#robotics Logs
Mar 13 2013
#robotics Calendar
00:03 Jak_o_Shadows Hmm, been a while since I looked at the mosfet side of it, do I sink or source from the inverter?
00:07 theBear err, n fet off of ground will sink to gnd
00:07 Guest63474 boop
00:07 Guest63474 I'll sink that fet to ground any day!
00:12 Rif theBear yep, and have tested it, is good when material is at least 2mm thick
00:12 Rif or else the heat warps it too much
00:15 Jak_o_Shadows Adding massive safety, that means I can bank on 1mA, so R = 15kOhm
00:16 theBear there's tricks to welding thin sheets, but they take skills to work well
00:17 theBear err, you sure ? that sounds ridiculously high
00:17 theBear oh, 15v ?
00:18 Rif yes we tried with 1.6mm to fabricate letters, the welders resorted to TIG, many hours of it
00:18 theBear also if that works out too slow for some reason, you can parallel inverter outputs
00:18 Rif 25 long horrible minutes to go
00:19 theBear they do it right ? they didn't just try to do beads or something silly like that did they ?
00:20 theBear even easier without flux and something that doesn't need/like shielding
00:20 Jak_o_Shadows Yeah, 15V, so yeah, that sounds right.
00:21 theBear something like that (nice and small) you could probly do with a heatsink bath to help
00:21 theBear Jak_o_Shadows, yeah, it does
00:21 theBear also if that works out too slow, i'm pretty sure most 74 families can do a fair bit more than 1mA
00:21 Jak_o_Shadows good thing I got that pack of 2000 resistors
00:21 theBear thank god !
00:27 Guest63474 thank buddah
00:28 Guest63474 theBear: I need booze...
00:36 Rif theBear did you see the pdf about ammeters i posted earlier
00:36 Rif has some good info on various multimeters
00:37 Guest63474 rif: Did you know theBear was famous? https://www.youtube.com/watch?v=zbWuxrYhflo
00:37 Rif will have to watch when i get home
00:38 est63474 facep
00:46 summersault hello, i intent to build an ultimaker like 3d printer, anyone has the link for BOM and suppliers?
00:52 rue_house summersault, do you know about #reprap ?
01:18 rue_bed ok
01:19 RifRaf rue_bed wheres the log for today?
01:19 RifRaf Guest63474 can you post the youtube link again
01:20 RifRaf ok so gonna use a voltage divider on the op amps input
01:20 RifRaf and run it from 5v
01:20 RifRaf only want max 2A reaing now instead of 20A
01:21 RifRaf reding
01:21 Guest63474 RifRaf: https://www.youtube.com/watch?v=zbWuxrYhflo
01:21 Guest63474 the actor looks just like theBear!
01:21 theBear he tyotally does
01:21 rue_bed RifRaf, tobbor was ill today
01:21 rue_bed !thislog
01:21 theBear 'cept not sure i worn a bandanna this century
01:21 rue_bed still is
01:21 rue_bed dont know the problem
01:21 Guest63474 haha
01:21 RifRaf lol, does remind me of him
01:22 Guest63474 well he's badass in the movie anyway
01:22 theBear i'm badass in real life too !
01:22 RifRaf rue_bed what problem?
01:22 Guest63474 there ya go!
01:23 theBear oooh... i'm very tempted to spend most of this fortnights money on that cheap wild turkey i saw up the corner
01:23 Guest63474 https://www.youtube.com/watch?v=DyjxIj4Vln0
01:23 theBear i really miss hard liquor, like, A LOT
01:23 rue_bed RifRaf, if I knew it would be fixed
01:23 rue_bed tobbor dies within about 3 mins of joining
01:24 rue_bed no errors in the log
01:25 RifRaf hdd failure
01:25 rue_bed no
01:25 rue_bed raid, iirc
01:25 RifRaf my big toe is so sore
01:25 Guest63474 theBear: I need boooze :(
01:25 RifRaf i can whine about aches and pains with you all tonight :)
01:26 theBear OMFG ! i just noticed a little hair gel and i've got the same haircut as that dude !
01:26 RifRaf i am no going drink for at least an hour, or till i try get somewhere with this stupid opamp
01:26 RifRaf geez already typing like i been on it for hours
01:27 theBear i've always wanted a redneck-super-mullet !
01:29 RifRaf theBear sorry i am too silly to hook up a few diodes, lets see if i can get 2 resistors correct
01:30 theBear i forgive you, but err, what exactly you doing ? the last thing you want is to lower the level coming out of the shunt, and depending on avr some forums earlier suggested you can run aref WAAAAY below 1v
01:30 theBear avr= which avr
01:30 RifRaf oh? mega328p
01:31 theBear heh, that's about 5 years newer than i recognise p/n's
01:31 RifRaf well running lm324 from 5V, use 2 resistors to give the opamp input 2.5V , and then my input adds onto that?
01:31 theBear and you do of course understand that aref is = max adc output value
01:32 theBear err, it doesn't work like that, you can't add onto that
01:32 RifRaf damn
01:32 RifRaf am looking at this schematic
01:32 theBear show me !
01:32 RifRaf in that pdf, will find it again
01:33 theBear and you do know that 99% of schematics found on the web are guaranteed not to work, apparently code also, and the other 1% probably doesn't work without modification :)
01:33 RifRaf http://www.alternatezone.com/electronics/ucurrent/uCurrentArticle.pdf
01:33 RifRaf this is in a pdf, and watched a 1 hour video by the author about it
01:33 RifRaf and he is aussie
01:34 est63474
01:34 RifRaf yes yes, he's is different, but he suggests 3 ways to use a single supply opamp to measure near 0 v
01:34 Guest63474 theBear: although everything I post DOES WORK
01:34 est63474 shi
01:34 Guest63474 why is it so cold
01:34 Guest63474 I think the lack of booze has me messed up
01:35 RifRaf no booze yet here and is way hot
01:35 theBear erm, what where ? that circuit only works cos it DOES have dual rails
01:35 RifRaf 4th last page?
01:35 theBear +-1.5v afaict
01:35 theBear yep, page 16
01:36 RifRaf yes, so i will give it +2.5 and -2.5 from my 5v supply?
