#robotics Logs

Oct 11 2014

02:30 wolfmanjm yea had a lot of green filament :)
02:30 wolfmanjm trouble is the servos are slightly too underpowered :(
02:31 wolfmanjm they can barely lift it up.
02:31 deshipu yeah, always the problem
02:31 deshipu 5V?
02:32 wolfmanjm yea 4 x nimh batteries
02:32 deshipu ahh
02:32 wolfmanjm so between 5 and 4.6v
02:32 deshipu nimh suck
02:32 deshipu won't work
02:33 deshipu too small current
02:33 wolfmanjm heh googling around seems to think nicd or nimh arebest for servos
02:33 deshipu might work for one leg
02:33 deshipu but not for 4 at once
02:33 wolfmanjm lipo are said to be definitely bad for servos
02:33 deshipu do the math
02:33 deshipu 600mA per servp
02:33 wolfmanjm they seem to be ok, voltage is steady with all 12 going
02:34 wolfmanjm oh these servos are under 100ma
02:34 deshipu lipo are bad because the voltage changes
02:34 wolfmanjm so what to use?
02:34 deshipu that's why you need a regulator
02:34 deshipu I use a 20C lipo and an UBEC
02:35 deshipu you could try with more nimh
02:35 deshipu in parallel
02:35 deshipu but they are heavy
02:37 wolfmanjm http://robot-kingdom.com/what-battery-should-you-use-on-your-robot/
02:38 deshipu wolfmanjm: so you have 12 servos, 600mA or more each
02:38 wolfmanjm nothey are 100Ma each
02:38 deshipu when they don't move
02:38 wolfmanjm so 1.2Amps
02:38 deshipu it's the stall current that you want, not the rest current
02:39 deshipu do the measurement
02:39 deshipu if you don't believe me
02:39 deshipu take one, hook up to a meter and see how much it takes when you are trying to force it off position
02:41 deshipu to measure current, you hook the meter up in series
02:42 deshipu oh, also make sure the leads going from the battery to the point where they diverge to all the servos are thick enough
02:42 deshipu it's 7A in there
02:43 wolfmanjm yea I don;t hink mine is drawing 7amps the wires would melt :)
02:44 deshipu sure they are not, because you have a volatge drop on the wires and on the batteries at that current
02:44 deshipu because the batteries can't handle it
02:44 wolfmanjm unde rload the voltage is still at 4.8volts at the moment
02:45 wolfmanjm actually I am curerntly usign NiCd, they have a very high current output capacity
02:46 deshipu so, the servos can take from 4.something to 6.somethingV, right?
02:46 deshipu have you tried adding one more cell?
02:46 wolfmanjm yea these ones are meant to be no more than 5v people report killing them over 5v
02:47 wolfmanjm I do have 5 cell nimh from other robots I have but that has a voltage of 6.5 v when newly charged
02:47 wolfmanjm actually can be as high as 7v after a fresh charge so I don;t wnat to try them
02:47 deshipu hehe, I'm powering mine directly from a 2S lipo :D
02:47 wolfmanjm I may try that later
02:48 deshipu 8.4V on fresh charge
02:48 wolfmanjm ea I need to get a UBEC
02:48 deshipu before you do, make the measurement for current
02:48 wolfmanjm or two
02:48 deshipu it's better to know
02:49 wolfmanjm Yea I'll measure it
02:50 deshipu high current problems are notorious for walking robots
02:50 deshipu it's frustrating
02:53 wolfmanjm what di you use to charge your lipos?
02:54 wolfmanjm wow 20C lipos are expensive!
02:55 deshipu I used to dabble in RC models, so I have a dedicated lipo charger
02:56 deshipu wolfmanjm: if it's large, it doesn't have to be 20C
02:56 deshipu wolfmanjm: C is a multiplier
02:56 deshipu wolfmanjm: mine are very small, only 300mAh, so 20C gives me 20*300=6A
02:57 deshipu wolfmanjm: but for a 2400mAh battery, 5C would already give you 12A
02:57 wolfmanjm oh yea they are much cheaper $5 each
02:58 deshipu my robots are tiny :)
02:58 deshipu did I show you a video?
