#robotics Logs

Jul 22 2015

02:04 deshipu ball ^^
02:04 deshipu oops, he left
02:04 deshipu Mushrooshi: I think it was me
02:04 deshipu Mushrooshi: but I think Battlebots are quite fake too
02:04 Mushrooshi im around
02:04 Mushrooshi deshipu: yeh it was you
02:05 Mushrooshi im not a fan of a lot of the reality TV-esque dramatization inbetween the battles in ABC's battlebots but the fights, if all the competitors words (including respected veterans) is to be taken, the fights are still authentic.
02:06 Mushrooshi i dont care for the reality/drama stuff, I just want the builds, bots, and battles.
02:06 Mushrooshi but. i guess if thats what you're considering, then Combots instead of Battlebots or Robot Wars.
02:07 deshipu I wonder if there is any realistic manga about building robots
02:07 hack i just started building my first one
02:07 deshipu I mean, not a Pokemon ripoff, but something that discusses actual challenges
02:08 hack not for battles, i'm just getting tiered of waiting on them to release NAO
02:08 deshipu in the style of Addicted to Curry or Bakuman
02:08 Mushrooshi about general robotics, or the robot combat sport specifically?
02:08 hack so i might as well make my own, for what i'd spend on that
02:08 Mushrooshi ohhh yea, I got a few volumes into bakuman.
02:09 deshipu there is a series of educational "mangas" released by No Starch Press
02:10 deshipu maybe something in that vein
02:12 Mushrooshi i actually didnt realize combots posted their matches until now
02:13 Mushrooshi and even if its probably too "dry" for television.
02:14 Mushrooshi i think combots presentation style i prefer over battlebots
02:14 Mushrooshi robotwars was able to combine the TV theatrics and charisma while still balancing having good pit interviews, talking about build progress, and ofc enough actual fighting too
02:18 deshipu I would really prefer there to be a little more tactics involved
02:18 deshipu for instance, if there were obstacles on the arena, or uneven terrain
03:46 LiohAu rue_house: you were talking about ROS and URDF ? => Robot Operating System, URDF => Unified Robot Description Format
04:55 Jak_o_Shadows anyone know of a linkage system that will take straight line tension and convert it to rotational motion?
05:41 deshipu Jak_o_Shadows: something like they have on the top servos here? https://www.youtube.com/watch?v=frTmPdNzVPI
05:51 Jak_o_Shadows Note quite. I have a back and forward linear motion that I want to convert to turning a ratcheting set of gears.
05:53 Jak_o_Shadows At the moment i'm thinking a rack and pinion, with the system being lifted on the return stroke to allow for the rack to be pulled back by a spring
07:59 Tom_itx Jak_o_Shadows, it's called a pistion engine
08:00 Tom_itx piston
08:00 Jak_o_Shadows Mmmm, yeah.
08:00 Jak_o_Shadows I really don't quite want to use rigid links though
08:00 Tom_itx rope wrapped around a pulley
08:00 Tom_itx several times
08:01 Tom_itx used for old auto radio tuners etc
08:03 Jak_o_Shadows I think I get you.
08:05 Jak_o_Shadows So it would be a loop? Then I get the one-way rotation I want because of trickery in the pulley base.
08:05 Tom_itx http://www.instructables.com/id/Fix-a-vintage-radio-tuner-string/
08:06 Tom_itx https://www.youtube.com/watch?v=1KfVQEAKawo
08:06 Tom_itx about a minuite in
08:09 Jak_o_Shadows Ok, I'm going to disagree with that being vintage, as I have one right under my desk, which I am meant to be fixing the string with (I have given up as it's fiddly)
08:09 Jak_o_Shadows Also, yes, that is what I was imagining.
08:10 Jak_o_Shadows But to go back a step (which is what I should have done first): I need to convert regular oscillatory linear motion into a (different scale) only increasing linear motion.
