#robotics Logs
Feb 09 2015
#robotics Calendar
00:59 joga adblock?
01:00 joga seems if I tell adblock to allow that page *and* tell noscript about five times to allow all on the page (sheesh), it seems to work
01:00 joga of course it wants to show you ads also
01:29 rue_shop3 I find it better to just use resolve.conf to block out all the google ad servers
01:29 rue_shop3 does anyone use anything else these days?
01:30 Jak_o_Shadows I'm not so fussed about google ads to be honest
01:33 rue_shop3 hmm I ahve a SOC764A opto isolator on a board, from what I can tell the device was never made
03:12 rue_shop3 Tom_itx, whats the name of the linux cnc channel?
03:12 rue_shop3 found it!
14:10 rue_shop3 Tom_itx, why should I switch to a g-code interpreter for my cnc if I have to write a cam package for it?
14:11 rue_shop3 why not just use the d-code interpreter I already have and write one for that
14:11 rue_shop3 we have kinda called it d code over theyears
14:17 Tom_itx because Gcode is an industry standard
14:17 Tom_itx and you can share code
14:17 rue_shop3 but I'd have to write software anyhow?
14:18 Tom_itx but i couldn't send you a part file to make if i wanted to
14:18 rue_shop3 my machines commands are prettymuch based on g-code, converting would be easy
14:18 rue_shop3 hm
14:18 rue_shop3 hmmm
14:18 SquirrelCZECH deshipu: tip tap?
14:18 rue_shop3 hmmmmmmmmmm
14:18 Tom_itx off today?
14:18 SquirrelCZECH rue_shop3: he is right
14:19 Tom_itx rue has his own way of thinkin
14:19 Tom_itx g
14:19 rue_shop3 99% of the work is in tool offsets and pocket pathing
14:19 SquirrelCZECH anyway
14:19 SquirrelCZECH while developing my cad-lib
14:19 SquirrelCZECH I again
14:19 SquirrelCZECH am at the point to redesign 1/2 of the thing
14:19 SquirrelCZECH s
14:19 SquirrelCZECH nah
14:20 rue_shop3 SquirrelCZECH, tell me about your cad lib
14:20 SquirrelCZECH rue_shop3: it started as simple python->scad
14:20 rue_shop3 does it do the thinking or the drawing
14:20 SquirrelCZECH than i started it to learn how to design part
14:20 rue_shop3 ah its 3
14:20 rue_shop3 d
14:20 SquirrelCZECH and now I am thinking about adding much more "meta" things
14:20 rue_shop3 your just making a program to correct the scad stupidities?
14:20 SquirrelCZECH like material, surface, weight, center of mass
14:20 SquirrelCZECH rue_shop3: for me
14:21 SquirrelCZECH python and scad
14:21 rue_shop3 yup, I'm not knocking it
14:21 SquirrelCZECH are like php and html for example
14:21 SquirrelCZECH :)
14:21 SquirrelCZECH "scad" is only vizualization of what's in "python" :)
14:21 rue_shop3 half the day is gone, but I'm awake
14:22 rue_shop3 its pouring rain, I was hoping to do thigns outside today
14:23 GuShH_Lap aww
14:23 rue_shop3 arc welding is something NOT TO BE OUTSIDE DISPITE THE RAIN
14:23 GuShH_Lap heh yesterday I was doing just that
14:23 rue_shop3 ^done
14:23 GuShH_Lap but it barely dribbled
14:23 GuShH_Lap managed to also prime the parts
14:24 rue_shop3 I hate it when the gloves get just wet enough to lightyou up every time you break the arc
14:24 SquirrelCZECH rue_shop3: and I am thinking about adding slicing into my lib too
14:24 GuShH_Lap lol even worse when the water turns to steam
14:24 GuShH_Lap that hurts.
