#robotics Logs

Mar 25 2013

00:00 MrCurious and can a single AVR/msp/pic handle 2 motors + 4 bit graycode, and what rpm it would bog the processor down at
00:00 MrCurious just playing devils advocate
00:01 summersault maybe there is an algorithm for that
00:02 summersault and you only have to read at beggining, then you can read the "changes" only
00:02 Triffid_Hunter MrCurious: you need to read the graycode more than twice per rev.. also when you convert rpm to microcontroller speeds you realise that the micros can happily keep up while the motor self destructs
00:02 MrCurious if you havent bought your motors... i got these < $10 ea
00:02 MrCurious http://www.robotroom.com/FaulhaberGearmotor.html
00:02 MrCurious and they were easy to make possitionally accurate
00:03 MrCurious i was going to make a LOGO bot with them. program it in logo language... repeat 5 fw 10, rt 90
00:06 MrCurious http://www.goldmine-elec-products.com/prodinfo.asp?number=G16279
00:06 MrCurious $8 for a motor + gears + encoder...
00:13 rue_more instead do python
00:14 rue_more its easier
00:14 rue_more http://eds.dyndns.org/~ircjunk/tutorials/prog/python/learn_py.html
00:14 rue_more cause you can amke C moduels for it
00:15 rue_more yesno?
00:16 rue_more its a conversion of the apple logo book
00:18 MrCurious python is ok, but to be honest, it eaves me feeling dirty after i use it, like perl did, due to its lack of strictly defined function ins/outs
00:18 MrCurious its a dirty language
00:18 MrCurious always shower after using
00:18 rue_more like basic?
00:18 rue_more and logo?
00:24 MrCurious i prefer languages like java/c++
00:25 rue_more ah, you like the obfiscation languages
00:25 MrCurious python's indent based blocking sucks. if you paste code and lose the indent, then you have lost information
00:25 rue_more yea, that sucks about python
00:26 MrCurious although, i saw a simplecv presentation that just may seduce me over to the python side
00:26 MrCurious (that and i have been using it daily at work for 3 years)
00:29 rue_more dont be fooled, the python code is almost 1:1 what C code would be
00:30 rue_more more then once I'v used python examples to help me use library calls in C
00:30 MrCurious python is slower than c/c++
00:31 MrCurious doing native calls to the c libs is fast as c, but once you let python diddle with your data, and copy and what not, you feel teh pinch
00:31 MrCurious aw man, i am getting all get off my lawn to python again...
00:32 rue_more well dont tell me you code in java for speed
00:33 MrCurious no. code in java for sanity
00:34 rue_more hahah
00:35 rue_more no, I'm sure there is an application thats true for
00:36 MrCurious your a python fan eh?
00:36 zap0 snakes are awesome1111
01:15 Hukka "Python is not pastable", that's a new one
01:16 Hukka Better get a decent pasting service, then
01:35 LeelooMinai http://i.imgur.com/4dWrzWP.jpg <- I am trying to figure out what screws to use there. 6.6mm through holes - seems like M6, but that 0.6mm seems to make loose fit to me... Any tips?
01:36 RifRaf 1/4 inch
01:36 RifRaf is 6.35
01:37 LeelooMinai Right, but this is metric part - it would be weird if they expected imperial screws, no?
01:40 RifRaf guess so, or maybe they made it slightly larger than m6 in case you had 1/4, both should work unless you are going into a thread
01:41 RifRaf is it some kind of pillow bearing?
01:41 LeelooMinai Those are common CHinese parts that support ballscrews on both ends
01:42 LeelooMinai Hmm... don't you use those to make robots here or something? :)
01:43 RifRaf i make my own pillow bearings
01:43 RifRaf so you are just bolting it to something, the M6 or 1/4 does not appear to matter
01:44 RifRaf or use M6.5
01:44 RifRaf just gonna cost more
01:45 LeelooMinai Right, well, I was thinking that it should not be too "loose" or the part will move horizontally
01:45 LeelooMinai But maybe if the force applies to screws is right, it will not (?)
01:45 LeelooMinai apllied*
01:46 LeelooMinai BTW, whre do you guys buy such screws?
