#robotics Logs

May 10 2014

01:14 RifRaf heaps
04:59 GuShH_ rue_more: I found one similar to this mixed in with the clamps http://www.ebay.com/itm/Vintage-Hand-Vise-Gunsmith-Jewelers-Blacksmith-Nice-/301174599057
05:00 GuShH_ not sure if I'll have a use for it, maybe sharpening small parts?
05:02 GuShH_ needs a bit of dressing and cleanup
05:03 GuShH_ maybe a new wing nut
05:07 GuShH_ https://www.youtube.com/watch?v=bcndMLZV7hs
05:32 GuShH rue_more: trying out the rust removal process with the cast iron parts, should work just as well, it's mostly gunk I need it to clean
10:04 GuShH rue_more: hmm found a marking on the hand vise... WG inside a crown
10:08 GuShH seems this guy had the same issue http://www.ukworkshop.co.uk/forums/crown-and-w-g-mortice-chisels-a-few-questions-t13215.html
16:56 f00bar80 Asking if a servo is set to 6 kg.cm (4.8v), 7.5 kg.cm (6v), Stall torque, can i use a power source of 9V 1A for it?
17:06 f00bar80 any comment/.
17:27 ace4016 probably not
17:28 ace4016 though i don't know the intimiate detail of R/C servos. you usually don't want to go too far from the ratings
18:22 Hyratel1 f00bar80, bad idea
18:22 Hyratel1 I don't know what they use for a processing chip, but it might burn out on a voltage in excess of the max rating
23:31 julby0 are encoders a separate thing from a servo motor or is it combined? i don't know how else to ask, sorry
23:31 LoRez servos are made up of encoders and motors
23:32 julby0 why do cnc machines use steppers?
23:32 julby0 at least my 3d printer does
23:32 julby0 also if a motor has a third wire, does that mean it's a servo
23:35 LoRez it can mean it's a servo.
23:35 LoRez 3d printers run steppers in open loop because it's cheaper
23:35 julby0 what does "open loop" mean
23:36 LoRez no feedback
23:36 rue_shop2 it means the controller has no way to know what happening with that its controling
23:36 rue_shop2 it means the controller has no way to know what happening with what its controling
23:36 julby0 servos cost more than equivalent steppers?
23:36 rue_shop2 hell no
23:36 rue_shop2 servos are cheap as dirt
23:36 rue_shop2 hobby servos
23:37 rue_shop2 proper servos will cost more than steppers
23:37 LoRez hobby servos don't do what steppers do though
23:37 julby0 because they don't do more than 180 degrees or something?
23:38 LoRez and don't move repeatable amounts for some given input
23:38 LoRez they're twitchy
23:38 julby0 "twitchy"?
23:38 julby0 are you saying they're less exact
23:38 LoRez don't hold position
23:38 julby0 oh, i forgot about the holding position thing
23:39 LoRez and if you set them to free-spin, you don't really have any idea what position they're in
23:39 julby0 what does "set them to free spin" mean
23:39 LoRez allow them 360deg rotation
23:40 julby0 how do you change that
23:40 LoRez "proper" cnc servos are usually three phase motors with encoders on them
23:41 LoRez remove the pot in them and hard-wire the inputs with a voltage divider.
23:42 julby0 if servos don't hold position, are they worthless for robotics?
23:42 julby0 more specifically
23:42 julby0 i'm doing a robotic arm
23:42 julby0 and it sounds like it can't say upright
23:43 LoRez how big an arm?
23:43 julby0 i don't know that yet
23:43 LoRez 1m tall, 2?
23:43 julby0 desktop size
23:44 LoRez hobby servos should suffice within their limitations
23:44 julby0 why won't the arm just collapse whenever it's not in motion?
23:45 LoRez because of the gearing in the servos. if you shut the signal off to them, they won't move, the problem is when you give them a position signal, they twitch around that position because of tolerances
23:46 LoRez well, they won't move much. you can twist them and force them to go if you want to