14:24 rue_shop3 not gonna help me, I need tool path offsets
14:24 SquirrelCZECH Isuppose that with slic3r it should be possible for me to make same interesting stuff
14:24 SquirrelCZECH like for example making holes for screws with more perimeters than other thinks
14:25 SquirrelCZECH or start to make some work with setting where is pressure on the part and making the library to force slic3r to enforce it in that parts
14:25 SquirrelCZECH etc etc etc :)
14:25 SquirrelCZECH *other things
14:26 SquirrelCZECH and lately when I was designing algorithm to control spider-robot
14:26 SquirrelCZECH I thought
14:26 SquirrelCZECH that if I would CAD that robot in my library
14:26 SquirrelCZECH I should be able to check for colision detection in mechanism when moving
14:28 SquirrelCZECH even create some algorithm to figure out maximum movements of parts :)
14:28 SquirrelCZECH buuut, for that "meta" stuff, changes have to be done
14:29 SquirrelCZECH hmm, and I suppose 1. is to get rid of transformations list (Scad way)
14:29 SquirrelCZECH and make each translate/rotate call to actually modify actual position
14:32 slidercrank хог1у, hello
14:44 SquirrelCZECH nah
14:44 SquirrelCZECH question
14:44 SquirrelCZECH what do you expect, whan you position something on some coords
14:44 SquirrelCZECH and than scale it?
14:44 SquirrelCZECH what will be it's position after that?
15:00 rue_shop3 Tom_itx, my cnc intpreter also does real circles, to the resolution of the machine
15:00 rue_shop3 instead of generating line segments
16:26 deshipu SquirrelCZECH: sorry, traveling
16:27 SquirrelCZECH yeah
16:27 SquirrelCZECH deshipu: wanna see my attempt to create 6dof freedom control for leg-based robot?
16:27 SquirrelCZECH three servos/leg
16:27 SquirrelCZECH it seems that it works :
16:27 SquirrelCZECH :D
16:27 SquirrelCZECH for the things I tried to simulate
16:28 SquirrelCZECH I am curious if I am completely wrong or not
16:28 deshipu I'd love to see it, later, when I get home tommorow evening
16:28 SquirrelCZECH deshipu: btw: that kickstarter small camera with wifi shield you mentioned
16:29 SquirrelCZECH found it
16:29 SquirrelCZECH and
16:29 SquirrelCZECH ITS AWESOME
16:29 SquirrelCZECH :D
16:29 deshipu it is
16:29 uirrelCZECH is just missing 12 pins for
16:29 SquirrelCZECH on it...
16:29 deshipu I can't wait to make a robot with it
16:29 deshipu well, I will use an arduino for that :)
16:29 SquirrelCZECH yeah
16:29 SquirrelCZECH but that camera, with wifi, arduino and 12 servos
16:29 deshipu talking over serial
16:29 SquirrelCZECH and exactly the thing I would be willing to build
16:30 deshipu damn, I could have left you one of my pcbs
16:30 SquirrelCZECH happens :)
16:30 deshipu maybe someone will be coming to brno and can take it to you
16:30 uirrelCZECH just started to think if he would find a reason to visit polands hackerspace..
16:30 deshipu the one in Poznan is not currently running
16:31 deshipu but the one in Warsaw is
16:31 SquirrelCZECH I see
16:31 SquirrelCZECH well
16:32 SquirrelCZECH still long run before I buy everything
16:32 deshipu the pcb is not required, it's just convenient
16:32 SquirrelCZECH so nowhere to hurry :)
16:33 SquirrelCZECH deshipu: how much can handle robot based on the blue servos?
