#garfield Logs

Jun 19 2020

04:29 AM polprog: who the hell came up with an exam at noon
04:35 AM polprog: i woke up at 9, it's 11:30 and im already tired
06:55 AM Tom_itx is now known as Tom_L
06:55 AM Tom_L: they wanted you to be hungry
07:16 AM polprog: oh man. what a carnage
07:16 AM polprog: time is over. now 5 people at once complain their internet went out/dog ate the paper/there was athunderstorm/whatever
07:16 AM Tom_L: hah
07:17 AM Tom_L: prof doesn't give a shit
07:17 AM polprog: pretty much
07:17 AM Tom_L: he's gettin paid either way
07:17 AM polprog: i wonder if i pass.. 2/3 problems i got a sane looking number as the end result
07:18 AM polprog: nah, they care a little.. Not very much but they care.
07:18 AM polprog: it's a small field of study.
07:19 AM polprog: the group is 18 people or so now. it was 30 at the beginning
09:27 AM rue_mohr: polprog, are people giving up and leaving the course?
09:28 AM polprog: pretty much yes
09:33 AM rue_mohr: were many of the people taking the course "just for extra points" or did they actaully need to take it
09:40 AM polprog: no, this is first year. the course is mandatory
09:40 AM polprog: they drop outta uni
09:40 AM rue_mohr: wow, I knew there was a weeding process, but wow
09:57 AM polprog: this is Maths 2
09:57 AM polprog: well, Phys 2 as well
09:57 AM polprog: hard to say which course made who give up
09:58 AM rue_mohr: https://twitter.com/HCI_Comics/status/1273495154100338689
10:01 AM rue_mohr: http://ruemohr.org/~ircjunk/tutorials/elex/ldvc/ldtc.html
10:03 AM polprog: that one is nice
10:03 AM polprog: but theres loads of new stuff so people just give up
10:03 AM polprog: im lucky i passed maths 2 by 1 point
10:04 AM polprog: to be exempt from the 1 st part of the exam. I dont know if i pass the 2nd part, wrote it this morning
10:04 AM polprog: ive done 2 out of 3 problems.. partly solved the 3rd one
12:10 PM polprog: https://m.imgur.com/MuAMn
12:10 PM polprog: from another channel
05:04 PM aandrew: Hm, any particular reason why I couldn’t use a ULN2003 to speed control a DC motor? It’s essentially just the bottom half of a half H bridge
05:06 PM polprog: who says you cant
05:06 PM polprog: if its a plain DC motor, then a ULN on the low side should be able to control it fine..
05:11 PM rue_mohr: yup
05:11 PM rue_mohr: use a UDN2903 for the top side
05:11 PM rue_mohr: I think
05:12 PM polprog: cant find an UDN2903, UDN29* gives some results
05:12 PM polprog: UDN2944 QUAD HIGH-CURRENT,HIGH-VOLTAGE SOURCE DRIVER
05:13 PM polprog: DUAL FULL-BRIDGE PWM MOTOR DRIVER
05:13 PM polprog: 2985 8-CHANNEL SOURCE DRIVER
05:13 PM rue_mohr: yea!
05:13 PM polprog: these are neato
05:13 PM polprog: ill have to ask at the shops next time i go there
05:13 PM rue_mohr: pnp is $$ tho
05:14 PM polprog: seems to be a mixed PNP+NPN pair
05:14 PM polprog: forgot the name for that
05:15 PM rue_mohr: oh, maybe its the 2983?
05:15 PM rue_mohr: dunno what I used
05:15 PM polprog: https://www.alldatasheet.com/view.jsp?Searchword=UDN2983
05:16 PM rue_mohr: oh, mine are UDN2982
05:16 PM polprog: subtle differences
05:17 PM rue_mohr: different resistors
05:17 PM polprog: datasheet shows an "electrosensitive printer" application
05:17 PM polprog: yeah
05:17 PM rue_mohr: yea, I used them for the vfd driver
05:17 PM rue_mohr: their better for it
05:17 PM polprog: i should get some
05:18 PM rue_mohr: I got a few from china
05:18 PM rue_mohr: I dont think they arrived yet
05:19 PM rue_mohr: polprog, but hey, look at AOP605
05:19 PM Tom_L: rue_mohr, got your hourly quota in for the week?
05:19 PM rue_mohr: I have to go back for work, came in for lunch
05:19 PM polprog: Complementary Enhancement Mode Field Effect Transistor ?
05:19 PM rue_mohr: its 3:10
05:19 PM rue_mohr: lunch is nice.
05:20 PM Tom_L: i wondered wtf
05:20 PM rue_mohr: this morning had problems and made the day stupid, bye!
