#robotics Logs
Jun 24 2018
#robotics Calendar
12:04 AM rue_shop3: feed rate on pvc can be really high...
12:52 AM rue_shop3: getting closer
12:52 AM rue_shop3: 1 of the 2 servos is finished
12:52 AM rue_shop3: waiting for parts to print
12:53 AM rue_shop3: doing a good job of making the second one just after the first one is proven
02:13 AM rue_: so, I wasn't sure how strong to make the motor driver
02:13 AM rue_: I wanted to go for 5A, then 3A was 'maybe ok' I did a measurement and 750mA was all I was using, so I went with 1A
02:13 AM rue_: I'v almost melted two motors at 1A
02:14 AM rue_: so, this is intersting
02:14 AM rue_: less than 1A and there starts to be no challange to it
02:38 AM tmqq is now known as dongge
02:39 AM dongge: Hello, anyone who knows the motor driver circuit?
02:41 AM rue_shop3: yes
02:41 AM rue_shop3: use TDA2050
02:43 AM dongge: thanks, but I need some help regarding DC link capacitor
02:43 AM rue_shop3: there is none
02:44 AM dongge: what do you mean?
02:44 AM rue_shop3: TDA2050 does not need one
02:45 AM dongge: TDA2050 is a HIFI amplifier, so I think you are misunderstanding me.
02:45 AM rue_shop3: yes, with current limit
02:45 AM rue_shop3: and overheat limit
02:45 AM rue_shop3: will drive 5A
02:45 AM rue_shop3: is to small for your motor?
02:45 AM dongge: are you a robot?
02:45 AM rue_shop3: not yet
02:45 AM rue_shop3: :( I hope to be soon
02:46 AM dongge: I'm debugging motor driving circuit.
02:46 AM dongge: do you know motor?
02:46 AM rue_shop3: oh, you already have circuit
02:46 AM rue_shop3: throw it away and use tda2050 :)
02:47 AM rue_shop3: If you do not show me your circuit, how can I help you with it???
02:47 AM dongge: you are kidding me
02:47 AM rue_shop3: I"m always kidding
02:47 AM rue_shop3: but nobody can tell :(
02:47 AM dongge: alright, it's reasonable.
02:48 AM rue_shop3: if you show me your circuit, I'll show you mine.
02:48 AM rue_shop3: but dont tell internet!
02:51 AM rue_shop3: :| oh no, your going to do it aren't you! YOUR GOING TO SHOW ME YOUR CIRCUIT!
02:51 AM dongge: yes
02:51 AM dongge: why not?
02:51 AM rue_shop3: {:| then I have to show you mine...
02:52 AM dongge: if you want
02:52 AM dongge: :P
02:52 AM rue_shop3: I.... I suppose....
02:52 AM dongge: http://e2e.ti.com/cfs-file/__key/communityserver-discussions-components-files/171/5140.FOC_2B00_DC-link.jpg
02:52 AM rue_shop3: oh I'm still drawing!
02:53 AM dongge: it's not classified
02:53 AM rue_shop3: oh my, its for brushless motor
02:53 AM dongge: yes, I was telling you from the start.
02:53 AM rue_shop3: but, has no control information, so ... its means nothing
02:54 AM dongge: ok, I use SPWM.
02:54 AM rue_shop3: from AVR?
02:55 AM dongge: no, it's a general bldc motor driver
02:55 AM dongge: I'm trying to figure out the dc link capacitor current
02:55 AM rue_shop3: ok, you want to know about buck filter?
02:55 AM dongge: yes
02:55 AM rue_shop3: L C
02:55 AM rue_shop3: what is motor voltage and current?
02:56 AM dongge: just in theory, no specific motor is used
02:56 AM rue_shop3: ok
02:57 AM rue_shop3: same as buck power supply calculation
02:57 AM rue_shop3: wait
02:57 AM rue_shop3: yes
02:57 AM rue_shop3: synchronous dc-dc buck converter
02:59 AM dongge: why? it's 3 phase inverter, the buck converter is only a single phase.
02:59 AM rue_shop3: yes
03:00 AM rue_shop3: middle section is dc-dc buck convterter to reduce voltage for slow speed
03:00 AM rue_shop3: but has no current sense, bad.
03:02 AM dongge: I have a doc telling me how to calculate.
03:02 AM dongge: https://www.ecicaps.com/wp-content/uploads/IEMDC_2009_11310_Final_Rev_4.pdf
03:03 AM rue_shop3: if motor short and driver have no sense, driver blow up
03:05 AM dongge: ΔV0.5t is calculated in formula (24) and (25), I don't know why they use 1/f=t
03:05 AM rue_shop3: read formulas for buck dc-dc
03:06 AM dongge: yes, but the current is related to torque, I don't have heavy torque.