08:12 Jak_o_Shadows But I can imagine this working
08:25 Tom_itx lever with an off center pin
08:26 Tom_itx will give you any ratio you want
08:26 Tom_itx but will reverse the direction
08:28 Tom_itx |
08:28 Tom_itx |
08:28 Tom_itx |------o-------------|
08:28 Tom_itx |
08:28 Tom_itx |
08:28 Tom_itx |
08:29 Jak_o_Shadows But one of them is oscillatory, while the other is more incremental
08:29 Tom_itx mmm
08:31 Jak_o_Shadows So far i'm thinking a system like this: https://dl.dropboxusercontent.com/u/104809629/oscillatory_linear_to_rot.PNG
08:31 Jak_o_Shadows the left hand gear is connected to the oscillatory linear as you suggested, so it rotates back and forth
08:32 Jak_o_Shadows but on the back-stroke, the gears slip, and then get pulled back by the spring
08:32 Tom_itx like a ratchet
08:32 Jak_o_Shadows yeah
11:15 codepython777 anyone here?
11:16 SpeedEvil no
11:18 codepython777 hi SpeedEvil :)
11:18 codepython777 what are you working on today?
11:19 SpeedEvil Blackcurrent cages
11:26 codepython777 SpeedEvil: What was your last robotic project? :)
11:28 SpeedEvil nothing recent
11:30 codepython777 SpeedEvil: any guess on what motors this -> http://rmp.segway.com/about-segway-robotics/segway-rmp440-le-and-se/ -> is using? What manufacturer?
11:30 SpeedEvil Brushless DC Drive Motors: Four independent and fully redundant drive motors
11:31 codepython777 I was looking for the more detailed specs -> rpm / manufacturer? voltage? current draw? specs
11:32 SpeedEvil It's not a very interesting question.
11:32 SpeedEvil you're not going to be able to buy them cheaply
11:32 SpeedEvil and they may well be custom
11:32 codepython777 SpeedEvil: who makes good brushless dc drive motors?
11:33 SpeedEvil If you care about price - the answer is pretty much 'get them made to your spec with appropriate QC im china'
11:34 SpeedEvil I would expect the motors to be in the range of 300W or so per axle
11:35 codepython777 SpeedEvil: I'm looking to build a good quality robot - probably need 8 motors - will build 2 or so. So I could pay a premium for someone who can deliver it in the US / and stand by their quality. Are there any companies like that? I'm looking to build something less powerful than the one I showed you. 30W motors would be nice - or around that range.
11:37 SpeedEvil There are 'proper' motor suppliers.
11:37 SpeedEvil They are not cheap.
11:37 SpeedEvil http://www.maxonmotor.co.uk/maxon/view/content/index
11:38 codepython777 US ?
11:38 SpeedEvil They are I think a US company
11:38 SpeedEvil Expect to pay $300 or so for a motor, I'd guess
11:39 SpeedEvil your other option is pretty much to find motors designed for something else that will work for you.
11:39 SpeedEvil For example, cordless tools may work OK
11:39 SpeedEvil Or you can take RC toy motors, derate them, and add appropriate gearing
11:39 codepython777 cordless tools use brushless dc motors?
11:40 SpeedEvil Some do.
11:40 SpeedEvil Why brushless?
11:40 codepython777 SpeedEvil: That company - maxon - says Swiss made - and the website says ".uk"
11:41 codepython777 SpeedEvil: More reliable? better control?
11:41 SpeedEvil They have for example sold to NASA and stuff
11:41 SpeedEvil they are premium motors with actual specs and guarantees.
11:43 SpeedEvil http://www.maxonmotor.com/maxon/view/news/comp_00000PGP
11:43 codepython777 i see
11:47 SpeedEvil http://www.hobbyking.co.uk/hobbyking/store/__9377__Turnigy_480S_BL_Inrunner_Motor_w_Impeller_1500kv.html - for example. This is nominally a 1000W or so motor. However, used at 50W power output at 5V or so, it will remain cold. You then need a 7500RPM->120RPM or whatever gearbox.
11:47 SpeedEvil This is well within the range of a small double toothed belt drive as found in lawnmowers
12:04 codepython777 SpeedEvil: I am buying turnigy lipo 6000mah and they never seem to be equal in the 3 cells for voltage, after recharging 1 or 2 times. Any ideas what causes this? Any recommendations for lipo? Lifepo4 batteries?
13:28 anonnumberanon codepython777, did you balance-charge the battery?
