#robotics Logs

Jul 24 2015

00:00 rue_shop3 hmm, well, I'm not sure on this driver, I was able to get 250Khz out of it, I'm just not sure if its up to snuff
00:00 rue_shop3 the switching times look better when I put aside the 100R dummy load and use an inductor
00:00 rue_shop3 0.25us or so
00:02 rue_shop3 which sounds good till you realize that at 50% duty, the on time is only 4us
00:03 rue_shop3 1/16th of the pulse is transition
00:03 rue_shop3 I could lower the switching freq, to say, 100khz
00:03 orlock rue_shop3: you know how i said my factory stepper controller had a really weird duty cycle?
00:03 rue_shop3 yea
00:03 orlock 6x 8.3ms pulses then 50ms off
00:03 orlock i'm wondering if that was to get the timing right
00:04 rue_shop3 not verry steady
00:04 rue_shop3 brensham dithering
00:04 orlock without needing to worry about microsecond loops
00:04 orlock its steady, not dithering
00:04 rue_shop3 |||||| ||||||
00:04 rue_shop3 opposed to
00:04 rue_shop3 | | | | | | | |
00:05 orlock yeah
00:05 rue_shop3 dithering
00:05 orlock anyway, i figured out how to correctly calibrate my homebrew motor's timing
00:06 rue_shop3 cool, does it need to sit out a night to do it?
00:06 orlock put a laser on it
00:06 orlock no!
00:06 orlock so its done already
00:06 orlock :)
00:06 orlock laser. mark point on wall (or fridge)
00:06 orlock point webcam (running motion) at the mark
00:06 orlock time how long till laser reaches mark again
00:07 rue_house ah
00:07 rue_house 360
00:07 orlock this was with 17millisecond pulses
00:07 orlock so ~12 hours for a complete rotation
00:07 orlock determine how many seconds it took for the complete rotation
00:08 orlock divide it my .17 to get total number of steps roughly
00:08 orlock i think it was 263943 or something,
00:08 rue_house cool
00:09 rue_house give it 2 turns and average?
00:09 orlock so given my hack way of measuring, i assumed 264000 steps per revolution
00:09 rue_house how about all those microstepping drivers out there for $2.50ea?
00:09 orlock or thereabouts - i may have bee a decimal place out
00:10 orlock these are all bipolar, and i dont need microstepping
00:10 rue_house but... microsteps
00:10 orlock to determine final drive rate
00:10 rue_house finer motion
00:10 orlock 86400 * 0.99726958
00:10 rue_house have it on some kinda closed loop pll
00:10 orlock ti get seconds in a sidereal day
00:11 orlock and then divide that by the amount of steps
00:11 rue_house controlled with a oven timesource
00:11 orlock gives me the time for each step
00:11 rue_house calbrated against an atomic clock
00:11 orlock which is something like 32757 microseconds
00:11 rue_house put in a chome case
00:12 rue_house heh, not quite 15 bits
00:12 rue_house er, within
00:12 rue_house 32768.. yea
00:12 rue_house I'm losing it
00:12 rue_house I need supper
00:12 orlock heh
00:12 rue_house if I cant remember 32k I'm in trouble
00:13 orlock 86400 * 0.99726958 / 264000
00:13 orlock maybe off a decimal place in there
00:14 rue_house microstepping
00:14 rue_house wait, how many steps per second are you now?
00:14 rue_house prety low, right?
00:14 orlock ~3 i think
00:15 rue_house microstepping would screw that up, but it would be smoother motion
00:15 rue_house do you get any noticable horizontal jiggle now?
00:15 orlock i can only do half stepping with the unipolars i think
00:15 rue_house or, its more rotational isn't it?
00:15 orlock yeah, and its fine enough its not noticable
00:15 rue_house yea, bit for $2.50 you can use a reprap stepper driver
00:16 orlock this is a geared stepper - geared stepper goes to another small+big gear combo
00:16 orlock that big gear turns a worm drive
00:16 orlock and then theres the final ring gear drive that ends up turning once every 23 hours, 56 minutes and 4 seconds
00:17 orlock individual steps are not noticable
00:25 rue_house so, can you relink me to the image?
00:27 orlock need to find it
00:27 orlock i know its on the server at home
00:27 orlock but since i moved my desk, my EoP stopped working
00:27 orlock which is really fucking me off
00:28 orlock EoP - link from where the internet is, to the workshop where server is
00:46 orlock hmm
00:46 orlock is 32 milliseconds .32 of a second?
00:46 orlock then 100 milliseconds would be 1 second?
00:47 orlock but 1000 millisecons is a seocnd
00:48 orlock 86400 * 0.99726958 / 2640000 = 0.03263791352
00:49 orlock 2640000 steps per revolution
00:51 rue_house "WAITOR! WAITOR!" "yes sir?" "THERE IS A FORK IN MY SOUP!"
00:55 mrdata "this coffee tastes like mud!" "well, sir, it was fresh ground this morning"
00:55 rue_house haha!
