#robotics Logs

Jun 14 2018

12:08 AM Tom_L: https://tinyurl.com/y9myuy7d
12:12 AM Tom_L: may be a winner
12:22 AM DIRT: I was planning on using a weed eater motor. $70 and they can make about 20 pounds of thrust or more depending on what you do to them.
12:23 AM DIRT: would doing a decent job decoupling the motor keep the sensors happy?
12:40 AM rue_mohr: yes
12:40 AM rue_mohr: I use one for the spindle of my cnc
12:40 AM rue_mohr: direct drive
12:55 AM DIRT: i imagine ryobi and homelite engines shake a lot. they are walmart weedeater engines
12:59 AM rue_mohr: DIRT,
01:01 AM rue_mohr: http://ruemohr.org/~ircjunk/projects/cnc/dscn7641.jpg
01:04 AM DIRT: slides
01:05 AM zhanx: rue_mohr: i remember that and i was like : you are crazy
01:06 AM rue_mohr: it works
01:06 AM zhanx: so does viagra but dont use it
01:07 AM zhanx: in California that cnc would need 1000 labels of death
01:07 AM rue_mohr: what I want to know right now is what filter to use for the pwm current regulator sense amp
01:09 AM Triffid_Hunter: rue_mohr: none.. just sample when PWM is on :P
01:09 AM rue_mohr: no I want average current
01:09 AM rue_mohr: the mtoors filter it a bit
01:09 AM rue_mohr: I think I want average
01:10 AM Triffid_Hunter: well the motors have inductance, so if you PWM fast enough they'll recirculate the current during the off/brake period when you can't measure it
01:11 AM DIRT: i want a metal 3d printer.
01:11 AM rue_mohr: yes, I also dont want to have to time adc readings carefully
01:11 AM DIRT: in califonria they have to warn people that living may cause injury or death
01:12 AM rue_mohr: and breathing
01:13 AM zhanx: California only state in the nation with Dictatorship levels of income fuck ups
01:15 AM DIRT: atleast parts of the state are serious about secceeding form cali
01:19 AM rue_mohr: ok, so
01:20 AM rue_mohr: I need to choose a pwm freq
01:21 AM rue_mohr: I'm thinking ~40Khz
01:22 AM rue_mohr: hmm
01:22 AM rue_mohr: if it wasn't for wanting a bipolar currrent source, I could easily hand this off to an analog circuit
01:24 AM rue_mohr: then again, I have dac issues
01:24 AM rue_mohr: hmm
01:32 AM rue_mohr: ok wait
01:32 AM rue_mohr: reality check
01:32 AM rue_mohr: how many bits do I need
01:32 AM rue_mohr: of current control
01:36 AM rue_mohr: seems to me, that 6 bits is probably fine
01:55 AM rue_mohr: oh and wait, I dont care what polarity the current is, just the amplitude
02:50 AM rue_mohr: I'v been trying to make digital hybrid systems, maybe I should attack the current detector differently
03:04 AM Jak_o_Shadows: rue, your robot arms, any of them not got much metal?
03:10 AM * Jak_o_Shadows should chck the letterbox
09:16 AM rue_mohr: most of them dont have much metal
09:17 AM rue_mohr: see arms 7 thru 9
10:49 AM veverak: https://youtu.be/Tp6ZCRdLzLk everybody likes leds
05:46 PM veverak: where there is no printf
05:46 PM veverak: there is itoa
06:17 PM DIRT: arm cpu or arms?
06:22 PM veverak: arm cpu
06:22 PM veverak: stm3
06:22 PM veverak: stm32
11:07 PM rue_shop4: Tom_L, did z show you his 3d printer progress?
11:09 PM Tom_L: i saw a pic of a glob
11:09 PM Tom_L: that was it
11:09 PM Tom_L: wish i could find a spindle motor
11:09 PM Tom_L: been to both ends of the spectrum looking
11:10 PM rue_shop4: what power/rpm mix?
