rue_shop3 its only 1mm high
23:18 rue_shop3 should be 1mm wide, but thats not the important bit
23:18 rue_shop3 its the distance between the right hand edges of two parallel sides
23:19 rue_shop3 should be 10cm both ways
23:19 orlock http://en.crypt.net.au/Prusai3/.thumb_20150411_134659.jpg
23:19 rue_shop3 no, print that one I sent you
23:19 orlock http://en.crypt.net.au/Prusai3/20150411_134725.jpg
23:19 rue_shop3 it compensates for trace width
23:19 orlock http://en.crypt.net.au/Prusai3/20150411_134659.jpg
23:19 orlock rue_shop3: ok will do now
23:20 rue_shop3 it'll literally take a minute and wont use up any significant amount of plastic
23:20 rue_shop3 so whats the peice for?
23:20 rue_shop3 you need to punch plastic saver holes in things :)
23:21 orlock rue_shop3: Its only like, 10% infill
23:21 orlock rue_shop3: Goes on top of equatorial head, (fastened by center bolt hole) , then two rings mount to the front and rear holes
23:22 orlock http://www.altairastro.com/altair-tms-150mm-guide-scope-rings.html (example image, not mine - first google search result for guidescope rings)
23:23 rue_shop3 is it done yet?
23:24 rue_shop3 totally printable
23:25 orlock printers outside - going to print now
23:25 orlock file scp'd over
23:25 rue_shop3 ah
23:25 rue_shop3 remember, dont take it off the bed
23:26 Triffid_Hunter rue_shop3: that's 40A with a perfect heatsink that keeps the tab at 25°C regardless of how much power the fet dumps
23:28 Triffid_Hunter rue_shop3: Rds(on) is 28mΩ and increases by up to 2.1x as the fet heats up, so max 59mΩ.. at 3A the fet will be dumping 0.55W which should make it warm
23:29 rue_shop3 ah, good numbers, k, .5w would be about what I see on it
23:29 rue_shop3 should have used the 1440
23:29 rue_shop3 I put a clip on heatsink on it
23:29 rue_shop3 that'll be part of the 'fix properly later' list
23:29 rue_shop3 ;)
23:30 rue_shop3 I just finished the fan stand that means I dont have to keep the 12V 7.2Ah battery under the fan
23:30 Triffid_Hunter 0.5W is ok, shouldn't need a heatsink
23:31 rue_shop3 it gained enough heat to lock on, so it seems
23:31 Triffid_Hunter at 62k/w that's only +30c or so
23:32 rue_shop3 yea, it was about 50
23:32 rue_shop3 I'll keep an eye on it
23:32 rue_shop3 started to freak out as the temp just kept going up
23:32 rue_shop3 that would be another new problem
23:33 rue_shop3 most of the problems I'm having now are caused by the sliders
23:34 rue_shop3 they have just a little play in them and it manifests badly
23:34 rue_shop3 I'm working on how to either preload them or come up with something else
23:34 rue_shop3 (reload the sider against ONE of the rods)
23:36 rue_shop3 ^p
23:40 rue_shop3 ah, if I cockeye the linear bearings, they will perform better
23:48 Jak_o_Shadows Hmmmmmmm. The thermistor doesn't fit through the hole in the heated bed pcb
23:48 Jak_o_Shadows Hmm, I could use that tar tape stuff.
23:54 rue_shop3 orlock, dude?
23:54 rue_shop3 Jak_o_Shadows, its supposed to fit in that hole?
23:54 rue_shop3 expalins why there is a mounting hole in the middle of the bed
23:55 rue_shop3 dosn't expalin the 6 lead led
23:55 Jak_o_Shadows My thermistor doesn't fit, so I can't do that. But yeah, I think it's meant to go there.
23:56 Jak_o_Shadows The holes are for a resistor (fo the LED), and a couple of LED's in opposite directions
23:56 rue_shop3 holes for resistors!? what are you smoking?
23:57 rue_shop3 how am I gonna make bed leveling things?
23:57 Jak_o_Shadows haha. I totally don't have a sinlge SMD part anywhere
23:58 Triffid_Hunter Jak_o_Shadows: buy some, they're super cheap :P
23:58 rue_shop3 take some off some old electronics
23:58 Jak_o_Shadows I should, but I dont get a lot of time anyway.
23:58 rue_shop3 not motherboards, they are pretty small
23:59 Jak_o_Shadows I'd need a new soldering iron, mine's only a tad better than a firestarter
23:59 rue_shop3 I'v got the bed of my new machine sliding back and forth
23:59 rue_shop3 less the bed top
23:59 rue_shop3 need to find a belt
23:59 rue_shop3 looks like I'm gonna go with the nema23 for the Y axis, for now