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41
Mechanics and Construction / Re: Pan/Tilt joint
« Last post by mklrobo on July 24, 2015, 02:09:38 PM »
 ;D Hello!
I would offer an opinion, where permissible.
You can follow 2 directions; Yogi beara said, " If you come to a fork in the road, take it".  ;)
If you are designing for  a hobby robot, the stressors in the robot will be specific, and thus,
you will have fun investigating the dynamics of that.
If you are designing a robot for functionality, then I would follow simplicity, reducing
design time, cost, and repair/programming issues.
Have fun, either way you go.  ;D  I have  not given the spine much thought, because I have
chosen to follow a path that did not require the use.(?) However,  ??? maybe there is an advantage
to the addition.
insofaras a suggestion, the study of Statics, physics should give an insight to the Free body diagram
you will need to determine loads, then torques, then motors to drive, then amps.
The Joys of Robotics!   ;D ;D ;D
42
I'd recommend doing what I'm doing - use modeling clay to sculpt parts, then coat the clay in either thread or cloth dipped in glue to form a hard shell.  You can cut the shell in half to remove the clay after and then glue it back together or leave the clay inside if you don't care about the weight.

An interesting idea. You may be able to wash out the clay.

On a related note you may wish to try either burlap (for reinforced strength) or cheesecloth (for details)
43
Mechanics and Construction / Re: Help needed to construct my First Robot
« Last post by cyberjeff on July 24, 2015, 03:38:08 AM »
Hi
Thanks for the tutorial.
Can you tell me how to implement Ackerman steering to my front wheels.
What equipment I need for the wheels to steer using a servo motor.

Ackerman steering appears to be rare in robots. What I suggest you do is look at RC cars where this type of steering is common, and  of course steered by a servo.

I have no interest in RC cars or for that matter wheeled robots but I have a friend who ran RC cars for a while and there is a huge selection of parts for steering gear, it's rather involved. You should be able to adjust your geometry for the length of the vehicle.

Most 4 wheeled robots need some kind of slip to turn sharply with the attention being concentrated on what a robot does and not so much on whether it has efficient steering.
44
Mechanics and Construction / Re: Help needed to construct my First Robot
« Last post by rahavoc on July 23, 2015, 10:15:29 PM »
Hi
Thanks for the tutorial.
Can you tell me how to implement Ackerman steering to my front wheels.
What equipment I need for the wheels to steer using a servo motor.
45
Electronics / Re: Grid Projection on the cheap
« Last post by cyberjeff on July 23, 2015, 06:09:41 PM »
Kinect works with the Raspberry Pi B almost out of the box.  I'm going to give it a try.

My thinking of the moment is to use an Arduino Due for the mechanics and the Pi B for the vision. It would seem possible to run everything on the Pi but I think the Due is easier to use with the mechanics (and i2C), also the Pi will have it's hands full. 

Down the road (and not far down) the Beagle Bone x15 might be a choice.

I've toyed with openCV before on a few devices and have some Arduino experience but robotics is completely new and I have no experience. I don't mind being told if I'm on the wrong track!

At the moment the fun is beating the exasperation, but I know that will change! Everything is theory now, reality will intervene.
46
Electronics / Re: Grid Projection on the cheap
« Last post by cyberjeff on July 23, 2015, 01:54:05 PM »
I've decided against the build your own computer vision.

I found this:

http://www.intorobotics.com/working-with-kinect-3d-sensor-in-robotics-setup-tutorials-applications/

This is the MS Kinect. The API also has speech recognition as well as being able to identify and track objects.

I've got a $34 used one on the way. It takes some horse power to run everything, perhaps:

http://liliputing.com/2013/12/odroid-u3-59-dev-board-with-the-power-of-a-galaxy-s3.html
47
Electronics / Re: Grid Projection on the cheap
« Last post by cyberjeff on July 23, 2015, 12:22:23 PM »
;D Hello!
I would offer an opinion, where permissible.
Yashamanic, on another post, is approaching the problem you indicated from another
point of view. He may solved the problem, but not posted it yet.  - ?  8)


Here is a setup on a beaglebone with structured light from a pico projector ($40 or so eBay)

http://www.hackengineer.com/hardware-overview/

The projectors aren't terribly bright so this would need color filtering to work on something closer to ambient. The article has a nice description on setting up openCV on the Beaglebone, which as I recall, was not trivial.

For my purposes, since my "catbot" is only a foot tall, I just need to know where things are sticking up out of the floor, x distance between vertical lines would be sufficient.

Jeff
48
Electronics / Re: Grid Projection on the cheap
« Last post by cyberjeff on July 23, 2015, 05:20:32 AM »
Quote
Years ago, flea markets used to be awash in cheap laser pointers with interchangeable heads with a wide assortment of designs. So, this can be done, where is it?

You might be able to find something on ebay. I did a quick search and found this:

http://www.ebay.com/itm/New-GREEN-LASER-GRID-PEN-Pointer-Marker-Paranormal-GHOST-HUNTING-tool-/110961982067?pt=LH_DefaultDomain_0&hash=item19d5d97a73

Thanks. Not quite what I want, but it may be the $13 solution for  the $150 part.

Laser patterns are called "structured light" and  is used not only in machine vision but MS  uses it in Kinect, which is their gesture sensor for XBox.

If you scroll down on the page, you will find that the laser can project several different patterns, one of which might suit your need.
49
Electronics / Re: Grid Projection on the cheap
« Last post by FIFO on July 22, 2015, 08:09:35 PM »
Quote
Years ago, flea markets used to be awash in cheap laser pointers with interchangeable heads with a wide assortment of designs. So, this can be done, where is it?

You might be able to find something on ebay. I did a quick search and found this:

http://www.ebay.com/itm/New-GREEN-LASER-GRID-PEN-Pointer-Marker-Paranormal-GHOST-HUNTING-tool-/110961982067?pt=LH_DefaultDomain_0&hash=item19d5d97a73

If you scroll down on the page, you will find that the laser can project several different patterns, one of which might suit your need.
50
Electronics / Re: Grid Projection on the cheap
« Last post by cyberjeff on July 22, 2015, 06:42:13 PM »
;D Hello!
I would offer an opinion, where permissible.
Yashamanic, on another post, is approaching the problem you indicated from another
point of view. He may solved the problem, but not posted it yet.  - ?  8)

Works for me. I have time.

I have no servos yet!

Jeff
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