#robotics Logs

Mar 15 2013

00:01 rue_house wonder what I did with that high side current sense circuit
00:02 rue_house Tom_itx, http://eds.dyndns.org/~ircjunk/circuits/dl32.png <-- do you know what that is?
00:09 jeet i am in need of a battery and chassis solution
00:09 jeet the chassis solution is for an add-on to accomodate all the hardware (not the core chassis)
00:57 Guest66169 jeet: arduino? I've got just the thing for ya: tupperware
00:57 Guest66169 as per the battery, lemons.
01:29 rue_house jeet, how big?
01:29 rue_house Guest66169, hard core man
01:34 rue_house http://eds.dyndns.org/~ircjunk/robots/flatbot/p1030677.jpg
01:34 Jak_o_Shadows an IRF 640 should be capable of more than 1W when properly heat-sinked and cooled?
01:35 rue_house what voltage?
01:35 rue_house or just 1W
01:35 rue_house it could prolly do 1W with little or no heatsinking
01:35 Jak_o_Shadows 16V at the source,
01:37 Jak_o_Shadows schematic is pretty similar to http://letsmakerobots.com/files/userpics/u8/mcu_1.png, except that instead of the op-amps, i'm using a hex inverter (with a resistor to limit current out of it), and i'm using 16V
01:40 rue_house ewwww
01:40 rue_house ok
01:41 rue_house 5 fets...
01:41 rue_house I wont say it wont work, but....
01:41 Jak_o_Shadows I don't quite understand the point of the bottom one.
01:41 rue_house pwm
01:42 rue_house he cant coast with the rest of the setup
01:42 Jak_o_Shadows why not?
01:42 rue_house and there are no flyback diodes, that will generate lots of heat
01:42 rue_house cause without the bottom fet your driving or braking
01:42 rue_house are you writing your own code
01:42 rue_house ?
01:43 Jak_o_Shadows Yes, I will be.
01:43 rue_house can I suggest some circuit changes?
01:43 Jak_o_Shadows Yeah, as long as it still uses irf 640s
01:43 rue_house ok, will you be using this for tractor robot drive?
01:44 Jak_o_Shadows One powered wheel, haven't decided whether it's at the front or back yet
01:44 rue_house one drive and one steering?
01:45 Jak_o_Shadows Steering is to be through a motor that controls something similar to ackerman steering (that was prebuilt)
01:46 rue_house Jak_o_Shadows, ok
01:46 Jak_o_Shadows At the end of the day, not steering like a tank
01:46 rue_house the switching will be really slow with that circuit, it will lose a lot more heat
01:46 rue_house I have to go to bed soon
01:47 rue_house have any scrap motherboards?
01:47 rue_house some of them have good fet driver chips
01:47 Jak_o_Shadows Nope. I have a hex inverter which I was going to use to go from uC to fet
01:47 rue_house using all N channel fets is more ideal, but harder to drive
01:48 rue_house is it open collector?
01:48 rue_house ugh, and he's only driving the fets with 5V
01:48 Jak_o_Shadows I can provide a voltage source for it to use as a reference for it to decide whether the signal is on/off, and a voltage source for the output voltage
01:48 rue_house how many amps do your motors pull?
01:49 Jak_o_Shadows Not too sure, it was a drill motor. The load won't be too heavy. <=6A?
01:49 rue_house the fets should be driven with atleast 10V, less than 20V
01:49 Jak_o_Shadows Yes, hence the inverter, it has an open collector.
01:49 rue_house that circuit will blow up near 3A for sure
01:50 rue_house open collector inverter with maybe a 680 ohm pullup to 12V (or even 9) is better
01:50 rue_house the 640 is a pretty woosy fet tho
01:50 rue_house 12A at ... 150V?
01:50 Jak_o_Shadows 18A at 200V
01:51 rue_house k
01:51 rue_house the lower voltage fets are way better, in the order of 32V
01:51 rue_house but ok
01:51 rue_house if your doing pwm its REALLY important to have flyback diodes
01:51 Jak_o_Shadows meh. I know it should work, the drill has an irf640 as the trigger
01:51 rue_house see the 4 little zeners in the transistors?