11:11 PM Tom_L: 750-1kw 3k - 5k rpm
11:11 PM Tom_L: https://www.ebay.com/itm/Brushless-DC-BLDC-Motor-Speed-Control-1100W-6000rpm-CNC-Sieg-X2-X3-BF20-G0704/153059732033?_trkparms=aid%3D111001%26algo%3DREC.SEED%26ao%3D1%26asc%3D20160727114228%26meid%3D45fda1351bfa4e74aaa3f318360fa75e%26pid%3D100290%26rk%3D1%26rkt%3D4%26sd%3D153059732033%26itm%3D153059732033&_trksid=p2060778.c100290.m3507
11:12 PM rue_shop4: up to the ? should be fine
11:12 PM Tom_L: somebody said that one was no good but i question his integrity
11:13 PM Tom_itx: http://www.dmm-tech.com/Dyn4_main.html
11:13 PM Tom_L: they've got a full blown servo setup but it's +10 -10v control and i'd rather have 0 - 10v
11:14 PM Tom_L: it would be way overkill
11:14 PM rue_shop4: hmm, I need a fet driver
11:15 PM Tom_itx: https://store.dmm-tech.com/products/dht-0-75kw-ac-servo-motor
11:15 PM Tom_itx: https://store.dmm-tech.com/products/dyn4-h01a2-00-dyn4-ac-servo-drive
11:15 PM Tom_L: and cables
11:15 PM Tom_L: but i'd have to interface it modbus or get a +-10v supply
11:15 PM Tom_L: and it's costly
11:16 PM rue_shop4: your 0-10V is really limiting
11:16 PM Tom_L: not as bad as that stupid sherline thing
11:16 PM rue_shop4: everything I'v seen uses 4-20mA
11:16 PM Tom_L: i can get a +-10v card
11:16 PM Tom_L: that's the standard
11:16 PM Tom_L: if you're doing analog
11:16 PM Tom_L: lcnc will do modbus too
11:16 PM Tom_L: i'd have to figure it out
11:17 PM rue_shop4: I mean, op-amp wise, converting 0-10 to -10-10 is easy
11:17 PM Tom_L: but it would cut like a sword thru butter
11:17 PM Tom_L: not for me
11:17 PM Tom_L: there are large gaps in my ability sometimes
11:18 PM rue_shop4: I think the + side of the amp @ 5V and matched resistors, say 10k
11:18 PM Tom_L: https://www.alibaba.com/product-detail/High-Torque-1100W-6000RPM-Spindle-BLDC_1723183578.html?spm=a2700.details.maylikever.5.6bcb5e2db6P1xG
11:18 PM Tom_L: same as the ebay one
11:19 PM Tom_L: i'd still have to come up with a -10v supply wouldn't i?
11:20 PM Tom_L: someone suggested i just put a copper tube around the sherline motor, water cool it and run it to death
11:20 PM rue_shop4: more, +-15
11:21 PM rue_shop4: remember that I looked at brushless for my last and it turns out its cheaper to just kill brushed one forever
11:21 PM Tom_L: it had thermal shutdown but it may be disabled now
11:21 PM Tom_L: i know it's cheaper
11:22 PM Tom_L: but bldc gives you torque at low speeds
11:22 PM Tom_L: aka rigid tapping
11:22 PM Tom_L: etd
11:22 PM Tom_L: etc
11:22 PM rue_shop4: I use regulated, so I still have the torque all the way
11:22 PM rue_shop4: remember my optic feedback, t13 regulated pwm?
11:22 PM Tom_L: no
11:23 PM Tom_L: the current motor has feedback but it takes a while for the PID to wake up
11:23 PM Tom_L: on a heavy load
11:23 PM Tom_L: it does great for somewhat steady cuts
11:46 PM cr1t1cal: I am controlling a miniature satellite object in a space simulation
11:47 PM orlock: KSP?
11:47 PM cr1t1cal: I am trying to get it to move from one location to the other, with the robots current position and destination position being represented by vectors
11:47 PM cr1t1cal: orlock: haha no
11:48 PM cr1t1cal: the robots atitude (direction it is facing) is represented by a unit vector.
11:50 PM cr1t1cal: how do I calculate the x, y and z forces I need to apply to the robot to move it to the destination vector while accounting for physical phenomena such as momentum/inertia
11:53 PM rue_shop4: you make sure the robot is strong and ridgid enough, then wrap it in a servo loop
11:54 PM cr1t1cal: rue_shop4: this is a simulation. the robots physical composition does not matter
11:54 PM cr1t1cal: rue_shop4: i just need to move it from one palce to the other as efficiently as possible
11:54 PM orlock: "assuming a spherical chicken"...
11:54 PM rue_shop4: orlock, dont be insane, the cow is sphereical