#robotics Logs

May 20 2015

02:34 deshipu http://www.industrytap.com/robot-master-chef-cooks-2000-recipes-cleans-dishes/28765
02:34 deshipu robot chef
02:35 LiohAu deshipu: thx for the article
02:36 LiohAu the details about the number of motors sounds correct, but why are there so much microcontrollers ?
02:53 deshipu probably to have enough pins to connect all the sensors ;)
04:34 LiohAu deshipu: inside a servo, there's a dc motor right? so is there also a motor driver inside?
04:35 LiohAu (I mean the H bridge)
04:39 Jak_o_Shadows yup
04:42 deshipu LiohAu: yes
04:42 deshipu LiohAu: and a PID controller
04:42 LiohAu ok, so i'm planning to make a robotic hand with like 20 cables
04:42 LiohAu I'm trying to choose between 20 dc motors + encoders, or 20 servomotors
04:43 deshipu LiohAu: hobby servos, or robotics servos?
04:43 LiohAu basically it's the same thing, but in one case, i'll have to make the 20 H bridge by myself
04:43 Jak_o_Shadows to be honest, my main factor there would be how much force they need to provide.
04:43 Jak_o_Shadows and how much it needs to move.
04:43 LiohAu maximum move is 5cm
04:43 deshipu have you seen MeArm?
04:44 LiohAu but if i'm using a larger horn winch, the cable move more with less rotation right?
04:44 deshipu if you make your own encoders, your microcontroller will be able to know the positions too
04:44 Jak_o_Shadows How much force do you need to activate the fingers?
04:44 Jak_o_Shadows actuate*
04:45 LiohAu as much as possible :P
04:45 Jak_o_Shadows ok, so that is an answer that absolutely doesn't help you make any decisions
04:46 LiohAu less than 1n.m
04:46 LiohAu Nm*
04:47 Jak_o_Shadows That is not a heck of a lot
04:47 deshipu that's 10 kg*cm
04:47 LiohAu yes
04:47 deshipu you have servos with 10kg*cm?
04:48 deshipu the little blue servos are 1.5kg*cm
04:48 deshipu the bigger ones are usually up to 3-4kg*cm
04:48 LiohAu deshipu: look here : http://bit.ly/1FuQQkP
04:48 LiohAu this is a servodatabase link
04:49 Jak_o_Shadows As a side note, finding the force would tell you how big a wheel/pulley you need, which tells you how much rotation you need, which tells you servos or motors
04:49 LiohAu there are a lot of servos having a torque greater than 10kg.cm
04:49 deshipu you forgot to check the price :)
04:50 LiohAu I need around 20 servos, I can afford 40$ max
04:50 LiohAu there are 7 models for this price/torque
04:51 LiohAu and I restricted to digital servos, using coreless/brushless motors only, and I also removed the plastic gears
04:51 LiohAu (40$ max by servo)
04:53 LiohAu deshipu: the best servo I found has a 380kg/cm torque, and it cost around 300$ ^^
04:53 LiohAu 250$ actually
04:55 LiohAu Jak_o_Shadows: whats does that mean : "That is not a heck of a lot" ? 1Nm is too much? or not enough?
04:56 Jak_o_Shadows It means that it's not a whole lot in engineering terms.
04:56 Jak_o_Shadows Where'd you pull that number from?
04:58 LiohAu Jak_o_Shadows: "BIOMECHANICS AND CONTROL OF TORQUE PRODUCTION DURING PREHENSION" by Robert W. Gregory
04:59 Jak_o_Shadows ok, fair enough.
04:59 Jak_o_Shadows carry on, you've doen the research, good.
04:59 LiohAu torque of fingers is never greater than 1.5 Nm
04:59 LiohAu I said 1Nm, because he used a 2Kg payload for its test, and I only want to lift objects around 500g
04:59 LiohAu so I have a fair margin
04:59 Jak_o_Shadows Fair enough, very good.
05:01 LiohAu If I exclude the cheap servos (deshipu: I mean the little blue ones :D), and I don't go on overpriced dynamixel, I can find intermediate servos from SpringRC, XQPower, Power HD or Hyperion, that have good specs in the 30-40$ price range.
05:02 deshipu LiohAu: sounds good
05:02 deshipu LiohAu: I think you would even be good with the $10 ones
05:02 deshipu with enough care
05:04 LiohAu this one : http://www.servodatabase.com/servo/towerpro/mg946r ?
05:04 deshipu yeah
05:05 deshipu http://www.aliexpress.com/item/10PCS-lot-MG946R-Torque-Digital-Metal-Gear-Servo-RC-Helicopter-Boat-FOR-Futaba-Hitec-Sanwa-GWS/32267576647.html
05:06 LiohAu didn't think to look for hobby servos on ali
05:06 deshipu it's my main source
05:06 deshipu they are crappy, but cheap
05:08 LiohAu ali? or this seller?
05:16 deshipu ali in general
05:16 deshipu at least the cheap ones
05:16 deshipu I'm sure there are ones slightly above the minimal price that are of better quality
09:30 rue_house !?!??!!
09:30 rue_house transInitFile(&tb, 8, "test.tf");
09:30 rue_house Status_t transInitFile(transBuffer_t *this, unsigned int count, char * filename) {
09:30 rue_house if ((retval = transformSetLoadFrom(this->tf, filename)) != OK)
09:30 rue_house Status_t transformSetLoadFrom(transformSet_t * this, char * filename) {
09:30 rue_house printf("open %s\n", filename);
09:31 rue_house Segmentation fault
09:31 rue_house !?!?!??!??!
11:07 Triffid_Hunter rue_house: filename is a dud pointer perhaps?
13:06 mrdata probably
13:07 mrdata except, it should be "test.tf"
13:08 mrdata is there any way to single-step and check
19:11 promet I have a lipo battery that is no longer being detected by its charger, is it possible that its voltage has dropped too low?
19:14 veverak try voltmeter
19:14 veverak promet: anyway, charger should warn that it's low voltage
19:14 veverak so it should detect it
19:17 promet veverak, I did, it's a 7.4v nominal, and reads 0.7v
19:17 veverak wrong cables propably than
19:17 veverak ouch
19:17 veverak or bad battery
19:17 promet veverak, indeed
19:17 veverak but shoudln't it drop just below the minimaln value ?
19:17 veverak like 5-6V ?
19:17 verak du
19:18 promet veverak, I suppose it was left connected to a circuit that kept bleeding it though it was off
19:18 veverak I see
19:18 veverak possible
19:19 promet I'd like to try some, non-extremely-dangerous way of putting a little charge back into it, so that the proper charge will recognize it again.
19:19 promet I think it's below the charger's "detection threshold"
19:25 zhanx anyone do freelance work? Designing an opensource home automation system and would love to have someone that is better than i design the screens?
19:46 promet Is it verboten to discharge a lipo battery via its balance charge leads?
19:47 SpeedEvil Balance leads are just wires.
19:47 SpeedEvil However, they're thin wires.
19:47 SpeedEvil Don't draw more than an amp or so, and there isn't an issue
19:52 promet SpeedEvil, thanks very much
20:09 Polthergeist_ Hi all!
20:10 Polthergeist_ I was wondering, does someone know/use a robot from the company called Kinova?
20:10 Polthergeist_ They got 2 robots, the JACO and the MICO.
20:16 Polthergeist_ Does anyone had to use a JACO or a MICO?
21:06 rue_house never heard of them
21:13 Polthergeist_ ok thanks
21:15 Polthergeist_ Anyone else ever tried one of them or both?
23:12 rue_house not i