05:20 PM polprog: when i was doing the internship at the last place we would go to lunch to the vietnamese takeaway. it was good times
05:30 PM polprog: rue_mohr: another thing is that outta 30 people that got in, 25 came to the beginning ceremony
05:30 PM polprog: so the numbers are not *that* bad
05:33 PM aandrew: Interesting on the udn2985
08:14 PM rue_shop2: one day I'll make a quad H bridge from the two chips
09:02 PM rue_mohr: so the project manager said to skip tonight
09:03 PM rue_mohr: come in at 8 tommorow, ahahah, no not 8
09:03 PM rue_mohr: I'm gonna sleep in, wake up, get the stuff I need for the shed, THEN I can go to work
09:15 PM Tom_L: heh
09:16 PM rue_mohr: I got both proportionate loop controllers going for the tilt and pan mirror
09:16 PM rue_mohr: remounted the backboard in the control box
09:16 PM Tom_L: dunno why but i'm bushed tonight
09:17 PM rue_mohr: yea, I'm out of energy after this week
09:24 PM rue_mohr: plasma cutter
09:24 PM rue_mohr: if I target 100 thou accuracy
09:25 PM rue_mohr: about 60cm dia pulley
09:25 PM rue_mohr: thats about 740 lines
09:25 PM rue_mohr: if I target 0.5m/sec
09:48 PM rue_mohr: ok, so, motor that can do 3300 rpm under some load, 1:21 gearbox, 60cm dia drive pulley, and a 9 line quadrature encoder
09:48 PM Tom_L: better not skimp on the encoder
09:48 PM rue_mohr: need a loop controller that can take step/dir input, and encoder feedback
09:48 PM Tom_L: it will be choppy
09:49 PM rue_mohr: Tom_L, I'll print the best encoder I ever done
09:49 PM Tom_L: hmmm
09:49 PM Tom_L: i recall milling some slots for something....
09:50 PM rue_mohr: oh right!
09:50 PM rue_mohr: I have encoder wheels
09:50 PM Tom_L: damn i forgot about those
09:50 PM rue_mohr: their like 32 pulse
09:50 PM rue_mohr: its all in a bag for "making encoders"
09:50 PM rue_mohr: I wonder if I can get those up to 3300rpm with signal
09:50 PM rue_mohr: might be too many lines, might not
09:51 PM Tom_L: too quick for the avr to read?
09:51 PM rue_mohr: the IR things are kinda slow
09:52 PM rue_mohr: getting even 500kHz is crazy
09:52 PM rue_mohr: thats 55rps
09:52 PM rue_mohr: if their 32 lines (?) thats 1.7kHz
09:52 PM rue_mohr: so, maybe!
09:53 PM rue_mohr: (3300 rpm)
09:53 PM rue_mohr: so, Tom_L did you tune the acceleration on your machine?
09:54 PM rue_mohr: like, set the max accel?
09:54 PM Tom_L: ?
09:54 PM Tom_L: i did at one point
09:54 PM Tom_L: wasn't very professional about it
09:54 PM rue_mohr: if you try to accel too fast the motors will slip
09:54 PM rue_mohr: ok
09:54 PM rue_mohr: so, whats your max accel set to?
09:54 PM Tom_L: yeah i backed them off from that
09:54 PM rue_mohr: if you know
09:54 PM Tom_L: i don't. but my website does
09:54 PM rue_mohr: k
09:55 PM Tom_L: http://tom-itx.no-ip.biz:81/~webpage/cnc/configs/NEW_MILL_2.7/new_mill.ini
09:55 PM Tom_L: 55 whatever that is
09:56 PM rue_mohr: whats the velocity in?
09:56 PM rue_mohr: 5inches/sec?
09:56 PM rue_mohr: inches/min?
09:56 PM rue_mohr: not 5 inches/min for yours tho
09:58 PM Tom_L: MAX_ACCELERATION = 20.0 - Maximum acceleration for this axis in machine units per second squared.
09:58 PM Tom_L: from the docs
09:58 PM Tom_L: mine is set to 55 and 45 in each axis
09:58 PM rue_mohr: and your units are inches
09:58 PM Tom_L: yes
09:58 PM rue_mohr: 1.4m/s^2
09:59 PM Tom_L: max velocity is the same... machine units per second
10:00 PM rue_mohr: so, your max vel is... 5inche/s
10:00 PM rue_mohr: interesting
10:01 PM Tom_L: i may not have it tuned as well as it could be
10:01 PM rue_mohr: so your 5 inches/sec and I'm targeting 196inches/sec
10:01 PM rue_mohr: says to me I should lower my number
10:02 PM Tom_L: heh
10:02 PM rue_mohr: THO this is for a plasma cutter
10:02 PM Tom_L: not alot of moving mass on that
10:02 PM MoonyMoon: rue_mohr: Prematurly home?
10:03 PM rue_mohr: tom said to give up on tonight, chew into it tommorow
10:03 PM MoonyMoon: ha!
10:03 PM rue_mohr: but he said to start at 8, and I cant do that
10:03 PM MoonyMoon: no doubt
10:04 PM Tom_L: skunkworks has a plasma cutter
10:04 PM rue_mohr: so I'll start after I wake up and get the stuff I need from gbs to build the shed
10:04 PM MoonyMoon: :)
10:04 PM Tom_L: he's the one that did the rippled tin cut i showed you a while back
10:04 PM MoonyMoon: https://www.youtube.com/watch?v=oj82Uu__xso
10:04 PM Tom_L: yeah the one he just posted :D
10:12 PM Tom_L: https://www.plasma-automation.com/partsdatabase/CuttingCharts/hpr260.pdf
10:21 PM rue_mohr: yea but
10:21 PM rue_mohr: in general
10:22 PM Tom_L: i'd ignore roycroft, he can be a real bitch
10:22 PM Tom_L: skunkworks knows his stuff