#robotics Logs

Dec 29 2015

00:42 rue_shop3 heh
00:42 rue_shop3 and your gonna learn how long it took you to tweek it into something that worked
00:44 Jak_o_Shadows well, to be honest I wasn't really happy with it before
00:44 rue_shop3 I did a settings overhual recently too
00:45 rue_shop3 I tend to do consecutive prints, so I had it not turn the heater completely off after a print
00:45 rue_shop3 got it at 30c
00:45 rue_shop3 save a bit of time reheating
00:45 Jak_o_Shadows Nice
00:46 rue_shop3 printer settings -> custom g code -> M104 S30
00:46 rue_shop3 (end g-code)
00:46 Jak_o_Shadows Cause my heatbed doesn't get as hot as I'd like until most of the way through a print I hand-edit gCode and tell it not to wait for it to heat up
00:47 rue_shop3 I'm building a new machine
00:47 rue_shop3 trying to nix some design problems
00:48 rue_shop3 gonna use 3-screw bed leveling
00:48 Jak_o_Shadows The reprap is REALLY hurt by the original idea of everything being printable
00:49 rue_shop3 yup
00:49 Jak_o_Shadows So many things are just dumb.
00:49 rue_shop3 today I had the thought "I'm a fabricator, why the hell should I limit myself to printing everything?"
00:49 rue_shop3 the Z axis rods
00:49 rue_shop3 the drive screws,
00:50 Jak_o_Shadows The y-ends. I made mine out of wood instead of tons of bolts & nuts.
00:50 rue_shop3 I used the lathe to drill a 5mm hole in the end, cut a slit across the hole, when you tighten 2 nuts in the slit threads, they squish in, on the motor shaft
00:50 Jak_o_Shadows Cantilevering the extruder off 2 bolts - both in the horizontal plane.
00:50 rue_shop3 its perfectly centred
00:51 rue_shop3 yea, todays second thought was to just print bearing holders and make the rest from sheet metal
00:51 rue_shop3 Jak_o_Shadows, did you post pics?
00:52 Jak_o_Shadows um, not recently
00:52 rue_shop3 my new machine is a bit larger than the normal one, I based it on the size it came out when I just cut the available threaded rod in half
00:52 Jak_o_Shadows haha.
00:55 rue_shop3 having 20cm peices of rod left over is stupid
00:55 Jak_o_Shadows I should start working on a design for a stewart platform (I have all the code: http://jak-o-shadows.github.io/electronics/stewart-gough/stewart-gough.html), but I don't have the pots from aliexpress now.
00:55 Jak_o_Shadows Yes, it is
00:57 rue_shop3 the X axis belt, squeezes on the Z axis rods, I suggest putting stops on the X axis sliders somehow, I'm using collars with a lock screw, drilling pins thru them would work too
00:58 rue_shop3 I think I'm gonna use one Z motor and link the two sides with a belt
00:59 rue_shop3 my printer uses 3mm plastic, I noticed the prints are distorted along the Y axis as the filament pulls and pushes on the carrige
01:06 Jak_o_Shadows What do you think of corexy?
01:15 rue_shop3 I think marlin works fine
01:15 rue_shop3 I dont need a freaking 32 bit arm to drive steppers
01:16 Jak_o_Shadows nah, the physical mechanism
01:17 rue_shop3 oh am I mixed up?
01:17 ace4016 what if you need to do more than just drive steppers?
01:17 rue_shop3 then I will use the freaking PC
01:18 e4016 has no idea what context this is all i
01:18 rue_shop3 Jak_o_Shadows, ah
01:18 rue_shop3 Jak_o_Shadows, thats been used for a long time
01:18 rue_shop3 I dont know what the gotchas are
01:20 Jak_o_Shadows ok
01:20 Jak_o_Shadows Also, I agree about keeping stuff on the pc
01:20 rue_shop3 the realtime stuff goes on the avr, the computational on the pc
01:21 rue_shop3 I have a problem with twisted filament, not sure how to deal with it
01:22 rue_shop3 http://i.imgur.com/qyFXZSH.jpg
01:22 rue_shop3 this method impressed me
01:23 Jak_o_Shadows x-y moving extruder, z bed?
01:23 rue_shop3 the way the xy works
01:23 rue_shop3 the siders are the stabilizers
01:26 Jak_o_Shadows oh yeah. I see
13:15 Hyratel god that's a hell of a sound - http://hackaday.com/2015/12/29/flying-planes-with-squirrel-cages/
13:17 ace4016 hehe
13:18 Hyratel I wonder how well an annular exhaust would work for a squirrel cage blower
13:18 Hyratel instead of a collecting centrifugal
13:18 ace4016 annular exhaust?
