#robotics Logs
Apr 24 2013
#robotics Calendar
00:56 Jak_o_Android Rif, did you ever manage to get that robotics arm working well?
00:59 Ademan_ is it possible/probable that my hobby servo with supply voltage of 4.5v is heedless of my 3v PWM signal?
01:00 GargantuaSauce i feed mine 3.3v with >6V supply so probably not
01:09 Ademan_ hrm
01:10 GargantuaSauce oh and 3v has worked also
01:10 GargantuaSauce mg996r and mg995
01:10 Ademan_ yeah it was my fault
01:10 Ademan_ I still cant electronics :-/
01:10 Ademan_ I had a capacitor in series with the + of the servo
01:10 Ademan_ apparently that's a no-no
01:10 Ademan_ now to understand why...
01:14 GargantuaSauce the cop-out response that anyone will give is that caps pass ac and block dc
01:15 Jak_o_Shadows I need to buy them, two weeks ago
01:16 Jak_o_Shadows hobbyking a good place for that?
01:16 Jak_o_Shadows GargantuaSauce: But don't you control servo's with pwm, hence not DC, hence you're probably just screwing the voltage levels around?
01:17 GargantuaSauce i am going to use the fact that it's 3 am as an excuse not to answer that
01:17 Ademan_ lol
01:17 GargantuaSauce because i cannot brain how to fix your understanding<
01:18 Jak_o_Shadows But anyway, is hobbyking a good place to get those servos?
01:18 Ademan_ Jak_o_Shadows: MG996r?
01:18 GargantuaSauce if you're in the us and need em quick, i guess
01:18 GargantuaSauce you will get them a lot cheaper if you shop around
01:18 Ademan_ you can get them way cheaper on aliexpress if you look around
01:18 Ademan_ yeah
01:18 Jak_o_Shadows What about australia?
01:19 Ademan_ sorry mate, you're boned
01:19 Ademan_ :-p
01:19 Jak_o_Shadows yeah, especially for time
01:19 Jak_o_Shadows about $7-8 from ebay
01:20 GargantuaSauce i got a pack of 10 on aliexpress for less than 5 each<
01:20 Ademan_ yeah, I was ~90 for 18
01:21 GargantuaSauce oh so you're making a hexapod too :)
01:23 Ademan_ biped actually, I just over ordered because I figured I'd kill more than a few in the process :-p
01:23 GargantuaSauce ah yeah, was going to suggest that
01:23 GargantuaSauce one typo and you can have stripped gears
01:24 GargantuaSauce http://www.youtube.com/watch?v=1HPVbuaONO4 here's what i threw together for servo control
01:25 GargantuaSauce just a bunch of 74hc595 shift registers fed by the microcontroller's spi
01:25 Jak_o_Shadows Hmm, I need 2 servos...
01:26 GargantuaSauce just go to a local hobby store if you only need a couple and fast
01:26 Jak_o_Shadows also, I like your desk.
01:26 Jak_o_Shadows Well, it's not exactly fast.
01:26 GargantuaSauce it's a kitchen table actually
01:26 Jak_o_Shadows but local hobby stores will charge be 10x the price for one with half the capacity
01:26 GargantuaSauce yes
01:27 GargantuaSauce again, my suggestion is mg996r from aliexpress
01:27 Ademan_ GargantuaSauce: hahahahaahahah
01:27 GargantuaSauce best bang for buck i think
01:27 Ademan_ also, STM32 ?
01:27 GargantuaSauce yeah, f4
01:27 Ademan_ I've been looking at getting the F3 for the gyro, accelerometer, and magnetometer
01:28 GargantuaSauce i dont think theres a mag onboard
01:28 GargantuaSauce might be wrong<
01:28 Ademan_ hrm, either way I primarily want the gyro and accelerometer lol
01:28 GargantuaSauce i use http://www.ebay.com/itm/300821362854 for an IMU
01:29 Ademan_ and when you get your hexapod working, you need to make it crab walk to some immortal
01:29 GargantuaSauce no i am saving immortal for when i make some videos in the winter of my quadcopter flying over a desolate landscape
01:30 Jak_o_Shadows What about say, http://www.aliexpress.com/item/Register-free-shipping-5pcs-lotMetal-Gear-Digital-12kg-MG945-Servo-High-Torque-Rc-Car-MG996R-MG946R/768767879.html ?
