#garfield Logs

Jan 10 2021

12:18 AM rue_mohr: ok so
12:24 AM rue_mohr: re-addressing the low pass
12:24 AM rue_mohr: I = (Vi - Vo) / 10.0; //
12:24 AM rue_mohr: Vo += I ;
12:24 AM rue_mohr: 10.0 would be the time constant
12:24 AM rue_mohr: I'm not sure how to get it approx to the equiv of 1k and 1uF
01:17 AM rue_mohr: ok, my -3db for this 1k / 1uF low pass is 159Hz
01:17 AM rue_mohr: hm
01:42 AM rue_mohr: the integration rate is a big factor to the low pass approximation
01:58 AM rue_mohr: Vo += (Vi - Vo) / k ;
01:58 AM rue_mohr: the cutoff freq is realted to the sample rate over the square of k
01:58 AM rue_mohr: Fc ~~ S/k^2
02:17 AM rue_mohr: no, not squared
02:23 AM rue_mohr: e^n?
02:27 AM rue_mohr: what fn = 10 when 1/fn(k) goes from 100 to 10.47
02:29 AM rue_mohr: could be 10^x
02:32 AM rue_mohr: no
05:59 AM rue_mohr: trial and error
05:59 AM rue_mohr: 10.492958
05:59 AM rue_mohr: and you know, that is a surprisingly common number on the internet
05:59 AM rue_mohr: Vo += (Vi - Vo) / 10.4929582 ;
05:59 AM rue_mohr: at a sample rate of 10khz,
06:00 AM rue_mohr: generates a -3db matching 1k and 1uF
06:02 AM rue_mohr: the low pass is 0db
06:34 AM polprog: https://i.ibb.co/2Yh25Z7/IMG-20210110-132006.jpg
06:34 AM polprog: :/ the boiler is causing problems again
06:35 AM rue_mohr: its 32 freezing?
06:49 AM polprog: the snow doesnt melt outside so probably yeah
06:50 AM polprog: the heat exchange circuit has not enough pressure and the valve that tops it up is stuck shut
06:51 AM polprog: turning it doesnt do anything, it just turns freely
06:51 AM rue_mohr: want to play with software high pass filters?
06:52 AM polprog: cant really now :/ mother and sister are genuinely pissed while we try to call a plumber to get the valve replaced
06:53 AM polprog: (we need to shut the water supply, replace this vavle and add another valve before the whole boiler)
06:53 AM polprog: valve*
07:18 AM polprog: todat being sunday doesnt help
07:18 AM rue_mohr: I think we could have fun playing, but I dont think we ever will :(
07:20 AM rue_mohr: I'v invented an over-unity RC filter :)
07:22 AM polprog: we could but its just unlucky turn of events
07:22 AM polprog: ive gotta vacuum the floors now
07:27 AM rue_mohr: hey I acccidently made that filter that goes _____/
07:29 AM rue_mohr: Vo = (Vi - Vo)*0.1;
07:31 AM rue_mohr: bah, I'm gonna go sleep on a book
06:16 PM aandrew: ok this is the second time in 3 days that this drive has just dropped off the bus. swapped it into another bay to see if it's the drive or the carrier it's in, since the carriers have a little circuit board on them
06:16 PM aandrew: ebay says they're about US$30 each so no biggie if it is a dead cage
06:29 PM MrTime: yo
06:41 PM rue_mohr: huh
07:47 PM aandrew: https://twitter.com/FLITTER/status/1348329830966767619 lots of good stuff in this thread
07:47 PM aandrew: my favourite is @cdeterline's post
08:12 PM aandrew: https://www.youtube.com/watch?v=jm6GXnV7c6E tonight's music
08:18 PM rue_mohr: heh
08:42 PM rue_mohr: https://www.cs.princeton.edu/courses/archive/fall08/cos436/DSP/DSP.html
08:43 PM rue_mohr: oh,
08:43 PM rue_mohr: I was wondering why my high and low pass were taking on the same forula
08:43 PM rue_mohr: "VI. Special Simple Filters: One Pole"
09:04 PM aandrew: I had a *REALLY* great book on DSP but I can't for the life of me remember what it was called
09:05 PM aandrew: it's somewhere in my half a terabyte of books I hope
09:06 PM aandrew: man I'm really loving this live set
09:06 PM aandrew: got me on a nice country music / country blues kick again
09:07 PM aandrew: I love almost all music genres, but country/alt country/blues country is unique in that it never ever sounds over-engineered
09:08 PM aandrew: some genres (modern rock/pop, EDM/trance/etc. of course) seem to be produced in such a way to make sure every possible nook and cranny of the audio stage is full of something, I find that if I listen to that too much that it starts to feel like someone's got a funnel jammed into my ear and they're forcing sound into my skull
09:08 PM aandrew: kind of like a foie gras goose or something
09:09 PM aandrew: most of the country genres except for the 'modern country' or pop country do not feel this way, they're sonically "open"
09:09 PM aandrew: I've been following Jason Isbell for years without knowing it
09:13 PM rue_mohr: yea I should put some music on
09:13 PM rue_mohr: I can only stay up 2 more hours
09:13 PM rue_mohr: and the stuff on this page isn't working
09:14 PM rue_mohr: https://www.cs.princeton.edu/courses/archive/fall08/cos436/DSP/DSP.html
09:19 PM rue_mohr: arg, thats the funkey upside down filter
09:20 PM rue_mohr: why cant these guys to proper log time x db graphs
09:21 PM rue_mohr: just because i cant get this doesn't mean its not easy