#robotics Logs

Mar 16 2015

00:03 rue_house that timer ran wifi on a mountian for years
00:07 mrdata perfulfate ...
00:08 mrdata i seem to proof read every word
00:08 rue_house see if you can find the erronious speeling of "drill"
00:09 mrdata sever holes
00:11 mrdata drillpres
00:11 rue_house theBear, is australlia on fire right now?
00:12 mrdata water and dired
00:13 rue_house http://s.twistynoodle.com/img/r/r-is-for-robot/r-is-for-robot-5/r-is-for-robot-5_coloring_page.png
00:20 fleshtheworld_ what gives or interprets logic within a computer, its not the cpu is it, the software on the storage device?
00:21 fleshtheworld_ i mean at what point does all the signal starts to be logic
00:21 fleshtheworld_ or something like that
00:38 rue_bed perphialio
00:38 rue_bed perphials (IO)
00:38 rue_bed well... depending on what your asking
01:37 theBear parephenalia
02:59 Loshki fleshtheworld: it's layered, like a network protocol stack (if that helps). The signal is low-level, the logic layer, higher level. Different descriptions of the same thing, at different levels of abstraction. Clear as mud, right?
03:03 fleshtheworld somewhat
03:09 fleshtheworld well im checking out https://www.youtube.com/watch?v=WIDzNyfVVg0
03:18 Loshki fleshtheworld: very good. Back in the day (before the internet) I took a class called 'hardware for software engineers' or something. It was excellent, not least because I discovered that working that far 'down the stack' bored the pants off me.
03:28 fleshtheworld_ Loshki, just had a sudden interest to learn how to build a computer from scratch. I dont mean a full blown modern computer but something as simple as sending a signal and then something happening because of the signal. I dont know if that is considered CPU in nature but as far as i know it is near the same thing, with a computer being more complex.
03:35 Triffid_Hunter fleshtheworld_: there are tons of folks who've made computers from logic gates or relays or transistors.. nothing particularly powerful of course, it's basically impossible to move signals between discrete components at anything resembling decent speed
03:36 Triffid_Hunter fleshtheworld_: stuff like http://www.atadiat.com/wp-content/uploads/2014/07/trace.jpg exists to make all the tracks the same length so that the speed of light in copper vs the length of the pcb track doesn't cause data to be corrupted
03:37 Triffid_Hunter and you know you're into some serious data speeds when you have to compensate for the speed of light in copper :P
03:39 Loshki fleshtheworld_: run with it. btw, one really good book is worth a 100 disorganized wikis.
03:53 fleshtheworld_ i am not sure what I am on about but, how does a few lights/transistors turning on and off in a certain pattern within a certain time frame (i assume), can then be interperted by something else (we will call it LOGIC) as 'logic' such as, if the light turns on 1 time in 1 sec then that means rotate left, if the light turns on 2 times in 1 sec then that means rotate right, etc.
03:54 fleshtheworld_ wouldnt the LOGIC have to have those preset of logic installed on it to determine that? and if so, how is that done. I assume this is kind of how a computer (eletronics in general) works.
03:56 fleshtheworld_ after reading that, i guess i shouldnt be concern about it too much. as soon as i start buying and doing experiments, things will just work
03:56 fleshtheworld_ following some example adn what not
03:56 Anniepoo your question's actually a better one thatn you think
03:57 Anniepoo digital systems work by distinguishing two states -
03:57 Anniepoo or more
03:57 Anniepoo what those two states are depends on the exact kind of electronics
03:58 Anniepoo the names depend on the document you're reading
03:59 Anniepoo the TTL standards, what simple integrated circuits use, speak of 'low' and 'high'
03:59 Anniepoo and have 'invalid' - a signal that is neither low nor high
03:59 fleshtheworld_ arent chips, kind of what is used to handle / do the logic?