01:30 Ademan_ hahahaha
01:30 Jak_o_Shadows I don't actually need that many of them.
01:31 GargantuaSauce that'd be fine Jak_o_Shadows, don't expect the specs to be uninflated though of course
01:31 Jak_o_Shadows course.
01:31 Ademan_ I'd heard people advising against MG995 in favor of 996r so I would assume the 945 would be a no-go, since the number is lower :-p
01:32 GargantuaSauce well 996r>995 because it actually has digital controls
01:32 GargantuaSauce i think the 945 might be digital too i cant remember
01:32 GargantuaSauce check the towerpro site
01:33 Ademan_ GargantuaSauce: that IMF looks pretty nice, and is reasonably priced, but an F3 board is still less hehe
01:33 Ademan_ I wonder how the sensors compare
01:33 GargantuaSauce the st one is probably better
01:34 Ademan_ IMU*
01:34 GargantuaSauce yeah the disco boards rule, and i'm sure they're sold below cost
01:34 Ademan_ yeah
01:35 Ademan_ I have no idea how sparkfun's IMUs are so expensive...
01:35 GargantuaSauce sparkfun is a big scam for people who don't know to google
01:36 GargantuaSauce same with adafruit and their other ilk
01:36 Jak_o_Shadows screw it, can't figure it out, i'll just make sure it's 996r
01:36 GargantuaSauce they just plain get away with shit prices because they got to ride the waves of the maker revolution or whatever
01:37 GargantuaSauce and revel in a constant bombardment of hype from hackaday and so on
01:37 Jak_o_Shadows GargantuaSauce: Local resellers of them are my backup plan
01:42 Ademan_ hrm my cheapie 9g servo chatters a lot
01:43 GargantuaSauce yeah those little ones are very unstable
01:45 Ademan_ now to figure out why I'm only getting 90 degrees of travel when they physically can move >180 degrees
01:45 Ademan_ pulse is 1-2ms right?
01:45 GargantuaSauce yes
01:45 GargantuaSauce actual response varies
01:46 GargantuaSauce some will happily take 0.5-2.5 and go 180 degrees
01:46 GargantuaSauce some will destroy themselves if you try
01:46 Jak_o_Shadows What's the best way to buy from aliexpress?
01:47 GargantuaSauce payment method?
01:47 Jak_o_Shadows yeah
01:47 GargantuaSauce i use a cc
01:47 Jak_o_Shadows also, screw their captcha
01:47 Jak_o_Shadows righto, a debit card will work then.
01:48 GargantuaSauce would be nice if they took paypal but makes sense that they don't
01:48 GargantuaSauce seeing as they're an escrow service and all
01:49 GargantuaSauce so Ademan_ map an easily-adjustible input like a potentiometer+ADC to 0.5-2.5ms, start in the middle and ease into it
01:50 GargantuaSauce a numerical output to an lcd or whatever would be of use so you can note it when you hit the endstops
01:52 Jak_o_Shadows bought.
01:52 Ademan_ that's a good idea
01:52 Jak_o_Shadows Just gotta wait till they get here.
01:53 Jak_o_Shadows Will probably need to buy some from a local shop for the mean time, but meh
01:54 Jak_o_Shadows also servos are just a single pwm signal yeah?
01:55 GargantuaSauce yes
01:55 Jak_o_Shadows cool, that's easy enough
01:57 GargantuaSauce yeah it only gets to be a pain when you're using more servos than your mcu has hardware timers
01:59 Ademan_ meh, I only have one timer :-p
01:59 Jak_o_Shadows I hope I have 3
01:59 Ademan_ I actually haven't tested my multi-servo code yet though...
02:04 GargantuaSauce sleepytime for me
02:04 Jak_o_Shadows have fun.
02:04 GargantuaSauce i expect progress reports!
02:04 Ademan_ night
02:04 Jak_o_Shadows haha
02:05 rue_bed I really want to make some good servo code
02:05 rue_bed (hobby servos)
02:05 rue_bed I have an idea
02:08 rue_bed make multiservo code with a 4017
02:09 Ademan_ rue_bed: I'll actually be doing that!
