#robotics Logs

Nov 04 2015

00:40 anonnumberanon thoughts?
00:45 adam789654123 hey anonnumberanon
00:45 adam789654123 unfortunately i cant help you with that
03:33 anonnumberanon rue_bed, the optocoupler is your power supply are to protect the computer?
03:46 deshipu veverak: what was that .cz shop you are buing modules at?
03:46 veverak which kind of ?
03:46 veverak or...
03:46 veverak http://wiki.base48.cz/Suppliers
03:46 veverak deshipu: ^^
03:49 deshipu hmm, I need pololu a-star
03:50 deshipu veverak: none of these, you looked for an arduino nano
03:50 verak ordered arduino nano from c
03:50 deshipu yeah, but you looked at the local shops first
03:50 deshipu nevermind
03:51 veverak anyway, they got it on hwkitchen.com
03:52 deshipu hmm, weird, didn't come up in search
03:52 deshipu thanks
03:52 veverak also snailshop.cz
03:52 veverak also postavrobota.cz (seems lowest price here)
03:53 deshipu pololu a-star?
03:53 veverak also robotstore.cz
03:53 veverak nooo, I was speaking about 'arduino nano'
03:53 veverak sorry
03:53 veverak hmm, will google somethin
03:54 deshipu they have it in tme.eu
03:54 deshipu but 9eur shipping
03:54 veverak sound like tme to me
03:54 veverak :)
03:55 veverak http://www.snailshop.cz/257-a-star?p=2
03:55 veverak deshipu: ^^ ?
03:56 deshipu awesome
03:56 veverak so far 'search' for cz shops usually sucks
03:57 veverak better using google: site:<...>
03:57 deshipu they want me to agree to some stupid terms
03:57 deshipu google, I mean
03:57 veverak I see
03:58 deshipu so I use other people as proxy ;)
03:58 veverak !!! :)
04:00 deshipu for some reason reading anything in Czech makes me feel better
04:01 deshipu hmm, they only ship to .cz
04:01 deshipu ok, tme it is then, but I need to order some more parts
04:14 veverak hmm
04:14 verak started to produce code for RGB
04:14 veverak withou owning one
04:14 veverak nah, can't test it :/
04:15 acetoline is there a commercial robotics platform with big wheels and chassis off the ground?
04:16 deshipu acetoline: I'm sure there is
04:17 acetoline really
04:21 acetoline which one
04:26 deshipu no idea
04:29 veverak now
04:29 veverak I need to pick mic for vumeter
04:53 deshipu veverak: wow, the owner of snailshop just e-mailed me that he can ship to Poland manually
04:57 veverak that's called customer support :)
04:59 deshipu that's called desperate seller
05:00 deshipu ;)
05:00 veverak :D
05:00 deshipu sadly I will get it from tme
05:02 deshipu my next keyboard is going to be transparent, and this module has a white pcb ;)
05:02 veverak :D
05:10 veverak http://robotstore.cz/obchod/arduino/lcd-displej-1602-klavesnice-keypad-shield-arduino-stit/
05:10 veverak looks cool for my project
05:10 veverak but nah, have to figure out what resources I will have after installing it
05:11 verak needs to use i2c on ard
05:11 deshipu nah, you can do 8 or 4 bit parallel communication with this
05:11 veverak ?
05:11 verak doesn't fo
05:11 deshipu that chip
05:11 deshipu it supports i2c and two parallel modes
05:12 deshipu i2c is a bus, you can have multiple devices on it
05:12 veverak oh, yeah
05:12 veverak hmm
05:12 veverak nah, will try it anyway and if i2c will be too busy ...
05:12 veverak well, I will worry about it AFTER it happens
05:13 veverak :)
05:13 deshipu if you have 5 free pins, you can do the parallel comm
05:15 veverak well
05:15 veverak on the other side, google says this LCDs can be problematic
05:15 veverak well, let's search more
08:55 maiden I love chinese internet :D you do net get those annoying mails and such..
09:36 rue_house problematic how?
11:21 anonnumberanon rue_house, the optocoupler in your power supply are to protect the computer, correct?
16:59 LiohAu_ what material would you recommend to build the underwoord of a torso that could support more than 40kgs? carbon fiber?
16:59 ohAu_ alumini
16:59 Hyratel LiohAu, what
16:59 Hyratel phrase differently
17:00 LiohAu_ well, you know inside every robot, there are motors, electronics etc.. and there is the structure part
17:01 LiohAu_ (i'm not talking about hubs for the motors for instance)
17:02 LiohAu_ with pictures it will be more clear. http://emerge.asu.edu/wp-content/uploads/2014/01/9687272347_f26e96b001_c.jpg < in this example, I talk about the black rod.