04:00 Anniepoo chips are integrated circuits
04:00 fleshtheworld_ special chips and the sort
04:00 Anniepoo we divide all electronics, roughly, into 'analog' and 'digital'
04:00 Anniepoo your toy train set is analog - more voltage means the train goes faster
04:01 Anniepoo digital systems impose on that a simple division - 'on' and 'off', or 'low' and 'high' , or 0 and 1, or space and mark
04:02 Anniepoo old teletype machines used current or no current
04:02 Anniepoo fiber optic cables use light or no light
04:03 Anniepoo bluetooth uses two different radio frequencies (if I recall)
04:03 Anniepoo there are different kinds of integrated circuits - called 'families'
04:03 Anniepoo and they have different definitions of these two states
04:04 Anniepoo the simplest integrated circuits are usually TTL
04:04 fleshtheworld_ so... analog is more like a direct user of electricity? while digital more or so relies on signals/patterns?
04:04 Anniepoo transistor-transistor logic
04:04 Anniepoo yes - what you say is getting at the difference
04:06 Anniepoo for my example of TTL - anything from 0 to 0.8 volt meand low
04:06 Anniepoo and anything above 2 and up the the supply voltage (usually 5 volts) means high
04:06 Anniepoo anything else is undefined
04:07 Anniepoo imagine we're spies, and I need to send you a signal without anyone knowing
04:07 Anniepoo like paul revere, the 'one if by land, two if by sea' thing
04:08 Anniepoo if lanterns don't make sense for this application, maybe I'll use passersby
04:08 fleshtheworld_ unfortuntely i dont know much about paul revere other than he tried to warn americans of the british or osmething :)
04:08 Anniepoo yes, he needed to send a small amount of information
04:09 Anniepoo first, that the attack was coming, and second, if it was from the land or the sea
04:09 Anniepoo (this was yorktown, I think)
04:09 Anniepoo well, he used a lantern.
04:09 Anniepoo but lets say he wants to be more subtle
04:09 fleshtheworld_ oh, i see, but either way, they were coming, 1 by land, 2 by sea
04:10 fleshtheworld_ i see what you mean
04:10 Anniepoo so he arranges - someone will pass by your house, and stop and dig a rock out of their shoe
04:10 Anniepoo if it's a really tall person, it's by land
04:10 Anniepoo if short, by sea
04:11 Anniepoo now, if I have common sense, I won't recruit someone who'se neither really tall nor really short
04:12 Anniepoo cause you won't know which it is
04:12 Anniepoo there's a cool story about the two states.
04:12 orlock Anniepoo: Possibly the first example of binary transmission of data!
04:13 Anniepoo oh, no, it goes back further than that!
04:13 Anniepoo smoke signals are binary.
04:13 Anniepoo they're binary serial encoded
04:13 orlock oh yes of course
04:13 Anniepoo talking drums are bilevel clocked binary
04:14 Anniepoo the romans used a code involving a waving flag
04:15 Anniepoo theres' a cool story about mark and space
04:15 Anniepoo those terms are in the low level specs for cables used in the internet, like cat 5 cable
04:15 Anniepoo (which is usually ethernet)
04:16 Anniepoo when they started using telegraphy, they rapidly discovered that
04:16 Anniepoo a) the data wasn't 'signed' - the operator could lie about what was said - a man in the middle attack!
04:17 Anniepoo and b) a good operator could send a lot faster than a good operator could receive
04:17 Anniepoo so on expensive, highly trafficed lines like transatlantic cables
04:18 Anniepoo they used a gizmo with a clockwork that pulled paper tape through the clacker (the solonoid thing that makes the 'clack clack' sound)
04:18 Anniepoo and attached a goose quill pen, which marked the paper when it was down, and left a space when it was up.
