#robotics Logs
May 16 2017
#robotics Calendar
12:03 AM rue_shop3: hmm cleaning my room looking for schematics
12:06 AM rue_shop3: gee I have a lot of stuff I dont need to keep
12:49 AM rue_house: !#$%#@$^% units dosn't know warp
01:04 AM rue_house: those lidar units are $150usd, just to note
02:31 AM z64555: YUP
02:31 AM z64555: err, lemme turn off capslock
02:31 AM z64555: ok there
03:18 AM justan0theruser is now known as justanotheruser
04:53 AM Jak_o_Shadows: RUE'S OFFLINE.
04:53 AM Jak_o_Shadows: His website is down
04:53 AM Jak_o_Shadows: I was gonna look at the lathe pics
05:52 AM Tom_L: his server is a different location
06:17 AM Jak_o_Shadows: ah
09:21 AM rue_house: power outage from 1am to 3:45am
09:22 AM rue_house: wonder what happened
09:22 AM rue_house: from the cleanness of the cut, something big
09:22 AM veverak: smurfs
09:22 AM veverak: definetly smurgs
09:22 AM veverak: *smurfs
09:23 AM veverak: thought about making 8 leg robot
09:23 AM veverak: 24 servo driver, number of servos is getting out of hand
09:23 AM rue_house: dunno, I suspect either someone slid off the road into a pole, a tree came down on the local line, or there was a reaaaaly big landslide up the supply chain
09:23 AM veverak: makes sense
09:23 AM rue_house: thats just 3 of my servo controllers on one bus
09:24 AM veverak: you use arduino?
09:24 AM rue_house: no I use the avrs direct
09:24 AM veverak: hmm
09:24 AM rue_house: I buy my avrs as arduinos cause its cheaper
09:24 AM * veverak was thinking of making board
09:24 AM veverak: https://www.adafruit.com/product/815
09:24 AM veverak: two of these
09:24 AM rue_house: $8 for an avr chip, or $1.50 for an arduino
09:24 AM veverak: (meaning the PCA9685 chip)
09:25 AM veverak: should be able to get the PCB milled on hackerspace PCB CNC
09:25 AM rue_house: ah yes, your going for high cost and horrid resolution I see
09:25 AM veverak: 12-bit is not horrid afaik
09:25 AM rue_house: you know you get less than 7 bits of actual resolution, right?
09:26 AM rue_house: no
09:26 AM veverak: I know
09:26 AM rue_house: you dont get the 12 bits
09:26 AM veverak: anyway
09:26 AM veverak: adding 3 arduinos is too big
09:26 AM rue_house: 12 bits is for 100%, but your max duty for the servo is 2/50ms
09:26 AM rue_house: have you seent eh pro mini?
09:26 AM veverak: but, maybe we will be able to mill pcb for arduino chip too
09:27 AM veverak: rue_house: yeah, I use only that version arduino for last 1 or 2 years
09:27 AM rue_house: how can adafruit be asking $15 for that board????
09:27 AM veverak: I don't care :)
09:27 AM * veverak didn't bought it from adafruit
09:27 AM rue_house: yea... but.....
09:27 AM veverak: 4$ ali?
09:27 AM rue_house: $15!?
09:28 AM veverak: it's adafruit :)
09:28 AM veverak: nah
09:28 AM veverak: 1.86$ on aliexpress
09:28 AM rue_house: hey can you bring up http://ruemohr.org ?
09:28 AM z64555: not including shipping
09:28 AM veverak: z64555: that's free
09:28 AM rue_house: not from ada
09:28 AM veverak: ah, was talking about ali
09:29 AM rue_house: so from ada its $15+chipping
09:29 AM z64555: jeez
09:29 AM rue_house: yea, or 1.86+0
09:29 AM z64555: rue_house: page keeps timing out
09:29 AM rue_house: :/
09:29 AM rue_house: yea here too
09:29 AM rue_house: I hope its ok out there
09:31 AM rue_house: power outage was local, reaaaaly local
09:31 AM z64555: "The output burnt out" local?
09:31 AM z64555: err, *outlet
09:32 AM rue_house: power went out
09:32 AM rue_house: at like 1am
09:32 AM z64555: "Just my house is dark" local?
09:32 AM rue_house: no, just my block
09:32 AM veverak: nah
09:33 AM rue_house: I'm beside a camp, trees from it fall on the line all the time
09:33 AM veverak: for testing phase I will get second PCA9685 and will decide what to use finally
09:33 AM veverak: I suppose I will make custom PCB anyway
09:33 AM rue_house: huh
09:33 AM rue_house: doteasy says they are doing a server upgrade
09:33 AM rue_house: but I'm just using them for dns, they have nothing to do with the webserver
09:34 AM veverak: every server is dead lister
09:34 AM rue_house: heh
09:34 AM rue_house: even pete?
