#robotics Logs

Jul 29 2014

00:11 MrCurious thinking i will need an mold to hold the rod to the bearing, then i can inject hot glue
00:11 MrCurious using a relaxant to free it
00:15 MrCurious wonder if my mill would be able to drill a 3mm hole in a 10mm steel ball bearing
00:15 rue_mohr2 https://static.hackaday.io/images/4617391405258229293.png
00:15 rue_mohr2 ball joints
00:16 MrCurious looks easy to make a 3d printer using those if you have a 3d printer to make those
00:17 MrCurious http://blog.lincomatic.com/wp-content/uploads/2014/06/efh1.jpg
00:17 MrCurious better plan
00:24 Hyratel1 innnteresting
00:24 Hyratel1 magnetic ball joints
00:25 MrCurious then again... if i can drill the balls... i could make them into non magnetic ball joints
00:25 MrCurious with enough clearance
00:30 MrCurious http://reprap.org/mediawiki/images/thumb/4/42/Delta-Pi_Carriage.jpg/400px-Delta-Pi_Carriage.jpg
00:30 MrCurious now THAT looks fabricatable
00:32 rue_mohr2 C no twist
00:34 rue_mohr2 on the link set I have, the balls aren't magnetic, its the rods that are
00:34 rue_mohr2 do youhave magnetic balls?
00:36 GargantuaSauce balls are touching
00:40 MrCurious dont know... never put them near anything iron based
00:42 MrCurious i wonder if a stiff spring would make for a viable universal joint...
00:42 MrCurious nope...
00:42 Hyratel1 that's how some mills do it
00:42 MrCurious the diameter would introduce error
00:42 deshipu MrCurious: bearing balls are made to be very hard, so drilling a hole would be difficult
00:43 Hyratel1 a steel coupler-spring
00:43 MrCurious deshipu: thinking using my vise and my mill and step drilling starting around 1mm
00:43 deshipu MrCurious: but I wonder if you could just have two U-shaped holds for them
00:44 MrCurious http://www.okey100.com/uploadfiles/goods/20130321/2013032102440373.jpg
00:44 MrCurious i have 12 of these
00:44 MrCurious but there are dead zones when they lack freedom to twist
00:44 deshipu that looks nice
00:44 deshipu yeah, if they had a bearing ball in the middle...
00:45 MrCurious maybe the answer is to mount a bearing on one end of each rod so its bearing- universal - rod - universal - bearing
00:46 deshipu or you could use some brass balls instead, you don't need them to be hard, and brass is self-oiling, kinda
00:46 GargantuaSauce MrCurious: if you do that you don't even need a universal joint
00:46 GargantuaSauce you need 3 bearings
00:47 MrCurious well i have an ass load of cheap bearings
00:47 GargantuaSauce if you arrange them like -|- where the lines represent axes of rotation
00:47 GargantuaSauce that's the same as a ball joint
00:47 MrCurious i see
00:47 MrCurious join 2 together along outside ring with one rotated 90 from other
00:52 GargantuaSauce and now that i got around to reading the scrollback, deshipu we need to talk about your power supply?
00:52 GargantuaSauce this is the quadropod right
00:56 deshipu GargantuaSauce: yeah, I finally got the replacement servos -- the old ones were too weak and overheated
00:57 deshipu GargantuaSauce: but now, surpsise, they get starved on startup
00:57 GargantuaSauce yeah the ones with decent torque ratings really pull a lot
00:57 GargantuaSauce the ones i use can draw 5A each
00:58 deshipu I have 12 of them I checked that it works fine until I connect the 8th
00:58 GargantuaSauce so what is powering them
00:59 deshipu http://www.hobbyking.com/hobbyking/store/__31420__TURNIGY_8_15A_UBEC_for_Lipoly_EU_warehouse_.html <-- this
00:59 MrCurious rue_mohr2: i think i may go with your idea of letting them rotate on the ends using screws that can twist in a hole
01:00 GargantuaSauce okay yeah so the problem is when you draw too much current the inductor in the buck converter saturates and the voltage on the output plummets, as you've probably figured out to some degree
01:00 GargantuaSauce a capacitor could help if it was *huge*
01:01 MrCurious damnit. its 11pm again and i am tumbling shapes in my mind. means no sleep tonight
01:01 deshipu GargantuaSauce: I plan on a 4700uF one
01:01 GargantuaSauce but really i think the best solution is to allow the servos' supply to droop (or use a bigger smps)
01:01 GargantuaSauce that will do dickall.
01:01 GargantuaSauce you should use a separate buck converter for the control electronics
01:01 deshipu well, I need a capacitor there anyways
01:01 deshipu sure, I do
01:01 MrCurious GargantuaSauce: are you are back on the servo sagging issue...
01:01 deshipu this is just with the servos being powered from it
01:03 MrCurious wonder if you could use those current limiting resettable fuses...
01:03 MrCurious servo gets too greedy, it depowers and resets...
01:03 deshipu the servo specs say Running Current: 180mA
01:03 deshipu but that's not the stall current, I guess
01:03 GargantuaSauce yeah definitely not
01:04 deshipu maybe if I shortened the legs...