01:46 RifRaf with 4 x M6 i think you will be bending the ball screw before it moves
01:47 SorcererX some screws are annoyingly hard to find
01:47 RifRaf well m6.5 is a bit rere, i use the boltorium in town for most stuff, and aliexpress if I want something extra small or odd
01:47 SorcererX for instance, where I live anything <M3 has to be ordered online
01:48 LeelooMinai I checked those cap hex screws (I think they are called that) - they seem to be about 30 cents per one, or $2 for titanium ones - but those are a bit overkill:)
01:48 LeelooMinai on aliexpress*
01:48 RifRaf they have a section of the shop dedicated to screws and bolts, they however wanted $2 a peice for M2 nylock nuts, and found packets of 25 nuts for just a bit more online
01:49 LeelooMinai Hmm, I think I saw such tiny screws and washer,s nuts, etc. - nylon, polycarbon and steel on... what wwas it... I think cobbyking.com site - RC guys
01:50 LeelooMinai hobbyking.com(
01:50 RifRaf any rc place is way to much for small screws, i have al that i need now though
01:50 LeelooMinai I remember it was not bad
01:50 RifRaf yeah round head hex m6 would suit your application well
01:51 LeelooMinai http://www.hobbyking.com/hobbyking/store/__124__58__Hardware_accessories_-Screws_Bolts_Nuts.html
01:51 LeelooMinai Those prices are not too bad imho
01:52 Hukka Where would you buy small torx screws?
01:52 Hukka I wasn't aware of aliexpress, but they don't seem to have any
01:53 RifRaf yeah the prices seem ok for a small quintity i guess, they get me on shipping though normally
01:54 Triffid_Hunter hobbyking have an aus warehouse now.. not a huge amount of stock yet but growing all the time
01:55 RifRaf Hukka, salvage the right rubbish, but you are right they seem rarer, i'll ask in town next time i drive past the bolt shop
01:56 RifRaf would have some if you just need a few
01:57 Hukka I don't have a need right now, but in general I prefer them to other screw ends
01:58 Hukka cross (both pz and ph) are too slippery for my needs (no power tools), and hex requires a humongous endcap in the smaller screws
02:01 RifRaf Hukka, you getting a new or used robobiulder?
02:02 Hukka Used
02:03 Hukka The bioloid is used too
02:03 RifRaf SorcererX, yes M2 used to be easy to get in packs from dick smith over here, but they don't do electronics anymore
02:03 RifRaf recently got a bunch of m2 from aliexpress as the prices elsewhere were crazy
02:03 RifRaf Hukka, awesome
02:04 Hukka HA!
02:04 Hukka Guess who ran the doorbell just now
02:04 RifRaf postman
02:04 Hukka YES!
02:04 RifRaf quick, he never rings twice
02:04 Hukka Öh I already got it
02:05 Hukka Boy, this packet is banged up
02:05 Hukka Almost all of the top side is torn off
02:05 RifRaf cool, give us a demo when you get it going
02:05 Hukka Perhaps I should take some photos, in case something is broken
02:06 Triffid_Hunter shouldn't have accepted it if it's that bad
02:07 Hukka Triffid_Hunter: Wasn't a courier
02:07 Hukka Just normal post
02:07 Hukka It's pretty much take it or leave it
02:08 Hukka They would say that it came on the plane looking like that, and of course the Roal Mail would say it was fine when they loaded it
02:08 Hukka If it was one company dealing all the way the blame would be obvious
02:08 Hukka Anyway, I think it's fine still, if it has been decently wrapped
02:12 Hukka Ah, there was a smaller packet in it
02:12 Hukka Explains why the front didn't hold so well
02:24 Hukka Looking good
04:57 Hukka It's electrically working, but cannot walk
04:57 Hukka I guess I have to check the servos one by one
05:05 Rif Tom_itx,
05:06 Rif you know those faulhaber motors with the right angle gearbox, try plugging in negative from one to positive of other, and neg to pos
05:07 Rif just reversed the gearhead on one, was odd size small setscrew
05:07 Rif gonna use em for a small balancing bot
05:21 GuShH Rif: any experience with small reverse osmosis systems?
05:23 Rif nope, but need to look up the words to be sure
05:24 GuShH o.o
05:24 Rif i have a water purifier on my kitchen tap if that counts :)
05:24 GuShH single filter?