04:18 Anniepoo 8cD
04:19 Anniepoo kinda cool that 'mark and space' are still in the telecomm specs
04:20 fleshtheworld_ 'kool story bro'
04:20 Anniepoo so yes - to send data serially you need something with two states
04:20 Anniepoo and a 'clock' signal, something to tell when to read the data
04:20 Anniepoo Paul Revere used 'no light' as no clock - and 1 or 2 lights as clock
04:21 Anniepoo my spy story uses 'rock taken out of shoe' as clock
04:22 Anniepoo RS-232 uses 'first move from negative to positive' to start timing from, and uses the actual time to clock the next 7 or 8 bits (with some complications)
04:24 Anniepoo and yes, sometimes you have to have circuitry to convert when changing from one technology to another
04:24 Anniepoo eg rs-232
04:25 Anniepoo most modern microcontrollers can generate the proper digital signals for rs-232 on the chip
04:25 Anniepoo but need external circuitry to convert 'low' and 'high' for the chip to the + and - 12 volts needed for RS-232
04:25 Anniepoo did I answer your question?
04:28 fleshtheworld_ will i got some nice examples, but who told the watchers these things?
04:29 fleshtheworld_ the obersevers waiting for the message
04:30 Anniepoo ah, that's a good question on it's own - this is called the 'contract' in software circles, or the 'protocol' for hardware/low level software.
04:30 Anniepoo and you have to agree on it
04:30 Anniepoo sometimes we agree to a standard
04:30 Anniepoo the USB standard's this big thick book
04:31 Anniepoo and it spells out things like what Douglas Hofstadter calls 'the outer message'
04:32 Anniepoo for USB - if you come to my house, and need a USB connection to my computer, you can look at the computer and see connectors shaped like the usual USB connector
04:32 Anniepoo and be pretty sure you're getting USB signals
04:32 Anniepoo just as you can go into a store in rural kansas and be pretty much assured you can speak English with the clerk
04:34 Anniepoo but in El Paso, that's not guaranteed - the clerk might speak Spanish. And if you try to speak English, they won't understand you.
04:35 Anniepoo so, the engineer 'tells' the receiving circuit what the protocol is,
04:36 fleshtheworld_ yeap, makes sense in concept, but id like to see how its done on those tiny little electronics
04:39 Anniepoo you mean physically?
04:40 Anniepoo the levels are generated by transistors - very tiny ones - printed onto the silicon during manufacture
04:40 Anniepoo and read by the bases of other transistors
04:42 fleshtheworld_ kind of like how intel and amd cpus can only work with devices/eletronics that follow their protocols/design. im not too famaliar with this but from what i know that seems to be the case
04:42 Anniepoo right
04:43 Anniepoo and if you don't plan for things to work together, then you end up with a lot of extra circuitry translating
04:44 deshipu but many protocols are designed to be as ellastic as possible
04:44 deshipu like I²C using pull downs
04:45 deshipu so it's independent of voltage
04:45 Anniepoo deshipu is right - there's always a range of acceptable signals
04:45 Anniepoo like ttl, low is allowed to be anything up to 0.8 volts
04:46 Anniepoo and paul revere, if the longfellow poem is to be believed, had some edge noise in his signal
04:46 Anniepoo cause he put up the first lantern, and it took him a moment to put the second one up
04:46 Anniepoo (well, whoever was signaling, I think Paul was the receiver)
04:51 fleshtheworld_ and now some random research into paul revere :)
04:51 Anniepoo 8cD sorry! I was looking for an example that I thought would be clear without a lot of technical background
04:54 Anniepoo And lo! as he looks, on the belfry's height
04:54 Anniepoo A glimmer, and then a gleam of light!
04:54 Anniepoo He springs to the saddle, the bridle he turns,
04:54 Anniepoo But lingers and gazes, till full on his sight
04:54 Anniepoo A second lamp in the belfry burns.
04:54 Anniepoo 8cD edge jitter!
04:55 Anniepoo he reads 'one if by land', then the signal changes to 'two if by sea'
04:55 Anniepoo serial protocols usually have a required wait time after the signal appears for just this reason
04:56 Anniepoo true fact: Galileo tried to measure the speed of light by sending an assistant to a hill a couple miles away with a shutter lantern
04:56 Anniepoo when he saw Galileo's lantern he opened his.