03:06 AM rue_shop3: t = 1/f assumes 50% duty, wrong
03:06 AM rue_shop3: brushless motors are short circuit, blow up driver easy
03:07 AM dongge: 0.5 duty cycle when the ripple is the biggest.
03:07 AM dongge: so it's right
03:07 AM rue_shop3: hmm
03:08 AM dongge: I detect the short circuit by detecting voltage across the MOSFET
03:09 AM rue_shop3: 8| too late for mosfet
03:10 AM dongge: maybe, but from my test result it works.
03:15 AM dongge: hello
03:15 AM rue_shop3: ok...
03:16 AM dongge: can we chat in private
03:24 AM z64555: y tho
03:24 AM rue_shop3: WHY!?!?!!?
03:24 AM rue_shop3: maybe I wanted to show him my circuit in private!?
03:25 AM z64555: its a circuit, not a skin mag
03:26 AM rue_shop3: I need 1 Ohm resistor...
03:28 AM z64555: at what wattage
03:28 AM rue_shop3: lets see ... 1A
03:28 AM z64555: so 1W, shouldn't be too rare
03:28 AM rue_shop3: mhm
03:29 AM rue_shop3: your going to find me one then?
03:29 AM rue_shop3: my problem is that I picked up his accent and I'm falling asleep
03:29 AM z64555: I don't know the way around your place
03:29 AM z64555: and I'm probably more than a few hundred miles away
03:30 AM rue_shop3: I'm almost in vancouver canada
03:30 AM rue_shop3: are you in a can?
03:30 AM z64555: I'm in Texas, near the coast
03:31 AM rue_shop3: well, yea, see, thats far away.
03:31 AM z64555: ya
03:31 AM * veverak wants to visit canada one day
03:31 AM rue_shop3: well, I have a spare bedroom
03:32 AM rue_shop3: earthquake!
03:32 AM rue_shop3: no, wait
03:32 AM rue_shop3: its my 3d printer
03:32 AM veverak: well, it will take some time, as a student, i dont give a europe<->canada flying ticket high priority
03:33 AM veverak: lol :)
04:10 AM rue_: dongge, http://ruemohr.org/~ircjunk/images/p1100258.jpg
04:10 AM rue_: this is my R-2R DAC
04:10 AM rue_: 8 bits
04:13 AM rue_: http://ruemohr.org/~ircjunk/images/p1100264.jpg
04:13 AM rue_: ^ the two servos I made today
04:43 AM rue_shop3: but, no time left to assemble my driver, I'm falling asleep
04:48 AM rue_bed: OH NO, too long making circuit today, blanket in washing machine. IS WET
04:48 AM rue_bed: ARG
04:48 AM rue_bed: I want to sleeeeeeep
04:48 AM rue_bed: no blanket :(
05:30 AM weyland|yutani: there is a nema connector only used in canada because 375Y600V systems for lighting and industrial applications
05:31 AM Jak_o_Shadows: pics?
05:31 AM weyland|yutani: nema 24
05:36 AM weyland|yutani: ups i misstyped 347Y600
07:27 AM BitEvil is now known as SpeedEvil
11:40 AM rue_: er, 3 phase UPS?
11:40 AM rue_: 347V Y 600V delta
01:50 PM rue_shop3: success today would be assembling two constant current drivers for my force feedback system
01:51 PM veverak: I finished cabal into cmake integration
01:51 PM veverak: now rest
01:51 PM veverak: than I may try to describe my motion planning using math
01:52 PM rue_shop3: cabal?
01:52 PM veverak: haskell build system
01:52 PM rue_shop3: oh
01:52 PM rue_shop3: what advantage is haskell????
01:53 PM veverak: my actual 'high level language' choice :)
01:54 PM rue_shop3: does it have built in hardware abstraction?
01:54 PM veverak: wat?
01:54 PM rue_shop3: does it have software abstraction?
01:54 PM veverak: what do you mean?
01:54 PM rue_shop3: does it have goal abstraction?
01:55 PM rue_shop3: well, can you write a 68M program in just 3 lines of code?
01:55 PM rue_shop3: that brings the most powerfull multicore computer to its knees?
01:56 PM veverak: I don't understand what you are asking, still
01:56 PM veverak: 68M program means what? RAM usage?