03:01 wolfmanjm yea
03:02 wolfmanjm ok I need to measure the current then get some UBECs and a couple of lipos
03:03 deshipu depending on the current, the NiCd batteries might be enough
03:03 deshipu it's becoming a money sink :(
03:03 wolfmanjm hmm most ubecs are escs too I don;t really want that ;)
03:03 wolfmanjm yea tell me about it :)
03:04 wolfmanjm if you want a money sink get into 3d Printing ;)
03:04 deshipu my first robot got into a growing loop
03:05 deshipu it started small, then I realized the legs are too short, added longer legs, then the servos were too weak, replaced with bigger ones, then the power was too weak, replaced battery, then it was too heavy, replaced the servos again, then the battery again
03:06 deshipu it's like an arms race
03:07 wolfmanjm yea same thing happens with 3D printers. I've designed 3 different types of 3D printer... and built them
03:07 deshipu with my second robot I decided to optimize the cost
03:07 wolfmanjm two are pretty big the last one was specifically designed to be small
03:07 deshipu got to $150 by making it really small
03:08 deshipu I'm working on a $30 one now, even smaller
03:10 deshipu but it's 2dof per leg, so the inverse kinematics are complicated
04:18 wolfmanjm measured the current using a 7amp 5v supply, 200mA when just sitting there peaks at 600mA when they all move or I put pressure on several of them
04:19 wolfmanjm but I can tether it for now anyway so I'll use the 7amp supply :) save buying expensive batteries and charger and UBECs
04:22 wolfmanjm that is all 12 BTW
04:29 deshipu wolfmanjm: you mean 600mA total?
04:29 deshipu wolfmanjm: wow, that's small
04:31 deshipu wolfmanjm: by the way, how are they connected to the battery?
04:42 wolfmanjm I'm using a https://www.adafruit.com/products/815
04:42 wolfmanjm so they all plug into that
04:43 wolfmanjm yea it's 600mA with all on and two legs being pushed, also when they all move like on a reset it peaks around there too
04:43 wolfmanjm probably would get upto 1amp or so if all the legs were under strain
04:44 wolfmanjm does seem to have a little more torque when running off the PSU
05:21 deshipu wolfmanjm: that's why I have a delay when I enable the servos
05:21 deshipu wolfmanjm: not enabling them all at once'
05:21 deshipu wolfmanjm: also makes a nice animation for the startup :)
11:18 rue_house aha! my state machine wasn't working because I forgot to change the state
11:19 Tom_itx TX?
11:19 Tom_itx CA?
11:19 Tom_itx FL?
11:19 Tom_itx MO?
11:19 Tom_itx KS?
11:19 Tom_itx which one?
11:19 rue_house state 1
11:20 Tom_itx that is a state of emergency!
11:20 rue_house state not one changes to zero, but zero never gives up
11:20 Tom_itx bail out!!
11:20 Tom_itx zero want's to be one
11:20 rue_house sweeet! I have a reader thread!
11:21 Tom_itx at least my spreadsheet wasn't too screwed up this time from robbing parts
11:21 rue_house heh
11:21 rue_house junk in, junk out
11:21 Tom_itx if >1k don't do a physical count just yet
11:22 rue_house I wonder how consistent the weights of most parts are
11:22 Tom_itx within grains i would suspect
11:24 rue_house and in the process of getting that working, I now have the callback system working in my serial library
11:25 Tom_itx cereal!... time for Cereal!
11:25 rue_house sure, frosted flakes is on the manu
11:25 rue_house Tom_itx, your cheerier when your making things
11:26 rue_house or vise versa, hmmm
11:26 Tom_itx nearly screwed up dk order
11:26 Tom_itx they have a 'combine' button
11:26 Tom_itx i added 1 item
11:26 Tom_itx and combined the orders
11:26 Tom_itx so now i have 3 orders coming
11:26 Tom_itx deceitful bastards!
