#robotics Logs

Feb 27 2018

12:10 AM mrdata_ is now known as mrdata
12:44 AM rue_: tommorow I can maybe finish wiring up the new printer
12:44 AM rue_: start fixing the things I broke building it,
12:45 AM rue_: rebuilding the things I'm not thrilled with
12:45 AM rue_: aligning it
12:45 AM rue_: and maybe print something
12:48 AM rue_: I think I'm working out how to build a good keyboard
10:18 AM diego_2: hello, could someone explain me (or direct me to some information) how hall sensor angle is to be chosen on a brushless inner rotor motor? Is it dependent on the number of rotor poles?
01:29 PM Arlenx: hi, i'm looking for an external chip that can generate a pwm at around 40khz. is there any (prefer max 8 legs )?
02:42 PM SpeedEvil: 555?
02:43 PM Tom_L: attiny4 5 9 or 10 would do it sot23-6 pni
02:43 PM Tom_L: pin
02:49 PM mumptai: strange time we live in, indeed
06:27 PM Toneloc: so, I'm thinking of ways to homebrew a linear actuator on the cheap that has to support a mass of 50g- anyone got any suggestions?
06:27 PM Toneloc: I don't want to do leadscrew because of wear and noise
06:27 PM Tom_L: syringe
06:27 PM Toneloc: length is approx 5 feet
06:28 PM Tom_L: well now you're just being picky
06:28 PM Toneloc: Tom_L- sytinge is a nice way to do it for sure
06:28 PM Toneloc: but I don't thik it can work at 5 feet
06:28 PM orlock: and not threaded rod?
06:29 PM Toneloc: orlock- wouldn't it wear out relaly quickly?
06:29 PM Toneloc: *really
06:29 PM orlock: no
06:30 PM Toneloc: thought about reciprocating mechanism, but I'm thinking the wheel size and con road would get very big
06:30 PM Toneloc: *rod
06:30 PM orlock: you could also use a wheel and threaded rod...
06:31 PM Toneloc: wear is the issue, and want to stick with something as little maintenance as possible
06:31 PM orlock: or even a rubber wheel and smooth(ish) rod
06:31 PM Toneloc: and locally obtainable parts where possible
06:31 PM orlock: https://www.thomsonlinear.com/website/com/eng/index.php
06:31 PM Toneloc: orlock- hmm, thats an interesting idea
06:32 PM orlock: but seriously - threaded rod and nuts is how all the cheap 3d printers do it
06:32 PM orlock: or
06:32 PM orlock: smooth rod and a belt
06:32 PM Toneloc: orlock- how about a rod/bar clamped very tightly between two rubber/ plastic wheels
06:32 PM orlock: do you want speed or torque
06:32 PM orlock: figure out your requirements
06:32 PM Toneloc: with one been driven by a motor, and the other an idler
06:33 PM Toneloc: orlock- smooth rod and a belt??
06:36 PM Toneloc: orlock, speed is more important than torque
06:37 PM orlock: Toneloc: Google "prusa i3" and take a look at the way it raises and lowers the print head (threaded rod + nut), and the X/Y platforms (pair of smooth rods + bearings, with belts+motors to provide motion)
07:56 PM rue_: Toneloc, I have a cnc machine with a leadscrew thats been running for 25 years, its not worn out and dosn't make noise
07:57 PM Tom_L: that's one long lead screw
07:57 PM rue_: Toneloc, how much speed do you need
07:58 PM rue_: 5 feet in how many hours?
07:59 PM Toneloc: Toneloc- wow, it must be high quality, not just store bought nut and bolt??
07:59 PM Tom_L: i need a material endstop for the vise
08:00 PM rue_: its just a regular threaded rod
08:00 PM rue_: 24 years
08:00 PM rue_: how fast do you need it to move
08:00 PM rue_: ^^^
08:00 PM Toneloc: 5 feet in 10 seconds
08:00 PM rue_: ok
08:01 PM rue_: that works out to 1 foot/second
08:01 PM rue_: cause when you see it take 10 seconds you wish it was more like 5
08:01 PM rue_: next question, how much force does it need to apply to what its operating?