17:02 Hyratel the word is 'chassis'
17:03 LiohAu_ yes sorry.
17:03 LiohAu_ thanks :)
17:03 LiohAu_ so phrasing differently, what materiel would you recommend to build the chassis of a robot torso :)
17:03 LiohAu_ material*
17:04 Hyratel not enough information
17:05 LiohAu_ what did they use for this one : http://www.extremetech.com/wp-content/uploads/2013/07/atlas-front-back-640x353.jpg ? it does not look like carbon fiber, is it aluminium?
17:06 deshipu that is probably steel
17:06 LiohAu_ steel? isn't it too heavy?
17:06 deshipu it's strong
17:07 deshipu so you can use less of it
17:07 LiohAu_ I thought carbon fiber was in the strongest material
17:08 deshipu there are different kinds of strenght
17:08 deshipu in different axes, etc.
17:08 deshipu also, carbon fiber is quite expensive and easy to damage
17:09 LiohAu_ Hyratel: I can add one information: looking for a cheap method for prototyping
17:10 LiohAu_ but not as cheap as wood.
17:10 Hyratel why not?
17:10 Hyratel why not wood?
17:10 LiohAu_ I don't like wood.
17:10 Hyratel you're thin on details
17:10 LiohAu_ :P
17:10 Hyratel too bad, it's a very good way to prototype
17:10 LiohAu_ well I don't know what details do you want :P
17:11 LiohAu_ moreover wood supporting 40kgs i'll need massive oak?
17:11 deshipu cardboard \o/
17:11 deshipu depron \o/
17:11 Hyratel LiohAu, what
17:11 LiohAu_ for the plane part we are using honeycomb aluminium
17:11 Hyratel what are you doing
17:11 Hyratel what are you making
17:11 LiohAu_ flat not plane sorry*
17:11 Hyratel we have no specs on your requirements
17:13 LiohAu_ Well, Hyratel i'm building an arm, and once it's done i'll make a 2nd one. I want to fix these arms on a torso
17:14 LiohAu_ the arms are going to be heavy, and i'll "stress-test" them using huge payload, so I want a solid torso that does not break before the arms do.
17:14 Hyratel plywood
17:14 Hyratel I'm serious
17:14 LiohAu_ no, this is not serious :(
17:15 Hyratel yes
17:15 Hyratel 3/4" plywood
17:15 LiohAu_ wood is perfect for flat parts
17:15 LiohAu_ but my issue is more on tubes and things like that
17:15 Tom_itx pvc
17:15 Tom_itx abs
17:15 Hyratel http://www.homedepot.com/p/Project-Panels-Sanded-Plywood-Common-23-32-in-x-2-ft-x-2-ft-Actual-0-703-in-x-23-75-in-x-23-75-in-1502014/202089017
17:16 LiohAu_ yes it's flat, and not pretty and I don't like :P
17:16 Hyratel http://www.homedepot.com/p/Unbranded-Particleboard-Panel-Common-3-4-in-x-4-ft-x-8-ft-Actual-0-734-in-x-48-in-x-96-in-165557/100040677
17:16 Hyratel too bad
17:16 LiohAu_ carbon fiber is not recomended?
17:16 Hyratel you're making a prototype
17:17 Hyratel prototypes are ugly
17:17 Hyratel deal with it
17:17 LiohAu_ a serious prototype
17:17 LiohAu_ not the 1st prototype
17:17 Hyratel no, it's a prototype
17:17 LiohAu_ let's say it's the final prototype :P
17:17 Hyratel then tell us more about it
17:17 LiohAu_ there's nothing more to say :( it's just that I hate wood
17:17 Hyratel only reason you should not be able to tell us more about a final prototype is if you're under NDA for the details
17:18 LiohAu_ no i'm not, i'm working alone
17:18 LiohAu_ but I don't know what to say
17:18 Hyratel erverything
17:19 Hyratel how big is it - how long are the arm segments - how much should it lift - what kind of degrees of freedom does it need?
17:19 LiohAu_ ok, I plan to make a kind of scara arm with 3 dof
17:20 LiohAu_ Z translation/rotation on the shoulder, and Z rotation on the elbow
17:20 LiohAu_ after the forearm, I don't know yet (I will probably play with a 3d printed hand)
17:20 Hyratel there we go. useful information
17:20 Hyratel 3/4" plywood
17:20 Hyratel or 2cm, depending on location
17:21 Hyratel / availability
17:21 LiohAu_ well the wood is easy to manipulate for horizontal parts
17:21 Hyratel and thick plywood, you can screw into the edge of
17:21 LiohAu_ but for vertical you have to use bolts and nuts
17:21 Hyratel so?
