#robotics Logs

Sep 22 2015

05:38 deshipu veverak: a robot hat for the rpi A+
05:42 veverak I see
05:43 veverak deshipu: using SPI to connect to rpi?
05:43 deshipu veverak: i2c
05:44 veverak I see
05:44 veverak hmm
05:44 deshipu hmm, I could actually also break out the i2c pins, you might want to put more stuff on the bus
05:44 veverak will it handle it?
05:44 veverak I mean speed-vise
05:44 deshipu and I need to move the power switch, as it clashes with the usb plug
05:45 deshipu I did it over 9600 serial...
05:45 deshipu so I think it should work :)
05:45 deshipu the servos are 50Hz
05:45 deshipu and you don't even send a new position for them that often
05:45 veverak I see, ok
05:46 deshipu I want to use those bent 90° headers for the servos, so that they fit between the boards
05:46 deshipu so you get a sandwitch
05:47 deshipu not sure how well it will all fit
05:47 veverak yeah
05:47 veverak got any repo?
05:47 verak would like to peek i
05:48 veverak also
05:48 veverak do you somehow check lipo battery if it doesn't have low voltage?
05:48 deshipu https://bitbucket.org/thesheep/tote/src/tip/fritzing/
05:49 verak hopes Analog port could be
05:49 deshipu yes, the two resistors and a cap
05:49 deshipu form a voltage divider
05:49 deshipu for the adc pin to check battery voltage
05:49 veverak awesome
05:49 deshipu I already soldered them for you on the boards I'm sending you
05:49 deshipu because it's hard to get smd parts in low quantities
05:49 veverak AWESOME! :D
05:50 deshipu I should go to the post office and send it now
05:50 veverak deshipu: ehm, do you receive payments in form of beer?
05:50 veverak :)
05:50 deshipu always
05:51 veverak (y)
05:51 veverak :)
05:56 verak is going to pick a bat
05:59 veverak deshipu: I suppose I don't have to worry about "C" rate of battery?
06:01 veverak http://hobbyking.com/hobbyking/store/__23318__Turnigy_nano_tech_900mah_1S_15C_Round_Lipo.html looks awesome
06:21 deshipu I have a bunch of those
06:21 deshipu not very nice -- it's very hard to attach wires to them
06:22 veverak nah, looks like it should be worth the struggle
06:22 deshipu veverak: I recomment LiFePO4
06:22 deshipu recommend
06:23 veverak ok
06:23 deshipu http://hobbyking.com/hobbyking/store/__14075__ZIPPY_Flightmax_700mAh_6_6V_5C_LiFePo4_Receiver_Pack.html
06:23 deshipu I use this one in one of the robots
06:23 deshipu (the downside, you will need a proper charger)
06:24 deshipu if you don't have a proper charger already, then get a 1S LiPo
06:24 deshipu and a boost converter to 5V
06:24 deshipu or use one of those powernbanks for cellphones
06:24 deshipu tote will run on 3.7V, but raspberry pi won't
06:24 veverak not downside, have many rc chargers
06:25 veverak nah, I suppose I will hate to make it 5V for raspbi?
06:27 deshipu you will either need a step up or 2S (or more) and step down
06:27 deshipu rpi doesn't like anything else than steady 5V
06:27 veverak yeah
06:28 veverak afaik most of the stepdowns are 6V+ ?
06:28 deshipu yes, that's why you need a 2S battery
06:28 veverak yeah
06:28 veverak also
06:28 veverak deshipu: that servos run fine on 1S batteries?
06:28 deshipu also, make sure it can handle the ampers
06:28 deshipu yes
06:28 veverak awesome :)
06:28 deshipu it's out of spec, but they work
06:29 veverak and ampers are? :D
06:29 deshipu 2A for the servos, max
06:29 deshipu well, roughly
06:29 veverak and 2A max for rpi?
06:29 deshipu in theory each of the servos can drain 400mA
06:29 veverak yaeh, I see
06:30 deshipu but in practice only the 4 knee servos get much loaded
06:30 veverak http://hobbyking.com/hobbyking/store/__14075__ZIPPY_Flightmax_700mAh_6_6V_5C_LiFePo4_Receiver_Pack.html seems like good choice
06:31 veverak 3.5A if my math is correct
06:31 deshipu yup
06:31 deshipu I use it with one of the Tote robots
06:31 veverak good
06:34 deshipu it also fits on the bottom, between the servos
06:34 deshipu so the robot stays compact
06:35 veverak yeah
06:35 veverak and I suppose I can use 5V arduino then
06:35 deshipu yes
06:35 deshipu no
06:35 deshipu no, you can't
06:35 deshipu rpi's gpio is 3.3V
06:36 deshipu and it does break when you use 5V on them for long
06:36 deshipu I killed one this way
06:36 veverak I see
06:37 veverak hmm
06:37 deshipu but you can power the 3.3V arduino with 5V
06:38 veverak deshipu: so I use 2S battery and use voltage divider to powerup arduino?