16:33 uirrelCZECH was thinking about mounting his webcam o
16:33 SquirrelCZECH with wwhich I watch my reprap
16:34 SquirrelCZECH so I can walk around it :)
16:34 SquirrelCZECH that would mean only servos + arduino :)
16:41 deshipu SquirrelCZECH: in theory the servos have 1.8kg*cm
16:42 deshipu femur is about 4cm long, tibia about 3cm
16:43 deshipu so it should be able to carry 1.8kg with the tibia vertical
16:43 deshipu which is obviously wrong
16:46 SquirrelCZECH yeah
16:47 deshipu the servos weight 9g each, the battery is about 30g
16:47 deshipu no idea about the box and the electronics, but should maybe another 30g
16:49 deshipu so 150g for the ankle/knee servos to carry
16:50 deshipu 72.5g each
16:50 deshipu well, with one leg up, that would actually be
16:50 SquirrelCZECH ok ok
16:51 deshipu (9 * 10g + 60g) / 3 = 40g per servo
16:52 deshipu sorry
16:52 deshipu in practice, you don't want them to be loaded too much all the time
16:52 SquirrelCZECH I can uderstand that
16:54 deshipu but it should be able to carry a webcam just fine
16:54 deshipu the problem is what to connect it to
16:54 deshipu something like VoCore, or raspberri pi A+ would make sense
16:56 deshipu or maybe odroid-w1
16:58 SquirrelCZECH it's allready connected
16:58 uirrelCZECH is using it to watch reprap, so cubieb
16:58 SquirrelCZECH but add some legs and I can look around :)
16:59 deshipu for that you just need pan and tilt
16:59 deshipu 2 servos
17:04 SquirrelCZECH *walk around
18:55 rue_shop2 yay! I have printable tractor tread!
18:55 Jak_o_Shadows woo!@
18:56 rue_shop3 I'll post on thingverse later
18:56 slidercrank it looks like many of you have a 3D printer
18:56 rue_shop3 I just got mine going a while ago
18:56 rue_shop3 its not the only tool you need
18:57 rue_shop3 it borders on frivilous
18:57 Jak_o_Shadows indeed. Yesterday I tried making brackets. Today I might just scraps of garden stake
18:58 Triffid_Hunter slidercrank: doing robotics without a 3d printer is daft ;)
18:58 GuShH_Lap rue_shop3: it's raining now! your fault!
18:59 slidercrank Triffid_Hunter, what 3D printer do you suggest a beginner to obtain?
18:59 slidercrank -to
18:59 Triffid_Hunter slidercrank: prusa i3 or mendel90, not super cheap ones (<$500) though or you'll spend the kit's cost again upgrading parts to make it work
18:59 slidercrank is it better to order parts or buy an assembled printer?
19:00 Triffid_Hunter slidercrank: it's best to come hang out in #reprap for a while before dropping any money anywhere ;)
19:00 slidercrank okay. thanks
19:00 Jak_o_Shadows ahaha, I spent < $500 on my i3
19:01 Triffid_Hunter Jak_o_Shadows: self-sourced?
19:01 Jak_o_Shadows Entirely. It took a little while
19:01 Jak_o_Shadows Hangon, pics: https://dl.dropboxusercontent.com/u/104809629/3d%20printer/3d1.jpg https://dl.dropboxusercontent.com/u/104809629/3d%20printer/3d2.jpg https://dl.dropboxusercontent.com/u/104809629/3d%20printer/3d3.jpg https://dl.dropboxusercontent.com/u/104809629/3d%20printer/3d4.jpg https://dl.dropboxusercontent.com/u/104809629/3d%20printer/3d5.jpg https://dl.dropboxusercontent.com/u/104809629/3d%20printer/3d6.jpg https://dl.dropbo
19:04 rue_shop3 there sure are a lot of wood workers making repraps
19:04 Jak_o_Shadows I hope you're not including me in that
19:49 rue_more for the most part, I banned wood and cardboard from my projects long ago
19:49 katsmeow-afk o
19:50 katsmeow-afk dimensionally unstable?
19:50 rue_more moistureally unstable
19:50 rue_more random structural failure
19:50 rue_more bad fatuige properties
19:50 rue_more excess flamability
19:50 katsmeow-afk bendy
19:50 rue_more :)
19:51 rue_more I dont want to sleep kat
19:51 rue_more what can I sell computer power cords for on ebay, given shipping from canada
19:52 katsmeow-afk a negative number, or bulk batches, give your postal service up there
19:52 rue_more http://www.ebay.ca/itm/Lot-of-20-Computer-PC-Monitor-3-Prong-Power-Cord-Cable-/350432501920
19:52 rue_more thats like, almost $1 ea
19:53 katsmeow-afk plus $12 shipping
19:53 katsmeow-afk plus $6.52 import charged into Canada
19:55 rue_more I think I can get $1 ea
19:55 rue_more thats enough
19:55 rue_more (+ shipping)
19:57 katsmeow-afk got any 18-2 with usa plugs on the ends?