01:52 Jak_o_Shadows yes.
01:52 Jak_o_Shadows get bigger ones?
01:52 rue_house not zeners tho
01:52 rue_house just power diodes
01:52 rue_house even 1n4004 is almost ok
01:52 Jak_o_Shadows Do they need to be capable of the expected amperage, or lower?
01:53 rue_house full load current rating is good, they will get that in pulses
01:53 Jak_o_Shadows Right, i'll keep that in mind
01:53 rue_house his circuit cant blow up nomatter what you do with the fet signals
01:54 Jak_o_Shadows Whats the way to fix it so it can pwm without the last one?
01:55 rue_house drive one side of the bridge indivitually
01:55 rue_house you still have 3 control signals
01:55 rue_house but them you have to be carefull not to turn on both fets at once
01:55 Jak_o_Shadows I think I get you.
01:55 Jak_o_Shadows I ordered a couple spare, but i'll try regardless
01:56 rue_house so, drive them with a pullup to 9 or 12V
01:56 rue_house put flyback diodes around the motor
01:56 rue_house use a 680R or so pullup resistor on the fets
01:57 Jak_o_Shadows Is there any chance of the inverter's being asked to sink/source too much current?
01:57 rue_house I would suggest a TTL gate on the two fets so cpu glitches or programming errors cant short the bridge
01:57 rue_house yes
01:58 rue_house it cant source too much, but when it goes low its basically shorting a capacitor
01:58 Jak_o_Shadows rue_house, (ignoring pwm), provide 1 signal from the uC and get the TTL gate to do the FETS?
01:58 rue_house have the gates so that you cant turn on both fets at once
01:59 rue_house A B | X Y
01:59 rue_house 0 0 0 0
01:59 rue_house 0 1 0 1
01:59 rue_house 1 0 1 0
01:59 rue_house 1 1 0 0
01:59 Jak_o_Shadows this is helping, thanks.
01:59 Jak_o_Shadows that looks like a XOR?
01:59 Jak_o_Shadows sort of reverse though
01:59 rue_house where A and B are from microcontroller and X Y are to the fet drivers
02:00 rue_house sorta
02:00 Jak_o_Shadows yeah, i'll figure that out
02:00 rue_house I have to go to bed :)
02:00 Jak_o_Shadows night
02:00 Jak_o_Shadows thanks.
02:00 rue_house gnight
02:00 rue_house oh, here
02:00 rue_house http://eds.dyndns.org/~ircjunk/circuits/motordriver.png
02:01 rue_house both cant turn on at once, tho its a bit reversed from what you want
02:01 Jak_o_Shadows thanks
02:56 sw0rdfish holy shit mother fracker Samsung S4 can track your eye movement lololol :D
03:25 theBear game consoles aren't exactly "computer vision" .... a 320x240 b+w webcam at 5 or 10fps would probably be fine for 99% of gaming-on-tv-output uses, and a 480p really isn't a big step up from that.. and believe it or not, the market for those cams is WAY smaller than even the webcam market, which these days tends to demand a good bit better than 640x480
03:26 theBear and rue, yeah, usually about 1", the old old old simpson i worked on a few months ago was more like err, just under 3/4" at the pulley mounts
03:29 SorcererX the PS eye actually handles low light conditions very well compared to most typical webcam offerings, but yes, far from ideal
03:30 SorcererX resolution is much lower of course
03:31 SorcererX but say a 5 MP sensor that works well in low light conditions, then you need to shell out atleast a few $1k, there are some industrial cameras that do 5-8 MP in the <$800 segment, but the pixel size on those are insanely small vs. forexample a 1.3 MP sensor in the same price segment
03:38 theBear some dude, err ??rninate (anti-highlight<grin>) was being err, socially arkward at best last night while i tried to help/explain, well what you just said, but in detail and refuting/correcting crazy assumptions/misdirections as i went
03:39 theBear for example that ms and logitech $100+ webcams are no different, if not slightly worse technically, than a $5 -$20 chinese noname webcam these days, to the point of many using the same sensors and controller ics :)
03:39 theBear and that "480p" isn't "HD(tm)" <grin>
03:41 SorcererX heh
03:42 SorcererX I have found Logitech cameras to be much better than Microsoft ones for some reason. we actually used some logitech cameras for a robot that managed 4th place in Eurobot :)
03:44 SorcererX but yes, a lot of junk around
03:44 theBear i've found both (seen a handful here and there over the last 10 or 15 years) to be horribly overpriced, literally 20x on average, and well, just webcams... for actual webcam use, or as a mirror to shave the bits of my hair that i haven't ignored all century, i still use the <$5 chinese noname my buddy brought back from china about 10 years ago, 640x480 at tv-ish refresh on a fast machine, long adjustable focus, it's pretty good !
