#robotics Logs

May 22 2017

12:01 AM mrdata_: rue_shop3, what sort of problem?
12:17 AM rue_shop3: they trip at the 1A they are supposed to
12:17 AM rue_shop3: even during a 5us pwm pulse
12:17 AM rue_shop3: _1_ pulse
12:22 AM rue_house: anniepoo, how did the day go for ya
12:22 AM rue_house: I got a number of my goals met
12:36 AM mrdata_: rue_shop3, seems like you want a low-pass filter
12:38 AM rue_shop3: yup
12:38 AM rue_shop3: want to see the circuit board I have to mod it into?
12:40 AM mrdata_: sure
12:44 AM rue_shop3: http://ruemohr.org/~ircjunk/robots/buddy_III/p1050579.jpg
12:45 AM rue_shop3: each board controls 3 motors, there are 3 current sense resistors that go into a maximum filter, that go into a 555 latch/relay driver that cuts the power
01:09 AM mrdata_: ok
01:36 AM mrdata_: rue_shop3, if the current-sense is a resistor, then seems like it would be easy to replace it with an RC Filter
01:37 AM rue_shop3: no, cause its 0.1R
01:42 AM mrdata_: rue_shop3, but what is the longest interval you want to suppress?
01:42 AM mrdata_: 5us ?
01:43 AM rue_shop3: thats what I'm not sure on
01:43 AM rue_shop3: what constitutes an overload
01:43 AM mrdata_: hmm
01:54 AM mrdata_: ok, if it were 1 ms, then you'd be looking at 0.1R * a huge capacitance, i guess
01:55 AM mrdata_: i wonder if an RL filter would do
01:59 AM mrdata_: no, still nuts
01:59 AM mrdata_: LC filter?
02:01 AM mrdata_: wait, no
02:02 AM mrdata_: f = R / (2 pi L) --> L = R / (2 pi f ) = 0.1 / (2 pi 1000 Hz) = 15.9 uH
02:04 AM mrdata_: so put a 15.9 uH choke in series with your load ?
02:05 AM mrdata_: rue_shop3, ^
02:08 AM rue_shop3: do you know how big a 16uH choke is?
02:09 AM mrdata_: smaller than the corresponding capacitor
02:10 AM mrdata_: it's only big if it has to be very low resistance
02:10 AM rue_shop3: I think its easier to intercept the aplified signal
02:11 AM rue_shop3: sorry, I have my head burried deep in an engine simulator
02:16 AM mrdata_: 49 turns on a 10 mm dia, 10 mm long cylinder is 16.2 uH
02:17 AM rue_shop3: air core?
02:17 AM mrdata_: yup
02:26 AM mrdata_: so, looking at 24 awg magnet wire, ampacity > 2A, wire dia < 0.6 mm with insulation, 16 turns per layer, so about 3 layers
02:27 AM mrdata_: overall inductance increases a bit so make that 48 layers, something around 20 uH
02:27 AM mrdata_: err, 48 turns
02:28 AM mrdata_: or even down to 44 turns maybe
02:30 AM mrdata_: 15 turns per layer, then
02:33 AM mrdata_: or 14 per layer, 42 turns total; so 1557 mm or so of wire, total series R is 0.13 ohm
02:34 AM mrdata_: so you could use the choke itself as the current-sense
02:34 AM rue_shop3: mmmmm
02:38 AM mrdata_: cutoff f around 1200 Hz
03:52 AM rue_house: hmmmm
04:13 AM Jak_o_Shadows: Hmm. If I used a couple of gears, I ould use a SG90 instead of a MG996
04:13 AM Jak_o_Shadows: (MG996 would be with a lever)
04:13 AM Jak_o_Shadows: But that'd slow down my fire rate
04:16 AM Jak_o_Shadows: Eh. 1/2 the point is to up the fire rate.
04:18 AM rue_house: ?
04:30 AM Jak_o_Shadows: nerf gun
04:52 AM Jak_o_Shadows: erm. To explain. It has a spinning disc, which accelerates the ammo. But the ammo needs to be pushed into the disc
04:52 AM Jak_o_Shadows: Which is just linear
05:44 AM rue_house: Jak_o_Shadows, draw
05:44 AM rue_house: t
05:44 AM rue_house: drat
05:45 AM rue_house: I meant to go over the makefile more
05:45 AM rue_house: or loading that binary on the ...
05:45 AM rue_house: its past 3am
05:45 AM rue_house: makefile
05:45 AM rue_house: I got it to compile
05:46 AM rue_house: the awk script wasn't supposed to add the processor and family, it was in the comments
05:49 AM Jak_o_Shadows: I load via opening it in gdb
05:49 AM Jak_o_Shadows: get openocd running.,
05:49 AM Jak_o_Shadows: then gdb, with make gdb, in that makefile of mine
05:49 AM Jak_o_Shadows: then just load
05:50 AM rue_house: I'm not in the shop
05:51 AM rue_house: or try that thing in the link you posted?