01:36 RifRaf somehow
01:36 Guest63474 dude just boost a negative rail using pwm from your mcu
01:36 Guest63474 use it as a dc-dc converter
01:36 Guest63474 bye! <sleep>
01:36 RifRaf you make it sound straingforward, but that would use up the rest of the week
01:36 theBear erm, ummm, it means a whole extra opamp, and your circuit will use current that is more than a single opamp can maintain so you'll need to buffer it with a pushpull stage, it's all bad
01:37 Guest63474 mein idea ist gut
01:37 RifRaf :( ok, so why won't the diodes work right then
01:37 theBear RifRaf, what is wrong with the circuit i suggested ? if nothing makes sense you might use a divider like that on the - input of the opamp, i'd have to do maths or simulate to be sure
01:37 RifRaf i will start again, have ripped everything off the opamp already
01:38 theBear pwm is a simple way to generate an arbitrary negative rail, but it means you gotta pwm stuff
01:38 Guest63474 you always gotta do stuff to do stuff
01:38 theBear gimme 10 mins, i do a schem and simulate it for yer
01:38 Guest63474 it's why you do stuff to do stuff.
01:38 RifRaf ok, so positive from supply to + of lm324
01:39 theBear make it 12, i need a coffee not a beer
01:39 RifRaf Guest63474 i am always doing stuff to do stuff, thats my life
01:39 RifRaf ok no worries
01:39 Guest63474 which is not the same as doing mrs stuff, or stuffing mrs do.... or stuffing mrs' don't
01:39 est63474 runs
01:39 theBear first make the slightly minus rail and the regular circuit work, then connect the opamp across the whole thing, then make it work... hangon hangon, isn't 324 a comparator ?
01:39 Guest63474 no
01:39 Guest63474 it's a quad op
01:40 theBear well, that's good
01:40 RifRaf should be a quad opamp
01:40 RifRaf single supply
01:40 Guest63474 and with that, to bed I go!
01:40 RifRaf or dual
01:40 RifRaf nite
01:40 Guest63474 boop
01:40 RifRaf ok will get it working how it was this morning, where it just does not like inputs smaller than 3mV or so
01:43 theBear huh, you saying it worked with everything except <3mV ?
01:43 RifRaf yes
01:44 theBear that means it was perfect but your neg rail wasn't far enough from 3mV !!!
01:44 theBear just 3mV more it woulda been fine !
01:44 RifRaf no theBear thats how this circuit works
01:44 theBear thats how what ?
01:44 RifRaf no input i get 3.6mV on opamp output
01:45 theBear so we fiddle the - input reference, heck, you could use a trimpot to tune it
01:46 RifRaf does not change for 100mA through sense, 4.5mV at 200mA , (still not good
01:46 RifRaf ok 300mA is where it starts gain, now getting 81.9mV opamp output
01:47 theBear you got it there now ? use resistors/pot to make the 820k (from memory) equal half of the rails the OPAMP sees
01:47 RifRaf so over 300mA i am good pretty good
01:47 theBear IF that doesn't work, you need another diode drop
01:47 RifRaf no diodes in circiut now theBear
01:47 RifRaf started from scratch, this is what i know works and is working, now to add the diodes
01:48 RifRaf same results as previous testing
01:48 theBear wait wait, what are you talking about ? yer missing WAY too many details for this to make sense
01:48 RifRaf so
01:48 RifRaf i have a lm324 connected to 12v supply, 2 resitors to get 81X gain on one opamp
01:49 RifRaf sensce resistor shares common ground and other end goes to opamp + input
01:49 RifRaf and thats all i have so far
01:49 RifRaf multimeter sharing common ground and measuring the opamp output pin
01:50 RifRaf the sense resistor is inline with negative lead of battery charger with controllable current output
01:50 RifRaf i could eagle this schem ok if you want
01:54 theBear wtf you got such a weird gain ?
01:55 theBear it's never gonna work with the input signal that close to the opamp rail(s)
01:55 theBear gimme a second
01:55 RifRaf theBear it becomes linear after 500mA or so
01:56 RifRaf will paste some results into pastebin
01:56 theBear https://www.circuitlab.com/circuit/2d7gs6/opamp-current-sense-with-sneaky-minusrail/ is what i got so far
01:57 theBear what does 100k/10k get me ? 100 times or something simple to see on a graph ?
01:57 theBear err, 1000k
01:59 RifRaf i think Vout = Vin (1+(R2/R1)
01:59 RifRaf so
02:00 RifRaf this is my results, issue should be clear http://imagebin.org/250065
02:00 RifRaf theBear i'll work it out for you, just a sec
02:02 RifRaf your circuit has ywice as many resistors as mine
02:04 theBear wtf ? why can't i make a opamp simulate
02:05 theBear herm, the version i linked shouldn't, unless it's autosaving or something
02:05 theBear now i'm just experimenting to workout wtf i can't get the opamp to work, maybe it doesn't work in dc simulation
02:07 RifRaf should i learn this circiut lab?
02:07 RifRaf ok and i'll keep experimenting here as well, looking at your circiut
02:10 theBear it's pretty easy, i just use it cos i don't got windows for nice-looking-spice
02:15 RifRaf maybe it won't simulate cause it doesn't like to work that way, mine not working either
02:15 RifRaf in real life
02:15 theBear yeah, but i'm doing everything i can think of and i can't get anything like a 10 or 100 times gain
02:16 theBear hmm, maybe i should check 324 datasheet, i'm still working off the 741 i remebmer from the other night
02:17 RifRaf ok try this, 1oM from opamp
02:17 RifRaf er i'll try again
02:18 theBear oooh, this sim seems to completely ignore voltage rails even when you pick an opamp that has them
02:18 RifRaf 10k from opamp - in to ground, 1000k from opamp - in to opamp out
02:19 RifRaf should close to 100x gain, with 10k and 820k i get 81X
02:19 RifRaf in reality about 79 to 80
02:19 theBear but i really can't see any reason in real life, if you null the opamp output with a pot between the rails instead of the gnd on the 820k, why it wouldn't work
02:19 theBear but wait before you change anything major
02:19 RifRaf as per the image i posted before which had gain on it as well
02:19 RifRaf yes, bad news is i poured a port, good news is i only have enough for 2 glasses
02:19 RifRaf so will be alert all night
02:20 theBear what circuit was that graph with ?
02:20 RifRaf the one hooked up now, as i tryed to describe before
02:20 theBear what rails to the opamp specifically ?
02:21 theBear 0v and v+?
02:21 RifRaf 12V + and 0
02:21 theBear like http://imagebin.org/250013 but 12v + 0v ?
