#robotics Logs
Dec 02 2017
#robotics Calendar
12:09 AM rue_mohr: @#$% damnit, I forgot thepowoer led
12:22 AM rue_mohr: ok there
12:22 AM anonnumberanon: why are you making amps?
12:23 AM rue_mohr: because the outputs of devices are not sufficient for the powered, amplified speakers I have
12:23 AM anonnumberanon: trying to get your projects to sing you a lulluby at startup, i see...
12:23 AM rue_mohr: the tablet does not put out enough signal for mycomputer speakers
12:23 AM anonnumberanon: oh
12:23 AM rue_mohr: and the computer in the shop dosn't put out enough signal for the speakers in the monitor
12:24 AM anonnumberanon: what did you use, an op amp circuit for that?
12:24 AM rue_mohr: mcp6002
12:24 AM rue_mohr: its usb powered
12:25 AM anonnumberanon: cool
12:35 AM rue_mohr: I tried an LM358, but its got too much overhead
12:36 AM anonnumberanon: man if i overclock atmega328p to 32 mhz i could theoretically run ~20 servos with 1 us resolution
12:36 AM rue_mohr: you dont need to
12:36 AM anonnumberanon: with possibility to increase pwm frequency
12:37 AM rue_mohr: there is no point, they need the 20ms to do their control pulse
12:37 AM anonnumberanon: right now my isr is 27 instruction cycles
12:37 AM rue_mohr: how many was mine?
12:38 AM anonnumberanon: yes but apparently running from 50 hz to 75 and 100hz makes the servo more torquy
12:38 AM anonnumberanon: and holds position better
12:38 AM anonnumberanon: anyway that' snot my priority
12:38 AM rue_mohr: you know how the servo works, right?
12:38 AM anonnumberanon: im not sure about yours
12:39 AM anonnumberanon: yours was using the decade counters so you fired each servo one after the other instead of all at the same time
12:39 AM rue_mohr: so, do you know what resolution mine was?
12:40 AM anonnumberanon: probably, i don't know last time i checked yours was like 6 months ago
12:40 AM anonnumberanon: don't remember your code
12:40 AM anonnumberanon: what was it?
12:41 AM rue_mohr: 47ns
12:41 AM rue_mohr: resolution
12:42 AM anonnumberanon: let me see?
12:43 AM Jak_o_Shadows: rue, I suppose you've looked, none of the ebay/ali strain gauges are any good?
12:43 AM rue_mohr: na, you had your chance and you weren't interested
12:43 AM Jak_o_Shadows: Or maybe just too annoying to mount?
12:43 AM rue_mohr: Jak_o_Shadows, tooo expensive, I need about 100+ of them
12:43 AM Jak_o_Shadows: oh yeah. That also makes sense.
12:43 AM rue_mohr: I'm looking at making my own lvdt's
12:43 AM Jak_o_Shadows: They're about $5 min yeah?
12:44 AM rue_mohr: I can get tire guages for $3 ea, digital
12:44 AM rue_mohr: the sensors are 'extractable'
12:45 AM anonnumberanon: if i said i wasn't interested most likely it is because the design was extremely limited and did not solve my engineering need
12:45 AM anonnumberanon: need/constraint
12:45 AM rue_mohr: but my problem is that I cant make a diaphram insensitive enough
12:46 AM Jak_o_Shadows: Going back to the usb amp, does it have a volume control knob? ./can it?
12:46 AM rue_mohr: anonnumberanon, you want to make your own road, even if I'v completely already done it, your not interested
12:46 AM rue_mohr: Jak_o_Shadows, no, I just want +3db
12:46 AM Jak_o_Shadows: Fair enough
12:46 AM rue_mohr: cause so I dont have to pin the volume of the equip.
12:52 AM rue_mohr: but I think I can modify one of those pen tire sensors into what I need
12:57 AM Jak_o_Shadows: They lose a bit of air.
12:57 AM Jak_o_Shadows: But if that suits you.
12:57 AM Jak_o_Shadows: How would you do it?
12:57 AM rue_mohr: I was just wonder about that
12:57 AM rue_mohr: I'll tear one apart
12:58 AM Jak_o_Shadows: They're strictly mechanical devices right?
12:58 AM rue_mohr: yes
12:58 AM Jak_o_Shadows: So if you put any extra force ont he stick, it'll lose calibration?