19:58 rue_shop2 they all are
19:58 rue_shop2 50+ lbs of them
19:59 katsmeow-afk you said your are 3-wire
19:59 rue_shop2 and 30 dvi cables
19:59 rue_shop2 and 75 usb AB cables
19:59 rue_shop2 oh, 2 wire, hmm no
20:01 tsmeow-afk debates buying who extension cords and cutting off the female ends, or buying spools of 18-2 and new cheap easy-attach male ends for
20:01 katsmeow-afk who-whole
20:05 katsmeow-afk i ask walmart search for extenson cords priced under $2, it presents me with selections of photographs
20:06 katsmeow-afk so i ask for under $10, it presents toilet paper, hoodies, and towels
20:07 rue_shop2 hmm
20:12 katsmeow-afk $1.47 , 6ft, 18-2, lop the female ends off
20:59 codepython7771 can someone point me to a good tutorial for different types of motors and how to control them?
21:00 tsmeow-afk looks sternly at everyone here for not having that data available,, and no bot to offer it ei
21:01 katsmeow-afk praps we can whittle it down....... ac or dc?
21:01 codepython7771 katsmeow-afk: dc
21:01 katsmeow-afk series wound, compund wound?
21:01 katsmeow-afk compound
21:01 katsmeow-afk or PM
21:02 codepython7771 those keywords i'll have to read up on
21:02 katsmeow-afk ah, there's a start, reading up on the correct buzzwords
21:02 katsmeow-afk wikipedia has a good description of them
21:03 katsmeow-afk car starters and golf carts are usually series wound
21:03 katsmeow-afk electric wchairs can be series (not usually) or PM, for flatter torque and not so much burning rubber take-offs
21:04 codepython7771 katsmeow-afk: which wikipedia link? Thanks.
21:04 katsmeow-afk ummm
21:04 tsmeow-afk tries "electric mot
21:05 katsmeow-afk https://en.wikipedia.org/wiki/Electric_motor <<== which also has links to the various types
21:11 codepython7771 katsmeow-afk: Thanks a lot. Reading now.
21:12 codepython7771 katsmeow-afk: would be nice if this was in a video being explained by a human :)
21:13 katsmeow-afk oh
21:19 codepython7771 katsmeow-afk: History = Sleep inducer :)
21:19 katsmeow-afk skip the parts that do not apply
21:20 katsmeow-afk hacking the motors can change things too, for instance you can make a repulsion-induction motor run on dc, they are quite powerful beasts
21:23 codepython7771 katsmeow-afk: I know servos are used in quadcopters. I'm mainly interested in building small robots. Seems like there is a huge list of type of motors. What other motors are used in small robotcs? a robotic arm or a rc car etc?
21:24 katsmeow-afk steppers are ac motors, strictly speaking, and generally 3-phase
21:24 codepython7771 i thought steppers work with dc as well -no?
21:24 katsmeow-afk robot arms tend to get powered with whatever the designer prefers or can afford
21:24 katsmeow-afk no
21:24 codepython7771 whats the best motors for these kind of applications? low energy, high torque, high precision?
21:24 katsmeow-afk a driver may accept dc and make the ac for the motor
21:25 codepython7771 i see
21:25 codepython7771 whats the difference between self commutated and externally commutated?