05:52 AM Jak_o_Shadows: Yeah. That did look about right
05:52 AM Jak_o_Shadows: I personally use gdb a lot
05:52 AM rue_bed: the two files it uses are in that stuff that was downloaded
05:52 AM rue_bed: I'v used ddd, butdont quite get with gdb
05:53 AM Jak_o_Shadows: I don't do much very complicated. breakpoints, command breakpoints, and printing out the odd variable
05:54 AM rue_bed: I generally dont use debuggers
05:54 AM rue_bed: almost everything I'v ever needed to do I could do with an led or scope off a pin
05:54 AM Jak_o_Shadows: I generally don't either.
05:54 AM Jak_o_Shadows: A scope is handy
05:55 AM Jak_o_Shadows: But being able to stop at one point is handy.
05:55 AM rue_bed: I think most of my ddd stuff has been diagnosing pointer problems
05:55 AM * veverak too find out, that "print" is only tool you need in coding
05:55 AM veverak: (most of the time)
05:55 AM rue_bed: yea, the stm32 has like 6 serial ports
05:56 AM veverak: in few minutes, I will be talking about this in full room of students
05:56 AM veverak: "training of recursion for students" we expected few, got a hundred maybe?
05:56 AM rue_bed: I dont disagree
05:57 AM veverak: little nervous
05:57 AM Jak_o_Shadows: I haven't actually setup a printf or debug over serial yet.
05:57 AM Jak_o_Shadows: I keep meaning to...
05:57 AM rue_bed: mmm, the temporal inflectionpoint of recursive code always gives me a headache
05:57 AM * Jak_o_Shadows wants a little dongle that logs serial to SD card
05:58 AM veverak: Jak_o_Shadows: that should be doable with arduino imho
05:58 AM rue_bed: the lines of code that are executed before the lines that preceed them
05:58 AM veverak: rue_bed: our students has headache from quicksort
05:58 AM veverak: *have
05:58 AM rue_bed: :)
05:58 AM veverak: in python
05:59 AM rue_bed: to think I'm rooted in BASIC
05:59 AM rue_bed: thats a scarry thought
05:59 AM veverak: :D
05:59 AM Jak_o_Shadows: Yeah veverak, you can buy them for about $8?
05:59 AM veverak: rue_bed: we used to taught them only 'C' first semester
05:59 AM * rue_bed pulls his C close
05:59 AM veverak: and wanted red-black tree coded after a year
05:59 AM veverak: really "cleansed" the rotten apples
06:00 AM veverak: Jak_o_Shadows: yep
06:00 AM rue_bed: red black tree?
06:00 AM veverak: more like
06:00 AM veverak: Jak_o_Shadows: 25$ for 10pcs of arduino pro micro
06:00 AM veverak: my favourite deal
06:00 AM veverak: rue_bed: yep
06:00 AM rue_bed: whats red-black tree?
06:00 AM veverak: https://en.wikipedia.org/wiki/Red%E2%80%93black_tree
06:00 AM rue_bed: you know the stm32 is only 1.73?
06:01 AM Jak_o_Shadows: I'm too rusty on proper comp sci. Like, I never quite got trees well enough.
06:01 AM veverak: complex selfbalancing sorted tree
06:01 AM Jak_o_Shadows: The rotation bit did my head in
06:05 AM rue_bed: huh
06:05 AM rue_bed: I'v not successfully written an editor or tetris, so I still regard myself as a coder fail.
06:06 AM veverak: lol
06:06 AM joga: code tetris editor where you have to pile up the file contents from falling characters
07:17 AM Gottaname is now known as Uchikoma
07:18 AM Uchikoma is now known as Gottaname
09:11 AM z64555: ball ammo, right?
02:15 PM rue_house: aparently everything is better in the shower, I managed to design the mechanical thing I been chewing away for days on
02:15 PM rue_house: in my head yea!
02:16 PM mumptai_: i know that, but my theory is that these ideas just like to hatch under the shower
02:16 PM mumptai_: maybe its smother to come out
02:17 PM mumptai_: (mhmmm, too much aliens movies?)
02:41 PM mrdata_: https://www.youtube.com/watch?v=Ps9o-dNj04U
02:41 PM mrdata_: what are typical reasons to want to mod a servo for continuous rotation?
02:45 PM Snert__: sail winch on an rc sailboat.
02:46 PM mumptai_: drive a wheel?
02:46 PM mumptai_: drive a propellor in a boat?
02:52 PM rue_shop3: I need a way of keeping earmuffs on my head without having them on my ears
02:52 PM rue_shop3: it sounds easy, but its not
02:55 PM rue_shop3: hmmm simple connection, should I weld it, or bolt it...