02:10 Ademan_ well, I dunno about "good". My idea of "good" code comes from a lot higher level code... not sure what good embedded code looks like :-p
02:12 Jak_o_Shadows Hmm, voltage level considerations: I have 2 switching mode regulators, one 16V battery (i think. Nominally it's 14.4, but i think that's under a decent load), and I need 5V for the ultrasonic sensor and inverter, and 3.3 for the uC
02:12 rue_bed my idea is to implament the highest res 2ms timer I can, and use it static on the predelay and variable on the postiion delay
02:15 Ademan_ rue_bed: you've lost me heh
02:15 Ademan_ Jak_o_Shadows: what uC? It might be worth it to power your uC from another source, from 16 to 3 is a lot
02:16 Jak_o_Shadows Texas Instruments MSP430
02:16 Ademan_ oh hey, me too
02:16 Ademan_ the one in the launch pad?
02:16 Jak_o_Shadows yeah.
02:16 Ademan_ cause you've only got two timers there :-p
02:17 Triffid_Hunter rue_bed: https://github.com/triffid/avr-servo/blob/master/avr-servo.c is for a 4514, should work on your 4017 if you ditch the servo selector stuff
02:17 Ademan_ though you have three CCRs which might get you what you want, but honestly I think it would be simpler to do it all on one timer with two interrupts
02:18 Jak_o_Shadows http://forum.43oh.com/topic/3734-robot-w-h-bridge-2-servos-2-bump-sensors/ is me.
02:18 Jak_o_Shadows well, I don't need to use two of the servos at the same time, so I could just swap it over?
02:19 Ademan_ Triffid_Hunter: wow that looks a lot like what I want to do
02:20 rue_bed you only need 1 timer for every 10 servos
02:20 Ademan_ I guess receive serial input, control servos is a pretty intuitive design though
02:20 Triffid_Hunter Ademan_: heh I've stared at the timer stuff in the arduino datasheet for so long that I can make them do almost anything now with ease
02:21 Triffid_Hunter Ademan_: and the most important principle when programming microcontrollers is, get the chip's hardware to do as much as possible
02:21 Jak_o_Shadows Scrolled back through about 100 tabs, found your HIP 4082 design Triffid_Hunter
02:22 Jak_o_Shadows I'm figuring out what resistance values I need/capacitor values
02:22 rue_bed 4082?
02:22 rue_bed or 8xxx
02:22 Jak_o_Shadows yes
02:22 Triffid_Hunter Jak_o_Shadows: for which bits? I just guessed on most of them. my ESC has 10uF mlcc for bootstrap capacitors
02:23 Jak_o_Shadows haha. I'm looking at Rdis atm
02:23 Ademan_ Jak_o_Shadows: can you paste it down here? I'm curious what you guys are talking about
02:23 Jak_o_Shadows http://triffid-hunter.no-ip.info/esc_sch.png
02:23 Jak_o_Shadows Ademan_: That forum link above contains all my schematics. Beware, the voltage divider bits are wrong
02:24 Triffid_Hunter Jak_o_Shadows: Rdel you mean?
02:24 Triffid_Hunter that sets the crossover delay.. 50k seemed about right when I read the sheet. could probably get away with a smaller delay but cbf working it out exactly
02:24 Ademan_ now... prepare for the atom bomb of stupid questions... ESC?
02:25 Triffid_Hunter Ademan_: http://www.thingiverse.com/thing:78390
02:25 Jak_o_Shadows Electronic speed control
02:25 Triffid_Hunter can see it right in front in that pic, just to the right of the steering servo
02:25 Jak_o_Shadows Nah, R DIS, from optional overcurrent latch.
02:25 Ademan_ ok cool, that was actualy what I was thinking, but isn't that usually associated with brushless DC motors?
02:25 Jak_o_Shadows Since i'm not using that, I suppose I can just kick it down to ground.
02:25 Triffid_Hunter Ademan_: this is for brushed DC. need 6 mosfets for brushless
02:26 Ademan_ Triffid_Hunter: ah that's really cool!
02:26 Triffid_Hunter Ademan_: http://triffid-hunter.no-ip.info/bldc_sch.png <-- bldc controller looks more like this
02:27 Ademan_ that's.... a lot of capacitors...
02:27 Ademan_ and are H1-H4 inductors?
