#garfield Logs

Jan 01 2021

12:32 AM rue_mohr: ok, what integrator would slew at 5V/194ms
12:39 AM rue_mohr: 1V/38.8ms
12:39 AM rue_mohr: I need that in V/ms
12:39 AM rue_mohr: .0258V/ms
02:34 PM TerminalMoon: .
02:35 PM Tom_L: o
03:01 PM rue_mohr: O
03:04 PM TerminalMoon: :)
03:04 PM Tom_L: moon, what you needin with power tools anyway?
03:04 PM Tom_L: drill press..
03:05 PM Tom_L: that's what rue_mohr's shop is for
03:12 PM rue_mohr: and my 12 speed drillpress
03:13 PM rue_mohr: 2HP just burns bits, big ones
04:51 PM Tom_L: slow it down
06:43 PM rue_shop1: ok, servo loop filter
06:43 PM rue_shop1: I like proportionate, cause the loop speed doesn't matter
07:04 PM aandrew: don't you need a bit of integral to get to zero error when you're almost there?
07:05 PM rue_shop1: I need to map the response to know where the peaks and falloffs are
07:05 PM rue_shop1: then make a filter to counteract it
07:05 PM rue_shop1: high freq falloff is the major thing, and that done with a high pass filter, which is derivitive
07:06 PM rue_shop1: but I have a pole in there
07:06 PM rue_shop1: if I give it a sine wave, the gain is more than 1 at some freqs
07:08 PM rue_shop1: want to play bode plot?
07:08 PM rue_shop1: I feed you points?
07:08 PM rue_shop1: polprog, ?
07:09 PM polprog: rue
07:09 PM polprog: hows it going?
07:09 PM rue_shop1: I'm ok
07:09 PM rue_shop1: playing with a servo
07:09 PM Tom_L: super
07:09 PM Tom_L: year came in with 5-6" snow
07:09 PM rue_shop1: I'm set up for gains and phase offsets, want to help chart points as I get them?
07:10 PM rue_shop1: the game is to try to work out the poles and zeros
07:10 PM rue_shop1: but a chart is a good start
07:11 PM polprog: im going to bed, i need to fix my biological clock
07:11 PM rue_shop1: :(
07:12 PM polprog: :(
07:12 PM polprog: yeah
07:12 PM Tom_L: oh poo
07:12 PM polprog: but i had to sleep off yesterday
07:12 PM polprog: er, tonight
07:12 PM polprog: i went to sleep at 8am and got up at 5 pm
07:12 PM polprog: painted the bathroom ceiling
07:13 PM polprog: done some poking around at the sound blaster front panel
07:13 PM polprog: im a bit tired, i should slee
07:13 PM polprog: sleep*
07:13 PM rue_shop1: ok quick if I have 2Vp-p into my system and 1.5Vp-p out, whats the gain in DB?
07:15 PM rue_shop1: Tom_L, you want to try that one ^ ?
07:15 PM Tom_L: working on eoy books
07:18 PM rue_shop1: 0.5Hz, 2V p-p in 1.92V p-p out 6.7 degrees
07:18 PM rue_shop1: 0.6Hz, 1.98V p-p out 7.3 degrees
07:19 PM Tom_L: do you get W2 up there or is it all different?
07:19 PM rue_shop1: rain, lots of rain
07:19 PM rue_shop1: 0.7Hz, 2V p-p out, 4.4 degrees
07:20 PM polprog: 20 log(vout/vin)
07:20 PM rue_shop1: redo on the angle, 6.9 degrees
07:20 PM rue_shop1: polprog, thankyou!
07:20 PM polprog: no, weird stuff is happening
07:21 PM polprog: -354 dB wtf
07:21 PM polprog: for 0.6Hz
07:21 PM polprog: that doesnt make sense
07:21 PM rue_shop1: I get -0.3545 using your formula
07:21 PM polprog: ohhh right
07:21 PM rue_shop1: ok last point was
07:21 PM polprog: i had my calc in engineering notation haha
07:22 PM rue_shop1: 0.7Hz, 2V p-p out, 6.9 degrees
07:22 PM polprog: didnt notice E-3
07:22 PM rue_shop1: :)
07:22 PM polprog: :)
07:22 PM polprog: how do you measure the phase?
07:22 PM rue_shop1: 0.8Hz 2.07V p-p out, 5.7 degrees
07:22 PM rue_shop1: the scope can do it
07:23 PM rue_shop1: there is some funkey stuff going on tho
07:23 PM rue_shop1: there is a pole in there
07:23 PM rue_shop1: gain is going up with freq
07:23 PM polprog: ah
07:24 PM rue_shop1: see it?