03:19 PM rue_shop3: hard metal, should have welded it
03:24 PM mrdata_: Snert_, mumptai_, just seems to me that you could use any motor for such tasks; but a servo wants a peculiar interface
03:24 PM mrdata_: one that is more complex than needed
03:25 PM mumptai_: but the servo interface is simple
03:25 PM mrdata_: what do you mean
03:25 PM mrdata_: you have to generate timing signals
03:26 PM mumptai_: my MCU or FPGA has no issues with that, but they can't drive a motor directly
03:26 PM mumptai_: therefore, it is simple to interface
03:27 PM mrdata_: ok we'll put "simple" in scare quotes then
03:28 PM veverak: yep
03:28 PM veverak: it's definetly simpler than driving motor directly
03:29 PM mrdata_: really depends on what you want to do
03:29 PM veverak: yep
03:29 PM mrdata_: i dont think you get speed control with the servo interface
03:29 PM veverak: I think you should
03:29 PM veverak: :)
03:30 PM mrdata_: the motor is trying to bring the arm to the right orientation as fast as possible
03:30 PM veverak: https://www.adafruit.com/product/154
03:30 PM mrdata_: but you took out the stops
03:30 PM rue_shop3: speed is just position/time
03:30 PM veverak: https://www.adafruit.com/product/154
03:30 PM veverak: Position "90" (1.5ms pulse) is stop, "180" (2ms pulse) is full speed forward, "0" (1ms pulse) is full speed backwards.
03:30 PM veverak: mrdata_: ^^
03:30 PM rue_shop3: I have my own linear interpolation library I use for that stuff
03:30 PM mrdata_: and defeated position control
03:30 PM rue_shop3: actaully, I have a trapazoidal library thanks to people asking questions and my playing
03:31 PM rue_shop3: ooh continious rotation?
03:31 PM rue_shop3: sure you do
03:31 PM veverak: mrdata_: with proper continous servo, you have speed/direction control
03:31 PM rue_shop3: just edge either side of the stop
03:31 PM veverak: just everything you need
03:31 PM rue_shop3: ?
03:31 PM mrdata_: veverak, but the link i shared wasnt a "proper" mod
03:31 PM rue_shop3: wait, whats is this
03:31 PM rue_shop3: why would you pay $12 for a servo
03:32 PM veverak: mrdata_: well
03:32 PM rue_shop3: you should get a bit of speed control on the edges of being stopped
03:32 PM veverak: mrdata_: you can buy continuous ones easily
03:32 PM veverak: mrdata_: and, things is
03:32 PM rue_shop3: YOU CAN MAKE CONTINIOUS ONES EASY
03:32 PM mrdata_: veverak, you missed the point
03:33 PM mrdata_: https://www.youtube.com/watch?v=Ps9o-dNj04U why would you want to do this?
03:33 PM veverak: mrdata_: I take arduino, mg90s
03:33 PM veverak: modiy them for continuous servos like in the video
03:33 PM veverak: glode it together literally, add some wheels
03:33 PM veverak: and have two-wheeled robot for extremely low price with simple way to control it
03:33 PM veverak: use arduino Servo library which is just import();
03:33 PM veverak: tadaaah!
03:34 PM veverak: mrdata_: beat this in simplicity
03:34 PM mrdata_: still missing the point
03:34 PM mrdata_: i'm not trying to do this, i'm puzzled as to why anyone would
03:34 PM mrdata_: do the mod in the video
03:36 PM veverak: you miss the point
03:36 PM veverak: mrdata_: what I described was simple robot to build
03:36 PM veverak: meaning, simple in effort needed, not complexity of mechanism
03:36 PM veverak: and low price
03:36 PM veverak: you can't beat that rellly
03:37 PM veverak: -> that's why people do it, because it gives tham "dc motor"-like solution with benefits in simplicity of using it
03:37 PM mrdata_: there are lots of dc motors
03:37 PM mrdata_: already cheap and simple to use
03:37 PM veverak: but they are not simple to control with arduino
03:38 PM veverak: with modified servo, you need just the servo itself and arduino
03:38 PM veverak: literally nothing more
03:38 PM veverak: "dc motor" requiers "dc motor driver"
03:38 PM veverak: not to mention the "import <Servo.h>;" part
03:39 PM veverak: not the mention the part if housing of it and gearbox
03:40 PM veverak: *part of housing
03:47 PM mumptai_: if a servo solves the problem, its a cheap problem, i usually don't care and just want to get it done
03:47 PM mumptai_: its a hack
03:48 PM mumptai_: i have some a braod set of motors, and the cheap servos are the cheapest
08:33 PM davr0s is now known as doomlord
10:38 PM Tom_itx is now known as Tom_L
11:47 PM rue_shop3: I really do need to focus on my todo lists more