03:44 theBear these days a similar priced one tends to be 1024x768 or better !
03:46 SorcererX well, say a Logitech C910 is less than $100
03:46 SorcererX they do 5 MP if you need it, I used them at 1600x1200 or so
03:47 SorcererX but the low light performance is rather bad, got them replaced with some EV76C560 industrial cameras now
03:47 SorcererX also, nearly all the consumer webcams you find have a rolling shutter
03:47 theBear without a quick websearch of the usual suspects, i'm quite sure $10-30 of your favourite kind of $'s will get a noname chinese equivalent on your doorstep, very possibly with better sensor or optics :)
03:47 SorcererX which is insanely annoying if you are trying to recognize things while moving
03:48 theBear yeah, not to mention they don't exactly choose the fastest sensors usually
03:48 theBear 15-30fps aint much use if it takes 1/4 second for the motion blur to calm down in some light situations :)
03:49 SorcererX yeah, this setup I have now has a EV76C560 sensor, it is 1/1.8" and 1280x1024
03:49 SorcererX the cameras do 60 fps though
03:49 SorcererX USB3 helps a lot vs. USB2
03:49 SorcererX with USB2 you need to use all sorts of crappy compression to even get 15 fps from two cameras at 1600x1200
03:50 Jak_o_Shadows1 I need to work more on my opencv (through python) obstacle avoidance. The problem is speckles everywhere
03:51 SorcererX we had a robot that I put stereo vision on, the exposure time had to be as low as 6 ms to get completely rid of motion blur (it could rotate rather fast)
03:51 Hukka If you'd need a better camera than a webcam, wouldn't it make sense to buy a used digital camera?
03:52 Hukka That would be the middle ground between 5$ webcams and multi-k$ pro stuff
03:52 SorcererX well, these cameras are 300 EUR a piece
03:52 SorcererX there are quite a lot of industrial cameras in the 300-1000 EUR segment
03:53 SorcererX but yes, if you need like 5 MP, and good low light conditions, you probably need to shell out like 2500 EUR
03:54 SorcererX Jak_o_Shadows1: lots of noise?
03:54 theBear Hukka, very possibly, depending on how 'interfacable' it is, not all of them have 'webcam output' modes for example
03:54 Hukka Well, sure
03:54 Hukka You'd have to pick one that works with that open source library, which I quite don't remember right now
03:54 SorcererX also, I am using stereo vision, getting some of those used digital cameras to trigger at the same time, at high frequency.. meh
03:54 theBear it was also put forward that a cheap modern dv-cam (camcorder thinger) with firewire video is a much higher quality solution, but that'll still be afew hundred
03:55 Jak_o_Shadows1 I'm trying to fill up with white from the bottom, to the nearest edge that's detected, but the problem is noise in the edge detection
03:55 SorcererX Jak_o_Shadows1: and blurring does not give you the desired result?
03:55 theBear hehe, blurring and edge detection aren't exactly complimentary :)
03:55 Jak_o_Shadows1 Not quite. dilating helps a bit, but then the edges arn't picked up enough
03:55 SorcererX the advantage of say an industrial camera, atleast for me, is that I can get the actual sensor data before demosaicing :)
03:56 Jak_o_Shadows1 plus filling from the bottom is slow.
03:57 Hukka gphoto was the one
03:57 SorcererX theBear: I suppose it depends on the edges :)
03:57 SorcererX theBear: I didn't mean a lot of blurring
03:57 theBear i know, i couldn't help myself
03:57 Hukka Then you can control the focus, aperture etc from the sw
03:58 Hukka SorcererX: I'm not a cameraman, but isn't raw exactly that?