02:21 theBear oh, and a non-infinite load (not an led with no resistor :)
02:22 RifRaf no diodes or led, let me redo schem as it is now, brb
02:22 RifRaf yeah the led modules have inbiuld resistors and run from 12v
02:25 theBear cool, IF it is how i think it is, and that graph makes sense above err, about 5mV input, then i'd have to say that amazingly (oh, you didn't DRAW an led module <grin>) that opamp works down to either 5mV input or more likely around 300mV output, then it means you should get away with an only SLIGHTLY negative rail, also, tho i've never tested it, just upping the gain a little might get you high enough for min desired to be in the working/linear range
02:27 theBear and if you wanted to be a bit dirtier, you could put say, 10r and 1k in series like a divider but connected to v+ instead of gnd, that would pull it up err x/1 = (1/1k)*(1/10r) or somthing confusing like that
02:27 theBear that's way off
02:28 theBear it'd be (V+ - vshunt)/110*10 instead of vshunt
02:29 theBear i THINK that's not linear, so you'd need math or a lookup, couldn't just fix it with a weird gain
02:30 RifRaf http://imagebin.org/250068
02:30 RifRaf i think thats what i have
02:31 theBear idea being that whatever you fiddle (if you decide to just work on the concept of extreme low input/output not working) will just be a simple ANYTHING that gets your input/output range up into working area
02:31 theBear yup, all looks good
02:31 RifRaf hrm ok, so try gain of 500x or so?
02:32 theBear also worth just checking the charger gnd isn't in any resistive way linked to your circuit gnd
02:32 theBear for an experiment, that'll at least tell you if it's unable to output as low as the graph wanted, or if it can't "see" an input that low properly
02:33 theBear even working that low is quite amazing for an opamp tho, i suppose at low voltages they must struggle a lot less
02:33 RifRaf ok will find some megohm, or lower the 10k? what would you do
02:33 theBear i always ask myself, what would brian boitano do ?
02:33 RifRaf lol
02:34 theBear umm, whatever you find first for a test, tho once you get to a meg you leave yourself a lot more open to noise pickup thru the high effective impedance of that bit of the circuit
02:34 RifRaf ok will try 1k and 820k, think 1k should be everywhere around here, should be 820x gain then
02:35 theBear imagine X noise in the air, say it is X into a 1meg aerial, that'll be 500X after the opamp, but likely with a 100k aerial it'll be X/10 at the input therefore X/50 at the output
02:35 theBear it's probably not usually that linear, but that's the idea
02:36 RifRaf so find a multi megohm then, brb
02:36 theBear or consider touching it with a finger to make a broken guitar buzz... then you can think of the 1meg/100k as a simple volume control, resisting the signal less to gnd (nothing in opamps eyes) or resisting more and hardly affecting it
02:36 RifRaf nope, found the 1k forst
02:37 theBear huh ? i'm saying whatever to test, but the higher you go, the more vulnerable you are to noise
02:37 theBear but i believe it still somehow effects your input impedance
02:37 RifRaf amazing how breaking your big toe takes the pain away from the little toe that was broken 3 weeks ago
02:38 theBear heh, always amazes me how you always do a 2nd one shortly after :(
02:38 RifRaf yes
02:38 theBear one night i didn't remember where i was and just 'stepped' out of that superhigh bunk i had, that one was BAD
02:39 theBear somehow magically remembered i had a bunk fo rthe first time in my life every other time :)
02:39 RifRaf ok still 3.6mV displayed for 0mA or 100mA
02:39 theBear check where the graph used to change, if it's any different
02:39 RifRaf 200mA is about 5mV, unstable
02:40 RifRaf same so far, but now
02:40 RifRaf 300mA = 835mV, 1M = 6.7V
02:40 RifRaf 1A*
02:41 RifRaf wow am getting alot of gain now
02:41 RifRaf 500mA = 2.58V
02:41 RifRaf not real linear now
02:42 RifRaf but we proved its just not liking less than 300mA across shunt
02:42 theBear really ? still should be in some range, i wonder, does it go linear up high ?
02:42 theBear like the same current that it used to, or does it run out of room ?
02:42 RifRaf 2A = 10.95V, that close to limit for 12v supply
02:43 RifRaf 3A = 10.96V
02:43 theBear oh, err, so it's the same input level as before it starts going, not the same output level ?
02:43 RifRaf yes
02:44 RifRaf does not really like less than 5mV at opamp input
02:44 theBear so ummmmmm... i guess that means it doesn't like an input that low, actually i suppose to prove that, you'd need to go for less gain and check that it is reliably outputting the lower values, assuming the input tells it to, or i suppose you could just do a quick spreadsheet/graph on the pullup voltage divider i mentioned and see if that would be acceptable
02:45 RifRaf ok ima dig out this -12 - 0 +12 voltage reg that runs from 12v+
02:45 RifRaf would you like me to charts values for the current setup?
02:46 RifRaf with 1K instead of 10K, it was more stable with the 10k
02:46 theBear i'm pretty sure it doesn't matter what the rails as (evenness,) but this is important for my 'minirail' to work, but i'm sure it does, and if you think about it, it's DIFFERENCE between the 2 inputs, so if the shunt is gnd referenced and the opamp is running ANYTHING lower and higher enough, it should be fine
02:46 RifRaf apart from at low inputs they were both the same
02:46 theBear not unless yer doing it anyway, you know bigger and smaller and meter moving and meter not moving :)
02:47 RifRaf well i was gonna add the 10k resistor back cause the numbers were more linear
02:47 theBear makes sense
02:47 theBear and then you got a graph to compare with the proper double rails
02:47 RifRaf could go to 100k and just have about 8x gain, but i need to use a negative input to fix it i think
02:48 theBear hehe, it really shouldn't take 2 grown men 2 days to get a simple slightly nonstandard supply opamp to work :)
02:48 RifRaf yep,
02:48 RifRaf i have never grown up yet, that could be the issue
02:48 theBear but we're getting close, nice sensible graphs and theories :)
02:49 theBear maybe, sometimes i worry i'm not a grownup yet either... i just look around nad notice i'm not doing what all the other grownups are doing, doens't matter where i am
02:49 theBear what, me worry ?
02:50 RifRaf ok back to roughly 80x gain once i get away from the low inputs
02:50 theBear hmm, do kieches (sp?) make you need to piss all day ? it's that or the lots of coffees or the several beers, one of them for sure !