11:27 Tom_itx i called them at midnight and they answered!
11:27 Tom_itx all fixed
11:27 rue_house yea, I'v called them at midnight one or twice myself
11:27 Tom_itx cost a bit more than mouser but all was in stock
11:27 Tom_itx got spare boxes now
11:27 Tom_itx if you need one
11:28 Tom_itx ordered quan to get $$
11:28 rue_house indeed
11:28 Tom_itx and china for the plugs
11:29 Tom_itx the plugs were the killer on that board
11:29 rue_house odd
11:29 Tom_itx so i'll mill ~25 boxes next week and be set for a while
11:34 rue_house not planning any design chnges?
11:35 rue_house the cats are dissapointed with the weather out the open window, they want out the door instead
11:35 Tom_itx no design changes, it works like a champ
11:35 Tom_itx unless you see a flaw
11:36 Tom_itx cats.
11:36 rue_house I'v never had any problems
11:37 Tom_itx i think all the bugs were worked out in the first couple revs
11:37 Tom_itx the rest were just feature addons
11:37 Tom_itx ever try the clock yet?
11:37 Tom_itx the only thing i don't like is on the blue one the clock isn't exposed
11:37 rue_house what was the last solution to the high voltage thing?
11:38 Tom_itx none
11:38 rue_house I'v not tried the clock, no...
11:38 rue_house oh, I thought you had two different things made
11:38 Tom_itx it's there if you ever need a nice 4mhz clock
11:42 rue_house that cerial got me stickey...
11:43 Tom_itx keep your face outta the bowl
11:43 Tom_itx been livin with cats too long
11:45 e_house stops licking his hands clean for a minute and thinks about
11:47 rue_house my libraries worked great, this program came out really clean
11:47 Tom_itx always good when a plan comes together
11:48 rue_house ok I have half a hour to put the shop back togethor
19:24 coffeina hello
19:24 coffeina all
19:24 coffeina :)
20:17 rue_house hi
20:17 Jak_o_Shadows hi
20:20 rue_house so, the line drawing system I have will take care of the forward kinematics for me
20:21 rue_house I just need to enter the angles
20:21 rue_house go SDL
20:26 Jak_o_Shadows forward kinematics is nice
21:25 RifRaf yay the encoder pcb blinks its leds when the magnet moves over the ic, only took a year to make it
21:25 RifRaf now to hook up to avr and try see some data
21:27 Jak_o_Shadows What's it do?
21:27 Jak_o_Shadows meant to be used for*
21:27 RifRaf linear encoder to make threadless ballsscrew system accurate
21:27 RifRaf using as5311 chip, 1024 pulses per mm
21:28 Jak_o_Shadows ooooh
21:29 RifRaf is nice that the pcb worked, will solder a few more up now, is so hard to see the 0603 components
21:30 RifRaf lucky that with solder paste they are forgiving, and somehow managed to get all 3 leds the correct polarity
22:37 Tom_itx RifRaf get a magnifier :)
22:38 Tom_itx it's about the only way i can see em anymore
22:38 RifRaf yep getting a new one, got any recommendations?
22:38 Tom_itx what are you lookin for?
22:38 RifRaf i thought big desk mounted with light
22:39 Tom_itx i have a binocular scope i use too
22:39 Tom_itx yeah i use that alot too
22:39 RifRaf a way to solder easier, and see what i am doing
22:39 Tom_itx get a big diameter magnifier
22:39 RifRaf yep
22:39 Tom_itx so you can see off to the side too
22:39 Tom_itx good for pick n place
22:40 Tom_itx i just did a pile of boards tonight
22:40 RifRaf cool, i might do a copule more while its daylight
22:40 RifRaf cannot find quad encoder code for rpi, will have to use an avr by the looks
22:41 Tom_itx i have some for avr
22:41 Tom_itx need it?