06:38 veverak oh
06:38 veverak I see
06:38 deshipu it has a linear regulator on board
06:38 veverak nice
06:38 veverak :)
06:38 deshipu plus, the microcontroller on board is exactly the same as with 5V
06:38 deshipu just the crystal is slower
06:38 veverak I see
08:35 rue_mohr sure use a shunt regulator :)
12:23 Votato Hey guys, I've went and got some proper wheels for the robot :P
12:23 Votato However, now I have a problem - how does one mount the wheels onto the motor?
12:23 Votato http://cosketch.com/SavedImages/purbcC9h.png
12:24 Votato I have 2 motors, 2 wheels and 2 wooden "axles"
12:26 Votato the holes on the wheels are massive compared to the motor
12:29 Votato Here is a picture taken by my potato quality camera - http://i.imgur.com/oIhCczL.jpg (the middle bit is the motor's turny thing)
12:40 Hyratel motor shaft
12:40 Hyratel you need a mounting bushing
12:40 Hyratel actually no
12:41 Hyratel you need a reducing gearbox because mounting a wheel directly to the motorshaft won't get you driving
12:41 Votato so.. I need gears? :P
12:42 Hyratel you need a gearbox
12:42 Hyratel there are several small ones available at sparkfun.com
12:42 Votato https://www.sparkfun.com/products/12606
12:42 Votato oh god..
12:43 Hyratel haha no
12:43 Hyratel https://www.sparkfun.com/products/12285
12:45 Votato http://www.amazon.co.uk/100RPM-High-Torque-Electric-Motor/dp/B006Z4K0UK/ref=sr_1_17?ie=UTF8&qid=1442942472&sr=8-17&keywords=gear+motor
12:45 Votato (I'm in the UK) Now forgive me for being incompetent at all electronics, but that says Gearbox motor?
12:45 Votato Or is it a mount only?
12:45 Hyratel it's a motor with a builtin gearbox
12:46 Hyratel it has two threaded holes in the face for mounting
12:46 Votato I see
12:46 Hyratel http://www.amazon.co.uk/2-5KG-Micro-Speed-Reducing-Motor/dp/B009AQLDSS/ref=sr_1_1?ie=UTF8&qid=1442942589&sr=8-1&keywords=micro+gear+motor
12:47 Votato so essentially I bought the wrong motor? :P
12:47 Hyratel yep
12:47 Votato yay
12:47 Hyratel there's only a few kinds of motors that can mount directly to a wheel but those are out of scope for your current knowledge (yet)
12:47 Hyratel stick to geared motors
12:47 Votato Judging by amazon it will probably take a week to get those :P
12:48 Hyratel a 'gearmotor" is shorthand for a motor with a gearbox pre-installed
12:48 Hyratel well awesome, you can use that time to get your learn on
12:48 tato s
12:48 Votato thanks for your help :P
12:49 Hyratel no problem
12:49 Hyratel and I know the feeling of "wrong part purchase, damnit"
12:49 Votato Is there any other way of making a wheel go?
12:49 Hyratel no
12:52 Votato Ok, better question, are geared motors used in other components?
12:52 Hyratel yes, for many things
12:53 Hyratel they're one of the most common and easiest ways to get thigns moving
12:53 Hyratel ever played with a Servo?
12:54 Votato First time I've played with motors :P
12:54 Hyratel aha ok
12:54 Hyratel well, just so you know
12:54 Votato My question can be translated as "can I take something apart to get them"
12:54 Votato :P
12:54 Hyratel a servo (hobby servo) is a gearmotor with a position sensor and two end-stops
12:55 Votato aha
12:55 Hyratel but you're better off using servos as servos
12:55 Hyratel a servo costs more because it has more to it
12:56 Votato also they look way bigger
12:56 Hyratel motor, gearset, sensor (such as a potentiometer), logic board, enclosure
12:56 Hyratel https://nikhiljgeorge.files.wordpress.com/2012/08/untitled8.png?w=300&h=184
12:57 Votato So those gears, that's the gearbox?
