#garfield Logs

Dec 15 2022

08:03 AM aandrew: rue_mohr: sounds like a class D amp :-)
11:23 AM rue_mohr: 3748
11:24 AM rue_mohr: is that a jump I cant find the last check-in
11:24 AM rue_mohr: ah not really
04:09 PM rue_mohr: ISBN 0-8306-7348-2
06:56 PM rue_shop1: so
06:56 PM rue_shop1: if a PMDC motor is at a stop
06:56 PM rue_shop1: and you need it to "step" a particular distance, there is an "impulse' (forward drive, then reverse) that will prettymuch get it there
06:57 PM rue_shop1: a question is, how does any pre-existing speed modify that pulse
06:58 PM rue_shop1: with a stepper motor, if your behind by too far, you will skip a step
06:59 PM rue_shop1: you might have to play with it
06:59 PM rue_shop1: well I also need to know how to properly "land" a pulse on the target position
06:59 PM rue_shop1: maybe it should be an expected velocity profile
07:48 PM Tom_L: why does it have to be so close?
07:49 PM Tom_L: i was working on spindle orient code that stopped the spindle in the exact position each time
07:50 PM Tom_L: it never did work right because of the sherline motor but i never revisited it on the bldc spindle motor
07:50 PM Tom_L: i'm betting it would do alot better
08:08 PM rue_shop1: its for the positioning motor :]
08:09 PM rue_shop1: it would be great to have a pile of those stepper -> dc motor drivers
08:09 PM rue_shop1: there will be a few counts for error
08:09 PM rue_shop1: I think I usually allow 10
08:10 PM rue_shop1: I'm trying to apply myself to the servo for the plasma cutter
08:10 PM rue_shop1: it was supposed to get done this year, a quick project
08:12 PM rue_shop1: I have a mostly assembled gearbox
08:12 PM rue_shop1: and some bearings in a chunk of plate
08:15 PM rue_shop1: I was doing some stuff earlier this year and learned some important tings
08:15 PM rue_shop1: like, if you do two drive pulses, forward, then reverse, to make a motor accelerate then stop, the pulses are not the same length
08:15 PM rue_shop1: lie /\
08:15 PM rue_shop1: like
08:16 PM rue_shop1: the time to stop is not the same as the time to speed up
08:16 PM rue_shop1: I think its 2:1
08:16 PM Tom_L: takes more to start than stop
08:16 PM Tom_L: friction, inertia etc
08:16 PM rue_shop1: because when you apply reverse power to come to a stop, its stopping about twice as fast as the speed up from zero
08:17 PM rue_shop1: being that its only going to 0 and not actually reversing
08:17 PM rue_shop1: :]
08:17 PM rue_shop1: so the controller I want to do will be different
08:18 PM rue_shop1: it wont add the pulse to an accumulator, then work out the position difference and apply a drive proportional to the error
08:18 PM rue_shop1: I'll put it right into full forward, then wait for the condition to slam it into reverse
08:19 PM rue_shop1: if its all done right, it should stop pretty close to target
08:19 PM Tom_L: hope emf don't getcha
08:19 PM rue_shop1: but the system can tweak the "landing" to adjust for error
08:19 PM rue_shop1: yea, the inrush currents will be nasty
08:20 PM Tom_L: funny when you're in the middle of a project you remember every little detail. 6mo-yr later i haven't the foggiest idea wtf i was doing
08:21 PM rue_shop1: you should see me and Sean trying to work out how to make sprayers at the start of the season
08:21 PM rue_shop1: heh
08:21 PM Tom_L: i'm not going to use it anyway so it really doesn't matter
08:21 PM rue_shop1: "wait, do we do that first?"
08:21 PM rue_shop1: we made two books
08:21 PM Tom_L: make an assembly sheet
08:21 PM rue_shop1: one for how to make the parts, and another on how to assemble the parts
08:22 PM rue_shop1: I did an assembly order diagram too
08:22 PM Tom_L: i started dating the directories for the parts cad
08:22 PM rue_shop1: we usually jump in thinking we remember and dont read the docs properly
08:23 PM rue_shop1: but a few things have changed, so if we didn't make notes, there is a bit of fun
08:23 PM Tom_L: did you ever try that tab bending jig i sent?