13:18 Hyratel -> ] }~~~
13:19 Hyratel er
13:19 Hyratel more like -> ] {
13:19 ace4016 confused what viewpoint that's at
13:19 Hyratel take the side exhaust and divert it to the shaft axis
13:20 Hyratel so you're using it like a ducted fan, instead of having a side intake
13:20 ace4016 ah
13:20 Hyratel make it hub face into the airstream
13:21 ace4016 you might be able to do it better with a mix-flow impeller (3D impellers like http://cdn2.hubspot.net/hub/509738/file-2859819985-jpg/blog-files/2013-07-12-11.53.15.jpg )
13:21 Hyratel so you've got the airstream coming straight into the "cup" of the cage, then make the air divert at right angles to shoot back
13:21 Hyratel aha I see how you mean
13:21 ace4016 the diffusers for that can send it inline
13:21 Hyratel yeah, i gotcha
13:21 Hyratel makes sense to me
13:22 ace4016 lots of interesting designs you could do :P
13:23 Hyratel a lot of novelty aeroforms you could do with a 3D printed shell backfilled with expanding foam
13:23 Hyratel I wonder if you could do an X-24C
13:23 Hyratel with EDF thrusters
13:24 Hyratel X-24 A/B used a liquid rocket, C was a paper plan to install ramjet sleeves on the belly
15:29 Anniepoo_ I'm starting a new project, going to use some drill motors as servo motors in a robot. Can anybody suggest a low fuss, low muss way to drive them and/or do the position feedback?
15:32 Hyratel anniepoo, look up "openservo"?
15:32 Anniepoo_ ok, thanks
15:32 Hyratel minus the stray ?
15:32 Anniepoo_ stray?
15:32 Hyratel it runs on a mega328 iirc
15:33 Hyratel wasn't supposed to be a question, just stray finger
15:33 Anniepoo_ ah, got it
15:33 Anniepoo_ thanks.
15:33 Hyratel http://www.openservo.com/
15:33 Anniepoo_ this isn't exactly what I was looking for
15:33 Anniepoo_ I know that drill motors (taken from cheap cordless drills)
15:34 Anniepoo_ are a common way to power hobby robots. I have a similar application, and didn't want to reinvent the wheel
15:34 Hyratel anniepoo, a servo consists of an actuator, a sesnsor, and a feedback loop to connect the two
15:34 Anniepoo_ So wondered if somebody had a canned solution to using drill motors in a closed loop
15:34 Anniepoo_ yes, I know that.
15:34 Hyratel Openservo is the feedback logic
15:35 Hyratel you'll have to roll your own sensor connection
15:35 Hyratel but, as far as I know, there is no turnkey "big servo with your own motor" solution
15:35 Anniepoo_ ok, great
15:35 Hyratel Openservo will give you a major leg up though
15:36 ace4016 yea, drill motor + feedback sensor (encoder of some sort) + openservo = home-made servo
15:36 ace4016 boom
15:36 ace4016 should be fairly straight forward i think
15:37 Anniepoo_ arduino might be simpler than fiddling with a board I'm new to?
15:37 ace4016 from what Hyratel said, it sounds like openservo will work on some arduinos
15:38 ace4016 any of the mega328 ones
15:38 Anniepoo_ yes, might
15:38 ace4016 probably more
15:40 Hyratel the firmware targets a mega168
15:41 Hyratel hell you could probably dead bug one up
15:41 AdrianG /part
15:41 Hyratel all you need is power and signal to the mega
15:41 Hyratel -> IC AVR MCU 16K
15:41 Anniepoo_ Seems as simple to just roll my own from an Arduino, I'd rather use a chopper wheel for feedback
15:41 Anniepoo_ yup, think that'll work
15:42 Hyratel anniepoo, chopper wheel?
15:42 Hyratel I don't know if the Openservo firmware supports that natively, but you can make a continuous rotation servo that way
15:42 Anniepoo_ wheel with slots in it, interruption mode photodiode + LED pair
15:42 Hyratel encoded servo
15:42 Anniepoo_ yes, I need continuous rotation
15:42 Hyratel "optical encoder"
15:42 Anniepoo_ thanks
15:43 Anniepoo_ brain was dropping a word 8cD I'm getting old
15:56 Hyratel <Hyratel> all I'm saying is it only costs as much as eating pickles #no context engineering
16:19 rue_house mm I need to work out software balance for the wheels on my new mowerbot
16:20 rue_house not sure if I want to put encoders on the wheels or use the castor
16:20 rue_house I suppose the wheels slip and the castor wont, really...