04:57 Anniepoo Galileo, no fool, sent him to a hill twice as far away to see if the delay increased
04:58 Anniepoo and, impressively, only reported that the speed must be instantaneous or faster than he could measure.
05:02 fleshtheworld_ Side question. In present day light is 'known' to have a delay - a speed. But what was Galileo's first thought on light, did he think it had a delay or that it was just instant? and what was the worlds thought on light then?
05:02 deshipu why would he attempt to measure the delay if he thought it was instant? :)
05:03 Triffid_Hunter he had no ability to measure the delay
05:03 Anniepoo he was a good scientist - he realized he didn't know
05:03 Triffid_Hunter he literally could not find out that it had a finite speed
05:03 Anniepoo so he devised a good experiment to set a lower bound on the speed of light
05:03 deshipu his approach was valid, just the distance was too small ;)
05:03 deshipu by several orders of magnitude
05:04 Anniepoo well, his experimental result was that the speed of light was greater than, if we assume he used
05:05 Anniepoo a 2 km path (he did measure it, but I don't know the values) and a max response time of 1/2 sec (he had no clock, he used his own perception of time)
05:06 Triffid_Hunter heh 4km/s is vastly short of celeritas :P
05:06 Anniepoo (motor response times for no warning, responding to a visual stimuli in Simple response mode, is that for slow reactors)
05:07 Anniepoo (this per Cristina and Rose)
05:07 Anniepoo =8cO
05:07 Anniepoo hope I didn't scare him off
05:08 Triffid_Hunter almost 6 orders of magnitude short
05:08 Anniepoo well, yes, his results could be improved on by reducing the uncertainty
05:09 Anniepoo but I'm impressed he was able to find a lower bound at all
05:09 Anniepoo hmm... trying to improve on his experiment, using only devices available to him
05:09 Triffid_Hunter lower bound isn't particularly hard, but I do admire the ability to even consider that one exists
05:10 Triffid_Hunter having the idea that light has a speed at all is vastly more difficult than finding what that speed is
05:10 Anniepoo agreed!
05:11 Anniepoo it was well known that sound had a speed - he mentioned the example, in the paper, of seeing the
05:11 Anniepoo woodsman swing his axe before hearing the sound
05:11 Triffid_Hunter speed of sound is within the ability of amateurs, 343m/s isn't ludicrously high
05:11 Anniepoo and said 'thus the speed of light must be greater than that of sound'
05:12 Anniepoo ok, here's a way - set up a mirrored surface (a shield?) at a distant visible place,
05:12 Anniepoo and a telescope pointed at it during a thunderstorm,
05:13 Triffid_Hunter photgraphic film moving at a fixed speed would be a fantastic combination with that setup
05:13 Anniepoo and see if you can see a difference between the direct flash from lightning and the reflected
05:13 Anniepoo (still won't see one, it's 3 microsec or somethign)
05:13 Anniepoo yes- and I've measured short time intervals by jsut that method
05:14 Anniepoo (I was a physics major)
05:14 Triffid_Hunter still, the proximity of the results would assure anyone that the speed of light is ludicrously high, and would require far finer experiments
05:14 Triffid_Hunter and that's a meaningful result by itself
05:15 Anniepoo yes- it would raise the lower bound on the speed
05:15 Anniepoo well, we still do these 'bound' experiments
05:15 Anniepoo for many years we had only a lower bound on the half life of the proton
05:15 Triffid_Hunter protons have half-lives?
05:16 Anniepoo 8cD we still don't know!
05:17 Anniepoo there's good reasons to think they do
05:17 Anniepoo (and I DO NOT understand the physics model that speculates they do)
05:17 Triffid_Hunter what do they decay into?
05:17 Anniepoo https://en.wikipedia.org/wiki/Proton_decay
05:19 Triffid_Hunter positrons eh?
05:19 Triffid_Hunter asimov would be happy :P
05:19 Anniepoo 8cD
05:19 Anniepoo yah - don't stand near one of Asimov's robots.
