#robotics Logs
May 14 2017
#robotics Calendar
01:00 AM rue_shop3: I wonder if I could have used the clear plastic to print this then...
01:03 AM rue_shop3: well, it was prettymuch a complete waste of time, half of it was fun,
01:03 AM rue_shop3: (the bit after realizing the gears were wrong for the thread pitch I was trying to cut)
01:19 AM Jak_o_Shadows: https://hackaday.io/project/20980-ananasstepper-20 looks cool
01:26 AM rue_shop3: high eff white led, with a reverse diode, in series with two 130k 1/4w resistors and a a .0047uF capacitor, all across 120VAC.... works ok
01:26 AM rue_shop3: _I_ can see the flicker tho
01:27 AM rue_shop3: but wait, I was going to use a neon
01:27 AM rue_shop3: so, hmm
01:27 AM rue_shop3: so, maybe I just tint the led oranage and call it good
01:27 AM rue_shop3: ?
01:28 AM SpeedEvil: Or 1K resistor in series with the LED, and 10uF 16V cap across those, or something
01:28 AM rue_shop3: if I added another diode maybe
01:29 AM rue_shop3: the led is pulling 0.2mA
01:29 AM SpeedEvil: Ok, 33K maybe then
01:29 AM SpeedEvil: I mean in place of the LED
01:29 AM rue_shop3: so, how big a cap to keep 1.4V above... hmm for 1/120 of a sec...
01:29 AM SpeedEvil: So you have LED + resistor, with the cap across them, in place of the LED
01:29 AM rue_shop3: no, I'm trying to make a 120V pilot light
01:29 AM SpeedEvil: err
01:29 AM rue_shop3: :)
01:30 AM SpeedEvil: sorry - 7AM from the wrong side
02:09 AM Anniepoo_: i'm pooped
02:10 AM Anniepoo_: 8cD much beating on metal
02:15 AM ace4016: i misread that as "much eating on metal"
02:29 AM * Anniepoo_ is here with an old fashioned mess kit, eating
02:41 AM rue_shop3: I made a 120V pilot lamp
02:41 AM rue_shop3: led
02:42 AM rue_shop3: with jewel
02:42 AM rue_shop3: and holder
02:42 AM rue_shop3: on lathe
02:42 AM rue_shop3: it.... was mostly a waste of time
02:42 AM rue_shop3: one of those, looking back, 'naaaa wont make more' projects
02:42 AM rue_shop3: once was enough
12:20 PM rue_bed: if I put heatshrink tight around a resistor, do you think the wattage rating goes up or down?
12:22 PM synja: go down and burn out quick?
12:23 PM rue_bed: or it has a heatsink effect
12:25 PM synja: if the rate of heat dissipation through convection is less than that of conduction of the heatshrink for the resistor, then yeah
12:25 PM rue_bed: so then the question would be what is the thermal conductance of heatshrink
12:25 PM synja: also the heatshrink needs to dissipate that heat too
12:26 PM rue_bed: yea
12:45 PM mumptai: probably more insulation
12:46 PM mumptai: but if there is no convection, most might still conduct throught the leads
01:09 PM pradu: Is there any good book/reference about how to design two-axis gimbals and how to make rotor designs that can tilt rotors?
01:09 PM veverak: that does not sound like a rocket science exactly
01:10 PM veverak: pradu: "rotor designs that cna tilt rotors" .... you mean what?