22:41 RifRaf yes please, have not done this stuff for long while
22:42 Tom_itx i forget what chip it's for
22:42 wolfmanjm there is an encoder library for avr that works with those
22:42 RifRaf what avr did you use it with, have a few arduinos
22:42 wolfmanjm arduino
22:42 wolfmanjm works off of the two interrupt pins whic you want to use otherwise you can miss steps
22:43 wolfmanjm RifRaf: I used an arduino mini pro or nano with thise linear encoders
22:43 RifRaf wolfmanjm, ah yes you have used the as5311
22:43 Tom_itx http://tom-itx.ddns01.com:81/~webpage/avr/atmega328/PCINT0/quadrature/
22:43 Tom_itx mega328
22:43 Tom_itx yeah 2 interrupts reading both edges
22:44 Tom_itx for true quad
22:44 RifRaf wolfmanjm, i have leds blinken on the pcb when i swipe the magnet arcoss the chip, so soldering looks ok
22:44 wolfmanjm I used this one I think http://www.pjrc.com/teensy/td_libs_Encoder.html
22:45 wolfmanjm RifRaf: yea that is good, but yo uwill know if the mag strips are correct when you measure the steps with a guage
22:45 wolfmanjm RifRaf: beware they sent me the wronf mag strips originally and I got all sorts of odd problems
22:45 RifRaf wolfmanjm, the strips are from ams
22:45 RifRaf oh
22:46 wolfmanjm there are 1.2mm pole length and 2mm you have to use the correct ones
22:46 RifRaf yep, pretty sure i ordered the 2mm ones
22:46 wolfmanjm and which chip so you have?
22:47 RifRaf as5311
22:49 RifRaf you don't have a zip file for them do you tom?
22:49 RifRaf i'd have the code on here more than likely already,
22:49 RifRaf made quad encoders years back with the hp motors
22:50 Tom_itx no zip
22:50 Tom_itx all you need is the make and c file
22:50 RifRaf http://roboreprap.com/robotics/html/quad1.htm
22:51 wolfmanjm I used the as5305
22:51 wolfmanjm as5306
22:51 RifRaf wow 2005, no wonder i don't remember
23:02 wolfmanjm FYI to check the pole spacing you can shake some metal fillings on paper and then put the strip under the paper you can then see and measure the pole length which is how I discovered their mistake. the package was labeled 1.2 but was the 2
23:03 RifRaf thanks for the tip
23:05 RifRaf just put quad code into an old mega168, will hook up encoder and see if it is doing anything
23:18 rue_house 1:14:28: .......rue_mohr:ok, its 5 hours later
23:18 rue_house 01:14:33: .......rue_mohr:who wanted what?
23:18 rue_house 01:15:03: .......rue_mohr:
23:18 e_house pours himself a d
23:18 rue_house 01:15:18: .....Robomaniac:rawr
23:18 rue_house 01:15:22: ......furrywolf:RifRaf says the encoder works great
23:18 rue_house ..rue_mohr:like really really?
23:18 rue_house 01:15:43: .......rue_mohr:realy!!!???
23:18 rue_house 01:15:56: .......rue_mohr:like IT WORKS!!!
23:18 rue_house 01:15:59: ......furrywolf:needed a slight adjustment to the lcd printing (a few spaces at the end of the line to erase left-over digits), but otherwise yes.
23:18 rue_house 01:16:02: .......rue_mohr:DOES IT WORK!!!
23:18 rue_house 01:16:06: ......furrywolf:yes :P
23:19 rue_house 01:16:11: .......rue_mohr:IT WORKS!!!!!
23:19 rue_house 01:16:25: .......rue_mohr:IT REALLY REALLY WORKS!!!!!
23:19 rue_house 01:16:35: .......rue_mohr:YEEEEEEEEEEEEEEEEEEEEEEEEESSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSS!!!!!!!!!!!!!!!!!!!!!