02:51 theBear i coulda filled a like just in the afternoon, and it's not even 4 yet !
02:51 theBear a err, lake
02:51 RifRaf i'd guess the beer on empty stomach
02:51 eBear stops subjecting the channel to his personal problems :) it's not easy being a bear in a mans w
02:52 theBear yeah, these 500ml cans are kinda, good for thirsty weather
02:52 theBear i keep buying the weird german beers noone else buys, every week they got a better special on some giant cans recently
02:53 theBear it's down to 1/l $4 this week ! and it's not bad beer
02:54 RifRaf theBear ima find and hookup this negative rail supply
02:54 theBear stop talking about it then :)
02:54 theBear don't let my ramblings put you off
02:55 RifRaf ok found it, but never used it, will hook it up
02:55 theBear don't make it backwards, that would be bad
02:56 RifRaf and did not get attacked by AVR's in the process of finding it
02:57 RifRaf crazy, the inputs are not labled, just the utput
03:00 theBear huh ? what kinda supply is this ?
03:00 RifRaf ebay
03:01 RifRaf ok i measure -12 and +12V on supply
03:01 RifRaf thats too much for the lm324 i think
03:01 RifRaf i can't win
03:01 theBear or is it a little switcher ? even a double insulated 'normal' traditional supply doesn't techincally have a act/neut, just two identical line-something and maybe a gnded case
03:01 theBear it aint too much
03:01 theBear all kindsa stuff runs them +-12v
03:01 theBear i mean 15
03:02 RifRaf yes has 2 x LM2575 on it
03:02 theBear i wonder how smooth it is, caps somewhere on the rails probly help
03:02 RifRaf ok will hook it upto breadboard, yes has lots of caps, will find a picture
03:03 RifRaf maybe it was sparkfun, had it for years
03:05 RifRaf futurlec, its this one http://www.futurlec.com.au/Mini_Power_Dual_12V.jsp
03:07 RifRaf am feeding it 15V DC input, so sound be fine as long as the lm324 likes it, so i give the opamp supply the -12 and +12, and connect the ) to breadboard for the sense input?
03:07 RifRaf 0
03:14 RifRaf ok i must be incredibly stupid, same results as before
03:15 fRaf starts finding out about how low my vref can be for meg
03:16 RifRaf if i can get a decent range from 0.1mV to 200mV i'll be happy
03:34 RifRaf ripped off, got some 2.5gram servos today, they are just 3.7gram ones without a label, so they weigh 3.5gram
03:35 RifRaf was curious when they were the same physical size as the 3.7
03:56 RifRaf well the avr has an internal vref of 1.1V
03:57 RifRaf will miss out on 90% of it still but may be enough
03:58 RifRaf can adjust voltage input from voltage sensor to max out at 1.1V so at least it'll be ok
03:58 RifRaf voltage sensor being a simple resistor voltage divider
04:14 RifRaf theBear you seem right about low vref, it says i can apply between 0v and 5v to vref, so i will give it 200mV and see what happens
04:28 theBear 0 and 5v eh ? where/what datasheet you find it in ? i found a few references to people that had seen them in my quick search last night, but couldn't find ANY avr datasheet with it for mega8 (was just the one i used to search, cos ya gotta search for soemthing :)
04:29 theBear put at least a cap (maybe cap and series inductor) on the aref when you do that to keep it clean.. i was musing the other night, i wonder what is a super-accurate way to generate a few hundred mv for a reference :)
04:31 theBear i suppose a transistor pulling up (so it's got more than a few hundred mv to 'work' with), maybe even a regular diode and resistor if not just a resistor or two to bias it for around whatever-hundred-mv .... i bet if you did a couple simple graphs, maybe even in yer head, you could make that approach quite accurate, probably even thermally couple the diode and transistor and arrange things so they (at least semi-) cancelled any heat affecting the thi
04:31 theBear ng
04:33 theBear i guess the idea is to make the transistor a current source , with a diode to gnd vs a resistor to v+ and a resistor collector to v+ (npn i suppose,)workout a sensible resistor for the emitter pulldown/output reference voltage.... i think that makes sense
04:35 theBear but that sounds kinda excessive, chances are just a 10kpot or something will be fine for this kinda accuracy, so long as ambient temp changes aren't extreme
04:58 RifRaf theBear i been working stuff out on paper, i only need to go upto 1A max, even 500mA or so
04:58 RifRaf and just found a 0.25R 5W resistor, it could be just about perfect hopefully, and a 1.5R 20W
04:59 RifRaf to use for sensing
04:59 RifRaf instead of the 0.01R
05:08 RifRaf works great, 1V at 5A, 499mV @ 2.5A, 199mV @ 1A, 20mV @ 100mA is lowest i can test just now
05:10 RifRaf so in theory i should have a 1mA resolution now using the 1.1V internal vref and scaling by 1024
05:10 RifRaf er 1024 divisions or watever
05:10 RifRaf nope 5mA
05:11 theBear so i guess err, .25v max, so long as you are cool with that... what IS the target load ?
05:13 theBear oh, and if you get yer best meter and fiddle the bananas and jam the leads hard together and manage to get pretty close to 0ohm, measure your resistor, they're often a little higher or lower than marked, consider err, 5% of 1r is err, .05r i spose, but in reality you can often see they're a point of a ohm over or under, assuming you can get the meter to read low enough that will mean something
05:13 RifRaf between 20mA and 1A generally i estimate, a typical led uses about 0.96w for a 4 led module
05:13 RifRaf oe 80mA
05:14 RifRaf but i wanna do strings of upto 20
05:14 theBear sidenote: often especially with cheaper meters, a good wiggle or even surface spray of the big mode selector 'knob' can eliminate some stray points of an ohm
05:14 RifRaf finding this 0.25R resistor is so lucky, just thought i would see what else was around
05:14 theBear on my oldest dirt cheap little pocket sized ratshack one from over 20 years ago, just a wiggle makes all the difference between the meter freaking out and randomly losing power and kohms of 'extra' resistance
05:15 RifRaf the voltage drop should be mimimal, trying to calculate it
05:15 RifRaf yep this one is pretty stable, has crocodile test leads, and we wiggled everything the other night
05:16 theBear remember you can parallel too, say 1a, 1r = 1w, if you had (bad example number wise, 4 ohm aint common value) 4 * 4ohm 1/4w (regular size) resistors you could make a single 1ohm resistor, if you had 10 * 10r 1/8th watt smd resistors, you could parallel them for 1r@ 1+2/8ths watt
05:16 RifRaf i have 1R 5W
05:17 theBear i suppose comparing to the low current range on a meter in series would be a reasonable tolerance test/check too
05:17 RifRaf and 2.2R 5W
05:17 RifRaf but they have bigger voltage drop and more heat no?