01:10 PM * veverak is confused
01:10 PM pradu: Like helicopters that can tilt the rotors to change lift
01:10 PM pradu: Instead of increasing/decreasing speed
01:10 PM pradu: like done on quadcopters
01:11 PM veverak: that is kind of rocket science
01:11 PM veverak: and depends on what you want
01:11 PM veverak: I would preferably buy such a rotor from RC helicopter and just use it
01:11 PM pradu: What I'd like to do is make a UAV that has three arms; each of them with a two-axis gimbal
01:12 PM pradu: and rotors that tilt to change speed instead of spin the motor faster or slower
01:12 PM pradu: tilt to change force*
01:12 PM pradu: But I don't know how to get started with the mechanical design
01:12 PM veverak: hmm
01:12 PM veverak: I don't think you want to ;)
01:12 PM veverak: pradu: rotating things are sensitive to proper parts
01:12 PM veverak: I mean, the parts have to be designed properly and machined properly
01:13 PM veverak: and it's kind of rocket science to do it right
01:13 PM veverak: bigger the RPM, bigger the requirements for precision
01:14 PM veverak: pradu: it's definetly interesting thing to build
01:14 PM veverak: bot not easy one
01:15 PM pradu: Yes and I definitly am willing to put the effort
01:15 PM pradu: I've worked out a controller for it
01:15 PM pradu: The UAV can fly in any direction in any orientation
01:15 PM veverak: hmm, maybe try to google some books?
01:16 PM pradu: Yeah I probably need a book on helicopter rotors
01:16 PM pradu: And not sure where to go for two-axis gimbal design
01:16 PM veverak: well, I don't think they are so complicated ;)
01:16 PM veverak: pradu: gimbal can be pretty easy
01:17 PM veverak: http://www.ebay.com/itm/2-Axis-Aluminum-Brushless-Camera-Mount-Gimbal-Frame-for-DJI-Phantom-Gopro-2-3-/401227075000
01:17 PM veverak: this looks representative
01:18 PM pradu: Oh that's for the camera
01:18 PM pradu: I meant one for the rotors
01:18 PM veverak: pradu: note the features: mounting with vibration absorbing parts, two brushless motors for rotation
01:18 PM pradu: Oh I see
01:18 PM veverak: ah, hmm
01:18 PM veverak: that can be more complex :)
01:18 PM veverak: pradu: tahn
01:19 PM veverak: pradu: *than
01:19 PM veverak: pradu: I would go for mechanism that tilts the motor and you use propeller directly mounted on the motor
01:19 PM veverak: definetly simple mechanism in the end
01:19 PM veverak: and make 2 axis gimbal for each motor
01:19 PM veverak: only downside is that you can't get "continuous rotation" on gimbal axis
01:21 PM veverak: pradu: anyway, keep in mind that such a gimbal needs to be able to handle power of that motor
01:21 PM veverak: for that you need to design adequate servo motors / brushless motors / whatever which ar estrong enough to handle it
01:21 PM veverak: and construction has to be strong enough
01:21 PM veverak: maybe try/error ?
01:21 PM pradu: Yeah I guess so
01:22 PM pradu: My first design is just with a 1-axis gimbal
01:22 PM pradu: A roll-gimbal
01:22 PM pradu: But if it flys in an odd orientation
01:22 PM pradu: You lose like 60% efficiency
01:22 PM pradu: So you need a two-axis gimbal to get it back
01:23 PM pradu: Maybe it is possible to put the thing on a free sphere
01:23 PM pradu: And have the rotor itself torque the gimbal to put it in some orientation
01:24 PM pradu: An unactuated gimbal*
01:32 PM veverak: :)
01:34 PM rue_house: Tom_L, would it be much to set up an fpga to push a 256x10bit table into a chip at 100Mhz?
01:35 PM rue_house: oh wait, my idea went bust
01:35 PM rue_house: it would have to be atleast 100x10bit @100Mhz
01:37 PM rue_house: oooh and thats not the 125Mhz version, its the 50Mhz, huh
01:37 PM rue_house: I'm probably better off with some dac from a laser printer
01:39 PM WaywardSon is now known as Wayward
01:47 PM rue_house: ok I set the text field to autofocus for my intranet pdf search page
01:47 PM rue_house: yay
01:47 PM rue_house: less clicking = better
01:48 PM Tom_L: how'd you wire the AC led indicator?
