#robotics Logs
May 09 2021
#robotics Calendar
12:13 AM rue_mohr: I'm trying to focus on dc servos
12:20 AM rue_mohr: I got a bunch of measurements off the stepper jig I had set up
12:20 AM rue_mohr: it takes a stepper up to 42ms to settle after a step
12:20 AM rue_mohr: they dont start to move until about 250us after power is applied
01:17 AM mrdata: ooh
01:17 AM rue_mohr: I'm trying to work out what happened
01:18 AM rue_mohr: it looks like I was working on making a simulator for digital versions of the filters so I could build and test an equiv to the analog version, but then a bunch of stuff came up and distracted me
01:18 AM rue_mohr: like the toilet trying to fall thru the bathroom floor
01:18 AM mrdata: op amps are not a strong point for me
01:19 AM rue_mohr: just watch the loop phase
01:19 AM rue_mohr: you do not want it to get to 360 degrees
01:19 AM rue_mohr: (your negative feedback becomes positive and it all goes to hell)
01:19 AM rue_mohr: and the phase changes with freq
01:19 AM mrdata: mhm
01:20 AM rue_mohr: the power supply I made is having this issue
01:22 AM rue_mohr: the voltage feedback is fine, but the current feedback is of bad phase
01:22 AM rue_mohr: there is a thing called an all-pass filter
01:22 AM rue_mohr: it only changes the phase of the signal
06:09 AM Tom_itx is now known as Tom_L
12:08 PM rue_mohr: so, how many of the nicks here are bouncers to NULL ?
12:08 PM rue_mohr: Tom_L, mrdata and flav0r are real
12:09 PM mrdata: some dead people might have bouncers
12:17 PM Tom_L: the walking dead!
12:19 PM rue_mohr: they aren't walking tho
12:19 PM rue_mohr: veverak, your still real aren't you?
12:22 PM rue_mohr: ok, so anyhow
12:22 PM rue_mohr: I need to reel in my howtos and docs back to the website, I been posting stuff on twitter and it kinda gets washed out with the tide
12:23 PM rue_mohr: it sure would be nice if irc allowed direct image drops
12:23 PM rue_mohr: however
12:23 PM rue_mohr: DC servos
12:24 PM rue_mohr: I got the data for the steppers, so I have a performance goal
12:24 PM rue_mohr: I need to re-assemble the dc servo I did in jan
12:24 PM rue_mohr: it worked well if the motor driver wasn't overheating
12:25 PM rue_mohr: you talking to me then?
12:25 PM rue_mohr: I suppose, just go with it ok?
12:25 PM rue_mohr: please continue
12:25 PM gartt: rue_mohr: Nah, I like IRCing with irssi on the console with screen and SSHing in from elsewhere :) No graphics is great
12:25 PM gartt: KISS, right?
12:26 PM rue_mohr: after getting the analog servo working, I was trying to set up code to do emulation of analog filters
12:26 PM rue_mohr: and it was a whole adventure thats done now, I have the results
12:27 PM rue_mohr: so, the goal is to take the filter params worked out for the analog version, and build a equiv digital filter
12:27 PM rue_mohr: ending in a digital loop controller
12:27 PM rue_mohr: ok, might I point out you could also just type this all into an editor/
12:27 PM rue_mohr: ?
12:27 PM rue_mohr: make a howto later?
12:27 PM rue_mohr: or just a lot
12:27 PM rue_mohr: he has a good point
12:28 PM rue_mohr: yup, ok, if its worth anything we pull it from toms log server
12:28 PM rue_mohr: your starting to think blog aren't you?
12:28 PM rue_mohr: I like talking here cause it gives people a chance to interact
12:28 PM rue_mohr: but nobody ever does
12:29 PM rue_mohr: yea
12:29 PM rue_mohr: so, here is a quetion, do we still have the servo assembled
12:29 PM rue_mohr: we should
12:29 PM rue_mohr: unless you didn't know what it was
12:31 PM rue_mohr: so, then we need to convert the fitlers to a digital equiv
12:32 PM rue_mohr: did we work out the relation between the filter constants and the real world stuff?
12:32 PM rue_mohr: I think so?
