#robotics Logs
Feb 20 2017
#robotics Calendar
12:34 AM rue_house: hahah, flipping thru old stuff, i apparentyly invented the fpga, ahhahahaha
12:41 AM rue_house: oh look, the verry first logic gate I got working, and it looks like a page of notes I made when I did it
12:44 AM z64555: Where will you be, when the nostalgia hits?
12:44 AM rue_house: I had state machines down long before I ever heard the name
12:44 AM rue_house: I didn't know why cpu's existed, didn't need them
12:46 AM z64555: uC's back then are a far cry from what they are today
12:49 AM rue_house: and I was designing computers with programmable interconnectable function blocks
12:50 AM rue_house: ... and cameras.....
12:51 AM rue_house: heh
12:51 AM rue_house: programming cards made of tinfoil with holes punched into it, on a cardboard backer,
12:51 AM justan0theruser is now known as OfficialLeibniz
12:52 AM z64555: mother of god, lol
12:53 AM rue_house: but, as an intersting note, most of the things I designed were done as 4 bit
12:55 AM rue_house: designes for 8 track tape players that mix digital and audio to speak
12:57 AM rue_house: heh, digital servo loop with a BIT too much gain
01:01 AM z64555: probably to double as the speaker driver
01:01 AM z64555: oh
01:01 AM z64555: wait, no
01:02 AM z64555: you said SERVO loop
01:02 AM z64555: nevermind
01:08 AM veverak: 7:39 AM
01:09 AM * veverak is still poor student, not used to waking up so early in the morning
01:09 AM z64555: could be worse
01:10 AM z64555: You could be coming into work at 12AM
01:10 AM veverak: ah, true
01:10 AM veverak: no work ;)
01:10 AM z64555: and then again at 8Pm
01:11 AM z64555: nah, 12AM is 7 hours earlier
01:11 AM z64555: 12AM is midnight, 12PM is noon
01:59 AM Jak_o_Shadows: hi
06:59 AM orlock: theBear been idle a while
07:10 AM mrdata_: awhile, sure, but still on my scrollback
07:10 AM orlock: timestamped?
07:12 AM mrdata_: idk the date; i have around 1000 lines of scrollback
07:14 AM mrdata_: so either he's busy, past couple weeks, and hasnt checked irc; or his murderous neighbour is out on bail and ...
11:55 AM rue_bed2:
01:24 PM LoRez_ is now known as LoRez
01:45 PM z64555: oh. huh.
01:46 PM z64555: You can implement templates by using a Macro
01:51 PM robotustra: G
01:56 PM robotustra: how is everything?
02:40 PM OfficialLeibniz: What should I use as sturdy spacing? I have an axle going through bearings and I need to increase the bearings height by 34mm, however I don't suspect using just threaded spacers would be able to handle the tension witohut tearing what it's mounted into.
02:41 PM OfficialLeibniz: standoffs*
02:50 PM z64555: use a standoff plate
02:50 PM z64555: you can even 3D print one
02:52 PM z64555: for a 4-hole plate, it would look like a hollow box with an X in it
02:54 PM z64555: the material between the holes links them together, so if shear forces apply to one fastener, it
02:54 PM z64555: is distributed to all fasteners
02:59 PM OfficialLeibniz: thanks
03:00 PM OfficialLeibniz: none on mcmaster, probably should just get some aluminum and machine it
03:00 PM OfficialLeibniz: also, z64555, if I go with the non-circular timing belt design, how do I reverse, woludn't the motor reversing just produce slack? I would need two timing belts, one for each direction of motion, wouldn't I?
03:01 PM z64555: not sure what you mean by "non-circular"
03:01 PM OfficialLeibniz: I mean not in a loop
03:01 PM OfficialLeibniz: both sides are given tension by a spring
03:01 PM OfficialLeibniz: unless it moves because of the tension of the spring
03:02 PM OfficialLeibniz: If that's the case, I need a stronger spring
03:02 PM z64555: ok
03:02 PM z64555: No, the motor won't produce a lot of slack
03:02 PM OfficialLeibniz: well if it rotates in the direction where the motor isn't applying force, it will?
03:03 PM OfficialLeibniz: and the spring will need to do the lifting
03:04 PM z64555: well, if your timing belt is good, it won't stretch under load
03:04 PM OfficialLeibniz: hmm?