12:58 AM Jak_o_Shadows: (albeit probably a constant offset)
12:59 AM rue_mohr: no idea
01:03 AM Jak_o_Shadows: Hmm. Do you know (yet) what sort of range these sensors have compared to the range you're interested in?
01:10 AM rue_mohr: https://www.aliexpress.com/item/MPS20N0040D-D-Sphygmomanometer-Pressure-Sensor-0-40kPa-DIP-6-For-Arduino/32826191137.html
01:10 AM rue_mohr: that one is an amazing deal tho
01:10 AM rue_mohr: I'm using 65psi for the mecha air muscles
01:16 AM anonnumberanon: ah okay there we go was limited to 8 servos. i don't doubt excellent resolution though with timer1 and that code structure (hobbydriverv3)
01:19 AM rue_mohr: you must mean the initial m328 version
01:19 AM rue_mohr: if you run two interrupt sources, you cant garuntee the service time of any of them
01:19 AM rue_mohr: thats the limit
01:20 AM rue_mohr: for 100% max ersolution
01:20 AM rue_mohr: you want to reduce it to 1us
01:20 AM rue_mohr: AND it turns out I have a new way
01:20 AM rue_mohr: using the timer to reset the pin without using an interrupt
01:21 AM rue_mohr: but requires external muxer (4017 or 74ls595 or 74ls164)
01:35 AM rue_mohr: I have code for running 32 servos on an stm32, but it can do 88
01:37 AM rue_mohr: no irq conflicts, cause the timers take care of the critical stuff and during the dwell the interrupt works
01:38 AM anonnumberanon: yes the stm32 is so fast
01:38 AM rue_mohr: its the processor I just happened to set up
01:54 AM rue_mohr: I think the best way to do it is to make bourdon tube sensors
01:54 AM rue_mohr: even simple diaphrams will require massive springs
01:54 AM rue_mohr: even small
02:37 AM rue_mohr: it occurs to me that all the pressure switches and regualtors I know of have massive springs in them
02:43 AM theBear: you should go out and try meeting some nice young pressure switches or regulators.. the young ones ain't half as massive, i would guess :)
03:01 AM rue_mohr: theBear, its midnight and I'm awake
03:01 AM rue_mohr: I need somthing to do, write a software library or soemthing
03:01 AM rue_mohr: and not fro running stupid hobby servos
03:02 AM rue_mohr: (please note I never thought they weren't stupid, but I did give in to them being really cheap and convienient)
03:02 AM rue_mohr: maybe I can design a 6 transistor PID circuit for making a real servo
03:03 AM rue_mohr: that gives me 5 transistors for a passive PID, and one for gain
03:03 AM rue_mohr: wait, suddenly this sounds plausable
03:03 AM rue_mohr: damnit
03:03 AM theBear: it's lunchtime and i'm awake, so err, touche !
03:04 AM rue_mohr: yea, but
03:04 AM rue_mohr: wait, aren't you a nightowl?
03:06 AM theBear: yeah, but it's a weekend, and i been sick with bad flu/cold for over a week until a couple days ago, so i'm kinda stretching into a overtired but quietly satisfied kinda slow day
03:06 AM rue_mohr: hmm, so your ill rolled you into a normal sleep schedule?
03:11 AM theBear: nah, i still tend to go on a rolling schedule, like the old "6 day schedule" for a 5-day week concept, cos i never tend to wear myself out physically or mentally due to not enough spine/legs to use up my always above-average kinda stamina, so i tend to spend rolling chunks of maybe 8-12 hours shuffling around doing this and that between reclining and watching excessive amounts of fta tv, and getting usually maybe 3-5 hours of nap at a time before i
03:11 AM theBear: gotta top up on some more very low-grade kinda painkillers or muscle relaxers.. tho yeah, on a day like this if i don't find myself waking up in the office chair wondering when i nodded off, i'll probly get a decent normal-length sleep somewhere early thisevening
03:14 AM Jak_o_Shadows: theBear, crickets on - don't be unaustralian :P
03:16 AM theBear: eff cricket ! it's even mroe boring to watch than it is to play ! i never believed much in observign others doing sports, it's just not-fun, kinda like topless bartenders... you get to see such nice things at such close range, even talk to them and such, yet never gonna be allowed to touch them (least not till after they finish the shift, but that's another story <grin>) ... not my idea of fun :)
03:16 AM theBear: also i don't mind the weird sleep hours these days.. i almost always got nowhere to be any particular time, and with modern 24hr supermarkets here and there i can do stuff like my shopping often in the middle of the night when all the fools and general-purpose idiocracy are dead to the world, which is nice
03:19 AM Jak_o_Shadows: I have a friend who did try that weird sleep hours thing.