01:04 GargantuaSauce that would probably help quite a bit
01:05 GargantuaSauce also if these are digital servos and the servo controller has outputs that can be individually disabled, you could turn all the servos on in sequence instead of all at once
01:05 deshipu hmm, good idea
01:06 deshipu I'm afraid they will have to move all at once anyways though, because of the inverse kinematics
01:06 Hyratel1 what's the power supply?
01:07 deshipu Hyratel1: see the link a screen up
01:07 GargantuaSauce well yes of course they'll need to move in unison, but that will be using less current than the case where they're all powered on in a significantly different position from that which they are being commanded to hold
01:09 GargantuaSauce also i am not sure to what degree the rating on that ubec is bullshit but i bet it's nonzero
01:09 deshipu of course :)
01:09 rue_bed I bet you can get really round beads with a hole in the middle that a tension cable could be run thru
01:09 GargantuaSauce http://www.dx.com/p/15a-dc-4-32v-to-dc-1-2-32v-converter-buck-adjustable-electronic-power-regulator-219807
01:09 GargantuaSauce this is the one i use in my hex
01:10 Hyratel1 deshipu, what is the need for this UBEC?
01:10 Hyratel1 and what's the power feed for it
01:11 deshipu a 3s 1c lipo battery
01:11 GargantuaSauce ...1C? seriously
01:12 deshipu GargantuaSauce: it's for the radios
01:12 GargantuaSauce yeah ok so the buck converter is not the problem
01:12 deshipu but it dies on mains current too
01:12 GargantuaSauce or, not the only problem :)
01:12 deshipu on a 12V 3.5A power supply
01:12 GargantuaSauce you WILL kill that battery by discharging too fast
01:12 Hyratel1 deshipu, why such a small battery system?
01:12 deshipu Hyratel1: it's what I had on hand
01:13 deshipu it's not small
01:13 Hyratel1 tip: use SLA
01:13 deshipu it's the size of my palm
01:13 Hyratel1 https://docs.google.com/spreadsheets/d/1hAHfLJN0cwo0ZgO68Hn3EXThfr4vXLOB_4a85thiPAM/edit#gid=0
01:13 rue_bed why are you using a battery for a 3d printer?
01:13 Hyratel1 "the size of your palm" is small
01:13 GargantuaSauce Hyratel1: your remote control car's implementation is not applicable to every other project
01:13 rue_bed are we still on the 3d printer?
01:13 Hyratel1 GargantuaSauce, stationary systems can have much larger batteries
01:14 rue_bed rue_mohr2, kick someone so I get some answers eh?
01:14 deshipu rue_bed: no, that's a quadruped
01:14 GargantuaSauce anyway deshipu you definitely need something that can supply 5A+
01:14 deshipu although a quadruped 3d printer would be interesting
01:14 GargantuaSauce i am gonna go to bed before this conversation gets too retarded
01:15 rue_bed prints the footprints it leaves behind?
01:15 deshipu GargantuaSauce: good night, and thanks for the help
01:15 rue_bed what design is the quad?
01:15 rue_bed how many axies?
01:15 deshipu it should have one big axe
01:15 deshipu and a couple of saw blades
01:16 rue_bed cmon, do tell about it
01:16 rue_bed have any images?
01:17 deshipu rue_bed: http://letsmakerobots.com/robot/project/kubik
01:19 rue_bed what are you gonna use for control?
01:21 deshipu I bought a cheapo sixaxis clone, but turns out the linux drivers only work with the original
01:21 deshipu oh
01:21 deshipu a raspberry pi for brains
01:21 Curious screams odroid-u3 then runs
01:22 deshipu meh, I just use what I have lying around, I can't find any other use for the pi
01:22 deshipu also, then I can show it off on all the pi-related forums ;)
01:33 MrCurious but that would be no good unless you could somehow control it with something like a game console controler
01:36 deshipu that's the plan
01:36 deshipu I actually have the software already
01:37 MrCurious on what platform? pi, or arduino?
01:37 deshipu pi, python :)
01:37 deshipu I'm a python programmer by trade
01:38 deshipu hacked pygame to run without a display
01:38 MrCurious python is a toy language
01:39 MrCurious did it for 5 years... thats 5 years i will never get back
01:40 MrCurious might as well do it in perl
01:41 MrCurious and while i am raging... anyone who uses nano editor by choice deserves a swift kick in the nutz
01:41 deshipu vim here :)
01:42 deshipu well, it may be a toy language, but I'm comfortable with it, and they pay me handsomely for coding in it, so I don't complain
01:42 deshipu not all software has to be system-level
01:42 MrCurious ahhh vi the one true editor
01:42 MrCurious not a week goes by i dont six some files
01:43 MrCurious python is a path to madness... and failure
01:43 deshipu if you say so :)
01:43 MrCurious remember the smell.... and run when you smell it next
01:44 deshipu hmm, why do they make all bearings so hard to mount?
01:44 deshipu why won't they add some screw holes or something?
01:45 MrCurious because if they were easier to mount, the planet would be over run with them instead of sheep??