01:48 PM Tom_L: FPGA could do it i'm sure
01:49 PM Tom_L: it would take review on my part to tell you how :)
01:50 PM rue_house: from HOT -> 100k resistor (1/4w) -> 0.0047uF cap (400V) -> led (with a diode reversed across it) -> 100k resistor (1/4w) -> neutral
01:50 PM rue_house: incase the top breaks/blows off, I used a panel jewel to set it back in the case
01:51 PM rue_house: I have pics I'll post
03:46 PM veverak: that feeling
03:46 PM veverak: when you realize making quadruped->hexapod is just changing configuration variables in project
03:46 PM veverak: meaning
03:46 PM veverak: "haw much legs I can add before it breaks?"
03:53 PM pradu: lol
03:53 PM pradu: I think quad is the most efficient for a square right?
03:53 PM pradu: Quadcopter or helicopter
03:53 PM pradu: They both have the same area for the rotors
03:54 PM pradu: And efficiency proportional to the square root of area or something
03:58 PM deshipu: veverak: I've heard C++ is good at stapling extra legs onto things
04:05 PM veverak: pradu: walking robot
04:05 PM veverak: deshipu: I think so too
04:05 PM veverak: will see
04:05 PM veverak: will see
04:05 PM * veverak should order more servos
04:05 PM veverak: like 120x SG90
04:06 PM pradu: ooh walking robot is cool
04:06 PM deshipu: veverak: I just got some SG50
04:06 PM pradu: Sort of like Boston Dynamics?
04:07 PM deshipu: https://cdn.hackaday.io/images/9233401494787353422.jpg
04:07 PM pradu: What is an SG50/90?
04:07 PM veverak: love that camble management
04:07 PM deshipu: type of the servo
04:08 PM veverak: deshipu: interesting
04:08 PM deshipu: yeah, I'm still struggling with all the wires
04:09 PM deshipu: they are not as small as I hoped
04:09 PM deshipu: about 2/3 of a SG90
04:11 PM Tom_L: servos should use mini harmonic drives for gear reduction
04:11 PM Tom_L: then they could be tiny
04:17 PM deshipu: Tom_L: good luck making that
04:18 PM Tom_L: i've never actually checked the gear reduction on a servo
04:18 PM Tom_L: it must be quite a bit
04:19 PM deshipu: it is, but that's not the problem
04:19 PM deshipu: tolerances are
04:24 PM Tom_L: http://www.harmonicdrive.net/_hd/content/documents/CSF_mini.pdf
04:25 PM deshipu: I know what a harmonic dive is
04:25 PM deshipu: drive
04:25 PM Tom_L: those are small though
04:25 PM deshipu: good luck manufacturing it for under the price of a servo
04:25 PM deshipu: from nylon
04:25 PM Tom_L: i didn't say it'd be cheap
04:26 PM deshipu: on this market cheap rules
04:26 PM Tom_L: yeah i know
04:27 PM deshipu: so that's why nobody does it
04:27 PM Tom_L: that with a pancake motor would be pretty small
04:27 PM deshipu: of course you can order super-expensive servos with harmonic drives
04:28 PM deshipu: the thing is, for a quadruped you need at least 12 of them
04:28 PM deshipu: 18 or 24 for a hexapod
04:28 PM deshipu: even with super-cheap plastic ones that easily goes up to $100
04:28 PM Tom_L: the point you decide to make one you're just burning money anyway
04:31 PM deshipu: not true
04:32 PM deshipu: it takes some experience to get there, but you can reliably design and build cheap walkers
04:32 PM deshipu: using off-the-shelf parts
04:39 PM Tom_L: actually, i don't know if nylon would be the best fit
04:40 PM Tom_L: i'm not sure what it is, but at the vo-tech here they printed some replacement timing belts for a machine here