02:27 Triffid_Hunter Ademan_: those are mounting holes
02:28 Triffid_Hunter Ademan_: I'm targeting 100A, see http://triffid-hunter.no-ip.info/bldc_brd.png for the board
02:28 Ademan_ oh, right, inductor symbol is wayyy different
02:28 Jak_o_Shadows Is there a benefit to parallel capacitors over a bigger capacitor, all costs/board stuff equal?
02:28 Triffid_Hunter Jak_o_Shadows: yes. lower ESR, lower inductance because both resistance and inductance reduce when paralleled but capacitance increases
02:29 Triffid_Hunter but if you look at the board you can see that the capacitors are spread all over
02:29 Ademan_ ah yeah
02:32 Jak_o_Shadows Hmph, i'm ready to make the board, more or less
02:32 Jak_o_Shadows presuming I can find the capacitors I need.
02:36 Triffid_Hunter Jak_o_Shadows: I've stocked up on 0603 smd parts, they're excellent.. fit beautifully between standard 0.1" headers
02:36 Jak_o_Shadows Yeah, I wish i could make a pcb, but knowledge/time/money constraints are too annoying.
02:38 Triffid_Hunter permanent marker, concrete cleaner and peroxide
02:38 Jak_o_Shadows , copper clad, board layout
02:39 Triffid_Hunter the blank pcb can be picked up for peanuts from ebay and similar
02:49 [1]RifRaf Triffid_Hunter, glad the car is fast, i do remember having one of those motors keeping up with cars on highway as i raced the car in a rest area alongside the highway did you print those wheels
02:49 [1]RifRaf Jak_o_Android, have been doing alot on the arm, cut final brackets today, is my plan to complete it this weekend
02:49 Jak_o_Shadows Cool
02:49 Jak_o_Shadows Long term goal for robot: Put an arm on it that can reload the nerf gun i'm going to put on it
02:50 Triffid_Hunter [1]RifRaf: yep those are printed wheels, they don't last long but they give me enough ground clearance to drive on gravel
02:50 [1]RifRaf Triffid_Hunter, the car got pretty smashed up when i tryed to turn at those speeds though
02:51 [1]RifRaf as it had big oversozed wheels to be able to get the speed
02:51 Triffid_Hunter heh i've only flipped it once so far
02:52 Triffid_Hunter still organising an Isense resistor that won't melt
02:54 Triffid_Hunter [1]RifRaf: is that how you twisted the frame? I had to heat it up to 150c to untwist it!
03:38 RifRaf Jak_o_Shadows, 4 x mg996r arrived today :) , ordered april 6th from ali
03:38 Jak_o_Shadows nice
03:39 Jak_o_Shadows yeah, I ordered some today. should've done it ages ago
03:39 RifRaf yep have got them a few times but was running out
03:41 RifRaf Jak_o_Shadows, the arm is stong as now, made up much better servo mounts and brackets etc
03:41 RifRaf strong even
03:42 Jak_o_Shadows nice.
03:42 Jak_o_Shadows How do you program it?
03:42 Jak_o_Shadows Like, how do you get a good range of motion?
03:43 RifRaf yeah controllable but upto 180°
03:43 RifRaf program with avrdude
03:43 Jak_o_Shadows No, like how do you program it to do specific things?
03:44 RifRaf using gait designer to develop moves
03:44 RifRaf and then program the developed moves in
03:45 Jak_o_Shadows yeah, gait designer is probably the bit i'm talking about
03:45 RifRaf yep well install and have a look, i'll be using it aging later and tomorrow so can answer your questions
03:46 RifRaf again*
03:47 Jak_o_Shadows i'm actually laying out my motor driver on some protoboard atm
03:47 Jak_o_Shadows apart from doing it mostly upside down, it's going ok.
03:48 RifRaf cool, just biulding arms here
03:52 Jak_o_Shadows Triffid_Hunter: IF i'm using +15V for Vdd of the HIP4082, is there any advantage in using +5V for AHI/BHI? It's just one less voltage source that needs to be on this section of board
03:55 Triffid_Hunter Jak_o_Shadows: check the datasheet for max voltage of ahi/bhi, if 15v is ok then go for it
04:10 Jak_o_Shadows Yeah, it's good to Vdd + 0.3, so that's a yes
04:14 Triffid_Hunter Jak_o_Android: if nothing else, learning to read datasheets is critically important for your future in electronics :)
05:10 Jak_o_Shadows Slo2lly flipping this circuit onto the right side of the protoboard
05:39 Jak_o_Shadows For some reason, i'm an idiot. This layout cannot work, as the hip 4082 chip is fundamentally backwards
10:26 DEADPOOL6 @find cuttin line
10:44 DEADPOOL6 Heloo
10:45 DEADPOOL6 Any experiences with automatic robot lines?