17:22 Hyratel I fail to see how that's an objection
17:22 LiohAu_ and that looks wobbly
17:22 Hyratel it's cheaper by far than welding steel
17:22 Hyratel ...
17:22 Hyratel if it's wobbly it's your own damn fault
17:22 LiohAu_ sure, I can't afford to buy welded steel
17:22 Hyratel and carbon fiber will be even MORE expensive
17:22 LiohAu_ but I was thinking about carbon fiber tubes, looks like they are sold at 50€ for 1meter
17:23 Hyratel Aluminum rail has to be bolted together
17:23 Hyratel ...
17:23 Hyratel you really are a dunce
17:23 LiohAu_ :D
17:23 LiohAu_ yes I have aluminium beams, and that's not perfect either :P
17:24 Hyratel you can get a 4'x8' sheet of 3/4" 9or maybe 2cm) for ~ $30
17:24 LiohAu_ things like this looks really easy to use : https://www.servocity.com/html/carbon_fiber_tubing.html#.VjqN94SsgTA
17:24 LiohAu_ and in my budget
17:24 Hyratel the price adds up fast
17:24 LiohAu_ and more durable/reusable than plywood
17:24 Hyratel I call BS to that
17:25 LiohAu_ BS?
17:25 LiohAu_ bullshit?
17:26 LiohAu_ maybe pvc tube can be cheaper than carbon ones and solid enough for my use case.
17:26 Hyratel it'll be bendy
17:26 Hyratel you can Design-a-stiffness with plywood
17:27 Hyratel you'll have a lot of Flex Slop in your positioning with PVC
17:29 LiohAu_ ok understood i'll seriously consider plywood :P
17:29 Hyratel yeah, youc an make 3D structures fairly simply with right angle butt-joints with thick plywood
17:46 LiohAu time to sleep. Thanks Hyratel for the advices
18:04 mbrumlow going to take it off line in a about 20 min (take it home and fix some things on it.) So if anybody wants a last chance today to roam the office
18:05 mbrumlow http://pluto.brumtopia.com:8080/indexl.html
20:35 ead how dose one interprate ≤ 0.3g· mm/kg
20:36 ead the spec is the minimum unbalance on a shaft that a balancer machine can get to
22:06 ace4016 micron
22:06 ace4016 maybe?
22:07 ace4016 hrm...
22:08 ace4016 wiki seems ot hint it's the mass * radius imbalance; that term is probably saying that's the mass imblance per kg
22:11 eadthem so .3 grams per kg of mass at 1mm distance
22:11 eadthem ?
22:11 ace4016 permissible redidual unbalance...
22:11 ace4016 residual*
22:13 eadthem dam where did i put that link
22:14 ace4016 seems to be mass(unblanace)*radius/mass(rotor)
22:14 ace4016 http://www.irdbalancing.com/downloads/techpaper1balqualityreqmts.pdf
22:14 ead http://jp-balancer.en.alibaba.com/product/244511496-205884004/Belt_Drive_Balancing_Machine.html
22:15 eadthem i seam to of opend more than 1 client :p
22:15 eadthem anyhow thats the link
22:15 ace4016 are you the same as ead? :P
22:15 eadthem ead short for eadthem
22:15 eadthem also coarsco and rainow
22:17 ace4016 yea, so basically i think it's the minimum achievable unbalance you can achieve, per mass of the rotor
22:17 eadthem so anyhow we have that machine at work
22:17 eadthem only everything we do seams to spit out random data
22:18 ace4016 so i guess bigger rotors generally have a higher minimum than smaller rotors
22:19 eadthem so what we get is .002 to .010 grams of adjustment at some angle on each side
22:19 eadthem or thats what it says
22:20 eadthem the rotor weighs prob about 2 pounds, and the adjustment points are about 35 to 40mm radius from center
22:20 eadthem i was just exploring, what if thats because were alredy so balanced the machine cant see the offset
22:21 eadthem so if the minimum is ≤ 0.3g· mm/kg
22:22 eadthem how do i do the math to see what the minimum is at 40mm from center
22:22 eadthem ?
22:22 ace4016 so .2721 g-mm is the best it says you can do
22:22 ace4016 i think...
22:23 eadthem grams at 1mm from center?