04:40 PM Tom_L: s/it/material it is
04:41 PM Tom_L: http://tom-itx.no-ip.biz:81/~webpage/cnc/temp/prints/plastic_prints.jpg
04:41 PM Tom_L: the red belt in the middle
04:47 PM deshipu: I'm sure it wasn't as cheap as nylon :)
04:47 PM deshipu: probably ninjaflex
04:55 PM Tom_L: i'm not sure
04:55 PM Tom_L: they print all sorts of things
04:56 PM Tom_L: including imbedded metal particles etc
05:03 PM deshipu: 3d printing is a very expensive way of mass-producing anything
05:04 PM Tom_L: mostly for test
05:05 PM Tom_L: first article for engineering test and evaluation
05:05 PM Tom_L: they print titanium etc as well
05:16 PM tumdedum_ is now known as tumdedum
09:04 PM zhanx: Evening
09:18 PM pradu: Hi
10:31 PM Anniepoo_: howdy
10:31 PM zhanx: hey Anniepoo_
10:31 PM Anniepoo_: hey
10:31 PM Anniepoo_: overdid it yesterday blacksmithing
10:31 PM Anniepoo_: sore all da
10:32 PM Anniepoo_: day
10:32 PM zhanx: garden is taking all my time right now but i was told we need 2 gary's today
10:32 PM Anniepoo_: LOL
10:32 PM Anniepoo_: You gotta do pix!
10:32 PM zhanx: i will but its prep time for my 100x100 garden
10:33 PM Anniepoo_: whats Gary going to be like?
10:33 PM Tom_L: any critters gettin in it?
10:33 PM zhanx: according to my kids gary is gonna be the faster snail ever
10:33 PM zhanx: Tom_L: tons that was half the work
10:33 PM zhanx: 16 hours on it today
10:34 PM Tom_L: when i had one, i wound up covering half mine with 1/2" mesh
10:34 PM zhanx: i get free mulch
10:35 PM zhanx: plus i have 300+ plants ready to drop in friday after possible last frost
10:35 PM Anniepoo_: Did you have lots of snails?
10:35 PM Tom_L: http://tom-itx.no-ip.biz:81/~webpage/house/house.jpg
10:35 PM Tom_L: old pic
10:36 PM zhanx: small one, my raised beds are bigger
10:36 PM Tom_L: yeah, big enough for us though
10:36 PM Anniepoo_: 8c9 snails are delicious!
10:36 PM zhanx: true but i love stuff fresh from the garden
10:38 PM Anniepoo_: eat the snails, then they won't eat your garden
10:38 PM Tom_L: you're gonna have to can some if you keep it all
10:38 PM zhanx: i can alot
10:41 PM Tom_L: haven't heard much about rue's garden
10:41 PM zhanx: is he doing one this year?
10:41 PM Tom_L: i guess
10:41 PM Anniepoo_: he said so once
10:41 PM Anniepoo_: IIRC
10:41 PM zhanx: I know i got 300+ plants ready but he is silent mainly
10:42 PM zhanx: next weekend my garden is going from weeds to plants
11:23 PM rue_house: rubarb is going nuts
11:23 PM rue_house: the spinich is just about done (trying like all heck to seed)
11:23 PM rue_house: mowed the grass :)
11:24 PM rue_house: planted the beans
11:24 PM rue_house: this week there are tommatoes going in
11:24 PM rue_house: the potatoes have already been done
11:24 PM rue_house: need to plant more green onoins
11:31 PM zhanx: your potatoes are done?
11:31 PM zhanx: mine are just starting
11:31 PM orlock: just fixed a 2 story tall robot
11:31 PM orlock: parts carousel
11:32 PM orlock: SQL server didnt come back up when a host was rebooted
11:41 PM rue_shop3: ooops
11:42 PM rue_shop3: a 2 story parts carosel?
11:42 PM rue_shop3: cool
11:42 PM orlock: rue_shop3: yeah
11:42 PM orlock: SQL server didnt come back up after patching
11:42 PM orlock: nneeded to start service manually