16:20 rue_house hmm
16:21 robotustra does not go strait?
16:21 robotustra put gyro sensot on it
16:44 rue_shop3 there are so many cars in the world, that if all the tires were deflated, the atmosphere of earth would get 1% larger
16:44 rue_shop3 90% of all statistics are just made up
16:45 Tom_itx which one of those statements is true?
16:46 rue_shop3 30% of them
16:46 robopal half
17:02 Snert_ I'm 100% sure that statistics may or may not tell the truth.
17:11 adv_ rue_house: any updates?
19:12 adv_ how can i make the lines curl by default instead of straightening out in inverse kinematics?
19:16 Hyratel I'm wondering when there will be a "Robot Pi" board. with the various GPIOs (or an I2C IO buffer chip) broken out to 3 pin PWM headers
20:26 akem hi.
20:27 robotusra_ .ih
20:33 akem do you know some step motors like the 28byj48 but stronger(unipolar 5 wires)? for a weight up to 5kg lets say
20:33 Hyratel why do you want unipolar
20:34 akem because the byj is, apparently, so it will works the same
20:34 akem 2 wires per coil and 1 vcc
20:34 Jak_o_Shadows Ok,using weight to define the torque of a motor is a terrible idea
20:35 akem hyratel you know some good bipolar ones?
20:37 Hyratel most are bipolar nowadays
20:37 Hyratel and the drivers are a pair of H-bridges
20:37 akem so what model you suggest me?
20:39 Hyratel I sugget you look at your mounting hole pattern and torque requirements and buy one to match
20:40 akem it's raw metal plates and bars
20:40 Hyratel that doesn't answer the question
20:40 Hyratel you figure out your requirements
20:40 Hyratel and buy a motor to match
20:40 akem but it need enough strenght to move up to 5Kg.
20:41 akem ok, i will look into this, jeeesus.
20:42 Hyratel I don't think you understand your own requirements
20:42 Hyratel are you using a lead screw, or a timing belt? or something else
20:48 Jak_o_Shadows Move 5kg how?
20:49 Hyratel Jak_o_Shadows, thats what I wanted to know
20:49 Hyratel but he got all huffy
20:49 Jak_o_Shadows Yep.
20:49 Jak_o_Shadows I wish servos & steppers advertisted/listed torque instead of weight.
20:49 Hyratel both are important
20:50 Jak_o_Shadows Nah, not wieght of the stepper/servo, I mean how they normally say 10kg.cm
20:50 Jak_o_Shadows that's literally a torque measurement in stupid units
20:51 Hyratel .. no
20:51 Hyratel well
20:51 Hyratel hm
20:51 Hyratel oh
20:51 Hyratel oh I see what they're doing
20:52 Hyratel they're using the imperial-style conflation of force and weight with metric units
20:52 Hyratel so written properly it should be 10kgf/cm
20:53 Hyratel which is still Wrong, but it's written correctly
20:53 Jak_o_Shadows Properly written it should be 0.98 Nm
20:53 Hyratel Jak_o_Shadows, I mean "writing the wrong notation correctly" would be kgf/cm
20:53 Hyratel which doens't make it Right, but makes it Make Sense
20:56 Jak_o_Shadows Yeah, you're right
20:57 Hyratel it's not Classroom proper but it conveys all the relevant information
20:57 SpeedEvil It's very inaccurate on the moon.
20:58 SpeedEvil But...
20:59 Hyratel it's very difficult to change your gravitational reference and anyone with such a scenario would be smart enough to convert out to generic units using the known reference units
20:59 Hyratel so there
21:00 Jak_o_Shadows It'd make it more obvious to begineers though
21:40 akem next robo one ahead(hache) whos ready to die?
21:43 jhylands I'm so happy
21:44 jhylands I build a power switching circuit for Roz that switches between battery power and wall power automatically
21:46 robotusra_ automatically?
21:47 robotusra_ 115V 60Hz?
21:49 jhylands yeah
21:49 jhylands I'm using an LTC4412
21:49 jhylands along with a p-channel MOSFET
21:49 jhylands http://cds.linear.com/docs/en/datasheet/4412fb.pdf
21:49 jhylands it works like an OR-ing diode, except there's no voltage drop
21:50 robotusra_ so actually you do not charge your battery pack?
