#robotics Logs

Jul 05 2015

03:53 rue_shop3 one goes to +5V
03:53 rue_shop3 one goes to -5V
03:53 rue_shop3 one goes to a variable voltage 0-30V
03:53 rue_shop3 when the variable one is at 0V, the common node is at 1.25V
03:54 rue_shop3 when the variable one is at 30V, the common node is at 3.75V
03:54 rue_shop3 solve relative values for the 3 resistors
04:03 rue_shop3 ok one range is 1.25-3.75V
04:04 rue_shop3 the other is 0-30
04:04 rue_shop3 at what voltage do the two cross
04:04 rue_shop3 Vin = Vout/12
04:04 rue_shop3 er
04:04 rue_shop3 +-
04:05 rue_shop3 Vin = (Vout/12)+1.25
04:05 rue_shop3 Vin-1.25 = vout/12
04:06 rue_shop3 12*(vin-1.25) = vout
04:06 rue_shop3 vin = vout
04:06 rue_shop3 Vin = (Vin/12)+1.25
04:06 rue_shop3 Vin - 1.25 = Vin/12
04:07 rue_shop3 12(Vin-1.25) = Vin
04:07 rue_shop3 12*vin - 15 = vin
04:07 rue_shop3 12*vin = vin + 15
04:08 rue_shop3 12*vin - vin = 15
04:08 rue_shop3 11vin = 15
04:08 rue_shop3 vin = 15/11
04:08 rue_shop3 1.36V
04:10 deshipu yawn
04:10 deshipu rue_shop3: working on the servos?
04:10 rue_shop3 power supply
04:11 rue_shop3 calc "((O/12)+1.25)(((O=1.3636)))"
04:11 rue_shop3 ((O/12)+1.25)(((O=1.3636))) -->> 1.36363
04:13 rue_shop3 ok, a votlage divider has a feed of 10V, its output is 6.364V
04:13 rue_shop3 whats the resistor ratio
04:14 rue_shop3 1000:571.42
04:17 Tom_itx https://github.com/yorikvanhavre/FreeCAD/wiki/Path-module
04:24 rue_shop3 interseting
04:24 rue_shop3 librecad is a branch of freecad that happened after a developer dispute (iirc)
04:30 deshipu yay
04:31 deshipu we need more of those
04:31 deshipu http://www.theroboticschallenge.org/finalist/nimbro-rescue
04:31 deshipu argh
04:31 deshipu wrong link
04:31 deshipu http://sheep.art.pl/Unix%20Koan
04:32 rue_shop3 I1 + I2 + I3 = 0
04:32 rue_shop3 R1 = 0.571438*R2
04:33 rue_shop3 VR1 = 5-Vout
04:33 rue_shop3 Vr2 = -5-Vout
04:33 rue_shop3 Vr3 = Vin-Vout
04:33 rue_shop3 Vin = (Vout/12)+1.25
04:33 rue_shop3 I1 = Vr1/R1
04:33 rue_shop3 I2 = Vr2/R2
04:34 rue_shop3 I3 = Vr3/R3
04:34 rue_shop3 -----------
04:34 rue_shop3 who can solve relative values for R1, R2, R3
04:35 Jak_o_Shadows Er, I can solve equations. But it looks like a bit too much electrical knowledge for me.
04:36 rue_shop3 those are all the equations
04:36 rue_shop3 its just math now
04:37 e_shop3 tries to dump it into wolfram a
04:40 rue_shop3 "Wolfram|Alpha doesn't understand your query"
04:40 rue_shop3 crap
04:41 Jak_o_Shadows So you don't have things quite in the form that I like.
04:41 Jak_o_Shadows ie. relative values, ick.
04:41 rue_shop3 yea
04:41 rue_shop3 its raw
04:41 Jak_o_Shadows through wolfram might be able to handle it; it can solve quadratic optimisation problems wiht linear constraints, which is kinda cool
04:57 rue_shop3 if you enter too many formulas it gives up
04:59 Jak_o_Shadows So you're unkowns are really only V1, V3
04:59 Jak_o_Shadows And your input variable is really only vout
05:07 rue_shop3 oh
05:07 rue_shop3 the unknowns are R1 R2 R3, input is Vin and output is Vout
05:07 rue_shop3 electrically
05:07 deshipu here's a project idea
05:07 Jak_o_Shadows Eh
05:07 rue_shop3 I should say that Vr1+Vr2 = 10
05:08 deshipu use a face recognition program and a couple of sensors and implement this: https://youtu.be/XbsDvGtTRWU?t=157
05:08 rue_shop3 might help to know that Vout = 5-Vr1
05:08 Jak_o_Shadows So basically most of your variables are very closely coupled.
05:08 rue_shop3 no luck from wolfram yet
05:08 Jak_o_Shadows so you can simplify.
05:08 rue_shop3 yea
05:08 rue_shop3 it should boil down really well
05:13 Jak_o_Shadows Do you know vout?
05:14 Jak_o_Shadows Or is that an unknown?
05:15 rue_shop3 I have three points
05:15 rue_shop3 Vin Vout
05:15 rue_shop3 ----------
05:15 rue_shop3 0 1.25
05:15 rue_shop3 30 3.75
05:15 rue_shop3 1.364 1.364
05:19 Jak_o_Shadows Are you sure you're going to get a single lot of values for the resisters? Because I have R1 in terms of Vout, R3. So that gives R2 as well
05:19 rue_shop3 so far, wolfram says G2 = 4.75691...
05:19 rue_shop3 er R2
05:20 rue_shop3 but there are issues...
05:20 rue_shop3 maybe this isn't solvable.......