03:04 PM OfficialLeibniz: it's not stretching, it's slacking
03:04 PM OfficialLeibniz: let me give you a picture of how I'm imagining it
03:05 PM OfficialLeibniz: https://imgur.com/edy4Uf8
03:05 PM OfficialLeibniz: ignore the misuse of orthographic paper
03:06 PM * z64555 waits on his slow internet
03:06 PM OfficialLeibniz: if the motor (top) rotates counterclockwise it produces slack
03:07 PM OfficialLeibniz: unless the spring causes the shaft on the right to rotate as much as the motor rotates
03:09 PM z64555: where would the motor be
03:09 PM OfficialLeibniz: the motor we're concerned with here is the circle in a square in the top left
03:09 PM z64555: ok, and where do the springs attach
03:11 PM OfficialLeibniz: Spring A) an object whose position and orentation are fixed relative to the motor. Spring B) same except its relative to the axle that the belt is doing work on
03:11 PM OfficialLeibniz: If the motor rotates counter clockwise, it seems it would slack
03:12 PM z64555: I don't think it would, so long as spring B is still providing tension
03:12 PM z64555: the only *slack* that would be in there is at spring A
03:13 PM z64555: er, that was supposed to be double quotes, not stars
03:13 PM * z64555 refills his coffee cup
03:13 PM justanotheruser: sorry my laptop died
03:13 PM justanotheruser: I missed what you said after I said something
03:13 PM z64555: I don't think that there would be any slack in the belt, except between the motor and spring A
03:14 PM z64555: which shouldn't affect anything at all
03:14 PM justanotheruser: if it rotates counterclockwise then there will be slack, won't there?
03:15 PM z64555: there will still be tension on the belt
03:15 PM z64555: Ok
03:15 PM z64555: So, the tension is held up by the motor in that configuration
03:15 PM z64555: if the motor relaxes, i.e. rotates counterclockwise
03:15 PM justanotheruser: is this because you're saying the tension of the spring is greater than the load?
03:17 PM z64555: eh, I can't tell from that configuration if there's tension on the belt from just the springs
03:18 PM z64555: say that they were
03:18 PM justanotheruser: well basically my concern is that the spring an the load would reach an equilibrium and the motor wouldn't rotate anymore
03:18 PM justanotheruser: err, the motor woludn't cause the load to rotate anymore
03:18 PM z64555: Then the motor would then effectively add/subtract tension to the belt
03:19 PM z64555: um, hold up, we got out of sequence
03:20 PM z64555: The forearm will rotate so long as there is tension provided by spring B
03:20 PM justanotheruser: yep
03:20 PM z64555: or by the forearm itself
03:20 PM justanotheruser: I think what I want is the timing belt to go over the axle, not under it
03:21 PM justanotheruser: that way if the motor loosens, the belt will retain tension from the load
03:21 PM justanotheruser: rather than the spring carrying the load
03:21 PM z64555: on the forearm?
03:21 PM justanotheruser: yes
03:22 PM z64555: hm, you won't have the teeth engaged on the pulley if you did that, though
03:23 PM z64555: Have you made a system of equations for this yet?
03:24 PM justanotheruser: no.
03:24 PM justanotheruser: let me send you a link
03:24 PM justanotheruser: this is how the teeth would be caught
03:25 PM justanotheruser: https://imgur.com/tALQHMb
03:29 PM justanotheruser: any advice for setting up a system of equations for this? Basically the inputs would be the angle of the load and the mass of the load. The functions derived using this system of equation would be the spring length, the motor torque and tension, the timing belt tension, etc
03:31 PM z64555: Probably try setting up individual equations first, then derive an equation that boils down to torque seen by the motor shaft
03:32 PM z64555: can alternatively translate the motor torque into linear force, to match up to what the springs and belt are seeing
03:32 PM justanotheruser: Will do
03:33 PM justanotheruser: probably should do something with the torque of the forearm load and how that effects the bicep motors torque
03:33 PM z64555: yes
03:33 PM justanotheruser: wouldn't want to break the motor
03:33 PM justanotheruser: :p
03:34 PM z64555: nah, you can always put a bigger pulley on the motor. I'm more worried about the belt
03:34 PM z64555: :D
03:35 PM justanotheruser: I'm setting up a binary that communicaties with the servos, I'll write this system of equations into it so it shuts down or does something to reduce the torque if for some reason my bad code above this level breeches it
03:35 PM justanotheruser: though I have no way of measuring the loads weight right now actually..
03:37 PM justanotheruser: that will need to be added as well.
03:40 PM z64555: put use a linear pot
03:40 PM z64555: *could use a linear pot on the springs
03:41 PM justanotheruser: hmm, but isn't most the tension on the motor, not the spring? :p
03:45 PM z64555: both springs
03:45 PM z64555: There may be slack between Spring A and the motor, but Spring B won't
03:53 PM justanotheruser: looking at both springs doesn't give me the load though?
