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Multiple Servos

(Peter Graven) #1

Using the Pixhawk and Raspberry Pi… anyone using additional servos beyond a camera servo?

Not sure if settings for Servo are quite right
(Rusty) #2

Hi Peter,

It’s possible to add more servos right now but we don’t have a simple way to set up control of them. Can you tell me how you would like to use the servos so that we’ve got a better idea of how they might be controlled?


(Peter Graven) #3

I have students looking to add a (one servo) gripper with an additional degree of movement using an additional servo.

(Tim Pierce) #4

Auxiliary ports 1 through 4 on the pixhawk should theoretically allow servo hookups. 5 and 6 are apparently different. I plan on also splithing the existing camera servo output to control a second light panning servo, but your student could use that to get an additional axis sort of?

(Jacob) #5

We have recently added some buttons that can be configured to step up to three servos on Aux ports 1-3, but the implementation of this is subject to change. We need to figure out what works best for all applications.


(Tim Pierce) #6

I’m pretty sure that most people adding a robot arm are going to want a Gripper open, gripper close button. For my application I would also want a “rotate arm clockwise, counterclockwise” and “tilt arm up or down” buttons, and a “switch auxiliary camera input from 1 to 2 to 3” channel using this multi camera switcher http://www.readymaderc.com/store/index.php?main_page=product_info&products_id=1283 . which I’m guessing most people will not have. The intent there is to have 3 lower quality auxiliary cameras (https://hobbyking.com/en_us/mini-cmos-fpv-camera-520tvl-120deg-field-of-vision-0-008lux-14-x-14-x-29mm-ntsc.html) I can cycle through to watch the back of the ROV, the down view (for landings) and possibly a 3rd one to watch the arm from a different angle than the main camera.

(Enrique) #7

This is an interesting feature. It would be nice to add also additional axes, since there are several gamepads (such as F310) with 6 axes

(Altum Operations) #8

Our team would be using this type of robotic arm with two servos, so would we use the multi-camera switcher to swap which servo we would be controlling? Or would we be able to swap which one we would be controlling using QGroundControl?

Emma Hagen
CEO and CFO of Altum Operations

(Tim Pierce) #9

My battery charger hasn’t arrived yet so I can’t confirm, but that camera switcher doesn’t switch servo Inputs. Just video feeds. There may also be a similar servo Input swapping device out there though

If there was one more servo channel available I’d add another arm axis.

(Altum Operations) #10

I think what she means is the camera tab in QGroundControl where you set up the servos for the camera tilt/pan. Would there be a way to control multiple servos using the “camera servo” function even if not for a camera and if they are “standard” servos not micro?

Tobin Cox
Electronics and Software engineer of Altum Operations

(Tim Pierce) #11

you can split the signal to that servo with a Y splitter as long as you don’t need the full current. I’m actually going to do that with the existing camera tilt servo and my lightbar pointer servo in the tertiary hull down below.

(Altum Operations) #12

But if you tried to control it that way, wouldn’t it just control the two at the same time, both doing the same thing? We would want ours to be independent of one another in terms of when they turn and how far they turn.

Emma Hagen
CEO and CFO of Altum Operations

(Altum Operations) #13

Would they be configured as motors, camera servo gimbals, or something else?

Emma Hagen
CEO and CFO of Altum Operations

(Jacob) #14

They would be set up as general-purpose servos, and joystick buttons would be set up to open/close or increment the servo angle.


(Jacob) #15

The problem here, is that the MANUAL_CONTROL message only provides 4 axes. We will need to make a new mavlink message to support this. This is something that may happen in the future, and would definitely be useful concerning controlling a robotic arm.