21:50 jhylands not from wall power, not
21:50 jhylands its to power the robot while I'm testing on the bench, so I don't waste the battery
21:51 robotusra_ because I want to charge the robot
21:51 jhylands I need something to keep power running, because I'll be adding a Raspberry PI
21:51 robotusra_ no direct AC
21:51 jhylands no
21:51 jhylands wall power is a 12 volt DC supply
21:51 robotusra_ ok
21:52 robotusra_ I'm building a controller to charge batteries from 24 volts
21:52 jhylands ah, okay
21:52 jhylands building a 3-cell lipo charger is not simple
21:53 robotusra_ I will use standart BEC
21:53 robotusra_ for lifepo
21:53 jhylands lifepo's are much safer
21:53 robotusra_ yeah, but are more expensive
21:54 robotusra_ and I want to use 2 24 V batteries and after dc-dc stepdown to 12 V
21:55 robotusra_ and one more backup 12 V lipo battery
21:55 robotusra_ in case it will discharge everything, to come back to docking station
21:56 robotusra_ hope it will work
21:56 robotusra_ how is you robot finds charger?
21:56 robotusra_ do you have any video?
21:57 robotusra_ how does your robot find charger?
21:58 jhylands it doesn't
21:58 jhylands I don't have any automatic charging
21:58 jhylands I may do that at some point
21:59 jhylands but its going to be running SimpleCV with stereo cameras, as well as having a Lidar-lite
21:59 robotusra_ I mean does it plug itself?
21:59 jhylands no
21:59 robotusra_ ok
22:00 robotusra_ I browsing throu the internet trying to find ppl's sites dedicated to home made robots
22:00 robotusra_ almost nothing
22:00 robotusra_ may be I'm looking at wrong places
22:01 robotusra_ people really do not do much by hands
22:02 jhylands I don't have a dedicated page for Roz, but mainly talk about it on my blog
22:04 robotusra_ yeah, I know a couple of guys from here who build something
22:04 jhylands you've seen my videos of Roz, right?
22:04 robotusra_ but there is no good description in the internet
22:04 robotusra_ yes
22:04 robotusra_ I saw them
22:05 robotusra_ but still,
22:05 robotusra_ there are not so much interesting stuff
22:05 robotusra_ usually a 4 wheel robot
22:05 robotusra_ not so much legged robot
22:06 robotusra_ I mean the description how to build it
22:06 robotusra_ usually they are built from kits
22:06 jhylands I don't own any kit robots
22:06 robotusra_ me too
22:07 robotusra_ I prefer to build from scratch
22:08 robotusra_ but as soon as I see there is no GOOD kit to build humanoid robot
22:09 robotusra_ I mean full size adult robot
22:09 jhylands full sized humanoid robot is really difficult
22:10 jhylands the actuators are non-trivial to build
22:10 robotusra_ true
22:10 jhylands you really need compliant actuators at that scale to be safe
22:10 robotusra_ :)
22:11 robotusra_ you are real canadian, care about safety
22:12 robotusra_ if the real inventors shouldn't care about safety :)
22:12 jhylands well, I care about my own safety
22:12 jhylands but I also believe strongly that compliant force-driven actuators are the only reasonable way to go
22:13 jhylands for large-size limbed robots
22:16 robotusra_ if actuators will be weaker than human muscles - the human is safe
22:17 jhylands but then you can't actually do anything useful with the robot
22:17 jhylands and you certainly couldn't make it walk using legs
22:18 robotusra_ actually, I can
22:18 jhylands I mean with weak legs
22:18 jhylands a full-sized (human size) robot
22:18 robotusra_ tha ctuator could produce big force at low power
22:19 robotusra_ do you know what is the power of average human?
22:19 jhylands nope
22:19 jhylands I've never looked that far into building a large sized limbed robot
22:19 robotusra_ sportsman on the bike do only 300 Watts at full speed
22:20 robotusra_ average power of human is about 100 Watts
22:20 jhylands you can't just look at power though, there are a lot of efficiency tricks we use to walk
22:20 robotusra_ and we are walking and doing things
22:21 jhylands and we have compliant, springy actuators in our bodies
22:21 robotusra_ sure, but electric motors are much power that we need to have
22:22 robotusra_ true, but it means that in theory I need only 100 Watts to make full scale walking robot
22:22 jhylands Good luck with that
22:22 robotusra_ let's say 50 more Watts for electronics
22:23 robotusra_ first I have to make 30-40 Watts hand
22:25 robotusra_ Human muscles could develop a big force but at quite low speed
22:25 robotusra_ that's why we spend not so much power