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Topic: Recreating the BMW Kinetic Sculpture? (Read 2980 times) previous topic - next topic

iejun

Found this ....its seems if i use a couple of these i can use 128 servo's

https://www.iprototype.nl/products/robotics/drivers-controllers/servo-controller-8-servos

CrossRoads

Pricey. 6 or 8 or 16 boards will add up.
For the price of a couple of those you could just get a 2nd Mega and do 96 servos.
Or find a less expensive source.
Does provide a convenient way to plug 8 servos in tho.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

iejun

aye ..but then you need to find a way to sync 2 omega boards ..or is that easy done

MarkT

hey all,

I'm trying to create a miniature version (less balls) of this just because it looks cool:

http://www.youtube.com/watch?v=hlx-M53dC7M&feature=related

It looks like they attach string to a ball and then this gets moved up or down on the y axis. Together they create a 3d object.

I  thought about stepper motor to move the balls up and down accurately but they are expensive especially as i would need loads so thats out of the question!!

I then thought of modding some mini servos to have 360 rotation but can't work out if i will be able to still maintain accuracy needed to postion the ball correctly?
There is no accuracy of any kind if you just use a motor (a continuous rotation servo is not a servo, its
a motor + driver).  You would need to sense position or angle somehow.
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Then i thought about standard dc motors with a gearing system and B&W sensors so that as the motor turns it can detect repeating blocks of white and black to detect where it is but thats a little to complicated!
A DC gearmotor with an encoder would work.  Cost is the issue.

What about just using a hobby servo with a long actuator arm and a very light ball on the string?
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Anyway i was wondering if anyone had any ideas on the accuracy of modded servos? can i still position it accurately? Or does this sound like a stepper motor job?
I suspect you could use the potentiometer of a modded servo to keep track of position and turn count
in some rather hacked together way as a crude encoder - probably with a gap on every rotation for a bit!
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

iejun

So Cross and all, I managed to do some tests with the Adafruit 16 ch servo board. Playing around with the functions etc. now in order to calibrate for instance 64 servo's i need 64 sensors to track each ball's movement. Mainly when they all go upwards to calibrate. Now 64 Ultrasones is an option but i think using a IR Infrared sensor that lets the servo stop when he sees the black ball or an other black piece. cheaper and more simple

Would this be a better solution ? and what multiple sensor board could you recomend ?

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