12:57 Hyratel yes
12:58 Votato I did open up a sharpener once and found a metric ton of gears :P
12:58 Votato Electric sharpener that is
12:58 Votato protip: loud noises don't work well with pets
12:59 deshipu depends on the pets
13:01 Votato Parrots are a no
13:02 deshipu deaf parrots are fine
13:02 Votato *frowns*
13:02 deshipu dead ones too
13:03 deshipu lovely plumage
13:03 Votato It's an ex parrot
13:03 Votato *thinks*
13:03 Votato Don't DVD drives have motors in 'em?
13:04 deshipu they do, usually at least three
13:04 Votato Ooh
13:04 deshipu two steppers and one DC
13:04 Votato Do you think they'd be geared? :P
13:04 deshipu no
13:04 Votato damn
13:04 deshipu well, the dc one is geared, but it's a linear gear
13:04 deshipu for moving the tray
13:04 deshipu you can do a trick
13:05 deshipu mount the wheels on screws or nails or whatever, so that they can move freely
13:05 deshipu put a piece of rubber hose on that metal shaft of the motor
13:05 deshipu and mount the motor so that the shaft with the rubber touches the top of the wheel
13:05 deshipu probably with some springy metal
13:06 deshipu like a strip cut out of a tin can
13:06 Hyratel if you don't have a dead DVD player.. you're wasting more money than you're spending on new motors
13:06 Votato it /is/ dead :P
13:06 Votato It's as dead as a dodo
13:07 Votato deshipu: Can you make that in diagram form?
13:08 Votato Doesn't have to look pretty, I just suck at visualising ideas
13:08 deshipu let me find a picture
13:12 deshipu those old do it yourself books are great
13:12 deshipu http://paste.sheep.art.pl/e32e1ecd-cee2-4463-9939-24b6493557dd/%2Binline
13:13 Votato Oh I see
13:13 Votato And this works on my current motors?
13:14 deshipu who knows
13:14 deshipu it will better than attaching the wheels directly to the shaft
13:15 deshipu personally I just use cheap hobby servos modded for continous rotation for such things
13:15 deshipu I don't need a H-bridge then
13:17 Votato Yeah, I bought a L293 for that
13:17 tato waits until everyone says it was the wrong
13:18 Hyratel it's servicable
13:18 veverak deshipu: also
13:18 veverak deshipu: how many servos do you expect for logicoma to use?
13:18 Hyratel there are fancier ones but that'll work fine
13:19 Votato Right, time to get to work then, thanks :P
13:19 Votato CUE THE MUSIC - https://www.youtube.com/watch?v=wyz_2DEah4o
13:19 deshipu veverak: 14, with two pairs sharing the signal
13:20 veverak so ordering 15 servos should be OK
13:20 veverak hmm, or maybe 20?
13:20 deshipu veverak: 8 for the legs, 4 for the wheels -- sharing the signal for each side, 1 for the eye and 1 for the hands
13:20 deshipu I like to have some spares
13:20 veverak yeah, 20 seems more reasonable
13:21 deshipu note that the logicoma uses a different leg configuration than Tote
13:21 deshipu it only has 2 degrees of freedom per leg
13:21 veverak yeah
13:22 veverak just wanted to have some reserve if I would want to upgrade
13:24 deshipu get 10 SG90s and 5 SG92Rs
13:25 verak is more thinking about 10 an
13:25 verak got multiple project
13:29 Votato Robot case material suggestions for someone that doesn't have a 3D printer?
13:29 veverak Votato: depends
13:29 Hyratel Votato, plywood
13:29 verak would ouse some cheap wood and hotglue pi
13:29 Hyratel veverak, those aren't even structural!
13:29 ratel bad
13:30 veverak :D
13:30 Votato I have access to a hot glue gun... at work :P
13:30 veverak aaaand ruler, pencil, rubber
13:30 veverak time
13:30 veverak yeah, that could work :)
13:31 veverak also some plastic "profiles", L/U shape could be also handy
13:31 veverak Votato: maybe if you are willing to buy something there are sold these alu profiles
13:32 Votato veverak: I am, I am just really unprepared
13:32 veverak http://www.ehlinik.cz/produkty/CBU0000101/15.jpg
13:32 veverak this shape
13:32 veverak you can see many things built from them because they are sort of universal
13:32 Hyratel Votato, you're going to have to knuckle down and buy tools
13:33 Votato Hyratel: I didn't have a soldering iron until 2 weeks ago :P
13:33 Votato I've already fixed seventy billion things with it
13:33 veverak http://solidsmack.com/wp-content/uploads/2013/10/gmax-3d-printer-render.jpg
13:33 veverak you see that these profiles can be connected with "plates" that you can make
13:33 veverak could be handy
13:33 veverak :)
13:34 Votato hm
13:34 veverak Votato: I would suggest "dremel" tool if you don't have any tool for this
13:34 veverak but bevare that it will take you some prototypes before it is really nice, like with any other tool
13:34 veverak :)
13:37 Votato If I made cars, they would look like this - http://i.dailymail.co.uk/i/pix/2012/06/23/article-2163557-13BFBC77000005DC-114_638x463.jpg
13:39 Votato Whoa guys wait
13:39 Votato Going back to geared motors, would an Xbox controller have some?
