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Topic: Options for camera gimball control using Arduino (Read 2889 times) previous topic - next topic

stef_stuntpiloot

Hello, I'm new here on this forum and got kind of intimidated about the large amount of information
that is present. I am kind of new to arduino allthough I have allready used it in my multicopters. This
is also the reason why I started this thread because:

I would like to control a gimbal for a camera ( that is possible and not that hard to accomplish)
but not using regulair servo's but stepper motors. I want to do this because I see better results
in gimbals that use steppermotors.

Is this idea possible, and is it possible to accomplish for a novice such as myself?

Thanks in advance for your help!

johnwasser

Yes, it is entirely possible.

You can drive a unipolar (5 of 6 wire) stepper with some simple buffers like the ULN2004.  For a bipolar (4-pin) stepper motor you will need a Quad H-bridge motor control shield (2 H-bridges per stepper).

You might want to use small geared steppers because you don't need really high speed but you do need enough torque that you don't miss steps.

You might also want some kind of index sensors so that you can recover from a power failure.  Without some way to sense a 'home' position you won't be able to get to an absolute position, only relative.
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stef_stuntpiloot

Hello John,

Thank you for your reply, It's good to know that it is possible, Can I use the multiwii code and board as a basic? this allready contains the code for
the stabilisation using a ITG3205 3-axis MEMS gyro and BMA180 3-axis acceleration sensor installed on this board:
http://www.goodluckbuy.com/crius-upgrade-version-multiwii-standard-edition-flight-controller-v1-0-se.html

This board is capable of controlling servo's as it is. as you can see in this video:
http://www.youtube.com/watch?v=Nzxhb9VodvQ

I am trying to accomplish this:
http://www.youtube.com/watch?v=vrtLS4kc_xI

Thanks again!

johnwasser

Are you saying that you want to take the PITCH and ROLL servo outputs of the MultiWii flight controller and use an Arduino to translate those signals to stepper-motor controls?
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stef_stuntpiloot

Well that's the point, I dont know if that's necessary. This multiwii controller uses Arduino as well right?
I tought it would be compatible in some way and that it might even be possible to connect this ULN2004 that
you talked about straight to this board.

So I guess the answer to your question is yes.

johnwasser

You need at least two output pins to control each stepper.  You only need 1 for a servo.  Do you know if you have output pins to spare?  If you want to be able to recover automatically from a power failure or reset you will probably need one more pin for the home sensor/switch.

The second video seemed to be showing 3-axis stabilization.  That would require a YAW output from the controller.
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stef_stuntpiloot

Exactly it does have 3axis stabilisation, this would be perfect especially if it is possible
to turn it off in flight but pitch and roll first. If I can get that to work it would be great.

So to recap:
I need a gyro/accelerometer (this can be used from the multiwii controller board)
I need a ULN2004 or Quad Hbridge depending on the type of steppermotor used.
I can connect these together but do need to programm it to get it to actually work together.

Is this correct?

The gimball will be perfectly balanced so the force needed from the motor's won't be to high,
it does need to be able to accelerate fast and smooth (as seen in the second video)

The multiwii controller has loads of inputs and exits, woud it be possible to reconfigure the
outputs to match these output pins that you talked about?

My Apologies for the large amount of questions. I'm kind of a newbie, getting it working smooth
with servo's was a big step for me, reprogramming this to accomodate steppermotor for me
quite a big project.

If I am correct I should be able to reconfigure the outputs of the MW board using the arduino tool
and connect it to the steppermotor controller and steppermotor. Do I need to program this steppermotor
controller? or is it just a sort of translator?

stef_stuntpiloot

Another idea, maybe it´s more easy to control a brushless motor such as the one in this link:

http://www.maxonmotor.com/maxon/view/catalog/

This motor is also used in the second video that I posted.

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