08:02 PM rue_: stay with me, I'm falling sleep and if you dont answer in time I might doze off
08:03 PM Toneloc: it needs to be able to carry a mass of 50 grams
08:03 PM Toneloc: sorrr rue_
08:03 PM rue_: so 250g load at 1 foot/sec
08:03 PM rue_: you MUST BE CANADIAN
08:04 PM rue_: ok, threaded rod is not reasonable
08:04 PM Toneloc: 50g mass
08:04 PM rue_: thats what I said 250g
08:04 PM rue_: at 1 foot/sec
08:04 PM rue_: over 5 feet
08:04 PM Toneloc: ok
08:04 PM rue_: electric drive right?
08:05 PM Toneloc: yes
08:05 PM rue_: does the control of the speed in the middle matter?
08:05 PM Toneloc: speed is not the most critical, a somewhat accurate position is better
08:05 PM rue_: like, does it have to be steady, or just pull hard still turned off?
08:05 PM Toneloc: but I can get awath limit switches
08:06 PM rue_: ok, ever heard of a linear induction motor?
08:06 PM Toneloc: *away with
08:06 PM Toneloc: just has to be steady
08:06 PM rue_: ok, ever heard of a linear induction motor?
08:06 PM Toneloc: turned off doesn't matter
08:06 PM rue_: ok, ever heard of a linear induction motor?
08:07 PM Toneloc: like in a railgun?
08:07 PM rue_: yes, bit usually inside out
08:07 PM rue_: and a motor
08:07 PM rue_: not an impulse thing
08:08 PM rue_: iirc they are easy to make for being AC driven
08:08 PM Toneloc: expensive?
08:08 PM Toneloc: or a diy item?
08:08 PM rue_: as usual, the wikipedia page sucks
08:09 PM rue_: http://www.e-driveonline.com/main/markets/motion-control/new-polynoid-linear-actuator-line/
08:10 PM rue_: they use them in power transfer gear
08:10 PM rue_: AHH!
08:10 PM rue_: you might be able to ask an electrical company for an old power transfer box, it'll have the motor coil in it, the rest is just a copper pipe
08:13 PM Toneloc: hmm, like a fail-over switch?
08:13 PM rue_: yup
08:13 PM rue_: they fail sometimes and get replaced
08:13 PM Tom_L: rue_ you got your printer done?
08:13 PM rue_: you just need the fancy coil from the "motor" that operates the switch
08:13 PM Tom_L: you're wasting time here if you don't
08:14 PM rue_: not yet Tom_L
08:14 PM rue_: I know
08:14 PM rue_: I'm waking up, or going to sleep, I'm not sure
08:14 PM rue_: I think I got a reply from the post facility
08:14 PM Tom_L: got my softjaws hole pattern programmed
08:14 PM rue_: they sent it registered (??)
08:14 PM rue_: ok
08:14 PM Toneloc: rue_ I used to work in a tv station and we had loads of those
08:14 PM Tom_L: they mean business...
08:15 PM rue_: Toneloc, if your in a large area, an electrical company can probably find you an old one
08:15 PM rue_: you just need a new copper pipe 5' long
08:15 PM Toneloc: would have to be an industial electrical place
08:16 PM rue_: it actaully looks like their really easy to make too
08:16 PM rue_: just 2 coils and a capacitor
08:16 PM Toneloc: I wonder are there any on ebay...
08:17 PM Toneloc: I guess maybe it is driving them that is the issue, with phases and such?
08:17 PM rue_: no
08:18 PM rue_: insert AC on one coil have a cap in series with the other coil
08:18 PM rue_: capacitor generates phase lag
08:19 PM Tom_L: how do you discharge them for the next shot?
08:19 PM rue_: no its AC
08:19 PM rue_: you jsut power them
08:19 PM Tom_L: ok
08:19 PM rue_: works like an induction mtoro thats been laid out
08:31 PM Toneloc: could I also fulfillthe requirement with a belts and a linear guide?
08:32 PM Toneloc: *fulfill the
08:36 PM orlock: Whats it for, anyway?
08:37 PM Toneloc: a dvd autoloader
08:37 PM orlock: how archaic
08:37 PM Toneloc: for a duplicator machine
08:37 PM orlock: even more archaic
08:37 PM orlock: goddamnn, optical media.
08:37 PM Toneloc: orlock- a deprecated product for a deprecated people..
09:00 PM rue_: do what cha like
11:45 PM mrdata_ is now known as mrdata