05:20 Triffid_Hunter what is 8cD?
05:20 Anniepoo if they have positronic brains, they're also probably strong gamma emitters
05:20 Anniepoo sorry - that's my crazy smiley
05:20 Triffid_Hunter I thoroughly enjoyed asimov's robot psychology
05:21 Anniepoo I've worked in social robotics
05:21 Triffid_Hunter that's a mere shadow of a field currently
05:22 Anniepoo XcO three laws? We're Soooo far from that
05:22 Anniepoo yah, well, the paychecks didn't bounce.. but yup.
05:22 Triffid_Hunter yeah absolutely, I know enough practical computing to fully understand that the ability to apply those three laws is decades away
05:23 Anniepoo I was just trying to get realistic eye moveement
05:23 Anniepoo http://www.robokindrobots.com/
05:23 Triffid_Hunter was a lovely concept in the 50s but it's not even remotely realistic
05:24 Triffid_Hunter Anniepoo: looks like fun, any openings?
06:45 veverak Triffid_Hunter: I found three laws funny
06:45 veverak it's just code in the firmware of the robot
06:46 veverak it can fail in a same way as today: you just code it wrong
06:47 Triffid_Hunter veverak: and often did, creating literary intrigue and complexity
06:47 deshipu humans don't have the ability to apply the three laws
06:47 veverak Triffid_Hunter: yeah, I've read Isacs 'The Complete Robot'
06:47 veverak but didn't finished it completely yet
06:47 deshipu it was a literary gimmick, not really technical
06:47 Triffid_Hunter hence my interest.. rigid laws are obviously useless in a world full of grey zones
06:48 deshipu and the book wasn't even about robotics, it was about humans, it was just disguised as robots to be more scifi
06:48 veverak I would say 'laws' are useless by design compared to the ideal 'state'
06:48 veverak but that 'ideal stat' is utopy, so we have to use that unperfect laws
06:48 Triffid_Hunter the laws are ideal if you want an entire race of stupidly inept slaves
06:49 deshipu veverak: well, "laws" in design are nothing more than constraints on the optimization algorithms
06:49 Triffid_Hunter which create an entire industry just managing their ineptitude
06:49 veverak deshipu: and constraints are usually something that eventaully holds you back
06:49 Triffid_Hunter never said I admire asimov's work, I just enjoyed it :P
06:49 deshipu veverak: not really
06:49 deshipu veverak: it may be somehting that keeps you together
06:50 deshipu veverak: like the constraint telling you the limits of your joints
06:50 deshipu veverak: disable that, and it's going to hurt a lot :)
06:50 veverak deshipu: I don't wnat to disable! :D
06:51 veverak I was more like: eventually you will find out that you would want 'smaller' constraints of your joints
06:51 deshipu the problem with the three laws is that they are not really constraints, they are wishes
06:52 deshipu and they are not even satisfiable in all cases
10:01 TK_ Hiya!
11:15 Hyratel stoopkid, you still here?
16:09 dpy hi guys
16:09 dpy does anyone know how the numbering of JST XH connectors goes? (ltr or rtl?)
16:10 dpy I've tried the datasheet, but no mentions of numbering
16:11 dpy to make matters worse, I have found two unofficial sources, and they contradict each other
19:50 MrMobius Hi, I've never tried to drive motors before. I have a 754410 chip but the motors I have seem to draw about 3A. Can I just put power transistors on the 754410's outputs to drive a bigger load?
20:07 Triffid_Hunter MrMobius: possibly, better off getting a chip that can handle it though
20:08 Triffid_Hunter MrMobius: VNH2SP30 perhaps
20:09 MrMobius Triffid_Hunter, right. I just have these chips here and my shop didnt have anything else.
20:28 rue_house hmm sleep or rebuild lawnmower...
20:41 Anniepoo Rebuild lawnmower into battle bot?