08:23 PM rue_shop1: well, I'm going to be up about another 7 hours, I ought work out what I'm gonna do
08:23 PM Tom_L: i don't remember
08:23 PM rue_shop1: Tom_L, we havn't had any heads to use it on yet
08:23 PM Tom_L: oh
08:24 PM rue_shop1: yea
08:24 PM rue_shop1: I kept the instruction images up on one of the browsers
08:24 PM Tom_L: got a good vise?
08:24 PM rue_shop1: yep
08:24 PM Tom_L: i used my machine vise
08:24 PM rue_shop1: I should probably get the machine cutting some heads, but there's been a buckshot of power outages and I'm gunshy
08:24 PM Tom_L: beats beating the hell outta em with a hammer
08:25 PM Tom_L: he didn't want me to make any?
08:25 PM rue_shop1: I have the machine with a blank for activation levers, waiting for the power to be stable
08:25 PM rue_shop1: Tom_L, he wants to check the cost, we have $200 of material here to make ones here
08:26 PM Tom_L: should be alot of material
08:26 PM rue_shop1: you can whip them off WAY faster than we can
08:26 PM rue_shop1: its 4' strips,
08:26 PM Tom_L: iirc i cut one up and can get 12-15 from a strip and i think i have 2-3 of them
08:26 PM rue_shop1: 11 strips, 3" wide, 4' long
08:27 PM Tom_L: i measured so i wouldn't waste any
08:27 PM Tom_L: i got my setup working at 3" width too
08:27 PM Tom_L: just cut some ears off and keep feeding fwd
08:27 PM rue_shop1: I think we get like 11 in a 4' strip?
08:28 PM rue_shop1: ?
08:28 PM Tom_L: i'd have to measure it
08:28 PM rue_shop1: I need to make a special encoder for this plasma cutter servo
08:29 PM rue_shop1: I started it
08:29 PM Tom_L: i'll check
08:35 PM Tom_L: yep 11 every 4' but i cut mine up different
08:35 PM Tom_L: each piece has 4 so it will fit inside the enclosure
08:35 PM Tom_L: and mine were 5' strips i think
08:36 PM Tom_L: probably 12' from the yard
08:36 PM Tom_L: and i used some probably
08:40 PM Tom_L: http://tom-itx.no-ip.biz:81/~webpage/rue/Can_Holder/A9_New/MODS/A9_A10_plates.jpg
08:41 PM Tom_L: now i just cut those tabs off and feed it fwd against the dowel pin stops
08:41 PM Tom_L: instead of cutting the plates
08:44 PM rue_mohr: :)
08:44 PM Tom_L: http://tom-itx.no-ip.biz:81/~webpage/rue/Can_Holder/A9_New/MODS/fixture/A9_Fixture17.jpg
08:44 PM Tom_L: http://tom-itx.no-ip.biz:81/~webpage/rue/Can_Holder/A9_New/MODS/fixture/A9_Fixture18.jpg
08:47 PM rue_mohr: :)
08:48 PM Tom_L: should save time if it works ok
08:49 PM rue_mohr: whenever the season starts, I think we want to have parts for 40 sprayers ready
08:49 PM rue_mohr: I think that was our guess on the upcomming annual
08:50 PM Tom_L: how many feet of that A9 material do you have?