03:20 AM Jak_o_Shadows: He liked it, but unfortuantely the rest of his life didn't.
03:23 AM theBear: mmm, i occasionally remember that idea (err, poly-something cycle i think they call it) and think that i may finally be perfectly poised to give it a proper go like noone (i'm aware of) has ever done yet, due to you know, working obligations and general craziness due to lack of sleep being unnaceptable during the transition period... i'm already drugged to the eyeballs 90% of the time, probably got more than a small running sleep-defosit (sp?) and
03:23 AM theBear: not a long way off of the "theoritcally ideal" cycle now, plus i notice that more often than not i do seem to slip rapidly and easily from awake to sleeping and back again for various reasons most of which i touched on already, which i suspect means my body already getting not-too-bad at the quick transition to more-effective sleep/brain states and back to conscious agian, which seems to be the key to why the whole thing should give you so much more
03:23 AM theBear: useful awake time IF it can work with ya know, a human body/mind rather than just driving it slowly insane/to-death via lack-of-sleep :)
03:24 AM Jak_o_Shadows: I think it would be good.
03:24 AM Jak_o_Shadows: Or at least, a siesta type thing.
03:26 AM Jak_o_Shadows: But ¯\_(ツ)_/¯
03:26 AM theBear: on that note, i'm gonna wander off, if not nap at least recline a bit more than typing at the desk allows for a while ;-) l8r taters
03:26 AM Jak_o_Shadows: cya
03:27 AM rue_mohr: ok I got it
03:27 AM anonnumberanon: good na[
03:27 AM anonnumberanon: p
03:28 AM rue_mohr: max7219
03:31 AM Jak_o_Shadows: what was this for? that's a led driver
03:34 AM rue_mohr: well, I was asking myself eariler in the week to hook an m328, 7219, and ds1308 togethor
03:34 AM rue_mohr: I'v got all the code, but never put it togethor
09:05 AM Riemann: https://science.slashdot.org/story/17/12/01/2124235/voyager-1-fires-up-thrusters-after-37-years
09:05 AM Riemann: Isn't it truly amazing?
09:10 AM SpeedEvil: Moderately.
09:26 AM anonnumberanon: It's not as exciting as say, Riemann finally having sex after 37 years...
09:31 AM Riemann: anonnumberanon, dude what? :\
09:37 AM durrf: is it gonna make it go faster?
09:38 AM anonnumberanon: this is my queue to go to bed
01:42 PM rue_bed: OH THAT EXPLAINs THE Phonecalls
01:42 PM rue_bed: its 12
01:42 PM rue_bed: guess I need to wake up
02:15 PM rue_mohr: ok I got it
02:16 PM rue_mohr: make a material that crushes under pressure, like air infused silicone
02:16 PM rue_mohr: then work out how to make the opaticy change as its squished
02:16 PM rue_mohr: then run an optical beam thru it
02:16 PM rue_mohr: there, pressure sensor
02:17 PM rue_mohr: hey, I wonder if I mixed glitter into silicone
02:18 PM rue_mohr: the gaps between it would let thru an amount of light, but as it crushes, it would close off the paths
04:02 PM rue_mohr: http://elm-chan.org/works/vlp/report_e.html
04:02 PM rue_mohr: http://elm-chan.org/works/vlp/report_e.html
04:02 PM rue_mohr: http://elm-chan.org/works/vlp/report_e.html
04:02 PM rue_mohr: http://elm-chan.org/works/vlp/report_e.html
04:02 PM rue_mohr: http://elm-chan.org/works/vlp/report_e.html
04:05 PM AchiestDragon: yay :D vector grraphics
04:06 PM AchiestDragon: although motor driven servos are not as quick as crt deflection
04:06 PM rue_mohr: no, capacitove position sensor
04:08 PM rue_mohr: http://ruemohr.org/~ircjunk/tutorials/elex/ldvc/ldtc.html
04:17 PM AchiestDragon: k
04:23 PM AchiestDragon: you know the 32F072BDISCOVERY Discovery Kit dev board has a capacative sensor example on and it uses far fewer components http://www.mouser.com/ds/2/389/en.DM00099403-1149711.pdf
04:24 PM AchiestDragon: cant find the dam link for the data sheet that had the schematic for it in it
04:25 PM AchiestDragon: the one i was looking at had a lcd on it also
04:26 PM AchiestDragon: but anyway the pcb printed "cap" type pattern and a couple of resistors caps and rest done on the micro dio , prob same as the way you do d to a by using a rc network and
04:28 PM AchiestDragon: varable c v fixed c rather than varible r against fixed r ,, principles the same and code not much diferent
04:30 PM rue_mohr: does it output a variable position signal for things like servo shafts?
