#robotics Logs

Feb 04 2014

00:00 rue_shop3 or even if it was a stepper
00:00 rue_shop3 I wonder if the serial latency would be an issue
00:01 rue_shop3 or an air muscle
00:01 rue_shop3 oh my
00:01 MrCurious going to add pid into that
00:01 MrCurious for good measure
00:02 rue_shop3 well the controller would take care of the loop calcs, and the control io
00:02 MrCurious you mean the tiny13
00:04 rue_shop3 no, something like a mega32 would do the loop calcs and the control io
00:05 rue_shop3 it would do it for several loops
00:05 rue_shop3 the t13's would capture the position data and forward/translate the driver instructions
00:06 rue_shop3 eee gad, I just found out, the chip on my desk, is a 1974 calculator chip
00:06 rue_shop3 which makes the date code make sense, C7409
00:06 rue_shop3 week 9, 1974
00:06 rue_shop3 TMS0137NC
00:13 rue_shop3 ok bedtime
12:25 SilentAssassin if the zero moment point is outside the surface of the foot, how do I calculate the angular acceleration that will cause the robot to tip over
18:24 GuShH_ rue_house: hmm got a brushed ac motor here that nearly stalled, not sure if due to the load siezing up or due to internal fault but I noticed two contacts on the commutator are slightly different than the rest, with nearly "cold solder" chunks in between, as if they somehow shorted together... the brushes are intact and lots left, I wonder if the damage is secondary or primary
18:25 GuShH_ ie. did the motor get overloaded and thus the contacts nearly burnt up when it almost stalled?
18:25 GuShH_ it actually stalled for a second.
18:25 ShH_ pokes Tom_itx just for good mea
18:26 om1 slams a galliger sledgehammer on GuShH_ 's
18:27 GuShH_ atom1: what did I ever do to you!
18:27 GuShH_ oh yey free tools
18:27 GuShH_ forgot to mention the windings don't look burnt up at all
18:27 GuShH_ the bearings are perfect
18:27 m_itx hi 5's a
18:28 GuShH_ it's from a power washer.
18:28 GuShH_ power/pressure, however you like to call 'em.
18:28 GuShH_ I assumed the brushed had failed due to end of life, but that's not the case.
18:28 GuShH_ brushes*
18:28 GuShH_ they're 50% spent
18:35 GuShH_ cap is ok...
18:35 ShH_ kicks Tom_itx's c
18:50 GuShH_ commutator feels rough against the brushes... I think those two contacts are lifting up... wonder if I could cement them down with varnish and then brush the contacts clean, don't have a lot of access though only through the brush housing, the two halves of the motor are plastic and I haven't found a way to separate them yet...
19:02 GuShH_ ok got most of the housing / shield off... those two contacts are quite bad and they do read differently than the rest... hrmm
19:02 GuShH_ shouldn't all contacts read the same? ie I get 0.8 ohms every two contacts (1, 2) but between the damaged ones I get a higher reading.
19:24 GuShH_ ok it's all apart, got the rotor out... I'm pretty sure those two contacts went bad, but I don't know if it's supposed to be like that (ie have a bigger gap between two of the contacts) it does look as if it overheated....
19:31 GuShH_ http://gushh.net/tmp/p_20140204_220839f.jpg not the best pic but it shows the two contacts I presume to be damaged
19:32 GuShH_ did they lift up and wear unevenly or are they shaped like that on purpose and if so, why?
19:32 GuShH_ the coils are only dark due to carbon dust
19:33 rue_house GuShH_, its a shorted winding
19:34 rue_house do an impedence (not resistance) test and you will probably see it
19:34 GuShH_ rue_house: why would it short, the contacts somehow bridged?
19:35 rue_house vibration
19:35 GuShH_ and the pic is after a quick clean up with a rug
19:35 rue_house two of the wires shorted in that armature
19:35 GuShH_ it's mounted on rubber caps and very well balanced
19:35 GuShH_ and the rest is kinda potted on these
19:35 rue_house its happens a lot
19:35 GuShH_ Hrmm I'll check impedance
19:35 GuShH_ if so I wonder if I could get it rewound...