08:50 PM rue_mohr: they get sized per order, so we aren't realyl fully assembling them
08:50 PM rue_mohr: 11 4 foot peices
08:51 PM rue_mohr: we must have started with 16
08:51 PM Tom_L: 121 parts
08:51 PM rue_mohr: I think the 4'x4' cut up was $200
08:51 PM Tom_L: i get it in 3" strips
08:51 PM Tom_L: 12'
08:51 PM Tom_L: the cut cost you alot
08:52 PM rue_mohr: I think the machine takes us 2.5hrs/A9-10
08:52 PM Tom_L: ~15 min
08:52 PM rue_mohr: no, the material price is crazy out here
08:52 PM Tom_L: i'm sure it's higher here too
08:52 PM rue_mohr: I think it was $40 or $50 for the cutting
08:52 PM Tom_L: that's probably 2 12' for me if i was guessing
08:53 PM Tom_L: i'd have to check again for sure
08:53 PM Tom_L: and this is softer than that aged stuff i had
08:53 PM Tom_L: T651
08:53 PM rue_mohr: I'm interested to see how the ones I had to anneal hold up
08:54 PM Tom_L: on that first stuff you had to anneal
08:54 PM Tom_L: they should do good, they're age hardened
08:54 PM rue_mohr: I'm not sure if they will stress fracture around the can eaiser
08:55 PM rue_mohr: I think they will either be stronger or weaker
08:55 PM rue_mohr: :]
08:55 PM Tom_L: so you've got ~3 yrs of material for those
08:55 PM rue_mohr: hah
08:55 PM rue_mohr: we been buying larger lots, cause the prices are going up so fast
08:56 PM rue_mohr: iirc the $200 in material was about $130 last time we got some
08:56 PM Tom_L: so should the end product
08:58 PM Tom_L: i finally found some jig saw blades that cut al real good
08:58 PM Tom_L: wish i had a band saw or chop saw but i don't and don't have room for one
08:58 PM rue_mohr: :] course tooth wood bits typically do ok, providing its not too course
08:59 PM rue_mohr: time do dig a basement
08:59 PM rue_mohr: wait you alrady did
08:59 PM rue_mohr: ;]
08:59 PM Tom_L: yup
09:00 PM Tom_L: this point in time i'll make do with what i have
09:01 PM rue_mohr: hey
09:01 PM rue_mohr: did you see the yt vid about cutting gears with a saw?
09:01 PM Tom_L: i'm not sure
09:01 PM rue_mohr: 100-and-some odd cuts?
09:02 PM Tom_L: just got these the other day: http://tom-itx.no-ip.biz:81/~webpage/cnc/calipers/Mitutoyo_case.jpg
09:02 PM Tom_L: my kid took my other set
09:02 PM rue_mohr: https://www.youtube.com/watch?v=eC-OctJoWv4 ?
09:02 PM Tom_L: added the pocket for the gage block
09:02 PM rue_mohr: tahts it
09:04 PM rue_mohr: so, I suppose I'll make up the encoder for the plasma cnc motor
09:05 PM rue_mohr: I'm eager to get a chance to use your wheels on some encoders
09:05 PM rue_mohr: sadly not this one
09:07 PM rue_mohr: I have a prototype mostly assembled
09:07 PM rue_mohr: it might be worth it to have osh make the pcbs
09:08 PM rue_mohr: I need a cnc lathe :]
09:08 PM rue_mohr: one of the parts of the encoder is a modified bolt
09:08 PM rue_mohr: its the bits with the thread
09:08 PM rue_mohr: 3/8NF iirc
09:13 PM Tom_L: i remember what i was gonna do now but it's too late now
09:17 PM rue_shop1: note it for tommroow
09:17 PM rue_shop1: you could put it here, but I might babable yet
09:17 PM Tom_L: not a big deal
09:18 PM Tom_L: set of mechanical digital micrometers the counter is off on
09:18 PM rue_shop1: ... off?
09:18 PM Tom_L: the counter doesn't go to zero
09:19 PM Tom_L: it skipped a tooth or something
09:19 PM rue_shop1: digital...
09:19 PM rue_shop1: zero button?
09:19 PM Tom_L: mechanical digital like an old car odometer
09:19 PM rue_shop1: ah
09:26 PM Tom_L: well that was easy
09:33 PM Tom_L: cheap bluepoint mic but it will do for every day use
10:45 PM rue_mohr: :]
10:45 PM rue_mohr: nothing broken?