05:24 GuShH RO units have 4 or more stages
05:24 Rif well a single thing i replace
05:24 Rif k
05:24 GuShH the one I'm looking at is 5, I want a 6 stage one (with UV)
05:25 GuShH single ones are OK for some types of solubles but not really a complete filtration system
05:26 Rif yeah i just have bad tank water supply
05:26 Rif would not drink it, the taps block up all the time, so i filter what i drink, and comes out clear
05:26 GuShH mine sucks
05:26 GuShH hence why I want a RO unit
05:27 GuShH a bit expensive for me though but it's even more expensive to buy bottled water
05:27 GuShH thing is, 3 first stages have to be replaced every year
05:27 GuShH the last two every 3 years
05:27 GuShH 400 liter a day (small unit but plenty enough for drinking, cooking, pets)
05:28 GuShH the water here has a high content of iron and other salts
05:28 GuShH calcium ++
05:28 Rif yep the dirtier the more you have to replace the filters i guess, i am trying to do it every 3 months, but is cheap
05:28 Jak_o_Shadows1 Apparently the water here is bad.
05:28 GuShH So I've been buying drinking water by the 20 liters, doesn't last long at all
05:29 GuShH I've tried the tap water, it's not good. even after boiling it and making coffee, you can taste a huge difference
05:29 Jak_o_Shadows1 Never really know any different though
05:29 GuShH Jak_o_Shadows1: what do you mean?
05:29 Jak_o_Shadows1 Same sort of thing, metal salts and such.
05:30 GuShH I'm willing to spend a few 1000s if it means I don't have to buy any more water
05:30 GuShH even your clothes suffer from shitty water
05:30 GuShH the washing machine gets clogged up at times
05:30 GuShH I'll need to inline a filter to that sucker.
05:31 GuShH the one it comes with is just a thick membrane and it lets a lot through
05:31 Rif these are my filters http://www.clarencewaterfilters.com.au/products/R2-R2C-R2CB-Waterpik-Instapure-Replacement-Filter.html
05:31 GuShH they sell these water "softener" filters but they're not good if you've got big sediments, so you also need a sediment filter inline
05:31 Rif does it rain much there?
05:31 GuShH it's raining right now
05:31 GuShH but usually it's once a month if you're lucky
05:32 GuShH even if I collected the water, I'd need to RO it before I would dare drink it
05:32 Rif k, i like how out rain is still pure water
05:32 Rif our* , but we get too much
05:32 GuShH not sure I've got the required minimum water pressure upstairs though
05:32 Jak_o_Shadows1 Ours isn't quite that bad, but it's apparently bad enough that if you're used to rainwater, it's not drinkable
05:33 GuShH Rif: it can be pureish but once it hits whatever surface collects it.... it tends to get dirty
05:33 Jak_o_Shadows1 GuShH: Still better than bore water
05:33 GuShH I'm used to tap water in the city, it's chemically treated and it tasted OK
05:33 Rif yep during the last flood i gurneyed all the room and gutters, but is so much shit in the tank, need to get it out
05:33 Rif have a big syphon brush thing half made
05:34 Rif roof*
05:34 GuShH Jak_o_Shadows1: it is friggin bore water, not sure the depth.
05:34 Rif many around this valley are on bore water, its hard water but pretty good
05:34 GuShH the city uses bore + river afaik, mostly river now.
05:35 Rif have one here somewhere but never bothered to find it yet
05:35 GuShH lol
05:35 GuShH after RO it's better than most bottled water though
05:35 Jak_o_Shadows1 Ours is river, which is bad because it's fairly empty half the time, and rainfall in resovoirs
05:35 GuShH which is why I won't bother to get a deeper bore, way too expensive and there's always the risk it won't come out good
05:36 Jak_o_Shadows1 Rif: Send some more water down the murray eh?
05:36 GuShH Now if it were to dry out... I'll be pretty upset
05:36 Rif i thought even you guys have water these days Jak_o_Shadows1
05:37 Rif ima go catch me a murray cod over easter i hope
05:37 Jak_o_Shadows1 We have water, but only because it's rained for.
05:37 Jak_o_Shadows1 For some stupid reason water restrictions have been relaxed
05:37 GuShH You wouldn't believe it but I know someone with a 400 meter deep bore
05:37 GuShH purest water you can get from the ground
05:37 Rif have to go inland about 400km but has been raining out there too
05:37 GuShH in this location
05:37 Jak_o_Shadows1 Rif: 1 murray cod: 30 carp
05:37 Rif not where i go
05:37 Rif no carp yet
05:38 Jak_o_Shadows1 lucky.
05:38 Rif one of the few rivers not infested, one you go north towards the QLD border you get em, an further out west
05:39 ShH thinks an inline sediment + softener filter at the inlet of the water tank would be i
05:39 Jak_o_Shadows1 murray is infested. I see people fishing at our local wetlands, which dries out a fair bit, makes me lol.