21:25 katsmeow-afk small servos usually have the electronics n them to take DC and a control signal to make ac to drive the motor
21:27 katsmeow-afk a brushed motor has brushes do the "commutation"
21:28 katsmeow-afk in many smaller motors where you want themt o last forever, with no brushed, a signal if made to toggle electronics which switch the electric currents
21:29 katsmeow-afk like an optical toothed rotor, or a magnet on the rotor
21:29 katsmeow-afk with electronics switcing, you can change the timing of the switching with software
21:30 katsmeow-afk with burshes, you must physically move the brush holder assy to change the timing
21:30 katsmeow-afk (which is possible, some motors are built to do that while it's running)
21:31 katsmeow-afk the wording "internal" vs "external" is a lot fuzzy to me, because some motors have the non-brush electronics built into them
21:31 Triffid_Hunter codepython7771: quads use BLDCs which is a silly term for low voltage permanent magnet synchronous AC motors
21:32 Triffid_Hunter steppers are 2-phase AC, BLDCs are 3-phase :P
21:33 katsmeow-afk well, cept for the 3-phase steppers i have seen
21:33 Triffid_Hunter codepython7771: what application? BLDCs have excellent power density, the cost is increased electronics complexity
21:33 Triffid_Hunter katsmeow-afk: there are apparently 5-phase steppers around
21:33 tsmeow-afk
21:34 katsmeow-afk PM magnets may have 1/2 the max torque of a series wound, and suffer magnet damage if overheated
21:37 Triffid_Hunter conversely, series wound requires slip rings to the rotor, which limits power density because brushes wear rapidly with high currents
21:37 Triffid_Hunter also the brushes must be periodically replaced rather more often than the end bearings
21:38 katsmeow-afk not slip rings, but commutator bars
21:40 Triffid_Hunter I've been waiting for something that combines the advantages of mosfets and IGBTs to make BLDCs practical for EV use
21:40 Triffid_Hunter currently, IGBTs can handle the voltage and current, but their typical Vce(sat) of 2-3v is a significant power loss
21:40 tsmeow-afk ag
21:41 Triffid_Hunter a device with Vf of 0.5v at 500A and ability to handle 1.2kV would be amazing
21:43 katsmeow-afk i spose you might initially close the switch with an IGBT and then engage a massive number of regular transistors to get the loss under a volt
22:01 Triffid_Hunter katsmeow-afk: the problem with BJTs is they don't share current, so you need to add emitter resistors.. another problem is the large base current required because the Hfe of high power devices is low
22:02 tsmeow-afk ag
22:03 katsmeow-afk the base current may be 10% of the losses you have now with the lone IGBT
22:03 katsmeow-afk smart current monitoring can be used to modulate the base drive, and lower the emitter resistor valuse to near nothing
22:04 katsmeow-afk but i agree, 100 amps @ 1v for base drive would be a miserable task
22:04 katsmeow-afk efficency would be horrible, no matter whatone designs, i imagine
22:06 Triffid_Hunter nah, buck switcher would work, modern CPUs have power profiles like that
22:06 katsmeow-afk yeas, but you'd lose as much in the psu diodes as used in the BE of the pass transistors
22:07 Triffid_Hunter diodes? at 100A? synchronous :P
22:07 katsmeow-afk synchronous mosfet switching would help
22:07 katsmeow-afk heh
22:20 codepython7771 whats a BJT?
22:20 katsmeow-afk bipolar junction transistor - a regular transistor
22:20 codepython7771 Triffid_Hunter: I am mainly interested in what a lipo can drive? - mostly for low power applications (< 20v, 10Ah)
22:21 Triffid_Hunter codepython7771: lipos are crazy, can easily set fire to things if you short one
22:21 Triffid_Hunter but they're also awesome, no need to worry about brownouts even with big motors
22:21 codepython7771 Triffid_Hunter: I also have a lead acid :) 2Ah
22:22 codepython7771 Triffid_Hunter: so DC motors, looking for low energy, lightweight - high torque, high precision movement :)
22:22 Triffid_Hunter codepython7771: precision comes when you slap encoders on them
22:23 katsmeow-afk or use steppers with small angular movement
22:23 katsmeow-afk steppers aren't so great for making efficient amounts of hp tho
22:25 codepython7771 how do people make 0.01 degree movements? can one do that using servos?
22:25 katsmeow-afk gears
22:25 Jak_o_Shadows codepython7771: I still question your need to make 0.01 degree movements
22:26 codepython7771 Jak_o_Shadows: I don't need it yet, just trying to understand things. I'm sure you needed that in your 3d printer design?
22:26 Jak_o_Shadows er, I just followed the prusa i3 parts
22:36 codepython7771 Jak_o_Shadows: do you know of a good introduction video to dc motors and their controls?
22:37 Jak_o_Shadows nup