01:56 PM rue_shop3: no, the application size
01:57 PM rue_shop3: of the file that is the program
01:57 PM veverak: maybe, dunno
01:57 PM veverak: does not seem relevant
01:58 PM rue_shop3: ok
08:05 PM rue_shop4: :/ my motor drivers output is oscillating at 13Mhz
08:05 PM rue_shop4: its doing a better job than my signal generator
08:09 PM z64556 is now known as z64555
08:24 PM rue_shop3: http://www.vwlowen.co.uk/arduino/AD9833-waveform-generator/AD9833-waveform-generator.htm
08:39 PM Tom_L: doesn't sound like a desired effect
08:43 PM rue_: nope
08:43 PM rue_: reading up on it
08:44 PM rue_: I can try some things, but this is a pretty mean oscillation
08:44 PM Tom_L: coming from the driver itself?
08:45 PM rue_: yes
08:45 PM rue_: from +12 to 0
08:45 PM rue_: the 0 to -12 part is ok
08:45 PM Tom_L: hmm
08:45 PM rue_: and yet, the driver dosn't know where 0 is
08:45 PM rue_: hmm
08:46 PM rue_: the ref comes from the 5V rail, and the 5 and 12V rails are from the same supply
08:46 PM Tom_L: using a star ground configuration?
08:47 PM Tom_L: i've learned that's important
08:47 PM Tom_L: they become antennae otherwise
08:47 PM rue_: 13-14Mhz is pretty insane
08:48 PM Tom_L: pretty out there yes
08:48 PM rue_: I mean, HiFi audio amp, but ... really..
08:48 PM Tom_L: it's screaming for help
08:49 PM Tom_L: can't sleep but i should be
08:49 PM rue_: it just needs some pot to ease up its reaction speed
08:49 PM Tom_L: gotta take my kid at 2am
08:49 PM rue_: ouch
08:49 PM Tom_L: goin for his national competetion
08:49 PM Tom_L: in Louisville Ky
08:49 PM rue_: mhm
08:50 PM Tom_L: he took 1st in state
08:50 PM rue_: sweet
08:50 PM Tom_L: if he won at national he goes to Shanghai
08:51 PM rue_: THATS a long drive
08:51 PM Tom_L: or swim
08:51 PM Tom_L: it's for cnc
08:51 PM rue_: its good to excersize before a competition tho
08:51 PM rue_: cnc?
08:52 PM rue_: why did I think it was sports related
08:52 PM Tom_L: hand written and tests for measurments etc blueprint reading and such
08:52 PM Tom_L: it's a national skills competetion
08:52 PM Tom_L: heard of mike rowe?
08:52 PM rue_: heh, I know a mike rowe, but no
08:52 PM Tom_L: dirty jobs show?
08:53 PM rue_: oh damn, him too
08:53 PM rue_: ok
08:53 PM Tom_L: he's a major contributor
08:53 PM rue_: cool
08:53 PM Tom_L: and he will have dinner with him
08:53 PM Tom_L: big banquet
08:53 PM rue_: neat
08:53 PM rue_: so, who started the competition then?
08:53 PM rue_: and how does it work
08:54 PM Tom_L: https://www.skillsusa.org/
08:54 PM Tom_L: https://www.skillsusa.org/competitions/skillsusa-championships/
08:55 PM rue_: so, does he do any cnc stuff otherwise?
08:55 PM Tom_L: not as an occupation yet
08:55 PM Tom_L: he's still in school
08:56 PM Tom_L: just finished 2 associates degrees goin on to engineering school
08:56 PM rue_: k
08:57 PM Tom_L: the venue covers 20 football fields, it's a huge convention center
08:58 PM rue_: so, do they give them a plan and they have to make the parts?
08:58 PM Tom_L: yeah something like that
08:58 PM Tom_L: manually
08:59 PM Tom_L: write the gcode
08:59 PM Tom_L: along with other test requirements that's one
09:01 PM rue_: I'm circling the drain on designing a capacitive position sensor, it would be built like an old radio tuner cap, but with an offset. One sine channel, one cosine. Have the cnc cut out the disks
09:02 PM rue_: a bunch of brass plate to make them from would be nice, oh well
09:02 PM Tom_L: find some thick shim stock
09:02 PM rue_: heh
09:02 PM Tom_L: stack it and wedge between 2 plates and cut them at once
09:02 PM rue_: you overestimate how much manufacturing is done out here
09:02 PM Tom_L: shimstock is sold online
09:03 PM rue_: so are optical encoders...
09:03 PM Tom_L: uh huh
09:03 PM rue_: $
09:06 PM rue_: well, I got some things done on my vaccation anyhow
09:06 PM rue_: no solar panels :(
09:06 PM rue_: I got some 623zz bearings from china
09:06 PM rue_: the ID is 3.1mm
09:06 PM Tom_L: odd
09:06 PM rue_: they said "isn't that close enough to 3mm?"