05:20 rue_shop3 I was sure it was
05:20 rue_shop3 I wasn't sure if the solution would have a linear input/output function
05:21 Jak_o_Shadows You could probably put it as an optimisation problem in terms of R3
05:21 Jak_o_Shadows Course, with only 3 points, it's not crazy, nor crazy accurate
05:24 rue_shop3 the constants are R1, R2, R3
05:24 Jak_o_Shadows Ok: to rephrase, you might be able to choose R1, R2, R3 such that Vin, Vout best match the values you have
05:25 rue_shop3 wolf says R1 = 2.7183, R2=4.75691
05:25 rue_shop3 I cant find a way to solve R3
05:25 rue_shop3 apparently it cant either
05:26 rue_shop3 wow, at 3am, even the cats go to sleep
05:27 Jak_o_Shadows R3 = ( 5*(a+1) - Vout*(a + 1)) / (R1 * (Vout - Vin))
05:27 Jak_o_Shadows Where a = 1/ 0.571438
06:38 veverak guys
06:38 veverak what's ideal
06:38 veverak to setup behavior for pwm-controlled-device
06:39 veverak "set it for this pwm value, and it have to reach it in <n> seconds" ?
06:39 veverak like, I actually send "A" pwm value, want to change it to "B" and want tha transition to take <n> seconds
06:40 deshipu depends what you need
06:40 deshipu there are millions of ways of doing tweening
06:40 deshipu linear, exponential, sine-shaped
06:40 veverak linear I suppose
06:40 veverak well, I have this flying thing
06:41 veverak and it can turn its motors
06:41 deshipu there you want pwm probably anyways
06:41 veverak but nasty thing is that servos are slow compared to the motors, that spin up to value they need really quickly
06:41 veverak aaaaand I suppose that could have some nasty side-effects
06:42 deshipu you do pid on them anyways, so that takes care of it, no?
06:42 veverak not directly?
06:42 veverak setup is that
06:43 veverak I have vector that defines where user wants the thing to go, another vector is values from sensors where it actually controls
06:43 veverak from that is calculated vector, that tells where it actually should go
06:43 veverak aaaand pid are used in that calculations
06:44 veverak after that vector is calculated, it's used to calc values that are send to the motors
06:44 deshipu the parameters of PID control how fast it will go there
06:44 veverak yeah
06:45 veverak maybe that will remove the negative effect
06:46 veverak but I suppose I will at least research how to keep motors synced with servos at least to know what to do if it posses problem
06:49 deshipu motors synced with servos?
06:49 deshipu what?
06:50 veverak nah
06:50 veverak nevermind, bad usage of words
06:50 veverak O:)
06:53 Jak_o_Shadows argh, stupid horrible PID for the hot-end
06:57 veverak ?
07:00 Jak_o_Shadows Been having trouble with my 3d printer hot-end
07:01 Jak_o_Shadows not helped by it doing an abysmal job of keeping to temperature. So it keeps overheating and shuttign down
07:03 veverak OT: I found this as great example of PID https://github.com/br3ttb/Arduino-PID-Library/
07:03 veverak or, I do it just because he provdied really nice tutorial about it
07:03 veverak is it still valid and proper or are there any new/better ?
07:06 Jak_o_Shadows TBH, I only have the basics. Which doesn't extend to actually implementing it
08:22 knott_rays how do i make metal parts without a set of metal tools D:
08:26 SpeedEvil LASERs
08:27 knott_rays if i cant afford metal tools how the hell could i afford lasers
08:27 knott_rays is there anything online?
08:28 SpeedEvil What are you trying to make
08:28 SpeedEvil you can go a long way with files/hacksaw/drills
08:29 knott_rays hmm
08:29 knott_rays custom metallic and plastic parts for casings for stuff
08:30 knott_rays so far ive used a little saw and a hammer
08:30 SpeedEvil sand-casting can be useful
08:30 SpeedEvil depending on what size you mean
08:32 knott_rays interesting stuff
08:42 deshipu also very dangerous
08:42 deshipu why metal?
08:45 password2 I have found second hand files to be in almost new shape but at 15% of the cost
08:49 password2 where my leds i ordered
08:49 Orpheon depending on where you live, you might also have the luxury of having a communal workshop or hackerspace near you
08:49 Orpheon and they might have tools
08:49 password2 i paid like 1 min ago :P
08:49 password2 whoops , this is not ##e
08:52 password2 i bought 6 files for $2 a while ago with the purpose of making knives , the first one is almost finished , i softened the one with a blow torch and was able to shape it with the other files
08:54 password2 quite useful technique is you want to make small parts
09:30 knott_rays there are a few schools with tools but they only offer courses including materials and time limits
20:49 rue_shop3 zlog
20:50 rue_shop3 Jak_o_Shadows, thanks for the help, I was sleeping on it and realized why your right
20:50 Jak_o_Shadows No problem. Yay, I was right.
20:51 rue_shop3 wow, there is a forrest fire close by and the sky is red
20:52 rue_shop3 its really hot and smokey
20:52 rue_shop3 46% humidity
20:52 Jak_o_Shadows Should you still be there?
20:52 rue_shop3 its still quite far away
20:53 rue_shop3 tho, they are apparenltly doing a porr ass job of controling it at all
20:53 rue_shop3 when it started they threw 2 air loads of water on it and 6 people
20:53 rue_shop3 next morning it was 20 acres big
20:53 rue_shop3 I'm told its 0% under control
20:54 Tom_itx why did they throw 6 people on it?
21:11 rue_shop3 exactly, everyone knows it takes a lot more than that to put out a fire
21:11 rue_shop3 piles and piles of bodies
21:24 Tom_itx what started it?
23:32 rue_shop3 rumor has it some people firing guns off at an old mine