12:32 PM rue_mohr: directory is RC_filer
12:33 PM rue_mohr: wow this will be interesting
12:34 PM rue_mohr: oh I left off working out how to make filters that had orders other than 3db/decade
12:35 PM rue_mohr: Vo += (Vi - Vo) / k ; // low pass
12:35 PM rue_mohr: #define k 4.0173757128
12:35 PM rue_mohr: you had a fancy tool for calculating the constant
12:36 PM rue_mohr: drwxr-xr-x 2 root root 4096 Jan 24 21:11 kcalc <-- random guess
12:36 PM rue_mohr: int cmdTau(char * unused) {
12:36 PM rue_mohr: printf( "Hello\n");
12:36 PM rue_mohr: return 0;
12:36 PM rue_mohr: }
12:36 PM rue_mohr: bad news
12:37 PM rue_mohr: double RC2Tau(double R, double C) { return R*C; }
12:37 PM rue_mohr: double Fc2Tau(double Fc) { return 1.0/(2*M_PI*Fc); }
12:37 PM rue_mohr: double T2Fc (double T) { return 1.0/(T*2*M_PI); }
12:37 PM rue_mohr: double TSR2k (double T, double SR) { double x = T*SR; return x*pow(Phi, (1.0/x)); }
12:37 PM rue_mohr: good news
12:38 PM rue_mohr: I think we can re-work it out
12:38 PM rue_mohr: good news is that its all generally here
01:03 PM veverak: rue_mohr yes :)
01:55 PM Tom_L: rue_mohr> it sure would be nice if irc allowed direct image drops
01:55 PM Tom_L: matrix does
01:55 PM Tom_L: with the riot client
01:55 PM rue_mohr: without us all using the one client in the world that does :)
01:55 PM Tom_L: you used to be able to join it from irc
01:55 PM Tom_L: but i think that link is broken
01:56 PM Tom_L: https://matrix.org/docs/projects/client/riot
01:57 PM Tom_L: https://matrix.org/docs/projects/client/element
01:57 PM Tom_L: new version i guess
01:58 PM Tom_L: maybe riot was too violent a name?
01:58 PM rue_mohr: developers get stupid and break up
01:59 PM rue_mohr: then the project changes name and gets refactored
01:59 PM rue_mohr: and starts out as crumby software again
01:59 PM rue_mohr: ok! I think my constant calculator program works
01:59 PM rue_mohr: zippo:/files/programming/c/RC_filter/kcalc# ./a.out -R 3k -C .047u -S 1k
01:59 PM rue_mohr: / Fc = 1128.75846164
01:59 PM rue_mohr: #define SR 1000.00000000
01:59 PM rue_mohr: #define k 4.2795781195
02:00 PM rue_mohr: I should be able to emulate analog rc filters properly on an avr
02:01 PM rue_mohr: I'll need to build some filters and test
02:01 PM Tom_L: ok i got distracted yesterday and i think i got my tool list all sorted out, now maybe i can test one of those fancy cutters
02:01 PM rue_mohr: carefull its still generating the right numbers!
02:02 PM rue_mohr: Vo += (Vi - Vo) / k ; // low pass
02:02 PM rue_mohr: low pass filter
02:02 PM Tom_L: it'll just go boom if not
02:02 PM flav0r: dudes !! good news !!
02:02 PM rue_mohr: Vc += Vo / k;
02:02 PM rue_mohr: Vo = Vi - Vc;
02:03 PM rue_mohr: high pass filter
02:03 PM flav0r: i finally got this thing finished and ready to order !
02:03 PM rue_mohr: flav0r, your back
02:03 PM flav0r: yeah !
02:03 PM Tom_L: these things don't contain blue smoke but some of them do tend to release human blood
02:03 PM rue_mohr: so I need to make a jig for testing filters on avrs
02:04 PM rue_mohr: ADC->uc->DAC
02:11 PM flav0r: dude you always seem to be doing something funky !
02:11 PM flav0r: what you up to today ?
02:11 PM rue_mohr: DC servos
02:11 PM Tom_L: something funky
02:11 PM Tom_L: what flavor are you today?