09:07 PM rue_: :/ well, ... no.
09:07 PM rue_: dunno what to use them for... I have lots...
09:09 PM Tom_L: it's an international thing: https://www.worldskills.org/media/calendar/
09:09 PM rue_: doyou know where the winner came form last year?
09:09 PM Tom_L: it would be posted on their site
09:10 PM Tom_L: i think the actual scores are held private
09:12 PM Tom_L: i think this is the first year for that particular competetion for cnc
09:12 PM Tom_L: 1st or 2nd
09:15 PM Tom_L: watch the intro video, it shows the different areas of competetion
09:16 PM rue_: grr, cant cut steel sheet with the sherline...
09:16 PM Tom_L: no not so easily
09:16 PM Tom_L: how thick?
09:17 PM Tom_L: i cut some encoders on mine once
09:17 PM rue_: steel?
09:17 PM Tom_L: yeah
09:17 PM Tom_L: thin
09:17 PM rue_: 0.3mm or so
09:18 PM rue_: soup can
09:19 PM Tom_L: http://tom-itx.no-ip.biz:81/~webpage/cnc/new_pulleys/new_pulley_mounted2.jpg
09:19 PM Tom_L: cut the center out of that one on the sherline
09:19 PM rue_: http://ruemohr.org/~ircjunk/images/canosc1.jpg
09:19 PM rue_: the trick is to etch the disc
09:19 PM Tom_L: saw that
09:20 PM rue_: I'm glad yours has no more protection than mine does
09:20 PM Tom_L: new one does
09:21 PM Tom_L: http://tom-itx.no-ip.biz:81/~webpage/cnc/Mill_Steel/Paint/Paint3.jpg
09:21 PM Tom_L: made that from thin sheet
09:21 PM Tom_L: somewhat thin
09:21 PM rue_: soup can is thinner
09:21 PM Tom_L: http://tom-itx.no-ip.biz:81/~webpage/cnc/Mill_Steel/Paint/Paint6.jpg
09:21 PM Tom_L: mounted
09:21 PM rue_: I honestly dont know how I'd hold it down
09:22 PM Tom_L: sandwich
09:22 PM rue_: have you been playing with it anymore?
09:22 PM Tom_L: some
09:22 PM rue_: so whats to become of the sherline
09:22 PM Tom_L: did you see the wrench i made with it?
09:22 PM rue_: I dont think so
09:22 PM rue_: do show
09:22 PM Tom_L: it's still sitting where it was motorless
09:23 PM Tom_L: http://tom-itx.no-ip.biz:81/~webpage/cnc/Mill_Steel/Assembly/Final/Vise_parts/Speedhandle1.jpg
09:23 PM rue_: you have looked at brushed mtoors right?
09:23 PM Tom_L: o
09:23 PM rue_: I mean, how many times have you changed the brushes in your sherline?
09:23 PM Tom_L: i'm gonna avoid them
09:23 PM Tom_L: it never got used enough
09:24 PM Tom_L: because it was such a dissapointment
09:24 PM rue_: mhm, and how many hours did you put on it? 20000? 50000?
09:24 PM Tom_L: no idea
09:24 PM Tom_L: 2nd motor
09:24 PM rue_: !
09:24 PM rue_: oh
09:24 PM Tom_L: i screwed up the first one changing the brushes
09:24 PM Tom_L: but i did fix it
09:24 PM Tom_L: it's a spare now
09:25 PM rue_: the one I borrowed from armyofevilrobots needed new brushes after a while, but he's never done it and he got it used and put a LOT of time on it
09:25 PM rue_: so, you took its motor, but there was a spare
09:25 PM Tom_L: external or internal brush access?
