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/diy/ Do-It-Yourself

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Anonymous 2015-09-29 02:36:42 No.881501

[Missing image file: ]

Any ideas for a project where the device is either useful or fun to play with?

I built a small rover and I got bored with using it in less time than it took me to build it! At the end of the day I had a slow remote control car. I was planning to build a little robotic arm based on pic related, but I'm concerned it will be just like my rover - once I built it I won't use it. I want to make something that's more than just a novelty. I have a 3D printer, an Arduino-clone, a Raspberry PI, and a few servos and sensors to work with (and I'm not opposed to getting more parts if needed).


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Anonymous 2015-09-29 03:18:55 No.881523
>>881501
Servo based robotic arms like this are shit and aren't really good for much.

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Anonymous 2015-09-29 08:23:50 No.881604
>>881523
it would be if OP would somehow make a pcb vile out of it, other than that i can't think of any other useful uses either.

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Anonymous 2015-09-30 22:15:06 No.882320
>>881501
I'm looking at strenghening the shit out of some cheap strong but not so resistant chinese servos.
I want to use them for a fighting humanoid robot.

Thread: >>881039

Anyway, do you know anything about inverse kinematics?

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Anonymous 2015-09-30 22:25:01 No.882325
Some cum guzzlers in my interfaces class said my project was too easy so mid semester I was forced to scrap it. Now I want to create a robotic arm that accepts controls from a modified wiimote. Gas to be able to use the accelerometer. Anybody know how I would best go about that?

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Anonymous 2015-09-30 22:25:57 No.882327
>>881501
6-axis sex robot.
this shouldn't even be a question

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Anonymous 2015-09-30 22:39:32 No.882339
Can you program it to make you breakfast in the morning?

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Anonymous 2015-09-30 22:57:12 No.882349
>>882325
why use a wiimote?
Accelerometers are not being used with gas, ever.
Mind explaining that?

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Anonymous 2015-09-30 23:01:39 No.882354
>>882327
but... you only need one axis

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Anonymous 2015-09-30 23:13:08 No.882362
>>882349
I want to turn the wiimote into a ghetto peregrine glove and use the motion recognition to control the bot.

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Anonymous 2015-09-30 23:22:18 No.882371
>>882325
Simple. Use your arduino to build the arm as normal, slap on a wiimote shield and bind actions to outputs. Essentially just 'do the same thing you were doing and slap a wiimote on it'.

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Anonymous 2015-09-30 23:26:41 No.882374
>>882362
but why a wiimote specifically?

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Anonymous 2015-10-01 00:27:51 No.882418
necessity is the mother of all invention.

what the fuck do you need?

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Anonymous 2015-10-01 02:19:05 No.882466
>>881501
>>882418

Guys like us don't actually need anything so pursuing a useful finished product is a futile endeavor. Find what other people need and then build and sell it.

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Anonymous 2015-10-01 04:03:04 No.882499
Six-axis arm...

Most arm "kits" use servos, is there a particular kind of servo that doesn't suck?

A DC gear motor with built in encoder sounds good, the encoder won't drift like the pot in a servo, but the encoder gives the relative change of position, how would I get an absolute position?

What do industrial arms use?

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Anonymous 2015-10-01 12:06:23 No.882592
>>881501
home automation:
automatic blinds
voice controlled lighting
automatic plant watering system
online weather logging

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Anonymous 2015-10-01 12:34:33 No.882607
>>882499
Industrial servos are mostly DC or AC motors with encoder feedback. If you know a reference position, you keep track of absolute position with said encoder feedback. Also as an added bonus, this angle you keep track of can be used in the inverse kinematics.

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Anonymous 2015-10-01 12:39:48 No.882612
>>882607
Someone explain to me how to interpret the maxon servo specs. They list Mn as a handful of millinewtonmeters of torque for 200w motors and that makes no sense to me. How do I work out the holding torque for a motor on their website? Say this is for a linear actuator for a man machine interface I am working on.

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Anonymous 2015-10-01 12:58:33 No.882620
>>882612
Thats funny, i work on a student team that is sponsored by maxon motors. I know for a fact that they really like people doing stuff with their motors and will surely try and help you with it. Why not try and send them an email?

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Anonymous 2015-10-01 13:26:38 No.882630
>>882499
>biggest one can hold 10oz(283g)
>360usd
that's not even big enough to hold a small dildo
I got my hopes up damnit

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Anonymous 2015-10-01 22:21:56 No.882791
>>882630
Stop fucking around.. use right device to job !!!
For small Robotic project I will suggest using Hybrid Stepper motors, if needed with gearbox, you can get small Nema 17 or 23 with planetary gearbox, take 1:100 and you will have so much holding torque to lift a bucket of water. ( depends on length of arm ) lets take 2Nm stepper motor and add 1:100 you should be able to get bit more then 100Nm on shaft after gearbox ( gearbox will take some power you cant never get 1:100 ratio i torque this ratio is for speed !!! )
but if you want to build something much more powerful and much faster you need proper Servo motors, Mostly AC because is much easier to control them by 3 phase then DC motors.
They need to have 2 stage encoders on them, etc whole construction getting much more complicated.
But Stepper motors in this days are really easy to get with integrated controllers too. for flew $ from e-bay ( China economy slowing down but not stopping )

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Anonymous 2015-10-01 22:53:06 No.882803
>>882791
sorry I'm makes a mistake its a simple should be 100:1 ratio not a 1:100 :)

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Anonymous 2015-10-02 02:23:30 No.882842
>>882791
>>882791
So, would you recommend this, for example?
http://www.robotshop.com/ca/en/12v-17a-416oz-geared-bipolar-stepper-motor.html

To hold a position, do I just keep that phase powered? That isn't going to burn out the motor?