05:17 theBear depends, between stupid cheap and sensible cheap, meter specs differ AMAZINGLY once you start looking closely, things like tolerances in various ranges
05:17 RifRaf and 1.5R 20W, its about a 80mm long brick
05:17 theBear 1r will have 4 times voltage drop and err, 4 times the dissipation at 1a
05:18 RifRaf yep, i like the 1/4R
05:18 RifRaf its perfect
05:18 theBear but 1a * 1r = 1v 1v*1a=1w, so it's only one watt if you really only go to 1a usually
05:18 theBear yeah probly, just mentioning, i often forget that i can make nice big resistors i don't have from little tiny ones
05:19 theBear what IS the target application for this setup, just outta interest, and a final possible 'problem' to at least avoid
05:19 RifRaf well i can forget the opamp now, thats wonderful
05:19 theBear hooray !
05:19 RifRaf leave them back in the 90s where they belong
05:20 theBear you actually tested with a few hundred mv aref yet ?
05:20 theBear lol, i knew how to use them in the 90s, maybe thats the problem, my brain knows they obsolete :)
05:20 RifRaf no avr is unplugged so i don't kill it with this testing :)
05:20 theBear :)
05:21 RifRaf will power up in morn and try, the code is ready for an adc input but i need to get the internal vref working first
05:21 RifRaf would be set for 5v now am pretty sure
05:21 RifRaf which i can still test with now
05:21 theBear in general remember when yer worried/cautious, avr has clamp diodes on all the useful pins, so if you have a series resistor that's a few hundred r or more, you might not get a 100% accurate reading on the adc say, but it would take CRAZY voltages to cook the pin by accident
05:22 theBear didn't look too hard at the current graphs, and that was the older atmega8, but it looks like the adc only presents a few mA load at most input levels
05:22 RifRaf oh yeah, for the target , well it was a flash in the pan idea i had one day after i made the colour sensor detect all different kinds of leds
05:23 theBear hmmm, so likely to just be powering AND measuring somethings eh ? still battery powered ?
05:23 theBear i mean, ultimately
05:23 RifRaf just making an LED tester, to give me power use over various voltages, verses distance to led, white colour value etc
05:24 theBear yeah cool.... apart from curiosity, i was just thinking that if you ever tried to use it with some circuit kinda thing on a common supply or where a gnd got shared that it wouldn't work, the sense/shunt would be shorted to gnd by the other thing/common gnd
05:25 RifRaf and then add the colour sensor to me robot when i learn all this stuff
05:25 theBear hmm, it's kinda very interesting if the vref can go down to 0...
05:25 theBear whaddya think, i should get some hairgel and have the supermullet like that dude in the movie ?
05:26 RifRaf yeah i guess the unit would supply the power and i could control the voltage via a pot, and it could log it all to an sd card then make pretty graphs
05:26 theBear i thought i had a mr t style mohawk only long, but it struck me thismorning, it's a supermullet with no 50s rockstar lump or tintin at the front :)
05:26 RifRaf yeah go for it, just don't walk around with the guns as well
05:27 theBear heh, like him i'm dangerous even in handcuffs, i dunno if i could jump out of them all backflip style tho, not these days
05:27 theBear bet i could still get outta a straight jacket on a good day
05:27 RifRaf lol
05:27 theBear if you ever see one you GOTTA grab it for me, they so hard to find these days, shouldn't have missed the opportunities when i was young in syd
05:28 RifRaf ok will keep an eye out
05:28 theBear heh, i suppose on the same note, if you come across a small crane and a human sized vertical fishtank that someone is about to take to the tip, hit that shit !
05:28 theBear it'll have to live at yours and visit to use it tho, i can't have even a small crane in this flat :(
05:28 RifRaf starting your own magic show?
05:28 theBear i'd move back to that, or maybe move to forster ... i enjoyed my time there
05:29 theBear i dunno if i'm awesome enough to be a magician or even a professional clown, but i think i gonna experiment a bit when i get better at the unicycle again
05:30 theBear surely there's crazier things i could do than move in with a single mother of 3 a few hours south of you <grin> she's pretty special AND sister of my good good buddy mr maxi who recently got married there
05:30 theBear i mean, 3 "GREAT" lakes at your doorstep, that's gotta be a selling point for starters
05:30 theBear a pub with a pool in the middle of the beergarden !
05:30 theBear it doesn't get much better than that
05:31 theBear i like kids, they got toys and we can play and stuff
05:31 RifRaf yep they have had some good floods down that way the last few weeks
05:31 RifRaf some big pools
05:31 theBear pool table too !
05:31 theBear heh i can imagine... a lot of it aint far above water level :)
05:31 theBear and that's when it's not raining
14:49 RifRaf my adc reading is 1143mV for a 820mV input, should be more accurate eh
15:00 theBear how you decide it's 1143mV ? what is the aref ?
15:00 theBear measured, not calculated
15:03 RifRaf aref is 5000mV
15:03 RifRaf and measured the 820mV on multimeter, is output from a simple voltage divider
15:04 RifRaf cannot change the reference it appears, yet, http://webbot.org.uk/WebbotLibDocs/object.jsp?id=27205
15:08 RifRaf and the 0.0052V is showing up as 0V , so need to change aref
15:09 RifRaf 0.0052V is about 25mA accross the 0.25R powering a single led
15:23 RifRaf rebiulding the libraries to use internal vref i hope
15:27 Guest8892 you still working on this?
15:30 RifRaf yes :/
15:30 RifRaf is like 2 steps forward 1 step back
15:30 RifRaf at least i feel like i am getting somewhere
15:33 RifRaf i think vref is the internal 1.1V now, raw adc output is 780 for the 820mv input
15:36 RifRaf 780 adc = 845mV , 780*1.1 = 858 , i think this is starting to take shape
15:36 RifRaf and late for work
15:36 est8892 b
15:36 fRaf hobbles
15:36 Guest8892 I'll burp you to work!