07:24 PM polprog: yeah
07:24 PM rue_shop1: 0.9Hz 2.11V p-p out, 4.7 degrees
07:24 PM polprog: you are getting 2.07 vpp out for 2vpp in
07:24 PM polprog: so it has Ku > 1
07:25 PM rue_shop1: and look at the phase angle, where is it going>?
07:25 PM polprog: i guess its a bad thing
07:25 PM rue_shop1: Ku?
07:25 PM polprog: gain
07:25 PM rue_shop1: ah
07:25 PM polprog: thats how we denote it in class at least
07:25 PM rue_shop1: could u be polish?
07:25 PM polprog: yes
07:26 PM polprog: its not ku*** :)
07:26 PM polprog: hmm, the phase angle is going back and forth
07:26 PM rue_shop1: 1Hz 2.13V p-p out, 6.2 degrees
07:26 PM rue_shop1: so, can we tell from that were that pole is?
07:27 PM polprog: somewhere above 1Hz?
07:27 PM polprog: hmm, i wonder if i could automate bode plotting with querying my scope via serial port
07:28 PM rue_shop1: the phase angle changes a lot when I zoom in...
07:28 PM polprog: sounds like a good project. all id have to do then is to slowly turn the frequency knob up
07:28 PM polprog: thats a brilliant idea
07:29 PM rue_shop1: larger steps now
07:29 PM rue_shop1: 1.5Hz, 2.37V p-p out, 13.8 degrees
07:29 PM polprog: were still nearing the pole
07:30 PM rue_shop1: going up 0.5Hz at a time, tell me if you see we should back up
07:30 PM polprog: mm
07:30 PM rue_shop1: 2Hz 2.17V p-p out, 68 degrees
07:30 PM rue_shop1: did we just fly past it?
07:31 PM polprog: i think so
07:31 PM rue_shop1: ok, how much do you think I should back up by?
07:31 PM polprog: try 1.75hz?
07:31 PM polprog: binary search :v
07:32 PM rue_shop1: 1.75Hz, 2.45V p-p out, 20.4 degrees
07:32 PM polprog: closer
07:32 PM polprog: a bit more.. 1.8?
07:32 PM Tom_L: seems polprog missed his date with the sandman
07:33 PM polprog: seems so
07:33 PM polprog: im listening to some music now
07:33 PM rue_shop1: 1.8Hz 2.48V p-p out, 32.8 degrees
07:33 PM polprog: ill go to sleep when we find the pole
07:33 PM polprog: hmm. 1.85?
07:34 PM polprog: am i right if you connected the input to output, ac coupled, would it oscillate at the pole frequency?
07:34 PM rue_shop1: 1.85Hz, 2.4V p-p out, 45.3 degrees
07:34 PM polprog: looks like its between 1.8 and 1.85
07:35 PM rue_shop1: I can adjust by .01
07:35 PM rue_shop1: 1.83?
07:35 PM polprog: it would be phase shifed by 90 degrees iirc
07:35 PM polprog: yeah lets try 1.83
07:35 PM polprog: ill have to do that with my new freq gen too
07:36 PM rue_shop1: 1.83Hz 2.45V p-p out, (I zoomed in) phase 32.2
07:37 PM polprog: hmm
07:37 PM polprog: 1.85?
07:37 PM polprog: whats this filter/circuit anyway?
07:37 PM rue_shop1: we did that, but I'll try zoomed in
07:37 PM polprog: ah
07:37 PM rue_shop1: its that servo I posted on twitter
07:37 PM polprog: 1.84 then
07:37 PM polprog: hmm must be somewhere there
07:38 PM rue_shop1: 1.85Hz vout 2.41V p-p, 37 degrees
07:39 PM rue_shop1: 1/84Hz 2.44V p-p, 35.2 degrees
07:39 PM polprog: weird
07:39 PM polprog: must be somewhere in between there
07:40 PM rue_shop1: but at 1.8Hz we had 2.48V p-p
07:40 PM polprog: hmm
07:40 PM polprog: how do we know we are at the pole?
07:40 PM rue_shop1: peak of the gain was at 1.8Hz
07:40 PM polprog: yeah
07:41 PM rue_shop1: I dont think the phase angles tell us anything
07:41 PM rue_shop1: accept maybe how many system poles there are
07:41 PM polprog: i dont remember much, i read about that on wikipedia long time ago
07:41 PM polprog: so ita a digital servo?
07:41 PM polprog: its*
07:41 PM rue_shop1: well, for a simple system, you dont hit a pole at 32.8 degrees :)
07:41 PM rue_shop1: 1 sec
07:42 PM rue_shop1: https://twitter.com/RueNahcMohr/status/1344889692546744322
07:42 PM rue_shop1: I closed the loop with an atmega8 doing proportionate
07:43 PM polprog: ah
07:43 PM rue_shop1: https://twitter.com/RueNahcMohr/status/1344972193076113408
07:43 PM polprog: whats Kp? proportionate gain?
