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How do I monitor an angle?

Former Member

Hi all,

 

To say that I am new to robotics would be an understatement.  My first "mini project" is putting a camcorder on a turntable-style bearing.  The turntable has (will have) wires fed through the center, so I would like to limit the movement of the turntable to 360 degrees in order to avoid twisting up the wires.  I would also like to be able to find out the exact angle in which the camcorder is pointing so that I can chart the angle in an application.  From the searches I've done, it seems like the right tool is a absolute position encoder.  Am I on the right track?  Can anyone recommend a good product that I could use in conjunction with a turntable?

 

Thanks!

Parents

  • I was working on the same question for my rov, since the theter cable cannot twist... You did not mention what type of micro you're using, if you use an avr, I can send you the library for reading one electronic compass module, you did not mention what type of motor are you using, (if you use a stepper, you can count the steps) also the most simple solution is the use of an hobby servo that has it's own encoder, but only does like 340 degrees of turn).

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  • I was working on the same question for my rov, since the theter cable cannot twist... You did not mention what type of micro you're using, if you use an avr, I can send you the library for reading one electronic compass module, you did not mention what type of motor are you using, (if you use a stepper, you can count the steps) also the most simple solution is the use of an hobby servo that has it's own encoder, but only does like 340 degrees of turn).

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  • in reply to Former Member

    About hoby servos, I havn't used may of them, but as I kow, there are continiuos rotation and 180 (usualy bit more the 180) deg servos. never seen something like 340 deg. Can you give me some samples? Sometimes it is realy goot to have more then 180 deg rotation servos image

    About steppers, Yes, you can cant your steps and depeding on mow much you table turns from one stem you can calculate current possition. but for that juo have to have a sensor for 0 pozition. because application can lounch at anny position. So for zero possision detection you need a back swich or better optical bariar to detect that possition and make an auto callibration function at application start image

     

    Composs is good way too, but it is sensetive to metal parts around and magnetical or electromagnetical noice. I remember my last Robot Intelect 2012 competition in Kaunas, and ve hade problams with composs becouse it reacted at metal stage parts and speaker electromagnetical wawes image robot got crazy and started dancing (turning left and right all the time) image

    So sometimes simplest solution is the best. image

  • in reply to Ramu

    I agree with aurel that the stepper motor is the easiest.

    If you use a hall effect switch with a magnet on the turntable you can easily calibrate/reset to 'zero'.

    (There other reliable options, but this is the easiest)

     

    Servos basically turn a pot inside, this matches the incoming pulse width, and therefore stops rotating.

    Continuous rotation basically never turn the pot.

     

    You can make your own servos, and I once had a link for a very large one, but I have lost it......sorry.

     

    Some of these might interest you http://www.openservo.com/StepByStep

     

     

     

    Cheers

    Mark