04:32 PM AchiestDragon: only prob i can see in using something like that for linear position sencing is static build up from associted printed parts and dust , when the assembly is moved but not its position it could affect the charge
04:32 PM rue_mohr: its supposed to be in an enclosure
04:33 PM AchiestDragon: well they got that demo as a tuch position votage slider
04:33 PM rue_mohr: BUT, its differential, so it can do away with most problems
04:33 PM rue_mohr: no, thats not the same
04:33 PM rue_mohr: that thing outputs a voltage based on the rotation/position of the differential capacitor
04:34 PM AchiestDragon: but a proper varible cap ie like the old radio tuning ones have no phiscial contacts to waire down like a var-res does
04:35 PM rue_mohr: correct
04:35 PM rue_mohr: my linear version was just a throw-togethor to see if it worked
04:35 PM rue_mohr: and it worked amazingly well considering
04:35 PM rue_mohr: more than a few volts difference for just a few pf of change
04:37 PM AchiestDragon: since you have a rc network then for sencing the position ,, you could use that to generate a pwm position pulse directly using a comparitor and with something like a pwm ic like the ne557 (i think is the pll) you got pwm servo control with capacative position sencing
04:38 PM rue_mohr: I'm just playing with the thought of looking at the phase diffrence as a digital thing
04:39 PM AchiestDragon: pll is just that phase locking adjusting one phase till the other matches it
04:41 PM AchiestDragon: youd prob need a multiturn pot to calibrate it though
04:46 PM AchiestDragon: yea wrong number ne567 http://www.ti.com/lit/ds/symlink/lm567c.pdf
04:46 PM Tom_L: rue_mohr, 68332 used phase shift for pwm
04:50 PM rue_shop3: I'd like to keep almost nothing analog
04:51 PM rue_shop3: esp avoiding adc
04:52 PM Tom_L: rue_shop3
04:52 PM Tom_L: let's build a mill
04:55 PM AchiestDragon: it was on the pic they did a bit of code , it takes 2 dio pins you have a c to gnd on 1 with a r between the 2 dio pins , you turn both outputs off ie to 0 to discharge the cap , and trun the one conected to the res and cap to an input , and set the other as output , and time how long it takes for the cap to charge , causing the input (pref smit triggerd ) to change from 0 to 1
04:58 PM AchiestDragon: you just need to have some method of calculating your capacatance range to find a value to use for r that gives you enough resolution
04:59 PM AchiestDragon: https://sub.allaboutcircuits.com/images/10245.png or https://www.digikey.co.uk/en/resources/conversion-calculators/conversion-calculator-time-constant
05:06 PM AchiestDragon: like for 2.5v (half of 5 v if 5v smmitt trigged) 0.01 uf and 4m ohm = 40us
05:07 PM AchiestDragon: and down to 0.001uf = 4uS
05:13 PM AchiestDragon: so with a 0.001 to 0.01 uf varible cap you got between 4 and 40 us if you sample at 1uS intervals then you got a (36/100)% position acuracy of the range
05:22 PM AchiestDragon: finding a 10nf varable though is like trying to walk though a re enforced concreate wall sideways and blindfolded
05:28 PM AchiestDragon: http://embedded-lab.com/blog/making-a-digital-capacitance-meter-using-microcontroller/ but 1-150pf is the range you need to mesure ,
05:31 PM AchiestDragon: now if the cap plates are prximaty touch plates the chage is done though the object that is close to it like your hand , that would can provide a far bigger capacatance than just plates alone as you act like an air spaced plate to it , of a size that gives it a nice value
05:42 PM rue_shop3: I think your missing part of the objective
05:42 PM rue_shop3: speed
05:42 PM rue_shop3: and minimal resources
05:42 PM rue_shop3: I like to do this by operating out of the box