07:43 PM rue_shop1: 6
07:43 PM rue_shop1: 7 starts to oscillate
07:44 PM rue_shop1: we can just go by the gain to find the pole, right?
07:45 PM polprog: maybe? i think so
07:45 PM rue_shop1: it shouldn't be much different than an LRC mess
07:46 PM rue_shop1: but at 2Hz the gain dropped way back, so I must have passed a zero?
07:46 PM polprog: yeah
07:46 PM rue_shop1: er, I'm also looking at the phase angle, of 45 degrees, but if this is complex, that wont tell me much
07:47 PM rue_shop1: if the pole is about 1.8Hz, then the signal will drop after that
07:47 PM rue_shop1: I'll do 1.9
07:48 PM rue_shop1: 1.9Hz Vout = 2.29V p-p, phase 49
07:48 PM rue_shop1: that phase angle is on the run
07:48 PM polprog: yeah. phase is still rising
07:49 PM rue_shop1: sharp too!
07:49 PM rue_shop1: I'll redo 2Hz
07:49 PM polprog: ill be going to sleep soon
07:49 PM rue_shop1: 2Hz vout 2.15V p-p, phase 59.5 degrees
07:50 PM rue_shop1: 3Hz? or smaller steps?
07:50 PM rue_shop1: hey wait
07:50 PM polprog: lets do .5 hz
07:50 PM polprog: what
07:50 PM rue_shop1: 1.9Hz 49 degrees
07:50 PM rue_shop1: 2Hz 68 degrees
07:51 PM rue_shop1: 2.5hz 59.5 degrees
07:51 PM rue_shop1: er
07:51 PM polprog: thats weird
07:51 PM rue_shop1: no I'm at 2
07:51 PM rue_shop1: sorry
07:51 PM rue_shop1: I didn't do 2.5 yet
07:51 PM rue_shop1: its still going up
07:51 PM rue_shop1: ok, 2.5Hz
07:52 PM rue_shop1: 2.5Hz, 1.55V p-p out, 90.7 degrees
07:53 PM polprog: 90 degrees!
07:53 PM polprog: weird...
07:53 PM polprog: very weird
07:53 PM rue_shop1: 3Hz next...
07:54 PM rue_shop1: 3Hz, 1.2V p-p out, 115 degrees
07:55 PM polprog: i think it was 180 deg that was special case
07:55 PM rue_shop1: my initial measurements guessed this thing to have an attenuation of like 18db/decade
07:55 PM rue_shop1: er -18db/decade
07:55 PM rue_shop1: 180 is the limit, I think
07:55 PM rue_shop1: 3.5Hz...
07:56 PM rue_shop1: 3.5Hz, 940mv p-p out, 130 degrees
07:57 PM rue_shop1: so its still just the one pole tho
07:58 PM polprog: hmm
07:58 PM rue_shop1: 4Hz, 750mv p-p out, 138 degrees
08:00 PM rue_shop1: 4.5Hz, 650mv p-p out, 130 degrees
08:00 PM rue_shop1: it just turned around I think
08:01 PM rue_shop1: the phase angle
08:01 PM polprog: im going to slee
08:01 PM polprog: sleep*
08:01 PM polprog: good night :)
08:02 PM rue_shop1: 5Hz, 540mV p-p out, 150 degrees
08:03 PM rue_shop1: 5.5Hz 450mV p-p out, 140 degrees
08:04 PM rue_shop1: the phase angle just went ballistic
08:09 PM rue_shop1: ok redid the angle measurements, and its steady going down
08:22 PM rue_shop1: 7Hz is 174 degrees
08:22 PM rue_shop1: things are getting hard to measure
08:23 PM rue_shop1: heh, phase angle is now negative
08:24 PM rue_shop1: so it passed 180 degrees!?
08:25 PM rue_shop1: 190 degrees, but the attenuation bottomed out
08:25 PM rue_shop1: I dont think its true gain anymore
08:26 PM rue_shop1: the servo is just responding to the input
08:29 PM rue_shop1: it looks like the phase bottomed out at 195 degrees?
08:29 PM rue_shop1: that takes a 3rd order system I think?
08:37 PM rue_shop1: wow cool
09:36 PM rue_mohr: http://ruemohr.org/~ircjunk/tempimage/p1180389.jpg
09:36 PM rue_mohr: http://ruemohr.org/~ircjunk/tempimage/p1180392.jpg
09:36 PM rue_mohr: http://ruemohr.org/~ircjunk/tempimage/p1180393.jpg
09:40 PM Tom_L: looks like you had a WTF moment as well
09:43 PM rue_mohr: that phase angle bit does NOT add up
09:43 PM rue_mohr: I have no idea whats going on there