19:35 GuShH_ I don't want to buy a new pressure washer, too expensive for a good one
19:35 rue_house I did it once, vowed mever to again
19:35 GuShH_ rue_house: no I won't, but I know a couple places that do
19:36 GuShH_ there's no friggin way I would attempt it, I don't have the patience and I'm not that insane.
19:36 GuShH_ rue_house: so do I meaure impedance against every pair of contacts and then check the "bad" ones?
19:36 GuShH_ one bad against one good?
19:37 ShH_ is not an electric motor
19:39 GuShH_ rue_house: ok impedance on the "bad" pair is slightly higher than the rest of the pairs
19:39 rue_house individual coils are between adjacent comutators
19:40 rue_house an open?
19:40 rue_house I'd expect a short, an open will do it too
19:40 rue_house oooh wait
19:40 rue_house !
19:40 GuShH_ not open
19:40 GuShH_ 0.087mH vs 0.092mH
19:40 GuShH_ ie most pairs are under or exactly 88 the "bad" ones are 92
19:40 rue_house IF its an open, its because one of those stupid little tabs thats folded over is nolonger bitten into the wire
19:40 GuShH_ I cleaned them up slightly with 600 grit just now for the test
19:40 rue_house sand/solder them, and you will be ok
19:41 rue_house if its an open
19:41 GuShH_ they aren't open otherwise I'd get no reading
19:41 rue_house I remember an old fart told me that once
19:41 GuShH_ they crimp them though because it's more reliable than a solder joint
19:41 rue_house nono, if the impedence is high, your only seeing one side of the loops
19:41 GuShH_ and it has to be at those RPMs
19:41 GuShH_ so tell me how to probe it
19:41 rue_house ok, you play, tell me if you get it fixed by impenence
19:42 GuShH_ I might go for a coffee and some icecream to cool down...
19:42 rue_house make sure the ac impedence (say at 1Khz) is the same on all windings
19:42 ShH_ frowns at his LCR meter and then frowns back at rue_h
19:42 rue_house excuse me I have packages from china to deal with
19:42 GuShH_ rue_house: how are the windings wired?
19:42 rue_house GuShH_, sure, use that, whatever
19:43 rue_house like a flower
19:43 GuShH_ the hell
19:43 GuShH_ I'll play along... what type of flower
19:43 rue_house where the pedals all around are the windings
19:43 GuShH_ yes I can see that, but I don't know what makes a pair, every how many contacts?
19:43 rue_house the motor dosn't activate one winding at a time, it de-activates the one in line with the magnetic poles,
19:44 rue_house its a continious series ser of windings, all the way around
19:44 rue_house draw a daisy
19:44 GuShH_ the motor began to slow down and sound funny, so that's what I'm looking at, I'm leaving the pump aside for later because I already identified those two funny looking contacts and I believe that's part of the problem
19:44 rue_house each outside pedal is a winding, each inside point is a commutator point
19:44 GuShH_ but it could be the pump temporarily siezed
19:44 GuShH_ I will service it if I can get the motor to run properly.
19:45 ShH_ never took apart one of those 100BAR pumps be
19:45 rue_house isn't 100bar like 5kpa?
19:46 GuShH_ rue_house: most medium sized washers for home use are 100BAR
19:46 GuShH_ 180BAR are "professional"
19:46 GuShH_ china shit are under or about 80BAR if you're lucky
19:47 rue_house they just say that till its consumer grade, then they raise the bar
19:47 GuShH_ anything over 180BAR is industrial
19:47 GuShH_ no this is k�rcher
19:47 GuShH_ germany with italian components
19:47 GuShH_ even the rubber caps on the bearings are made in italy!
19:48 GuShH_ actually the bearing isn't, it's from thailand (circa 1992) and it does have what I would call play, could that also contribute to commutator failure?