22:23 ace4016 i don't know; you'll probably want to ask one of the techs or mechEs :P
22:23 ace4016 this is the first time i've seen this stuff
22:24 eadthem ya i mistakenly voulnteered to look at it, after engineering said they couldnt get it to work.
22:24 ace4016 lol
22:24 eadthem as i specialise in the difficult robot stuff.
22:25 ace4016 lets see...mass of imbalance * radius of mass...
22:25 ace4016 or, sorry
22:25 eadthem i dont see it being .3 grams at 1mm
22:25 ace4016 radius of imbalance
22:26 eadthem im going to pm you a photo
22:26 ace4016 so if the adjustment point is 40 mm...and the object is .907 kg....
22:26 eadthem That photo is after i hooked the sensors up to a oscope
22:26 zhanx evening eadthem
22:26 eadthem evning
22:26 eadthem green channel is the once per revolution RPM pulse,
22:27 eadthem pink is left pizoelecric strain guage
22:27 eadthem blue is right
22:27 eadthem i have i think a 4 ounce neodyinan magnet stuck to the rotor on the right side
22:27 eadthem lets say 3-6 ounce
22:28 eadthem Looking at that, im seeing, OMG the signal is noizy (Vibration)
22:28 eadthem and that i cant see it noticeing more than say 2 ounces at 40mm swing
22:29 eadthem because 4 ounces barely shows up
22:30 ace4016 hrm...so you should see a much bigger mass unbalance
22:30 ace4016 about 5001 g*mm/kg
22:30 ace4016 assuming the rotor was balanced from the get go
22:31 eadthem thats about 5001 g*mm/kg?
22:31 eadthem ya
22:31 eadthem we havent gotten a balanceing machien to work right yet
22:31 eadthem the other one is to small, and i dont trust its data with something this big
22:31 ace4016 maybe call the OEM and see if everything is set up properly?
22:32 eadthem the small machine seamed ok when running low RPM's
22:32 eadthem say 300RPM
22:32 ace4016 know the max weight it can handle?
22:32 eadthem that data was captured at 900RPM's
22:32 ace4016 actually, nevermind. says on that page
22:33 eadthem http://jp-balancer.en.alibaba.com/product/60029570383-215937847/JP_0_3_1_1kg_Self_Drive_and_Belt_Drive_Balancing_Machine.html
22:33 eadthem thats the small machine
22:33 ace4016 .907kg is less than their lowest max (1.6kg)
22:33 eadthem i cant see this one doing less than 1.6kg
22:33 eadthem i dont think this rotor is big enough to do on it
22:33 eadthem maby
22:34 eadthem sadly we have the 380 mesuring system
22:34 eadthem the one without a computer
22:36 ace4016 i'd probably check to make sure the unit was isntalled correctly and calibrated properly
22:36 eadthem we did the calabration thing, a couple of times now
22:36 eadthem dont know
22:36 ace4016 supposed to enter in any data about the part in the machine?
22:37 ace4016 like telling it the adjustment points?
22:37 ace4016 mass of the rotor, etc?
22:37 eadthem the biger one you enter distance between bearing and left correcton
22:37 eadthem left to right correction distance
22:37 eadthem and right correction to right bearing
22:38 eadthem and then the Radius of the left and right correction
22:38 eadthem thats it
22:38 ace4016 well, this has all taught me something about how the propeller balancing equation works out its thing at work :P
22:38 ace4016 hrm..
22:38 eadthem ya that doc you have i might print out and quietly leave on the machine for the next guy
22:38 ace4016 lol
22:38 eadthem the small machine you calabrate each rotor profile before you use it
22:39 eadthem calabration is you add a weight to the left, and tell it the weight and angle from 0 in rotation
22:39 eadthem spin it up, and then the same for right side, and then just the rotor with no weight
22:39 eadthem both calabrate the same.
22:40 ace4016 hrm
22:40 ace4016 good luck my friend :P
22:40 eadthem but the big machine you dont have to calabrate each rotor. just enter the dimentions
22:40 eadthem :p
22:40 eadthem thanks
22:40 ace4016 i think i'll have to read up on this stuff more in the near future though for certain planned projects
22:41 eadthem i can say,
22:41 eadthem if the rotor had a place to mount it between 2 needle bearings
22:41 eadthem thats easy
22:41 eadthem if the offset is large enough to make the heavy side go down
22:48 eadthem thanks
22:48 eadthem im off to bed
23:12 slidercrank https://i.imgur.com/V2u11ZP.gifv
23:20 rue_house hhahahahahahahahahaha
23:21 rue_house I LOVE IT!
23:22 rue_house https://www.youtube.com/watch?v=vn91XQST9qc