23:19 rue_house 01:16:55: .......rue_mohr:
23:19 e_house does backflip
23:19 rue_house 01:17:00: .....Robomaniac:RAWR
23:19 rue_house these things were said 19/08/2005
23:20 rue_house 23:35:55: ........RifRaf_:http://www.rifraf.info/quad1.htm
23:20 rue_house 23:36:48: .......theBear_:nice one
23:20 rue_house 23:38:17: ........RifRaf_:yep is amazing to think that this thing is sensitive to 1/2000th of a revolution
23:20 rue_house 23:38:27: ......furrywolf:you need to put an integrator before your 'scope or something to cancel out its obvious ac-coupled-ness.
23:20 rue_house 23:39:17: .......theBear_:seems to be reading fine in the picks....
23:20 rue_house 23:39:48: ........RifRaf_:yep does seem ok
23:20 rue_house 23:40:01: ........RifRaf_:am not up to scratch on scopes though even one as basic as this
23:20 rue_house 23:40:14: ......furrywolf:I take it the spaces on the end got rid of the stuck digits?
23:20 rue_house 23:41:20: ........RifRaf_:yep thanks
23:30 wolfmanjm RifRaf: if I were using that chip I'd use the serial interface and absolute mode rather than the quadrature encoded signal
23:32 RifRaf thats what the other pins are for i guess, cs clk and do, i just wanna see some numbers in putty
23:34 wolfmanjm do you have a PCB for this chip?
23:34 rue_shop2 use a T10
23:34 RifRaf rue_house, yep you helped the last time, am inspired to make it work again
23:34 rue_shop2 :)
23:34 RifRaf wolfmanjm, yep, got 6 from oshpark
23:34 Tom_itx haha
23:34 rue_shop2 two quad inputs and 1 serial out pin
23:34 Tom_itx got rue_shop2 after the t10 now..
23:34 wolfmanjm is it an opensource design?
23:35 RifRaf yep link in a second
23:35 Tom_itx if you use the newer gcc you can use c with the T10 now
23:35 Tom_itx otherwise it's asm only
23:35 Tom_itx you can get it from atmel
23:35 wolfmanjm cool thanks. I may ask them for some samples :)
23:35 Tom_itx it's tiny
23:35 rue_shop2 I got a rare tiny26 version of my protoboard going today
23:35 rue_shop2 etched 3
23:36 RifRaf wolfmanjm, http://www.sorens.in/posts/2014-8-12-linear-encoder
23:36 RifRaf eagle files on there too, and the parts were cheap
23:36 Tom_itx http://tom-itx.ddns01.com:81/~webpage/temp/tiny/tinyTPI1.jpg
23:36 wolfmanjm RifRaf: thanks :)
23:37 RifRaf was making a pcb and googled early in part, saved my lots of time, is only a month or so old so good timing
23:39 rue_shop2 Tom_itx, how long ya think it'd take me to make another arm
23:39 rue_shop2 think I can finish one by 4am?
23:40 Tom_itx how many pieces are you gonna use over?
23:42 rue_shop2 not taking apart any of the old arms
23:43 rue_shop2 but I might be out of 3/4" TA adapters
23:43 Tom_itx how many arms do you need?
23:44 Tom_itx oh i know...
23:44 Tom_itx have you used your silkscreen yet?
23:44 Tom_itx i wanna see results from that!
23:45 rue_shop2 so far: none
23:45 rue_shop2 :( no silkscreening yet
23:45 rue_shop2 I do to
23:45 rue_shop2 but right now I have an itch to make another arm
23:45 Tom_itx what were you gonna screen with it?
23:48 rue_shop2 haha! found a 3/4 TA!
23:48 rue_shop2 now I need a nut for it
23:48 rue_shop2 but I could raid the work van if I have to
23:48 rue_shop2 5 servos...
23:49 Tom_itx any progress toward converting your cnc to linuxcnc?
23:49 rue_shop2 I didn't round up a machine to install it on
23:50 rue_shop2 and I think I'v now lost the usb stick I put the installer on
23:50 rue_shop2 :/
23:52 rue_shop2 hmm a lathe can only be not-cleaned for so long...
23:53 Tom_itx yeah i try to clean the chips out each time