09:34 AM veverak: even pete lister, even pete
09:34 AM rue_house: even Ann in finance?
09:36 AM veverak: even Ann lister, even Ann
09:36 AM rue_house: even little Joey?
09:36 AM veverak: even little Joye lister, even little Joye
09:37 AM z64555: I have no idea what's going on
09:37 AM rue_house: funny enough www.ruemohr.org is ok, its the doteasy one
09:37 AM rue_house: z64555, watch the Red Dwarf series and find out
09:38 AM z64555: I'm afraid to, lol
09:38 AM rue_house: but whats up with ruemohr.org!?
09:39 AM veverak: so, current for sg90 is 6 idle, 220 free running, 650 load
09:39 AM rue_house: mA?
09:39 AM veverak: yep
09:39 AM veverak: load as horn locked
09:39 AM rue_house: sounds about right
09:39 AM rue_house: no, thats for more than one
09:40 AM veverak: https://www.addicore.com/Addicore-SG90-Mini-Servo-p/113.htm
09:40 AM veverak: but of course, it depends on SG90 you have...
09:40 AM rue_house: wait wait i just did this
09:40 AM rue_house: cuase I did the load detection
09:40 AM veverak: you did?
09:40 AM veverak: !!!
09:40 AM veverak: :)
09:40 AM rue_house: pause, I have diagrams and numbers
09:41 AM rue_house: ok, what was I babbeling about on...
09:41 AM veverak: ruemohr.org
09:42 AM rue_house: 2017:04:20
09:42 AM rue_house: zlog
09:42 AM rue_house: xlog
09:43 AM rue_house: (I think toms bot is clogged :) )
09:43 AM veverak: anyway, I have torque, current at 0/max load, weight of arm, center of mass of arm
09:43 AM rue_house: http://tom-itx.no-ip.biz:81/~tom-itx/irc/logs/%23robotics/2017-04-20.html
09:43 AM veverak: I think that for any movement I could get decet estimated about current needed
09:45 AM veverak: rue_house: should I see the data about load information somewhere?
09:46 AM rue_house: I'm looking for it
09:46 AM rue_house: maybe the date on my camera is out
09:46 AM veverak: I see
09:46 AM rue_house: no
09:46 AM rue_house: damn
09:47 AM veverak: min( torque_needed / max_torque , 1 ) * ( stall_current - running_current ) + stall_current
09:47 AM veverak: sounds like good estimate for current need
09:47 AM veverak: *needs
09:47 AM rue_house: the images I took are of the current detector output
09:48 AM veverak: I was thinking about giving somebody at university project: make 18-channel PWM driver with current sensing
09:48 AM rue_house: the detector uses a 10R resistor shunted across the EB of a pnp transistor
09:48 AM rue_house: want to see the circuit?
09:48 AM veverak: deifnetly
09:48 AM rue_house: haha well my webserver is down !
09:48 AM rue_house: haha
09:49 AM veverak: :/
09:49 AM rue_house: I'm missing a limb :(
09:49 AM rue_house: how can I post it...
09:49 AM veverak: imgur.com ?
09:51 AM rue_house: the motor will go to 100% duty if loaded enough
09:52 AM rue_house: http://imgur.com/a/4FK43
09:52 AM rue_house: god my keyboard look horrid in that image
09:52 AM veverak: it does
09:52 AM rue_house: (shop soldering station keyboard)
09:53 AM rue_house: if you measure the duty of the current pulse, you get the % load
09:53 AM veverak: interesting
09:54 AM rue_house: http://imgur.com/a/GmCAr
09:54 AM rue_house: timing relation
09:54 AM rue_house: control pulse on bottom
09:54 AM rue_house: be aware there is deadband, there is a min load for the servo motor to kick in
09:56 AM rue_house: I suppose I should make a compliant servo demo
09:57 AM rue_house: oh putz, I think my machine lost the writeup I did
09:58 AM rue_house: no here we go
09:58 AM veverak: hmmm
09:58 AM rue_house: I'm gonna put this into a webpage like the servo101, in the meantime
09:58 AM rue_house: ""
09:58 AM veverak: do iwant to use units in yaml config?
09:58 AM veverak: it should be possible
09:58 AM rue_house: part 1, reading position.
09:58 AM rue_house: The controller chip in a hobby servo uses a potentiometer to measure position. The potentiometer is powered from a regulated source in the chip, of about 2.5V (well below the minimum operating voltage of the servo) Reading the position is as easy as tapping the middle terminal of the potentiometer and feeding it to one of the hungry little ADC channels of your microcontroller.
09:58 AM rue_house:
09:58 AM rue_house: part 2, measuring the servo load.