13:39 Hyratel no
13:39 Votato Aw
13:40 Hyratel the rumble motors are eccentric-weighted with no gearing
13:40 deshipu there are also ready robot chassis with gears and all
13:41 deshipu I got this one some time ago, still didn't do anything useful with it: http://www.hobbyking.com/hobbyking/store/__26248__Simple_Expandable_Robot_Chassis_KIT_.html
13:41 Hyratel Votato, you'll spend less time and heartburn if you jsut buy a motor
13:41 deshipu the quality is rather poor, but it works
13:42 Hyratel and the price is right to learn with
13:42 Votato Hang on a minute
13:42 Votato What he's just linked me there
13:42 Votato Now that's also a geared motor?
13:42 Hyratel it's a motor and geartrain
13:42 Hyratel two, actually
13:43 Hyratel use your eyes
13:44 Votato I see, I'd have to precisely weight those
13:44 Hyratel why?
13:45 Hyratel what are you trying to accomplish?
13:45 deshipu you probably want something like http://www.aliexpress.com/item/E74-Free-Shipping-New-Gear-Motor-for-Arduino-1pc-Intelligent-Car-Gear-Motor-TT-Motor-Robot/32416335138.html
13:46 Votato No I'm just looking at the different types :P
13:46 deshipu this is a motor with the gearbox built-in
13:46 Votato Sorry, I can be annoying
13:46 Hyratel then why did you say something about weight
13:46 Votato the gear train
13:46 Hyratel why
13:46 Hyratel explain
13:46 deshipu try that trick with the shaft touching the wheel
13:46 Hyratel help me understand
13:47 Votato looked on wikipedia, saw maths
13:47 deshipu if that doesn't work, then try gears
13:47 Votato cried
13:47 deshipu robotics is a lot of math
13:47 Hyratel there will be math
13:47 Hyratel a lot of it
13:47 Votato yeah
13:47 Hyratel but again
13:48 Hyratel why weigh it
13:48 deshipu either math, or lots of time and money wasted on experimenting
13:48 Votato Sorry, I read it wrong, they're proofs
13:49 Hyratel Votato, why do you say you'd have to weigh the gears
13:50 Votato Not the gears
13:50 Votato the speeds
13:51 Hyratel you don't weigh gears to find out the speed
13:51 Hyratel you compare teeth count and input RPM
13:51 Hyratel the math is simple
13:51 Hyratel https://socratic.org/scratchpad/268e0caa73575a4eabde
13:52 Votato I stand corrected
14:07 theBear lol, weighing gears
14:08 theBear and it helps to think of it like a chain laid out like a caterpillar track flat on the ground.. x teeth:y teeth
15:04 Votato Sit rep
15:05 Votato I tried your solution
15:05 Votato Nope, the robot did not move
16:40 Snert_ Is a signal generator that can generate quadrature encoding ( 2 squares 90 out) sufficient to simulate a quadrature encoded rotary encoder?
16:45 SpeedEvil yes
17:08 Snert then I'm on the right track.
17:09 Snert I may have to simulate RS422 line levels with a pair of line drivers but no matter that.
17:10 Snert if anything else might be helpful pls let me know.
17:12 Snert I have no freq counter but I can do the math using the scope time base.
21:10 eBear stimulates rs422 line levels by flicking and lic
21:57 ace4016 find parts online can be an art for things that aren't "basic" electronics
21:58 rue_mohr rs422 works at like 5V anyhow
21:58 orlock heya rue
21:58 rue_mohr matter a fact, there is no point in simulating it, just hook togethor the two devices
21:58 rue_mohr heya
21:59 orlock i bought one another esp8266 board on a breakout board
21:59 rue_mohr I'v got unshop-feever
21:59 orlock comes with a 3.3v regulator
21:59 rue_mohr if I dont get a chance to make something soon somehow I'm gonna go insane
21:59 orlock annoying thing is - they feed the chip with the 3.3v but dont make it available via a header
21:59 rue_mohr orlock, one another?
22:00 Snert ace4016: What parts? Parts is parts.
22:00 rue_mohr it prolly cant handle any more current anyhow
22:00 Tom_itx rue_mohr should we taunt you with all our projects we're working on?