19:49 GuShH_ or just my suspicion of high load -> near stall -> damage
19:51 GuShH_ sigh.. now how am I going to clean up the driveway... darn it.
19:51 ShH_ refuses to use a
19:52 GuShH_ It did outlive it's warranty period by 20 times... I'm not complaining about that... it just sucks.
19:53 rue_house look, nothing you can just buy is a perfect product, if you want a product to be perfect you have to make it that way
19:54 rue_house all your given is an approximation, most people abuse things and throw them out too fast to ever notice
20:01 GuShH_ rue_house: I'm not complaining it lasted since 92 this is it's first problem, aside from the power switch which I simply replaced...
20:01 GuShH_ cars these days don't last a year without having some type of problem... as do most products
20:02 GuShH_ all the more reason I would want to fix it instead of buying a new one which I KNOW won't last a 10th.
20:02 GuShH_ it's all china shit despite the german brand, now they make them all in china, not in europe anymore.
20:03 GuShH_ and despite QC and whatever they may pay them, I don't think they will last 22 years.
20:03 GuShH_ not even 2 years.
20:06 rue_house I bought yellow lugs from aliexpress, got blue ones...
20:07 rue_house blue is ok, was looking forward to yellow
20:08 rue_house mmmm 200 14 pin dip sockets!
20:08 rue_house NOw I can take over the world!
20:09 rue_house +- not being abel to tell which wire goes where on account of lack of yellow headers
20:09 rue_house ok I bought a new battery for the cordless phone
20:09 rue_house in the meantime I put a li-ion in it
20:09 rue_house 3.6V niCad -> 4.2V li-ion, the li-ion should have been ok, BUT, the charger tried to charge it up to 4.5V
20:10 rue_house which left it feeling... bloated....
20:10 rue_house so, like, grrrr
20:10 rue_house I dont even know if the charger is in the handset or the base
20:14 rue_house it shouldn't have gone over about 4V
20:18 GuShH_ rue_house: almost always on the headset
20:18 GuShH_ and base are dumb delivery platforms
20:18 GuShH_ you are lucky it's a low current charger
20:18 GuShH_ otherwise that bloat would have turned into a poof.
20:19 GuShH_ rue_house: I'll show you a couple more pics this time higher res, so you can tell me where to probe and whether these two contacts look funny to you
20:20 GuShH_ I'm done cleaning it all
20:21 GuShH_ http://gushh.net/tmp/dscn5066f.jpg ---- http://gushh.net/tmp/dscn5067f.jpg ----
20:21 GuShH_ on 66 you can see the two suspect contacts, are they chewed up or is that how they are supposed to be?
20:22 GuShH_ on 67 you can see a dark line, looks like rust on the armature
20:22 GuShH_ err the steel laminations
20:22 GuShH_ of the rotor
20:23 GuShH_ but there are slight markings as if the bearing allowed to rub against the stators.... but it doesn't have -that- much play to me
20:23 GuShH_ it's suprising how much power this little thing can handle... 7 to 8A draw
20:24 ShH_ thinks the fan is way too small, but it lasted 22 years didn'
20:24 GuShH_ so I count 12 laminations, is that the same as 12 windings?
20:25 GuShH_ well not strictly laminations, since they go the other way... so 12 bars
20:26 GuShH_ robotustra: care to help with an ac brushed motor?
20:40 rue_house damnit, i ahve to change the fish tank wanter and all the garden hoses are frozen solid
20:41 rue_house solder the wires, the only reason they dont is because it takes time
20:46 Tom_itx your poor fish.
20:49 robotustra_ nice gripper http://www.youtube.com/watch?v=6lb5Ky5nEOI
20:49 robotustra_ for minirobot
21:08 GuShH_ rue_house: it's not the wires...
21:08 GuShH_ also, damn all wavy washers, damn them all.
21:08 GuShH_ can't lock one of the shields / mounts due to the wavy washers, they're way too strong
21:08 rue_shop3 one of those connections is bad!