09:58 AM rue_house: As described before, the servo controller uses a pulse stretcher to generate the error-correction pulse for the motor, the amount of average current in the motor is proportional to the time the motor is operated, which is proportionate to the load on it. The Logic circuit of the servo draws a really tiny amount of current, and the motor draws a lot of current, as such, its quite easy to build a 'current detector' circuit, this dosn't
09:58 AM rue_house: have to measure the actual current, just the amount of on-time of the motor, which is dead easy. This pulse goes into the microcontroller and gets measured.
09:59 AM rue_house:
09:59 AM rue_house: part3, knowing the polarity of the load.
09:59 AM rue_house: Because part2 only knows the amplitude of the force, this is required to know which direction the motor is trying to push to make the correction. Easy, cause the mtoor is driven by an H bridge, so what we do it tap one side of the motor, drop teh voltage a bit with a voltage divider, and feed it into the microcontroller. When the motor is pulling power, you check this new signal to know if its pulling or pushing. Between teh two signa
09:59 AM rue_house: ls you know the direction and amplitude of the force on the servo.
09:59 AM rue_house: ""
10:00 AM rue_house: so I end up with a servo that has two extra wires comming out of it, one off the pot and one off one side of the motor
10:02 AM rue_house: I'm annoyed that I'm still taking scope images without saying the votlage/time on them
10:03 AM veverak: hmm:)))
10:03 AM veverak: sec/60°
10:03 AM veverak: not my favourite unit truth to be told
10:13 AM rue_house: ms/300*
10:14 AM veverak: ... :)
10:14 AM rue_house: 6 us/degree
10:18 AM veverak: anyway
10:18 AM veverak: 0.1sec/60° for sg90
10:19 AM veverak: hard to believe
10:19 AM veverak: I wonder if I can figure out simple way to get better estimate based on torque needed
10:23 AM veverak: ok, so let's say that 0.1sec/60° is speed for servo without load
10:23 AM veverak: theoretically, speed at maximal torque should be slightly above 0
10:23 AM veverak: meaning
10:24 AM veverak: simple estimate is something like: min(torque_needed/torque_max, 1) * idle_speed
10:24 AM veverak: should be speed estimate?
10:24 AM veverak: if power is constant, speed should be in relation with torque
10:51 AM SpeedEvil: torque*rotational speed = watts
10:51 AM SpeedEvil: 1Nm*1 radian per second = 1W
10:51 AM veverak: yeah
12:59 PM anniepoo: hey rue - re mould became permanent fixture - I fiberglassed over layered laser cut
12:59 PM anniepoo: corrugated cardboard.
12:59 PM anniepoo: Pulled the cardboard out by soaking in water
01:03 PM SpeedEvil: Work well?
01:05 PM anniepoo: yes
01:06 PM anniepoo: I covered the cardboard in plaster cloth, then waxed that. It pulled free easily, but there's plaster residue, and scrubbing that off is a minor chore
01:06 PM anniepoo: next time I'll use paper mache.
03:02 PM Snert_: spray it with a release agent...PAM spray...silicone spray?
03:57 PM linuxburger: hi
04:43 PM tttb3 is now known as tttb
06:32 PM rue_house: veverak, did you work it out?
06:32 PM veverak: rue_house: I suppose it's as said
06:33 PM veverak: did not actually needed to write that part of the code yet
06:33 PM rue_house: do you want to try the force feedback?
06:34 PM rue_house: if you tap the servos for position feedback too, you dont ahve to have a glitch on startup
06:34 PM veverak: eventually
06:34 PM veverak: gn for now
06:35 PM rue_house: yay ruemohr.org is back up
06:36 PM rue_house: http://ruemohr.org/~ircjunk/tutorials/elex/hobbyservo/servo101.html
06:36 PM rue_house: 0.2A/div
06:36 PM rue_house: so, almost 0.4A whent eh motor turns on
07:05 PM justan0theruser is now known as justanotheruser
10:50 PM z64555: Hey anonnumberanon, did you get an instagram account?
10:50 PM anonnumberanon: yeah man
10:50 PM anonnumberanon: to have pictures to show on my Tinder z64555
10:50 PM z64555: k, just making sure
10:51 PM z64555: oh, tinder messages. alrighty then
10:51 PM z64555: I was gonna follow you, but now theres no point. lol
10:53 PM anonnumberanon: oh I'm glad you're stalking me though that's cool
10:55 PM anonnumberanon: although, I'm slowly getting ennoyed with white american girls (and porto rican girls). i really can't connect with them
10:55 PM anonnumberanon: and that's 90% of women around me
11:05 PM z64555: no I'm not stalking no. lol
11:10 PM z64555: and I'd offer advice but I'm absolutely clueless on the subject of "socializing"
11:14 PM z64555: I try to talk about circuits and robots and I just get glazed stares
11:18 PM zhanx: anonnumberanon: that is a social issue not a robotics issue
11:20 PM Snert: where is a good geekchick when ya need one.
11:23 PM anonnumberanon: been wondering for the past 5 years
11:32 PM rue_shop3: its quiet, there must be another computer off somewhere