15:36 RifRaf cheers
15:37 Guest8892 https://www.youtube.com/watch?v=wQbF1mxYEVY
16:00 theBear err, internal on the older datasheets i looked at was 2.something
16:00 theBear oh yeah, remember if yer using aref you need to change a couple fuses to switch from both avcc ref and internal weird voltage ref
16:01 theBear i suppose if you just use a variable psu as input while watching the adc output, when you JUST hit full, 0x3ff or whatever it is, that's the ref voltage you are using internally
16:10 Malinuss RifRaf, are you using a avr?
16:10 Tom_itx he is
16:11 Malinuss RifRaf, did you figure it out?
16:12 theBear i think he went to work instead.. it's err, 8am there
16:12 theBear err, should be 8, don't think their daylight saving is finished yet
16:13 theBear (/me used to live a few hours south of rif, bro and dad still do... know the timezone well)
16:13 theBear *BAM*
16:13 Malinuss okay
16:13 theBear Rif, you get to work at 8am ? you're amazing !
16:13 Rif yep
16:13 theBear on time too, even if you logged into irc before you sat down :)
16:14 Rif theBear did my numbers look ok before?
16:14 theBear any idea where i store my sieve these days ?
16:15 theBear ummm, i only read the bit before you said it starting to take shape... had some wild turkey tonight... but err, well, you know what aref(or fused equivalent)/10bits should look like
16:15 theBear or input/(aref/10bits) i suppose
16:17 Rif yep
16:17 Rif i need to use a lower aref still, will make a set low one this arvo
16:18 Rif sucks that the library does not let me select it, but at least i can recompile and change it
16:24 theBear afaik from the old datasheets, internal aref is either vcc, weird 2.something voltage, or aref pin depending on fuses.. i'd be tempted to get some kinda easily adjustable 0-a few volts input and watch adc output value looped (over serial or a lcd maybe) while i fiddled the aref pin to various low values, and check it still lines up with the variable test-input properly, to see if it really is happy to go down below 1b
16:24 theBear 1v
16:25 Tom_itx rif has some adjustable regulators with 7 seg leds he could test with
16:25 Tom_itx 1.1v internal is the lowest internal i believe
16:26 theBear Tom_itx, mmm, rif said he found a datasheet for his more-modern-than-i-know-avr-numbers chip that says it is happy down to 0v, i've seen various forums from a few years ago saying various things, but somewhere around 1.1v was a common 'limit' mentioned
16:34 Rif 1.1V in internal ref for mega328
16:34 Rif but i wanna use vref pin and give it 200mV
16:36 theBear i kinda hope you can't do that, or i'll finally have a convincing reason to stop using my old 90s series :)
16:36 Malinuss yeah the AREF can be between GND and VCC... the internal is however set to 1.1 and you can't change that
16:37 theBear on older chips it was something odd like 2.6v or so, datasheet i looked into the deepest was the long version of atmega8 i think
16:37 Guest8892 Malinuss: 100kV across the die says you can
16:37 theBear heh, 100kV across the die says the adc internal input opamp is slightly broken
16:59 Malinuss theBear, there is also the 2.56V yeah, but haven't seen any with MUX selection making it possible to choose it, no idea why it's there or what it is for
16:59 Rif the 2.56v seems to be on older chips like mega32 etc
17:01 theBear Malinuss, me too, i suppose IF you were doing 8bit it would divide nicely to err, .01v per bit, but otherwise it's a stupid voltage :)
17:02 Malinuss nah the never chips still have it, you just can't choose it for the ADC..
17:02 Malinuss *newer
17:02 Rif ah
17:04 theBear wtf ? what CAN you use it for then ?
17:04 theBear or at least connect it to ?
17:07 Malinuss nah I just checked, on the attiny85 you can choose it as the referance... It's just that you can't measure against it
17:07 Malinuss aka. use it as input
17:08 theBear on the ones i looked at the other night you coudl only fuse it to be the adc ref, vs maybe vcc or aref pin
19:07 Rif do ya think using 0.05V as vref would be ok value, like 50mV?
19:08 Tom_itx you should visit with inflex about that stuff, he's done quite a bit with that stuff
19:08 rue_house Rif, I think you need to be min about 1.2V
19:09 Tom_itx git appears to be working..
19:10 rue_house I think the shop has a network problem it explains some things
19:18 Rif why would they say i can set vref from 0 to 5V then?
19:18 Rif rue even the internal vref is only 1.1V
19:18 Tom_itx internal is selectable
19:18 Tom_itx 2 or 3 different values i think
19:18 Rif just the 1
19:19 Rif either 5V vcc or 1.1V internal
19:19 Tom_itx i use the 1.1v ref on my toaster oven PT100 sensor
19:19 Rif well i got 1.1 working this morning, but wanna go lower
19:20 Rif 20x lower if possible
19:20 Rif so i don't have to use opamps
19:20 Tom_itx you should use the op amps
19:20 Tom_itx to avoid the introduction of noise on the adc
19:20 Rif opamps suck tom
19:21 Rif 3 wasted days, useless for near 0 unless i go get special ones
19:24 Rif gonna see how low this aref can go before i try another opamp
19:25 rue_house Rif, want help now?
19:25 rue_house !time
19:26 rue_house !time
19:30 Rif rue_house sure, but am working
19:30 Rif how low can i go is the question?
19:30 rue_house ok, wait till weekend and we will fix you up
19:31 rue_house want a parts list?
19:31 Rif sure, have to go party all weekend again though
19:31 theBear go fer gold ! less chips is betters
19:31 Rif will try do tonight if you name some parts
19:32 theBear hehe, not on the weekend, ALL weekend, not choosing to, HAVE TO <grin> that's how we roll round these parts
19:32 Rif well is my cousins 40thm so will be a weekend, not driving 8 hours for a few drinks
19:32 Rif and having monday off work
19:32 theBear there's that too... err, there isn't 8 hours of road north i guess, meblin ?
19:32 Rif so yep ALL weekend :)
19:33 Rif north is brisbane
19:33 theBear 8hours north ? damn this country is big !
19:33 Rif i can go for 50 hours drive north before i hit water
19:33 Rif cape york
19:33 theBear heh, and those crazy foreigners think texas is beg
19:33 theBear big
19:34 Tom_itx texas is not a continent
19:34 Rif actually is more like 80 hours to get up there
19:34 theBear it's true, but let's be reasonable, you can fit 10 or more americas in our continent, and i'm pretty sure rif isn't even crossing a state line, if he is it'll be in the first couple hours
19:35 theBear even including hawaii :)
19:35 orlok i thought all of australia wasnt that much bigger than CONUS?