03:53 PM justanotheruser: really all it would give me if the load wasn't moving is the angle of the forearm I think
04:11 PM z64555: yes it does
04:11 PM z64555: well, wait
04:12 PM z64555: hm, no, it doesn't
04:12 PM z64555: there's the joint at the root
04:12 PM z64555: So
04:13 PM z64555: you'll have to monitor the current that's going through the motor
04:14 PM z64555: Just place a shunt resistor between the motor and its power source, then grab the voltage across the resistor
04:23 PM justanotheruser: is there a word for a pulley that just allows the timing belts no-teeth side to glide along with it
04:23 PM justanotheruser: basically so the friction doesn't have to be across the axle
04:44 PM veverak: oh god
04:44 PM veverak: std <algorithm> is somewhere between awesome and awesome
04:44 PM veverak: love this with lambdas <3
04:48 PM z64555: justanotheruser: try guide pulley
04:48 PM * deshipu drops veverak into a lambda calculus
04:50 PM * veverak feels happy
04:50 PM veverak: somehow
04:51 PM veverak: I ended up writing custom C++ container for my stuff
04:56 PM veverak: but hey, it drops complexity of search of the data rapidly
05:18 PM justanotheruser: z64555: thanks
05:19 PM veverak: no my container is json serializable ;)
05:19 PM veverak: tomorrow, reread to code and do proper checks
06:12 PM justan0theruser: I think I'm going to make a smooth pulley using two washers and a bearing
06:19 PM z64555: won't work very long, the belt will wander off of it
06:20 PM justan0theruser: z64555: the washer diameter is greater than the bearing diameter
06:20 PM z64555: and if you use fender washers, which would be larger in diamter of the bearing, the belt will snag on the washers
06:20 PM justan0theruser: it will?
06:20 PM justan0theruser: just because of the small amount of friction?
06:20 PM z64555: yes, because the washers are static to the inside of the bearing
06:20 PM justan0theruser: true
06:20 PM z64555: not to the outside of the bearing
06:21 PM justan0theruser: I made the bearing 1/16th larger than the belt though
06:21 PM justan0theruser: so it won't be stuck between two washers, it'll probably bump into them though
06:21 PM justan0theruser: unless that's still problematic
06:21 PM z64555: If you can recess the outside of the bearing a tiny bit, it'll work
06:22 PM z64555: even without the cheeks
06:22 PM justan0theruser: good idea, I'll add 1/16th of an inch there too so the washers can can move as well
06:22 PM z64555: so that the belt will sit in a groove
06:22 PM justan0theruser: sit in a groove?
06:23 PM z64555: more of a concave curve, than an actual groove
06:23 PM z64555: thats how the old belt drums kept belts on them
06:24 PM justan0theruser: where is the curve?
06:24 PM justan0theruser: I thought you were saying give a little rolling room for the washer
06:25 PM z64555: no
06:25 PM justan0theruser: you said recess the outside, you mean recess the inside?
06:25 PM z64555: the curve is on the cylinder of the bearing
06:25 PM z64555: outside
06:25 PM justan0theruser: but won't that make it *more* prone to slippage?
06:26 PM z64555: if it's a hill, yes, but not if it's a valley
06:26 PM justan0theruser: right, so if you recess it wouldn't that make it a hill?
06:26 PM z64555: ---
06:26 PM z64555: _| |_
06:26 PM z64555: Ok, that's the side of the bearing
06:27 PM justan0theruser: this is the side of the bearing: o
06:27 PM z64555: -__-
06:27 PM z64555: _| |_
06:27 PM z64555: that's what you want it to look like
06:27 PM justan0theruser: ok, so recess the center
06:27 PM z64555: yes
06:27 PM justan0theruser: yes, that should work, thanks
06:28 PM z64555: remember, smooth curve!
06:28 PM justan0theruser: smooth!
06:28 PM z64555: if you can't make a smooth curve, a shallow V will work, too
06:28 PM justan0theruser: hmm, wonder how I can do this, maybe sanding
06:43 PM z64555: ideally, you'd chuck it into a lathe and do the sanding
06:44 PM anniepoo_: 8cD
06:51 PM Tom_L: i don't remember... can i dual boot windows 7? or was xp the last one to do that...