05:39 GuShH problem, the commercial units I've seen all use 1 inch piping, I've got a 2 inch inlet
05:41 Rif 2 inch pipe at a time is alot to filter well
05:41 Rif can't you just reduce it
05:41 Rif Jak_o_Shadows1, where abouts are you near?
05:41 Jak_o_Shadows1 Adelaide.
05:42 Rif nice, never been there but always wanted to go
05:42 GuShH it's the inlet, can't restrict it or it might mess up the pump
05:43 Jak_o_Shadows1 Weather is more extreme in some ways then other places. Our hot is dry as hell, while our cold is cold.
05:43 GuShH a softener at the inlet would solve lots of problems with calcium deposits
05:43 Jak_o_Shadows1 So, um, come in spring or autumn.
05:44 Rif yep is amazing how hot it gets, i guess cause you are near the desert as well
05:44 Rif yu guys had like 50C + this year didn't you?
05:48 Hukka How cold is cold?
05:52 Jak_o_Shadows1 oh, not too bad, mostly, not below -3
05:52 Jak_o_Shadows1 adelaide, the city, rarely gets below 3
05:53 Jak_o_Shadows1 and yeas, some places out in the sticks get 50+, but adelaide the city easily got 45
05:53 Jak_o_Shadows1 so I guess our cold isn't too bad really
05:55 Rif yeah we get maybe -3 or so, have been in -6 up the mountain trout fishing, but inland a bit of there they had -10 or more this year
05:59 Rif working out how to mount these round motors is pretty awkward, nead to make a hub oh sorts as well, but a nice motor and gearhead
05:59 Rif with quad encoders
06:01 Hukka Ah
06:02 Hukka If I said "cold is cold", I would mean something below -30C
06:02 Rif heh, thats scary cold
06:02 Hukka Though here in the coas -20C is pretty bad. That 10m/s wind of 100% humidity is scary
06:03 Hukka It can numb your cheeks in a few minutes even close to zero
06:03 Hukka But you know, cold isn't as bad as hot
06:03 Hukka You can always wear more stugg
06:03 Hukka stuff*
06:06 Rif i wouldn't last long, hate that knida cold, and have no fat reserves
06:08 Rif but when the air gets a few degrees hotter than your blood i think that does odd things to your head as well
06:56 Jak_o_Shadows1 My view is, harder to get ill from cold.
06:56 Jak_o_Shadows1 hot*
07:44 Celelibi human body can adapt to extrem conditions. Some people find 40°C is just ok and not even hot.
07:52 Hukka I've adapted to 30C so far
07:53 Hukka But even then big part is tool assisted, like keeping a cooler with me
07:53 Hukka Chocolate would melt without!
07:55 chris_99 weird question, is it possible to lathe quartz?
07:57 zap0 i doubt it.
08:00 Hukka I don't think any crystal material can be
08:06 zap0 ice
08:09 Hukka Ice is crystal only on a micro scale, IIRC
08:10 Hukka It doesn't have those clear planar cuts aligned with the crystal planes
08:31 Triffid_Hunter Hukka: zirconia can be machined
08:31 Hukka ok
08:34 Triffid_Hunter an acquaintance is making reprap hotends with zirconia insulator section.. I'm sure there are other machinable ceramics/crystals too :)
08:39 chris_99 i'm sort of wondering how they make these http://www.robsonscientific.co.uk/quartz_tubing.php
08:39 chris_99 maybe they can melt the quartz?
08:40 Hukka The image on top looks like glass blowing
08:40 Triffid_Hunter chris_99: yep, can melt quartz
08:41 Triffid_Hunter chris_99: glass is basically quartz + additives
08:41 chris_99 aha, ~1670C apparently
08:41 chris_99 glass is silica isn't it
08:42 Triffid_Hunter chris_99: quartz is pure SiO2, glass is SiO2 + Na2O + CaO or similar depending on the type
08:42 chris_99 oh which quartz is too :)
08:42 chris_99 nice
08:42 chris_99 didn't know that
08:42 Triffid_Hunter chris_99: while you're at it, corundum (sapphire, ruby) is Al2O3 - aluminium oxide :D
08:43 Triffid_Hunter also corundum was the first artificially produced gemstone
08:43 chris_99 cool, i'm just trying to find the melting point of glass now
08:44 chris_99 hmm around 1425�1600 �C or less
08:45 Triffid_Hunter yeah the additives reduce the melt point, make it stronger, slightly more flexible.. all those good things that additives generally do :)
08:49 chris_99 mm