09:25 PM rue_: internal
09:25 PM rue_: had to take it all apart
09:25 PM Tom_L: they suck to change
09:25 PM rue_: annoying, but I been there
09:25 PM Tom_L: the new one has screw access to them
09:25 PM rue_: mhm
09:26 PM rue_: anyhow, when I worked out motor pricing, its worth going brushed
09:26 PM Tom_L: http://tom-itx.no-ip.biz:81/~webpage/cnc/Mill_Steel/Assembly/Final/Vise_parts/Speedhandle_profile.jpg
09:26 PM Tom_L: i cut those straps on the new one
09:26 PM Tom_L: 1/4" steel
09:26 PM rue_: I'v put over 1000 hours on armyofevilrobots machine, and prolly over 2000 on the one I made
09:27 PM rue_: the one I made is just running a drill motor
09:27 PM Tom_L: yeah
09:27 PM Tom_L: i set that handle up to run all in one program
09:27 PM rue_: one brushless set costs about 12 motors
09:27 PM Tom_L: 3-4 op stops to move clamps etc
09:27 PM rue_: and its likley I'll never make it thru 12 motors
09:28 PM rue_: :)
09:28 PM Tom_L: yeah but the problem is the motor isn't big enough for this mill
09:28 PM rue_: you can get huge brushed mtoors
09:28 PM Tom_L: i know
09:28 PM Tom_L: but then i'd need another driver too
09:28 PM rue_: get a motor from an old disability scooter
09:29 PM rue_: er, current might be high
09:29 PM Tom_L: and i'm not good at matching those up so that's why i've been looking at servos / amps that are paired
09:29 PM rue_: get some aircraft mtoor
09:29 PM rue_: mhm
09:30 PM Tom_L: but all the chinaco spindles are a bazillion rpm and i don't want that
09:30 PM rue_: someone must have some amazing electric motors in a scrap pile up there
09:30 PM Tom_L: i want low end torque
09:30 PM Tom_L: haven't found them yet
09:30 PM Tom_L: i'd consider a 220v 3 phase and get a VFD to drive it
09:30 PM rue_: huh, my understanding is that aircraft use 600Hz 3 phase motors
09:30 PM Tom_L: no idea
09:31 PM Tom_L: most of those are 24v i thought
09:31 PM rue_: your in the right place in the world tho
09:31 PM rue_: possibly
09:31 PM Tom_L: not much electric shows up here
09:31 PM rue_: no, as in in 747
09:31 PM Tom_L: i know but none of the electrical shows up as scrap
09:32 PM rue_: they dont havea grave yard up there?
09:32 PM Tom_L: they moved one but i don't know where they put it
09:32 PM Tom_L: it was from test craft i believe
09:32 PM Tom_L: stress tests
09:32 PM rue_: > > google earth
09:32 PM Tom_L: they probably weren't complete
09:33 PM rue_: prolly had an electric-hydraulic motor
09:33 PM rue_: or two
09:33 PM Tom_L: i've driven by one but they moved it
09:33 PM Tom_L: they wouldn't let the general public in there anyway
09:33 PM rue_: I'd say a 747 is hard to hide, but I lose elephants in my shop all the time
09:34 PM Tom_L: hmm
09:34 PM Tom_L: i gotta get up in 3 hrs
09:35 PM Tom_L: http://tom-itx.no-ip.biz:81/~webpage/cnc/Mill_Steel/Assembly/Final/Vise_parts/table_slot1.jpg
09:35 PM Tom_L: final wrench assembly
09:37 PM Tom_L: i should go lay down a while
10:24 PM rue_shop4: if the tda2050 will oscillate at 14Mhz, maybe I should have more hope about doing pwm with it
10:30 PM rue_shop4: tho I'm trying to do current control, pwm isn't getting me far
10:30 PM rue_shop4: as, in analog, I can make the amplifier to the current control
10:30 PM rue_shop4: tho, I should try inserting a pwm amp
10:31 PM rue_shop4: pwm amp with current feedback, that sounds like a trainwreck already
10:32 PM rue_shop3: analog control of pwm current driver
11:36 PM AchiestDragon: arnt you supposed to convert the pwm signal into an analog voltage then use that voltage to set the current via a fet ?
11:39 PM AchiestDragon: then you get a constant volt/current out rather than one thats always trying to oscilate
11:40 PM AchiestDragon: well by constant one thats proportional to the pwm% over time
11:43 PM z64555: sounds familiar
11:43 PM z64555: PWM charges a capacitor, which controls a fet that amplifies it to a larger voltage/current
11:49 PM AchiestDragon: yea and the "slew rate" of the cap "charge discharge rate " defines the frequancy responce of the output
11:51 PM AchiestDragon: although you need have a good LPF after the cap to ensure you dont get the output oscilating at the pwm frequency
11:53 PM z64555: that's called ripple current, I think
11:54 PM z64555: depending on the application, some oscillation is acceptable
11:55 PM z64555: You're going to get oscillation no matter what, the LPF just reduces the natural frequency
11:56 PM z64555: hm, and maybe also the magnitude of the ripple current
11:56 PM z64555: its been awhile since I studied those
11:57 PM AchiestDragon: if the pwm is a signal level rather than load baring then you can get shut of most of the noise with a good lpf then use opamps to buffer the output to the drivers to drive the load