03:58 theBear pretty sure gphoto is just a generic v4l(2) and maybe fw cam kinda program
03:58 SorcererX Hukka: raw format, yes. you can get that from some digital cameras
03:58 Hukka SorcererX: From cheap used ones too
03:58 SorcererX Hukka: but even then that is after pixel remapping for instance
03:59 Hukka I see
03:59 SorcererX they don't want to show the consumers how many pixels on a typical CMOS or CCD are actually dead, or gives wrong readings
03:59 SorcererX :P
03:59 SorcererX it might be as much as 1% of all the pixels, and even then it is hard to see in the end result
04:00 theBear or how few there are before 'magic' upscaling :)
04:01 SorcererX one advantage of getting some industrial cameras, if you have a small robot for example, is that some of those cameras are really small
04:01 SorcererX while a used digital camera is rather large
04:01 Hukka I was thinking about something like Canon S100
04:01 Hukka But yeah, it's too big for a small humanoid, for example
04:02 theBear one of my old old old pal cams has gained a LOT of half-dead pixels the last 6months or so, at 'night' (points out the front window) there's a bunch of random-colour 'snow' semi-randomly distributed over the picture, very static, but very not what the cam sees, during bright/daylight most or all of them appear to work, as if the low end of their sensitivity was cut off, but past a point they start to work again
04:02 SorcererX and in my experience, typical cameras for still photos have very poor video quality (lots of noise)
04:03 theBear it has the stock ir filter in there, had a VERY hard life before i had it, but ran fine for years until recently....
04:03 theBear plus it's behind regular float glass maybe 4mm thick, it aint seeing a lot of uv or ir at the sensor
04:04 SorcererX yeah, half dead pixels are quite common
04:05 Jak_o_Shadows1 Hate IR filters that are lens coatings
04:05 theBear most of the cams i've been around/inside just have a seperate flat panel somewhere between the front lens and the sensor
04:06 theBear just yer standard dichroic "looks kinda purple on an angle" one
04:06 SorcererX yeah, same here
04:08 SorcererX well, more redish
04:08 Jak_o_Shadows1 Yeah, redish, but the two camera's i've taken apart had coatings
04:08 theBear i was just gonna comment that i can't see red too well, they probly aint purple even tho i seen literally thousands of them (used to work on a LOT of hid lights for work)
04:09 theBear got a nice box with a handful of nice big maybe 2"*3" ones somewhere
04:09 theBear the guy that had the job before me was kinda, overzealous about replacing some things, including those :)
09:08 rue_house on the topic of cameras, I use a composite video cam, with a cnverter, I find they self-adjust better
09:11 Tom_itx rue_house, help avr dude with a v divider issue
09:15 theBear actually on that note, although you need some kinda capture card, ALL composite cams give full pal or ntsc framerate all the time, and most if not all capture cards are happy to do the same
10:59 sw0rdfish soo are there gonna be other companies that make smart glasses like google's
10:59 sw0rdfish its uncomfortable for one player to have monopoly on any given technology
12:20 home hey rue_house , I got an ultrasonic sensor that has a pwoer and ground
12:20 home I aqm not sure how to get data from this thing...can't find any spec sheets
12:21 home XD
12:37 theBear err, you mean sensor or tranducer ?
13:11 jennie hi
13:16 Hukka Hi
13:40 jennie hi Hukka
13:52 Hukka hi jennie
13:53 jennie Hi Hukka
13:53 jennie whast going on ?
13:53 Hukka pea soup
13:53 Hukka But no robot made it
13:54 jennie ok
13:59 jennie you made it ?
14:08 Hukka Yeah, I with pressure cooker
20:15 rue_house I put tobbor on a 30 min cycle
20:31 gartt Cool, just did the same with my clothes dryer
23:36 rue_house ok lets try 10 mins
23:42 rue_house sweeet, I got my 20x 16 channel pwm chips from ebay today :)
23:42 rue_house 14 bit!
23:42 rue_house er 12 bit
23:43 rue_house still pretty good