20:53 rue_house no, I think the connector rod is comming off the crank
20:54 rue_house requires almost a complete teardown
21:03 MrMobius hmm, so some circuits put the motor between Vcc and the collector of an NPN and others put it between the emitter and ground. What's the difference?
21:32 Hyratel stoopkid, yooo
21:35 stoopkid Hyratel: yo
21:36 stoopkid Hyratel: i unbroke my PLC so that's good news
21:36 stoopkid for me anyway lol
21:45 Anniepoo MrMobius - the voltage required to turn the base on
21:46 Anniepoo are you sure the motor on bottom variation isn't PNP?
21:53 MrMobius Anniepoo, I thought maybe PNP too but look at the first picture here
21:53 MrMobius http://www.robotplatform.com/howto/L293/motor_driver_1.html
21:53 MrMobius I saw that somewhere else too
21:53 Anniepoo that's a strange way to do it
21:54 Anniepoo oh... maybe thats why...
21:54 Anniepoo ok, I was about to say 'if the motor runs freely the back emf turns off the motor'
21:54 Anniepoo but of course that's a speed regulating mechanism
21:54 Anniepoo still... seems odd to me...
21:55 MrMobius So no need to do it like that necessarily?
21:55 Anniepoo I think it's just 'information on the internet'
21:55 MrMobius :P
21:56 Anniepoo no, and in my many years of doing electronics on and off (and I started with tubes), I've never done that
22:30 rue_shop3 Anniepoo, are you into those crazy PNP amplifiers?
22:31 Anniepoo are they crazy?
22:31 Anniepoo whats crazy about them?
22:31 niepoo is here with a fluidic ampli
22:32 rue_shop3 seems the old stuff is all pnp
22:32 rue_shop3 based
22:32 rue_shop3 hydraulic logic?
22:33 Triffid_Hunter MrMobius: that way only works if the drive signal has the same voltage as the motor supply
22:33 Triffid_Hunter which is why it's fairly uncommon
22:34 Anniepoo pneumatic, actually, in most cases
22:34 Anniepoo fluidics was once a competitor to electronics for logic circuits
22:35 rue_shop3 yea
22:35 rue_shop3 its flow based, right, not pressure?
22:35 rue_shop3 I heard the mil did heli control with it once
22:35 rue_shop3 EMP proof
22:43 Anniepoo right, it's flow based - the amplifier uses a small amount of air to disrupt a vortex
22:55 rue_shop3 oh, I thoguht it was based on the way air sticks to edges
22:56 rue_shop3 how do you amplify it to do usefull things?
23:33 Triffid_Hunter rue_shop3: seen the tail rotor-less helicopters? they apparently redirect the downwash from the main prop and unstick it from the tail boom, there's small control surfaces there to disrupt or enhance the amount of wash to provide yaw control
23:37 Triffid_Hunter rue_shop3: oh, apparently there's a fan in the tail boom with air ducts, http://en.wikipedia.org/wiki/NOTAR
23:39 MrMobius so for putting bigger transistors on the outputs of a motor driver chip, i just need a diode between collector and emitter?
23:41 Triffid_Hunter MrMobius: your motor driver chip would basically take the place of the logic gates in http://www.talkingelectronics.com/projects/200TrCcts/images101-200/H-Bridge-3.gif however passing several amps through BJTs is gonna make them stinking hot
23:42 Triffid_Hunter make sure you heatsink them properly, and remember that the heatsink tab is connected to the middle pin so most of the time it must be insulated
23:42 Triffid_Hunter oh, you should also remove the resistors from that diagram, they'll only cause you problems
23:44 MrMobius Triffid_Hunter, I got huge heatsinks for the transistors and thermal paste
23:45 MrMobius Triffid_Hunter, I guess I am having trouble wrapping my mind around it. Just putting transistors on the outputs seems too easy...
23:46 Triffid_Hunter MrMobius: well that circuit is a classic bipolar emitter follower which provides current gain but not voltage gain. you already have the right voltage, current gain is all you need