21:09 Tom_itx rue_shop3 you know any good tests for routers?
21:09 Tom_itx security etc
21:12 MrCurious GuShH_: i just recieved a psychic notification that someone is messing with your bungalo....
21:24 MrCurious friend just gave me a 2' tall worie robot with a gimp hand... oh the possibilities
21:27 GuShH_ MrCurious: hm?
21:28 MrCurious GuShH_: brown people... in your house... spilling ethnic food on the floor...
21:28 GuShH_ rue_shop3: all cleaned up, rectified the brushes and the commutator, let's see if it works without a flaw, otherwise I'll follow the "solder it and hope" suggestion
21:28 MrCurious i can sene them!
21:28 MrCurious and the power is back on
21:28 GuShH_ MrCurious: this is not funny.
21:28 MrCurious ok, i wont tell you when i "sense" these things
21:29 GuShH_ It's not something you should joke about as it could happen to you one day
21:29 GuShH_ And then nobody will be there to support you
21:29 MrCurious no... i limit myself to 1 house and try to live in it. strangers get noticed fast
21:30 GuShH_ I sensed the pressure washer would go 10-20 seconds before it did, but that often happens.
21:30 MrCurious i sense hard drives failing all the time, but i get tired of having to give the backups lesson, so i stay quiet, and wait...
21:35 GuShH_ lecture
21:36 GuShH_ MrCurious: and if thats the case you are one major asshole...
21:36 wildmage ground control
21:36 GuShH_ wildmage: permission denied.
21:36 MrCurious http://s3.amazonaws.com/wootsaleimages/WowWee_Robosapien_V2_Robot_zvjDetail.jpg
21:36 MrCurious that is the free robot
21:36 GuShH_ I would shoot that thing with the 22
21:36 wildmage I still have V1 and works great!
21:36 GuShH_ that's all it deserves.
21:52 rue_shop3 GuShH_, if you put lower votlage dc into it and let it rotate slowly you can tell if its running smooth or not
22:10 GuShH_ rue_shop3: I put ac with a series resistor (heater) to limit, it speeds up but the way it runs I wouldn't call it "happy"
22:10 GuShH_ you reckon some dc volts with a push will allow it to keep rotating?
22:11 GuShH_ also I moved on to the pump, it might be stuck.
22:11 GuShH_ not siezed but with a blockage.
22:11 GuShH_ (or internal damage) ... I didn't know these had oil inside either
22:11 GuShH_ I released the torque on the bolts and it fizzed a bit, I reckon it's still got some bult up pressure inside
22:11 GuShH_ rated 120BAR on the casting
22:13 GuShH_ the way both halves were separating as I released tension on the bolts tells me there's either quite a lot of pressure or it's a big thick o-ring
22:37 rue_house its a universal motor, it'll run just fine on dc
23:12 GuShH_ rue_house: it's not a universal motor
23:12 GuShH_ and sure it'll run on DC, but at several amps, not just any random supply
23:14 GuShH_ I'm still on the pump anyway, the oil looks like chocolate milk.... I wonder if water has been getting in
23:15 GuShH_ should probably replace it with the same stuff I used on my air compressor I guess
23:15 rue_house its got a wound field and rotor, right?
23:21 MrCurious robotustra: http://www.newrepublic.com/article/116460/wooden-cock-putin-critics-car-russia
23:55 GuShH_ rue_house: looks like the pump valves are all pressed in... they either had a special removal tool or it wasn't meant to be serviced in that regard
23:55 GuShH_ the oil feels like ATF to me
23:55 GuShH_ but since it's a 3 piston/ spring valve setup almost any motor oil should do
23:56 GuShH_ the gaskets are rather dry... but there are no replacements for this pump anymore
23:56 GuShH_ the piston "gaskets" that is
23:57 GuShH_ it's got an offset/tilted shaft that as it rotates it pushes each valve in sequence
23:58 GuShH_ heh they claim it should be 15w-40 oil