02:11 PM rue_mohr: picking up the digital filter work I got lost in around Janurary
02:12 PM Tom_L: what was that you finished recently that you started 20 yrs ago? i forget now...
02:12 PM Tom_L: the rom stuff?
02:13 PM Tom_L: maybe the z80 stuff...
02:13 PM rue_mohr: I'm all over hte map
02:13 PM Tom_L: naw just N of Van
02:13 PM Tom_L: :)
02:13 PM rue_mohr: I'm trying to get the DC servo thing going so I can finish the 48"x96" cnc macihine
02:14 PM Tom_L: you got some wheel chair drives for that right?
02:14 PM rue_mohr: so I got lost in Jan when I was working on the digital filters and got caught trying to calculate the constants
02:14 PM rue_mohr: yes
02:14 PM rue_mohr: 4 motors in the shop
02:14 PM rue_mohr: 2 are frozen
02:14 PM rue_mohr: work on 'em later
02:14 PM flav0r: hehe wheelchairs
02:14 PM flav0r: should leave the chair attached
02:18 PM flav0r: well lets hope 3rd time is a charm
02:18 PM flav0r: this is the 3rd time im sending this thing off to be made !
02:18 PM rue_mohr: I need the motors to work against each other to take up the play in the gears
02:18 PM rue_mohr: whats it?
02:18 PM flav0r: i usually work against myself
02:18 PM flav0r: ah its jsut a reworking of this display i was making
02:19 PM flav0r: the first 2 iterations “work” .. just changed some shit up a bit
02:19 PM flav0r: its a VFD display .. so i was using AC on the filaments .. now using DC
02:20 PM Tom_L: you making a vfd?
02:21 PM flav0r: the tube itself ???
02:21 PM flav0r: noooooo
02:21 PM Tom_L: oh we're talking about 2 different things
02:21 PM Tom_L: i meant 'variable frequency drive'
02:21 PM flav0r: oh yah you probably thinking VFD for power
02:22 PM flav0r: nah this is vac fluorescent display
02:22 PM flav0r: https://imgur.com/a/qZPWGnK
02:22 PM flav0r: there .. thats recent iteration … latest will look the same and function the same .. just with DC
02:23 PM Tom_itx: nice
02:25 PM rue_mohr: why Dc filament?
02:25 PM rue_mohr: did you see the VFD drivers I did up?
02:26 PM rue_mohr: I neeed an online web brwoser to see imugr
02:26 PM Tom_itx is now known as Tom_L
02:27 PM flav0r: well the AC i had going seemed a bit weak
02:27 PM flav0r: also i had a heat problem
02:27 PM flav0r: you see dudes one of my issues is i am somewhat lackign on all the theory !
02:27 PM rue_mohr: I wonder what i have posted
02:27 PM flav0r: however these filaments are short and when i tested them with DC they looked good
02:28 PM rue_mohr: huh nothing specficialyl
02:28 PM rue_mohr: what are you using to drive the rest? pullup? pulldown?
02:29 PM flav0r: you mean the segments and the grids ?
02:29 PM rue_mohr: http://ruemohr.org/~ircjunk/projects/resistorbox/p1160124.jpg
02:29 PM rue_mohr: yea
02:30 PM flav0r: i am just driving those with HV5812
02:30 PM rue_mohr: http://ruemohr.org/~ircjunk/projects/resistorbox/p1160128.jpg
02:30 PM rue_mohr: there is my driver
02:30 PM rue_mohr: ah
02:30 PM rue_mohr: I think thats just filament...might do hv too..
02:30 PM rue_mohr: http://ruemohr.org/~ircjunk/projects/resistorbox/p1160130.jpg
02:30 PM rue_mohr: ok that
02:31 PM flav0r: i saw some dude wound his own small center tapped transformer
02:31 PM flav0r: with some other IC
02:31 PM rue_mohr: I wound that
02:32 PM flav0r: yah i kinda noticed !