06:54 PM Tom_L: seems i can
09:38 PM anniepoo_: Tom, you can use grub or similar and boot as many as you like
09:39 PM anniepoo_: most of my machines dual boot some winders flavor and some eunuchs
09:45 PM nuclearnadal: I need simple help
09:46 PM nuclearnadal: about Synchronous AC motor, who would know about such motor here? anyone please advice
09:48 PM nuclearnadal: http://www.ebay.com/itm//351369385923
09:54 PM SpeedEvil: nuclearnadal: what about them
09:56 PM nuclearnadal: SpeedEvil: did you see the ebayy link? one guy made crank VAC 120v power supply out of that single motor and no circuit, i wonder how many amps that motor can give/ i tried calculating watt = amps * volts but its comiing 0.033 amps which doesnt make any sense because the guy in youtube video has connect a cellphone charger in that motor and crancked that VAC cellphone charger and charged his phone. Please advice, if you want to
09:56 PM nuclearnadal: https://www.youtube.com/watch?v=pIqmWJg1RJs 3min 47seconds in
09:59 PM nuclearnadal: http://www.ebay.com/itm/262338296691 i want to use 120v one not 240v motor
10:07 PM Tom_L: anniepoo_, i had bad luck with grub
10:58 PM rue_shop3: the motor on the sherline is screwing up the usb connection
10:58 PM rue_shop3: it dosn't matter if I put it on a HUGE power filter either
10:59 PM rue_shop3: if the motor is running, the usb breaks
10:59 PM rue_shop3: my next step is to try opto-isolating it
10:59 PM z64555: ?
10:59 PM z64555: can you hook a scope up to the UBS + and - ?
11:00 PM z64555: oh
11:00 PM z64555: Uh, is the motor drawing power from the USB?
11:00 PM rue_shop3: I'v disconnected the 5V of the usb and connected the grounds of the computer and the arduino
11:00 PM rue_shop3: no change
11:01 PM rue_shop3: its fine till the motor is running
11:01 PM rue_shop3: it must be stray EMI
11:01 PM rue_shop3: its not thru power
11:01 PM z64555: did you try an RF choke?
11:01 PM rue_shop3: I might change it up to just ole school rs232
11:01 PM rue_shop3: hmm
11:03 PM rue_shop3: 8-/
11:03 PM rue_shop3: maybe a good call actually
11:03 PM z64555: the RF choke?
11:03 PM rue_shop3: its just lived longer than ever
11:04 PM rue_shop3: I had a clip-on emi choke
11:04 PM rue_shop3: ok...
11:04 PM rue_shop3: hmm
11:05 PM rue_shop3: well, damnit, why didn't you suggest that 3 days ago?
11:06 PM z64555: I didn't know about this 3 days ago!
11:06 PM z64555: :P
11:07 PM rue_shop3: but apparently the ground between the computer and the machine HAS TO STAY
11:07 PM z64555: well, yeah.
11:08 PM z64555: USB signals are referenced to its ground
11:08 PM rue_shop3: differential tho
11:09 PM z64555: ? isn't it?
11:09 PM z64555: oh
11:09 PM rue_shop3: isn't it bidirection differential?
11:09 PM rue_shop3: with built in clocking like ethernet?
11:09 PM rue_shop3: kinda, a "lets combine all the evil things into one"
11:13 PM z64555: yeah, it's a differential
11:13 PM z64555: perhaps the EMI from the motor is screwing up the power lines?
11:13 PM z64555: Or otherwise needs a path to dump energy
11:29 PM rue_shop3: well I regrounded the whole thing, and redid all the connections, and added power leds
11:29 PM rue_shop3: I'm adding a terminal on the back "Microcomputer earth"
11:29 PM rue_shop3: I think thats as olde as I can make it sound
11:33 PM rue_shop3: if it screws up again tho, I'm gonna opto-isolate it
11:48 PM rue_shop3: it ran for a long time without any troubles
11:48 PM rue_shop3: I wonder what got worse
11:48 PM rue_shop3: I wonder if this is a sign the brushes might be unhappy
11:50 PM z64555: graphite brushes, or wire brushes?
11:51 PM rue_shop3: graphite
11:51 PM rue_shop3: its a sherline
11:51 PM rue_shop3: and I alone have prolly put about 200 hours on it
11:51 PM z64555: hmm
11:52 PM z64555: might be uneven wear, or some sort of defect
11:52 PM rue_shop3: if the brushes are at their end, they might be generating more emi
11:52 PM z64555: yup
11:53 PM rue_shop3: there are no signs of distress from the motor yet tho
11:53 PM rue_shop3: sometimes its not immediatly apparent
11:53 PM z64555: when's the last time you took the motor apart?
11:58 PM rue_shop3: this is one of the old ones, its pressed togethor
11:58 PM rue_shop3: so never
11:58 PM rue_shop3: its not my machine
11:58 PM rue_shop3: its armyofevilrobots'
11:59 PM rue_shop3: http://ruemohr.org/~ircjunk/images/p1080531.jpg