19:35 theBear i'm not boasting about it, just surprises me how much they boast about so little :)
19:35 Rif yes one state line
19:35 theBear what's a CONUS ?
19:36 Rif theBear usa is close to the size of AU i think
19:36 theBear oh, continental youse eh
19:36 orlok Continental/Contiguous United States
19:36 theBear no way dude ! lemme find a map
19:36 Rif i remember from school
19:36 theBear oh wait, does continental include all the spanish speaking bits ?
19:36 orlok nah, United States
19:36 orlok as opposed to America as a whole
19:37 theBear holy crap ! your school was WAY better than mine.. i was under the impression two states were swapped in position even (shortly) after i moved to one long ago
19:37 theBear and yeah, it looks about the same siz
19:37 theBear e
19:38 theBear hot damn brazil isn't small either
19:38 theBear and canadia might be bigger, definately if you ignore the water.... you guys really should take over those guys, it'd be doing everyone a favour
19:39 theBear canadia is WAAAAY bigger than kim jongs country, you could build all kinds of mass destruction bombs and those crazy yanks would never find them :)
19:39 Tom_itx google earth to the southwest part of the US and you will find a bunch of craters
19:40 Tom_itx around area 51
19:40 theBear err, is that really worth all the clicking and wheel scrolling ?
19:40 Tom_itx not close but nearby
19:40 Tom_itx they're all marked with dates from tests
19:40 theBear and google earth isn't great with my vintage graphics cards
19:40 theBear ooh, now that i find cool
19:41 Tom_itx what?
19:41 Rif jeez am glad i don't cut mdf all every day, what shit stuff for dust
19:41 theBear test craters
19:41 Tom_itx most were in the 60's iirc
19:41 Tom_itx err maybe a bit earlier
19:41 theBear Rif, heh, it's illegal pretty much every other country on the planet, way too carcinogenic and poisonous
19:41 Rif yep have a mask on
19:42 theBear someone linked the bofh excuse page earlier.. favourite i seen today is "interference from french above-ground nuclear testing" :)
19:42 Tom_itx gotta restart the router
19:42 theBear good boy, and you shaved right ? cos while i never shaved the bits that matter with a mask, they are practically useless if you don't
19:42 theBear do as i say, not as i /action
19:46 theBear then again, i never wear harnesses 'cos they drive me mental, like being a baby on a leash, you go to take a step in the other direction and your body just stops and you look like a guy stepping on a banana in a cartoon
19:47 orlok it is like dust/powder, not sawdust
19:47 theBear yeah, thus how it can just float around in the air like a haze on a busy day
19:48 theBear i'll be very surprised if it isn't the 'next asbestos' 10 or 30 years in the future
19:48 theBear class actions of 1000's of wheezy middle aged carpenters giving testimony
19:48 lok swears at i
19:49 theBear heh, i gotta update my networking skills by about 10 years one of these days, actually create my first vpn/tunnel and maybe even look at stuff like ipsec :)
19:50 theBear workout how to read/firewall/nat ipv6 is definately on the cards
19:51 theBear 10 years ago i was a networking ninja, now i'm kinda, out of touch :(
19:51 theBear if what little i know is right tho, vpn's will make me very happy in my personal networking
19:52 theBear won't have to serve different dns for lan/outside, won't need to maintain dual settings for half the stuff i use remotely via the mobile etc etc
19:52 theBear i bet this dude knows how to do ipv6, he's doing it now !
19:54 orlok theBear: unencrypted tunnels are pretty trivial. ipsec isnt too much harder - its just specifying some algo's and an authentication method
19:55 orlok theBear: tricky stuff is when you get to vendor interoperability
19:55 theBear yeah, when i've glanced it looks pretty straightforward, just never actually tried :)
19:55 orlok multiple standards, all with different methods of configuration
19:55 theBear that's cool, my world is all linux based, and i'm happy to choose whatever works with my fairly stock android so long as it's not a gaping security/network hole
19:55 orlok and if both endpoints need to agree on the range thats being routed through a tunnel, then it gets tricky
19:56 orlok yeah, i've been doing linux ipsec stuff for well over 10 years now
19:56 theBear i suppose in theory it'd be nice if a stock windows could connect too, but i don't see it ever being an issue for one of MY machines :)
19:56 orlok and cisco for about as long
19:56 orlok but i have only been using Juniper gear for a week or two
19:57 theBear i could do cisco 10 or 15 years ago, but i think it's probably changed a bit, less serial console and more complex/powerful commands :)
19:57 orlok Juniper's run linux underneath, with a router cli thing on top
19:57 orlok so you can do a "start shell" and have a standard bash interface, tcpdump, etc etc
19:58 theBear and i'm still a ninja with firewalling/routing kinda stuff, even on bsd compared to most people, and i can't admin bsd any better than i would know how to open a browser on win8 :)
19:58 theBear wow,nice
19:58 orlok heh, i love bsd
19:58 orlok OpenBSD specifically
19:58 orlok just because Nessus knows NOTHING about it
19:58 orlok gotta keep doing bullshit reports for our Linux security audits
19:59 orlok OpenBSD.. "Nothing to see here."
19:59 theBear i very nearly switched some years ago when i was all into redundant serving and transparent changeovers and huge translation tables for various reasons, but then linux caught up a bit, and power got expensive so i stopped running a billion servers at home :)
19:59 orlok no vendor security notifications either
19:59 theBear these days my carefully maintained standard desktop grade p3 has better uptime than my isp, which is pretty damned good itself :)
19:59 orlok yeah, i need to set up a low power home server again
19:59 orlok heh
20:00 orlok some of the boxes at work havent been rebooted since i have worked here
20:00 orlok that were approaching a year then.. in 2007
20:00 orlok must be getting close to 2000 days uptime
20:00 theBear i do miss having a backup dns tho, adsl/local phone line single server authoritive dns is a bit touch and go <grin> but it's not doing anything commercial anymore, i think the last domain actually runs out at the end of the day, and while i been catching mail it hasn't been cared about by anyone for over a year
20:00 theBear i got over 300 days on my humble p3 a couple years back <grin>
20:01 theBear i'm too cheap, by that time i always gotta replace a 6gig hd or a fan or something :)
20:04 theBear damn it takes a long time troubleshooting late-build issues with gcc on a p3, even with distcc helping
20:04 Tom_L theBear, https://maps.google.com/maps/ms?ie=UTF8&t=h&oe=UTF8&msa=0&msid=116945134295436436626.00044ff490bf518b65562
20:04 theBear nice work, lets see how firefox/flash/x feels about accelleration this month
20:05 theBear very nice, and for the record, not too bad on the speed
20:06 Tom_itx one of the largest is near the top
20:06 theBear heh, very nice
20:06 theBear top of nevada ?