17:32 zhanx evening
17:33 SpeedEvil e
17:33 zhanx sup SpeedEvil
17:33 SpeedEvil https://www.youtube.com/watch?v=NMbM-ERy2Lk is a picture of a man inside a waterballoon
17:33 SpeedEvil other than that, not much
17:34 zhanx pcb layout for me
17:35 SpeedEvil I've also been wondering about cheap RC belt/chain drives using RC inrunner motors for ~500W or so wheelmotors
17:37 anx is thinking about researching light b
17:37 zhanx the wireless type
17:38 SpeedEvil All lightbulbs are wireless in one way
17:38 SpeedEvil Light doesn't go through wires
17:38 SpeedEvil esp8266+
17:38 zhanx wireless control of them, to a relay i am doing
17:39 zhanx but i am thinking to either not use a smart bulb at all and just use that combo
17:39 zhanx but the dimming of them is a plus
18:42 drac_boy hi
18:42 drac_boy slight offtopic but thought I'll still try ask here nevertheless: any particular pro/con to running four 6V batteries instead of two 12V batteries for a 24V output to run motors&lights with? not worried about weight n size on this one
18:45 zhanx discharge rates?
18:48 codepython777 drac_boy: which particular battery are you using?
18:48 codepython777 drac_boy: isnt it simpler to maintain one battery than 4 - and worrying about which one is bad out of the 4...?
18:53 Loshki codepython777: the bigger battery is really just more cells in the same package, so while it's easier to "maintain", one bad cell means the whole thing has to be replaced, unless you plan on swapping individual cells, which is fiddly.
18:54 Loshki drac_boy: Also, if you use lithium, you have to balance charge them.
18:55 orlock Blergh
18:55 orlock Somebody slap me with a motivational stick
19:00 drac_boy I was thinking of lead acid due to cost and supply but mm ty
19:28 codepython777 Loshki: I'm still looking for a dependable manufacturer for large lithium batteries (18v - > 5Ah)
19:28 codepython777 Loshki: I tried Turnigy so far - pretty bad
19:35 Tom_itx ask tesla
19:41 Loshki Tom_itx: I thought Teslas used NIMHs
19:42 Loshki codepython777: check out some of the RC forums, although I don't think they use the larger batteries much.
19:43 Tom_itx not sure
19:55 codepython777 Loshki: li-ion = tesla
19:55 codepython777 Tom_itx: most of these custom jobs are not available to the public for re-configuration
19:56 anonnumberanon codepython777, apparently this brand/model is top quality http://www.buddyrc.com/glacier-35c-5300mah-5s1p.html
20:04 codepython777 anonnumberanon: i've never heard of glacier. Did hear about A123
20:07 codepython777 anonnumberanon: seems like these guys sell good stuff
20:08 anonnumberanon codepython777, when i was doing research on quadcopter batteries this is the one i found to be the best but we already have a few other batteries and didnt' need to order anything
20:09 codepython777 anonnumberanon: do you know how many recharges do these batteries last?
20:10 codepython777 I am currently using 6000mah batteries. These goto only 5300mah...could live with that though.
20:10 codepython777 anonnumberanon: what esc did you use for the quad?
20:13 anonnumberanon codepython777, lemme check
20:14 anonnumberanon codepython777, this one: http://www.ebay.com/itm/RC-Turnigy-AE-30A-Brushless-ESC-/251611654269?pt=LH_DefaultDomain_0&hash=item3a9539287d
20:16 codepython777 anonnumberanon: pixhawk then? or somethign else?
20:18 anonnumberanon codepython777, I used an Arduino Uno and the gy 521.
20:18 codepython777 anonnumberanon: if i want to control a brushed dc motor (> 15W) using uno, what do i need?
20:20 codepython777 anonnumberanon: 18v / stall current = 30A - no load = 0.5A -- something like that
20:24 anonnumberanon codepython777, for a quadcopter?
20:24 anonnumberanon on quadcopter we use brushless
20:26 codepython777 anonnumberanon: just for rotating a brushed motor
20:26 codepython777 for quad you use brushless , hence the esc . How does the ESC talk to the uno?
20:30 anonnumberanon codepython777, you use a BEC for brushed I believe. Haven't done it. I just ran a motor once straight from the arduino but by sending a pwm into. The arduino cannot send a lot of current so only small motors at low speeds.
20:34 anonnumberanon codepython777, look up H Bridge to make the motor turn both ways.
21:05 codepython777 anonnumberanon: need to find myself some h-bridges
21:06 anonnumberanon codepython777, yeah, and then a way to change the speed of rotation, I'm not quite sure how to do that yet.