05:42 PM rue_shop3: using dc offsets to manipulate digital waveform times and measuring intervals or the like
05:45 PM AchiestDragon: k like https://meettechniek.info/passive/capacitance.html
05:46 PM AchiestDragon: most methods are not sutable for reading small value caps in the pf range
05:48 PM AchiestDragon: you would be better truning the rc network into an oscilator and mesuring its frequancy , more analog stuff with an rf element making screening of it important as changes in objecs proximaty afect the frequancy as much as the changes in the varible cap
05:51 PM AchiestDragon: have you not found that on that experiment you have set up with the pcb plate caps , that the frequancy changes quite a bit when your hands close to it
05:56 PM AchiestDragon: i know your using a diferential type of cap arangment with 3 plates to create a phaze difference , but would think that getting accuracy from it would be hard , added to all the 50hz interferance each time you tuch the plates or are close to
06:03 PM AchiestDragon: http://2.bp.blogspot.com/-ihyNlwU8Nts/VnAbV8HKZSI/AAAAAAAAAY4/693BzZN3QGk/s1600/virtual-ground-in-capactive-touch.jpg but if your using the sliding pcb to create a vertual touch then it should be easyer in theroy
06:06 PM AchiestDragon: what that does not show however is the amount of charge and chage level that c touch has , like what you get on the scope when holding the probe and or not gnd at the same time
06:07 PM AchiestDragon: + the resitance of the overlay that is in the 10's or 100's of M ohm's makes thise equasions a lot different
06:08 PM AchiestDragon: well the paramiters for them
08:03 PM anonnumberanon: I am pretty sure I am going to use this ic https://i.4cdn.org/sci/1512201567063.jpg
08:11 PM Tom_L: rue_mohr
08:11 PM Tom_L: i may rethink my mill design
08:18 PM Tom_L: to get better Y travel and clearance in Z
08:18 PM Tom_L: mostly better Z clearance
08:40 PM Tom_L: from what i see, a heavier stationary Z colum with and arm extending from it is a fairly standard way to do it
08:43 PM Tom_itx: https://www.youtube.com/watch?v=lVEPZ4JYDmc
09:06 PM orlock: hmmm
09:14 PM orlock: i want to try making a walking sumo bot
09:14 PM orlock: for the surface area
09:14 PM orlock: or i guess i could try rtacks
09:14 PM orlock: tracks
09:16 PM Tom_L: may slip too much
09:16 PM Tom_L: i used shore 30 urethane for good grip on mine
09:17 PM orlock: i use Loctite "Go2" gluie - seems to be quite stickym, but not enough to violate rules
09:17 PM Tom_L: http://tom-itx.no-ip.biz:81/~webpage/sumo_files/mini_r_side.jpg
09:17 PM Tom_L: mini sumo
09:17 PM orlock: a few of the others cast their own in urethane
09:18 PM orlock: i was looking to get as much surface area as possible
09:18 PM Tom_L: http://tom-itx.no-ip.biz:81/~webpage/sumo_files/sumo_new_index.php
09:18 PM Tom_L: those have excellent grip
09:20 PM orlock: hmm
09:20 PM orlock: i'm suprised work hasnt set up an empirical friction testing station
09:21 PM orlock: Tom_L: What was that for? School?
09:21 PM Tom_L: fun
09:24 PM orlock: Did it compete?
09:24 PM Tom_L: just locally
09:25 PM orlock: What brand's your binoscope?
09:26 PM Tom_L: amscope?
09:26 PM Tom_L: i think
09:26 PM * orlock cant see the Leica logo plastered everywhere, so not one of works
09:26 PM Tom_L: http://www.amscope.com/7x-45x-binocular-stereo-zoom-microscope-with-double-arm-boom-stand.html?gclid=EAIaIQobChMI9NnGzvLs1wIVDJ9-Ch2UAwiMEAQYBCABEgKN_vD_BwE
09:27 PM Tom_L: little different base but same zoom
09:27 PM Tom_L: you could probably find my exact one there
09:28 PM Tom_L: i added a clear filter to the bottom lens to keep solder smoke from fogging the acutal lens
09:28 PM orlock: yup
09:28 PM Tom_L: can be removed for cleaning
09:28 PM Tom_L: it was an odd size i had to order
11:40 PM justan0theruser is now known as justanotheruser