11:46 Somelauw Does anyone know a cross platform alternative to player/stage/gazebo and microsoft robotics studio?
11:46 Somelauw Something in java?
11:46 Somelauw or python
12:51 Hukka Somelauw: I haven't tried them, but collada is an option
12:52 Hukka And ROS might have something, though I think it was gazebo and I'm surprised that it's not cross platform
12:52 Somelauw I found webots, which looks nice, but is not free and even pretty expensive.
12:52 Somelauw Hukka: ros is not cross platform I think
12:52 Somelauw or at least pretty hard to install
12:53 Somelauw I'll take a look at collada
12:54 Hukka I have a list of other untested options too, if you want it
12:56 thinkanish hi
13:02 Somelauw sure
13:03 Hukka Let's see...
13:05 Hukka My notes contain:
13:05 Hukka http://stackoverflow.com/questions/1960738/whats-a-good-robotics-simulator
13:05 Hukka https://gitorious.org/simavr/
13:05 Hukka http://stackoverflow.com/questions/2533321/robotics-simulator
13:05 Hukka http://theroboticschallenge.org/aboutsimulator.aspx
13:08 Somelauw Hukka: thanks
13:09 Hukka np
13:09 Somelauw Collada requires ros or does it also work without ros?
13:10 Hukka It only has a plugin thingy for ros
19:58 RifRaf new stuffs http://www.youtube.com/watch?v=5VhbpxO4LIU
20:01 Jak_o_Shadows uh, cool
20:02 Jak_o_Shadows i was gonna ask if it was going to move
20:02 RifRaf yeah moves well
20:03 Jak_o_Shadows are you in a position to move it atm?
20:03 RifRaf yes
20:03 Jak_o_Shadows Was just thinking, you could livestream it with google + hangouts
20:03 RifRaf um, would have to get one of these $6 webca,s going first
20:04 Jak_o_Shadows haha, yeah hardware normally works better in linux than windows sadly
20:04 RifRaf well its just that i don't have one hooked up, will try
20:06 Jak_o_Shadows cool
20:14 Tom_itx ok my gcode is far more efficient now
20:15 Tom_itx and added another program that i did manually before
20:37 GargantuaSauce nice rif
20:45 RifRaf cheers
20:46 Tom_itx yeah, looks good rif
20:46 Tom_itx on the 2nd pass you should have it return the part to it's first location
20:47 RifRaf yeah have done nothing on the programming side yet, was just to show the mechanics work
20:48 RifRaf modified the servos, is a big help having support on both sides
23:18 Rif 2 Up time
23:19 rue_house you got the playback speed fixed, thats col
23:19 rue_house cool
23:21 Rif had not really set a speed for that clip, that was just playing in gait designer
23:21 Rif should i back heads or tails today
23:48 Jak_o_Shadows Hmm, for these odd diodes on the hip 4082 circuit, do they have to be power diodes or would signal diodes suffice?
23:49 GargantuaSauce link to schematic<
23:50 GargantuaSauce or are they just freewheel diodes across a motor
23:50 Jak_o_Shadows not freewheel diodes across the motor
23:50 Jak_o_Shadows can you accwss the pdf http://forum.43oh.com/topic/3734-robot-w-h-bridge-2-servos-2-bump-sensors/ ?
23:51 GargantuaSauce nope
23:52 Jak_o_Shadows rightio
23:52 Jak_o_Shadows https://dl.dropboxusercontent.com/u/104809629/Overview.pdf
23:53 GargantuaSauce d5,d6,d7,d8?
23:53 Jak_o_Shadows D2, D1
23:57 Jak_o_Shadows Those you mentioned have half-decent diodes on.
23:57 GargantuaSauce they can be small but not too small
23:58 GargantuaSauce cant go wrong with small power schottkys
23:58 GargantuaSauce also i am a little suspicious that d7,d8 are backwards