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61
Mechanics and Construction / Re: micro arm joints
« Last post by johan on May 16, 2013, 03:08:13 PM »
D'oh. It's actually been a while since I've been to this site and I'd forgotten about all the reference material here. That gearology PDF is pretty awesome.
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Mechanics and Construction / Re: micro arm joints
« Last post by johan on May 16, 2013, 02:52:26 PM »
Thank you very much, appreciate the response. Your methodology for making this, with motor last, makes a lot of sense. I'll go away and study the links etc - I have to say it's surprising that t'interwebs doesn't have some sort of wizard or findable explanatory site about combining motors, gearings and bearings!
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Electronics / Re: PCB design problems
« Last post by felipe80 on May 16, 2013, 02:07:25 PM »
For Pad size calculation use this formula.
Minimum Pad size, P = (2 x R) + FA + D
P = Pad size, R = Annular ring, FA = Fabrication allowance, D = Drill or tool diameter

For hobby level PCB design, add 1 to 2 mm to drill size to get the Pad size. 
64
Electronics / Re: H bridge voltage drop
« Last post by felipe80 on May 16, 2013, 01:50:28 PM »
A separate supply voltage VCC1 is provided for the logic input circuits to minimize device power dissipation. Supply voltage VCC2 is used for the output circuits
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Electronics / Re: DC Power Supplies
« Last post by felipe80 on May 16, 2013, 01:49:02 PM »
Normally we look for power supply with following features: Output voltage of 0 to 30V which is preferably adjustable. Current output should be at least 5A or more with current controlling option, short circuit protection, and thermal shutdown. It should be light weight and of small size.
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Software / Re: My first little PID: please comment
« Last post by jkerns on May 16, 2013, 01:09:43 PM »
You can translate your desired speed to the necessary pulse duration or pulses per second (which ever fits the time scale of your controller). Or, you can take the pulse duration / rate and convert it to speed.  And away you go.
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Electronics / Re: LM393 hysteresis calculation vs real circuit
« Last post by jwatte on May 16, 2013, 01:06:43 PM »
When looking at your circuit, consider the equilibrium states when output is high, and output is low.

High: Effective 50 kOhm pull-up; 100 kOhm pull-down, so 8V input to +. - would have to go above 8V to turn off.
Low: Effective 100 kOhm pull-up; 50 kOhm pull-down, so 4V input to +. - would have to go below 4V to turn on.
Thus, your calculations seem accurate.

Why would this particular circuit not behave correctly? I don't know exaclty, but maybe the current drive provided by the 100 kOhm resistors is not sufficient. Try 10 kOhm resistors instead. That may still not be enough for properly driving BJT transistors -- 5 mA seems to be a magic place, so perhaps you should actually try 2 kOhm resistors instead of 100 kOhm resistors.

From what I've found, a comparator is just like an opamp, except with worse performance. I'd use a rail-to-rail single-ended opamp rather than a comparator.
68
Robot Videos / Re: My first humanoid robot
« Last post by jwatte on May 16, 2013, 01:00:02 PM »
That looks like a lot of fun!
Does it need to tilt all the way to the side when it's actually walking, or is there some other way to lift the legs?
69
Software / Re: how to access on database?
« Last post by jwatte on May 16, 2013, 12:56:51 PM »
Where do the images come from?
How are they returned back to users?
What have you tried, and why didn't that work?
What errors are you getting?

Right now, your question sounds a lot like "I've tried nothing, and am all out of ideas."
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Mechanics and Construction / Re: micro arm joints
« Last post by jwatte on May 16, 2013, 12:55:48 PM »
You don't want the worm gear to have any lateral force -- it's not a structural, holding, kind of assembly.
Thus, you need a bearing of some sort for the rotating/pivoting action of the arm.
Once you have that, attach the worm gear to the rotating arm, and mount the worm leadscrew on the holding arm so that it properly contacts the gear, and then mount the motor so it drives the worm screw.
I've seen a number of worm screw/gears online at sdp-si.com; you may want to try that too.
Anti-backlash worm gears: https://sdp-si.com/eStore/Catalog/Group/210
Mating worms (screws) to those gears: https://sdp-si.com/eStore/Catalog/Group/211

Two other options I would look at:
1) Existing robot arms. For example, Trossen Robotics have a number of arms of different capacity. They will need some power for holding objects, but they are a ready-made solution.
2) Orbiting the camera around the object instead of the object in front of the camera.
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