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Topic: sort of delta robot/polygraph (Read 2 times) previous topic - next topic

Boffin1

well with each angle of the tripod changing with each step, lets see if anyone can come up with a formula :-)
With my mobile phone I can call people and talk to them -  how smart can you get ?

kerimil

It is possible - trust me

but...
I can barely understand trigonometry in 2d... so 3d is out of my league

justone

The tube being fixed at one end and the other end of the tube moves then the moving end becomes a point on a sphere.

Look into spherical to rectangular conversion.

justjed

I think I would punt and either:
* determine it empirically by driving the motor n steps and measuring the angle before and after, or
* use servos instead of stepper motors. servos are already designed to go to angle X and stay there.

OTOH, I don't see a huge math problem here. You just want to determine degrees of rotation?

So, imagine a 180 step stepper motor. So each step is 2 degrees. If you want 0.5 degree per step, then you'll need a 1:4 drive ratio.

Here are some stepper motors. Note these are all 1.8 degree steps. Or, you could by a 20-step per turn motor, then each step is 360/20 degrees -- for that, 1:20 drive ratio would get you 1 degree per step.

http://www.hansen-motor.com/step-motor-19.php -- 7.5 and 15 degree steppers. You can also get steppers with attached reduction gearboxes.

This is just multiplication and division, to determine how many degrees you get, based on your drive ratio.
... it is poor civic hygiene to install technologies that could someday
facilitate a police state. -- Bruce Schneier

kerimil

Thx for all the replies but you've been wrong. I think I know how to do it.
The best thing I can do is to model the entire setup in 3D using processing - keeping all the dimensions... that is I've got to setup up a gun model that can move to set elecation and azimuth and then use dist function to get distance from the barrel breacket where the wires are attached to both the step motors

I know it's kind of retarded but it will work, so I am fcking happy and feel damn intelligent (while feeling kind of dumb for not being able to come up with a formula) :-D

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