02:32 PM flav0r: lol
02:32 PM rue_mohr: as long as your primary inductance is reasonable, you ok
02:32 PM rue_mohr: http://ruemohr.org/~ircjunk/projects/resistorbox/p1160139.jpg
02:32 PM rue_mohr: seems that at rated, filaments slightly glow
02:32 PM rue_mohr: http://ruemohr.org/~ircjunk/projects/resistorbox/p1160140.jpg
02:32 PM rue_mohr: my overall
02:33 PM flav0r: yah i see a lot of opinions on filament driving
02:33 PM Tom_L: if it speak electronic chances are good rue has been there done that
02:33 PM rue_mohr: http://ruemohr.org/~ircjunk/projects/resistorbox/p1160145.jpg
02:33 PM flav0r: some folks say they really shouldnt “glow” to the naked eye
02:33 PM flav0r: others say no problem
02:33 PM rue_mohr: I used a chip socket to make my transformer into a pcb bump
02:33 PM flav0r: oh man I KNOW !
02:34 PM rue_mohr: http://ruemohr.org/~ircjunk/projects/resistorbox/p1160148.jpg
02:34 PM rue_mohr: hmm which design did I settle on???
02:34 PM flav0r: i might have to revisit the filament driver tho when i make something with these HUGE tubes i have
02:34 PM Tom_L: gonna make a clock?
02:34 PM rue_mohr: are the fils in those series or parallel?
02:34 PM rue_mohr: me? no
02:35 PM rue_mohr: that was my resistor box
02:35 PM Tom_L: no from the vfd
02:35 PM rue_mohr: http://ruemohr.org/~ircjunk/projects/resistorbox/p1160153.jpg
02:35 PM flav0r: calculator
02:35 PM flav0r: ?
02:35 PM rue_mohr: yea that was for my resistor box
02:35 PM rue_mohr: the leads on the screen I had were pretty fragile, I had to get creative to secure them
02:36 PM rue_mohr: http://ruemohr.org/~ircjunk/projects/resistorbox/p1160165.jpg
02:36 PM rue_mohr: the drivers were sourcing, so I only needed weak pulldowns
02:36 PM flav0r: ironically i even bought some toroids and wire
02:36 PM rue_mohr: fight off the capacitance
02:36 PM flav0r: just havent experimented with it yet :|
02:37 PM rue_mohr: http://ruemohr.org/~ircjunk/projects/resistorbox/p1160185.jpg
02:37 PM rue_mohr: driver board came out good
02:37 PM rue_mohr: http://ruemohr.org/~ircjunk/projects/resistorbox/p1160192.jpg
02:37 PM rue_mohr: I have the code dwell on a digit to act as a hilight
02:38 PM rue_mohr: its kinda a cursor when you are selecting digits to change
02:38 PM Tom_L: blink it
02:39 PM flav0r: just dont put a hot iron on the bench dude
02:39 PM rue_mohr: :) I was able to just hilight it
02:39 PM rue_mohr: :)
02:39 PM flav0r: https://www.tubeclockdb.com/images/stories/largevfd.jpg
02:39 PM flav0r: thats what these other tubes i wanna use look like
02:39 PM Tom_L: damn
02:39 PM rue_mohr: ooof
02:39 PM flav0r: but i think i will have to go AC with those
02:39 PM rue_mohr: that must draw some current
02:39 PM Tom_L: house current :)
02:39 PM flav0r: i havent done much wth those yet .. just tested them to make sure they all work
02:40 PM rue_mohr: http://ruemohr.org/~ircjunk/projects/resistorbox/slide.htm <- that project
02:41 PM rue_mohr: came out good
02:43 PM rue_mohr: I could have masked the screen in a bit more
02:43 PM flav0r: so shocking that you would have some home made plotter to draw out the traces
02:44 PM rue_mohr: no its commercial
02:44 PM flav0r: oh
02:44 PM flav0r: just assumed youd make that too :)
02:46 PM flav0r: hmm the next thing i have to work on is an IO board for a pi CM3
02:46 PM flav0r: gonna learn some shit for sure
02:52 PM flav0r: well the good thing is i know who i will be talking to at length when i get back to VFDs and driving the filament
02:52 PM flav0r: :D
07:10 PM rue_mohr: dc-dc converters, I went on a thing
11:18 PM flav0r: HEY HEY !
11:54 PM mrdata: good day