20:06 Tom_itx no the top of the blast site
20:06 theBear gotcha
20:06 Tom_itx lemme find a name
20:07 theBear hehe, looks like the moon
20:08 Tom_itx Sedan
20:08 Tom_itx is the name of the test
20:08 Tom_itx 104kt
20:09 theBear heh yeah, that's a crater :)
20:10 theBear i suppose to make a crater in solid 'ground' you gotta have enough force to push ALL that stuff out of the way, surely it couldn't just get 'squashed'
20:11 Tom_itx look at the dust scatter around it
20:11 theBear only half a km across, but man, imagine how long it would take with diggers to make a hole like that
20:13 theBear you ever seen those GIANT circular saws they got these days ? maybe 20' blade, attached to some kinda super heavy duty crane arm, used to slice into small mountains when they are building things
20:13 Tom_itx nope
20:16 theBear http://www.lakata.org/arch/Bucket%20Excavator%20Big.jpg that kinda thing, little bit more streamlined blade tho, that looks more like a digger than a chopper... seen a bunch of them at major road construction and huge building foundation-setups the last 10 years or so
20:16 Tom_itx oh i've seen those
20:17 theBear never seen one REALLY going for it, but i gather they gotta spin with some speed to cleave thru walls of rock like they do (seen the results, better than the old drill a few hundred holes in a row with some 10meter drillbit
20:17 Tom_itx not in person but on tv
20:18 Tom_itx is that a tarp under the roadbed they laid?
20:18 Tom_itx so they can clean up their mess after it's moved?
20:18 theBear mmm, something about cartoonishly large machines like that i can't help but like... i LOVE those giant tonka trucks they use at big mines, 10' or even bigger tyres, HUGE tipper on the back
20:19 theBear no idea, sounds likely tho, something like that would DESTROY whatever was under it when rolling around :)
20:19 orlok watch Megabuilders?
20:19 theBear only caught a couple episodes, i don't much watch tv in recent years... i like that one where they move whole buildings tho, seen a few episodes of that
20:21 theBear you know, someone wants to move their industrial business, so these guys come along and start propping under the entire frigging warehouse(s) and eventually slide a bunch of giant fancy trucks underneath, then roll a few meters, adjust all the wheels/beds to keep the giant building more or less vertical and flat, roll a few more meters, repeat, etc :)
20:22 theBear erg, transition period, i need another coffee now, otherwise that bourbon aint gonna feel good in the old tum tum
20:22 theBear bbs
20:58 Rif rue_house so wat parts list are you referring to?
21:01 rue_house for your curent sense amp
21:01 rue_house do you have some max 232 around still?
21:02 Rif yes
21:02 Rif hundreds
21:03 Rif well tens
21:03 rue_house good, we dont have to stuff with a 555 charge pump then
21:03 Rif goodo
21:03 rue_house you have some LM234?
21:05 Rif yes, but am hating them today
21:05 Rif no i have lm324
21:05 Rif is lm234 something else?
21:05 rue_house right 324
21:05 rue_house 324 is good
21:05 rue_house are you using a 0.01R resistor for current sense?
21:07 Rif well now i am using 0.25R io do have some 0.01 though
21:07 Tom_itx 1% or better
21:08 rue_house whatever
21:08 rue_house Rif, do you want a range of +-3A?
21:14 MrCurious why cant i find the pin designations on the SS411P datasheet! Honeywell fails!
21:29 ch1p53t join #ubuntu
21:34 theBear why ?
21:40 Rif rue_bed range 0 to 5a, 3 is ok though
21:53 MrCurious oh it does have teh pin outs on it, in a thin font that is half the size of surrounding chars
21:53 MrCurious erm, 1/3 to 1/4th size
22:26 orlok http://www.aircooledtech.com/tools-on-the-cheap/soda_blaster/
23:20 theBear http://www.squidoo.com/minigun holy skull of zombie jesus ! i mean, i knew the things existed, and that this guy really seems to wanna see how hot you have to get a large gun barrel before it grabs a bullet and goes banana on the next shot, but my god ! it just spews out the empty cartridges like rain ! sure, there's something kinda cool mechanically about belt feeding any revolving something at high speed, but is there really ANYTHING on this plane
23:20 theBear t so damned tough and dangerous that you need to invent build and transport such a ridiculous triumph of mechanical technology ?
23:21 theBear surely a regular little fully automatic gun or two, something modern and small, like those uzi things, is enough to cut any human or middle to large sized group of them almost in half, certainly past the point where they gonna pose a threat
23:23 theBear also wondering what kinda shape the inside of those poor barrels are after getting red hot and having MANY explosions constantly going on inside you and generally spitting out sparks as if you were being anglegrinded from the inside out !
23:23 eBear may still be a bit tipsy, but that thing is so far beyond outrageous it's not fun
23:25 est8892 f
23:25 Guest8892 OUTRAGEOUS!
23:25 orlok its all about not needing to aim, and sending bullets downrange
23:25 Guest8892 theBear: speaking of guns, I can't find the proper o-rings for my air rifle...
23:26 Guest8892 orlok: it is said in war people would often fire over head instead of aiming directly because they didn't want to actually kill their enemies
23:26 Guest8892 (and by direclty I mean to kill
23:26 Guest8892 you obviously need to account for gravitational drop vs distance
23:26 Guest8892 that's another story though.
23:26 Guest8892 we're talking trench + machinegun
23:27 Guest8892 theBear: Every time I re-seal with whatever o-rings I have in hand (rated for high pressure steam and such) it doesn't last long... I think the oil kills them
23:27 Guest8892 I should try silicone grease
23:29 orlok gasket goop?
23:37 theBear anyone know another term for a 'rolling sieve' or the process of doing it ? if you haven't heard THAT term, think ball mill with holes in the barrel