What kind of encoder would give me an absolute position? All I can think of is a pot.

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Anonymous 2015-10-02 02:27:59 No.882844
>>882842
>To hold a position, do I just keep that phase powered?

Yes.

>That isn't going to burn out the motor?

Not if you're using a proper current-limiting supply.

>What kind of encoder would give me an absolute position?

An absolute position encoder. Mind that even the cheap Chinese ones are like $40 each.

>>
Anonymous 2015-10-02 09:25:44 No.882931
>>882842
Go buy you self some 3d printer controller, its chaep realy cheap THX China !!
first in e-bay for example
http://www.ebay.co.uk/itm/3D-Printer-Kit-RAMPS-1-4-MEGA2560-A4988-LCD-12864-Controller-For-Arduino-RepRap-/271949370951?hash=item3f51721647
you will get 5 controllers.
and controlling board ( arduino ) they small A4988 bipolar hybrid drivers can put up to 2Ampers but safe is using them in range up to 1,5A phase and add a cooling fan and mini radiators.
you have 3 axis X Y Z and 2 semi axes E0 E1
Its trivial to reconfigure and reprogram it, then you can use simple g-code to control you robot. add those steppers with gearbox, in case of planetary gearbox 100:1 you even didn't need to keep motor powered in stable position ( at hold ) because reduction in gearbox is so great you really need to have something really heavy on shaft to turn it believe me.
G-Code is easy you can find lots of examples, and the LCD screen give you a option of manual controlling motors too. it's great even it isn't designed to be a robot controler. the same you can use some CNC controler and plug it into PC and control steppers by it.
http://www.ebay.co.uk/itm/4-Axis-Nema23-3-0A-Stepper-Motor-USB-Driver-Board-TB6560-USB-CNC-DIY-Controller-/261121281390?hash=item3ccc0a8d6e

Regards Anon

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Anonymous 2015-10-02 09:37:29 No.882935
>>882842
But why encoder ?
If you have as I'm suggested stepper motors, you know the step angle for most its 1,8 Deg step 200 steps per rev.
of course that's depends how you driving them, full steps / half steps, or some multi-sampling, up to 64 micro-steps per full step you can get great resolution, with great precision, Adding a 100:1 gearbox will reqiure thousand of controling pulses to do full rev on shaft.
(200 * 32 ) * 100
Where 200 its a steps per rev 32 its a micro-steps division, 100 its a gearbox ratio to 1.
640000 pulses need to be generated to do full rev on shaft of gearbox its enough precision ?
Absolute positioning in G-Code require just a simple end switch, Given Axis just trigle the switch and controller note its a home position, and from now its know where is according to it.
You can use linear or radial positioning system, its really handy, you can scale steps in linear mm or inch, or you can switch axis into radial and you will know 100 pulses its that's much of radian.

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Anonymous 2015-10-02 13:38:13 No.882968
>>882935
I need some way to know it's initial position. A 3D printer can just turn each the motor until it hits a limit switch. An arm or other robot can't necessarily turn it's joints linearly until it hits each joint's limit, there are many paths that have to be avoided (e.g. would hit an object).

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Anonymous 2015-10-02 14:43:39 No.882981
>>882968
Theyu Called "End Stops" but they are just a home switches.
There two ways physical limit switches, or software limits.
In your case i will suggest the second approach.
Home switch can be a limit switch but its not a rule it must.
lets say we will use a optical photo-interrupter as pic related. and we instal something on axis to block it in one position something locking as half moon plate, you set it to have home point at 0 deg, then you will set software limits for example at -90, and + 180 deg. then at start you arm will need to make a homing moves depends on it there is a signal from interrupter or not, it need pick correct way of homing because is on - or + side from 0 ( home ).
that you will need to work it by yourself, but it can be easy implemented in code for 3d Printer controller, Because normally you just homing in one direction
here you need to pick direction by reading initial signal from interrupter.

For Robotic arm when you projecting them mechanically you need to set stages of free moments that's simply means all axis has own minimums and maximums witch will at end effect in maximum and minimum area where you can use it ( the whole arm ).
You can design a some stages to be 360 or even limitless ( they can spin in circles ) but construction getting a bit complicated then, a specially cable connection power and signals, they need to be pass by some kind of multi connection commutator.
For a object detection and collision detection its a whole area of complicated code and solutions, witch i will strongly suggest to avoid in building such small arm.. but if you want to know 3d camera its a essential input in algorithm. But there isn't just simply g-code controller its a whole computer attached to it with many sensors, cameras etc.







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