00:56 rue_house https://hackaday.io/project/296-bench-power-supply
00:57 rue_house it occured to me that, with a switching converter, I could output more than 5A per channel using a 10A internal supply
01:12 mrdata yes
01:13 mrdata for a buck supply
01:15 anonnumberanon Ugh.. These needle gauges are making my eyes bleed.
01:18 Mushrooshi hmmm...
01:18 Mushrooshi is it bad for my servos if I put them all on a common ground with a switch to break it to "relax" the servos?
01:19 mrdata hobby servos?
01:19 Mushrooshi yes
01:19 mrdata i found theyre finicky
01:20 mrdata i destroyed one with a flakey controller
01:21 Mushrooshi i wish amazon had more and better-priced electronics components. prime 2 day shipping spoils me.
01:21 Mushrooshi i need some arcade buttons but amazon's are overpriced
01:21 orlock dx.com is pricy now too
01:22 Mushrooshi i have... exactly a week to get my DJ robot performance-ready.
01:22 Mushrooshi for a crowd of I think... 3000?
01:22 Mushrooshi @.@
01:23 Mushrooshi idk, it barely qualifies as a robot at the moment.
01:23 Mushrooshi its really just glorified automated turntablism
01:45 anonnumberanon mrdata> i destroyed one with a flakey controller
01:45 anonnumberanon what kind of damage?
02:11 Jak_o_Shadows Rue your instructions are good
02:26 anonnumberanon nice page rue_house are the gauges like this because you like that style or because that was a cheap good gauge? I prefer some 7 segment with blue color.
13:53 rue_house 7 segment is impossabel to read if the numbers jitter
13:54 rue_house I have a usb port on it that will show you it in digital, and it'll tell you the power
20:48 sector_0 is acrylic a good material to build a scara robot from?
20:49 sector_0 I'm thinking about either building a scara or a 5-bar mechanism tobot
20:49 sector_0 but I've heard people say that acrylic warps
20:49 sector_0 I wouldn't want to lose accuracy overtime
20:49 T3rr0rByte13 all plastic warps
20:50 T3rr0rByte13 are you 3d printing it?
20:50 sector_0 T3rr0rByte13, nope
20:50 sector_0 but I'm planning to see how it works as a 3d printer
20:50 T3rr0rByte13 well if your heating it up it will warp
20:51 sector_0 bummer
20:51 ace4016 should be fairly simple metal pieces though
20:53 rue_shop3 "The UC3842 and UC3843 have a maximum duty cycle of approximately 100%"
20:53 rue_shop3 ...
20:53 rue_shop3 approximately...
20:53 rue_shop3 how approx?
20:54 ace4016 depends on temperature and pressure clearly
20:55 T3rr0rByte13 basically it should come down to how much your project can tolerate warping, and selecting a plastic based on that
20:57 ace4016 use ceramic parts for almost no warping what so ever :P
20:58 T3rr0rByte13 so long as it can tolerate something brittle
20:58 ace4016 yea :P
21:00 sector_0 well I only intend to do light work
21:00 sector_0 pick and place, 3d printing, pcb mill maybe
21:00 sector_0 and plotting
21:16 sector_0 ace4016, T3rr0rByte13 i was looking at this design
21:16 sector_0 https://www.youtube.com/watch?v=h3k76gOvVUU
21:17 T3rr0rByte13 you're building the 3d printer?
21:18 sector_0 T3rr0rByte13, not exactly
21:18 sector_0 might use it for that, but that's not the only use I have in mind
21:18 T3rr0rByte13 I see
21:19 T3rr0rByte13 I don't know which plastic would be best, but as ace4016 says ceramic would be a good choice for this
21:21 ace4016 or metal
21:21 sector_0 T3rr0rByte13, ceramic might be tricky to work with
21:21 T3rr0rByte13 plastic warps during the cooling process so once its done cooling its not really gonna warp after that
21:21 ace4016 metal is tried and true :P
21:21 ace4016 not as cheap as plastics and certain ceramics
21:21 sector_0 personally I think the ideal material is metal but metal stock is difficult to come by where I live
21:33 T3rr0rByte13 Actually now that I think about it, ceramic might wear over time on moving parts, same to be said about plastic so you may see some play in parts
21:34 T3rr0rByte13 dare i say metal with ball bearings?!
21:35 ace4016 or ceramic bearings! :D
21:35 T3rr0rByte13 smooth for sure
21:35 ace4016 (ceramics are really cool, but usually impractical for the good stuff on a hobbyist budget i think)
21:37 T3rr0rByte13 uh, i have next to no knowledge on what it would take to fabricate custom ceramic parts, the material certainly has is benefits though
21:42 sector_0 T3rr0rByte13, the parts are going to be rotating on bearings, with washers between them
21:45 T3rr0rByte13 At this point select your best bet and pull the tigger, if your rotating parts on bearings your golden