22:00 orlock well, how much current does the lv side of a level shifter draw?
22:00 orlock anyway, got it working
22:00 Tom_itx not very much
22:00 Snert as much as it needs to :)
22:00 orlock $12 wireless webserver
22:01 rue_mohr all I can do is coding
22:01 Tom_itx you should have plenty of that by now
22:01 orlock i've been cadding up a nightlight for the daughter
22:01 Tom_itx what cad?
22:01 orlock openscad
22:01 rue_mohr ugh, I feel for you
22:01 Tom_itx no kidding
22:01 orlock i love openscad
22:02 Tom_itx been practicing on SW and catia at the same time here learning them both
22:02 rue_mohr not for organic shapes tho
22:02 orlock 3x groups of 6 led's embedded in it
22:02 orlock plus another centrally mounted
22:02 orlock its based on a design from MLP
22:02 orlock 6 pointed star with another star behind it
22:03 rue_mohr hmm
22:03 orlock i got some clear pla for free
22:03 rue_mohr carefull, if they are phosphor based leds you might have a time getting them dim enough
22:03 orlock cos it was "free" i wasted a pile on silly stuff before realising its awesome as a diffuser
22:04 orlock neopixels
22:04 rue_mohr yea, thats phosphor
22:04 orlock but its trivial to tweak the brighness down
22:04 rue_mohr heh
22:04 rue_mohr till your at a 20k resistor and its still not enough
22:05 Tom_itx rue_mohr, what's the difference between dimmable led bulbs and non?
22:05 rue_mohr filament led?
22:06 Tom_itx for house lighting
22:06 Hyratel Tom_itx, the dropout voltage
22:06 rue_mohr the dimmable ones will have a lot of flicker
22:06 rue_mohr the non-dimmable ones have NO flicker
22:06 Tom_itx why do they flicker?
22:06 rue_mohr I realized when one was behind a fan
22:07 Tom_itx i've been getting the dimmable ones...
22:07 Hyratel the filament LED bulbs are a series with working voltage ~ 100v
22:07 rue_mohr because they are waiting for the next pulse to work out how dim they are supposed to be
22:08 Hyratel that seems Off
22:08 Hyratel because it should sustain, right?
22:08 Hyratel with a tank capacitor
22:08 rue_mohr thats non-dimmable
22:08 Hyratel no i mean
22:08 rue_mohr they cost $8ea I'm not tearing one down
22:09 Hyratel that's fair
22:09 Tom_itx you're gettin screwed on them then
22:09 Hyratel but if it costs that much, i'd expect better design
22:09 Hyratel especially if it's a Name Brand
22:09 rue_mohr its not, its filament form china
22:10 rue_mohr 8w
22:10 rue_mohr 8 is the deal, they hit $13 easy
22:10 Hyratel oh
22:10 Hyratel see
22:10 Hyratel you didn't clarify that
22:10 Tom_itx i'm gettin GE etc
22:10 Hyratel I thought you meant a Driver-and-chip bulb
22:11 rue_mohr oh they aren't filament led then
22:11 rue_mohr so its just end-light
22:11 Tom_itx hope they last better than CF
22:11 rue_mohr or really crappy side light additions to an end light
22:12 rue_mohr an 8w filament led is as good as a 100w incadescent
22:12 rue_mohr an 8w non-dimmable led
22:12 Tom_itx these were ~10w and said 60w
22:12 Hyratel we only have one dimmer left in the house at this point
22:13 rue_mohr yea, but they aren't from china are they
22:13 Tom_itx they probably all are if the truth be known
22:13 Hyratel isn't filament like ~110 lm/w where SMT LED is ~80-90lm/w depending on diffuser?
22:14 Hyratel the dimming limitations on filament are in part due to the behavior of TRIAC-based dimming systems
22:15 Hyratel because you're cutting off the rise side of the phase, and if it has a tank capacitor, it'll suddenly turn off at about 40% on-time
22:15 Hyratel which is turn-on somewhere around ... 90v, descending
22:16 ace4016 Snert, i was looking for a 16-20 CFM blower
22:19 rue_mohr http://www.aliexpress.com/item/110V-120V-220V-230V-240V-Ultra-Bright-High-CRI-COB-4W-6W-8W-LED-Filament-Lights/1904781599.html?spm=2114.01020208.3.222.uMNjg2&ws_ab_test=201526_3,201527_4_71_72_73_74_75,201409_4
22:19 rue_mohr see the white collar at the bottom?
22:20 rue_mohr make sure it has that, or you really wont like its performance