01:46 deshipu ok, bad choice of words, you can tell I'm not a native speaker
01:46 deshipu s/mount/attach
01:50 MrCurious use glue
01:50 MrCurious before using glue, rough up one side using sand paper or a grinder
01:50 MrCurious gives glue some irregularities to find purchase to hold to
01:54 deshipu glue is very nice once you actually know what you want to build
01:54 deshipu not so great for prototyping
01:54 MrCurious hot glue is nice for prototyping
01:54 MrCurious easy removal, reworkable
01:55 MrCurious just remember "when you wonder if its still hot" and you will... the answer is always "yes"
01:55 MrCurious hot glue is hot
01:55 deshipu I'd love to have some grouwn-up meccano set, with thicker bars, bearings, gears, etc.
09:38 zero_coder hello
09:38 zero_coder http://www.snapdeal.com/product/godrej-gp-2xaa-2700mah-nimh/138537
09:38 zero_coder can i draw 2-3 A current from those batteries?
09:39 rue_mohr2 at 1c you can draw 2.7A
09:40 rue_mohr2 they should probably be good for more than 1c
09:40 zero_coder 1c?
09:41 zero_coder rue_mohr2, i am trying to power a robot which will require around 2.5 - 3A current at 6V
14:26 deshipu while I'm waiting for parts for my large quadruped, I'm thinking about building something smaller, like this: http://imagebin.org/316621
19:01 rue_mohr2 why are you using 6V?
19:01 rue_mohr2 if you use 12V its only as much as 1.5A
19:02 Hyratel1 rue_mohr2, because servos are 5/6v
19:13 rue_mohr2 but you can put a switch power supply between them
19:14 rue_mohr2 6V at 3A is 12V at 1.5A
19:14 rue_mohr2 constant power converter
19:18 rue_mohr2 24V at .75A
19:18 rue_mohr2 you see there is another advantage
19:20 rue_mohr2 a 7.2 battery is dead at 6V, a 14.4V is dead at 12V
19:20 rue_mohr2 (NiCd)
19:21 rue_mohr2 if your dead votlage is too low to be usable, you can use a higher voltage and convert it down
19:21 rue_mohr2 the lower currents are easier on the cells and you often get a more workable voltage range
19:38 ace4016 rue_mohr2, have a link to your most advanced/latest mowerbot?
19:42 Tom_L http://ruemohr.org/~ircjunk/robots/mowerbot2/
19:48 ace4016 thanks tom :P
19:52 ace4016 hrm, interesting design
22:13 bindigoat http://www.indymedia.org.au/2014/06/21/australian-association-of-radiation-mitigation-professionals
22:13 bindigoat swarm robotics & renewable energy
22:56 Mr_Sheesh Is the kicking insanity over now?
22:59 MrCurious think of it as filtering the dead wood.
22:59 MrCurious if you come back, you are live wood
22:59 MrCurious plaec has been too dead of late
22:59 Mr_Sheesh Annoyed live wood tho
23:00 Mr_Sheesh RL happens
23:00 MrCurious take it out by making a robot!
23:00 Mr_Sheesh RL doing that tho its a cat entertainment bot
23:00 Mr_Sheesh galvo never seems to arrive so I can aim mah lazer!
23:00 MrCurious a mouse entertainment bot would have more humor value
23:01 MrCurious now that most mouse diseases are cured, and they are living longer healthier lives sthan ever before
23:01 Mr_Sheesh I don't have mice
23:01 Mr_Sheesh if I had one, cats'd have fast food
23:01 MrCurious nah, they only kill the mice on accident
23:01 MrCurious until then, they are a toy
23:02 Mr_Sheesh LOL My older one's tried to catch a local squirrel several times; I've learned new swear words in squirrel. And the squirrel moved far away LOL
23:02 MrCurious bring inside a grasshopper
23:03 MrCurious cats are lethal to them
23:05 Mr_Sheesh Strings and worse mylar ribbons get fast killing bites here
23:08 Mr_Sheesh Was going to use RC servos but was suggested to use a Galvo so I'll make a line follower from the RC servos I think. Got beefy ones so they should do :)
23:48 rue_mohr2 oo whats up
23:48 rue_mohr2 I got a touchpad mouse and I keep having the reflex to slide it around on the desk
23:49 orlock heh
23:49 orlock though.. why??
23:49 orlock why touchpad i mean
23:49 rue_mohr2 I always told myself it was better than a mouse
23:49 rue_mohr2 now I can buy them
23:50 orlock i guess with the new sensors they have gotten a lot better than the old ones
23:50 orlock i had one about 15 years ago, little serial Synaptics thing
23:50 rue_mohr2 this is a "lofree MT-100" you can find them all over china
23:51 rue_mohr2 right click and scolling
23:51 rue_mohr2 ^ it does
23:51 orlock multitouch?
23:51 rue_mohr2 yup
23:51 rue_mohr2 tripple!
23:51 rue_mohr2 3 finger tap is right click
23:52 rue_mohr2 its wireless, didn't want that, it dosn't connect when plugged into usb but will run on the power
23:56 rue_mohr2 one problem is that its not wide enough for my screens
23:56 rue_mohr2 I wonder if there is a mouse app for an android tablet