Steps to setup an external servo on a 2.7?


#1

I currently have the six extra wires potted through the endcap free, is powering/controlling a servo with these feasible? I plan to use the servo operate a claw. I am a novice as far as the electronics and coding but imagine connecting the servo to those cables and any wiring on the boards would be similar to things done building the 2.7 from a kit and that I could copy the servo controls for the camera servo without too much effort. Any assistance or tips would be greatly appreciated.

Thank you,

Chan


#2

@codewithpassion has a plugin that he has been testing to enable servo control with the extra channels without having to code anything. Getting that would be the simplest solution.


#3

I would imagine my first steps would be to solder and heat shrink the servo wires for ground, power and control to 3 of the spare wires and use a multimeter to see where those wires connect on the board(unless the cables are marked in some way I hadn’t noticed). after that I am at a loss, would one option presuming no additional coding or plugin use be to wire wherever the extras wires connect to a servo connector and plug that in in place of the camera connector? Additionally where should I expect those 6 wires to be on the board?


#4

I’m not familiar with the plug-in referenced above, but for the hardware you’ll need to do a little work. You may want to see what the plug-in expects for a hardware configuration before modifying anything.

With that said, I think you’re on the right track. I believe what you need to do is trace your free wires at the end of the harness to whichever test points you want to use, e.g. 20, 21, and 22.

The test point pads on the PWB are the end of your lines. Once you know which test points you’ll use, I think you’d solder wires to the test points and run the other ends to the servo connectors near where the ESCs and camera servo plug in. If you’re a stock 2.7 right now there should be two available servo connections between the ESCs and camera servo connectors.

Once you do that, the software needs to drive it. I think that’s where the plug-in would come into play.

Hope this helps,
Lenny


#5

Chan:

You can download the schematic for the 2.7 Controller board off of our Github site. Follow the tabs on the top of the page for OpenSource/Electronics.

As Lenny says, the six spare wires terminate on the board right by the main connector, at the six test points marked TP20-TP25. To hook up an external servo, you’ll need to pick three of the spare wires. mark them as Ground, Power (BEC), and Signal, and then use a multimeter to see which test pads they are at on your Controller board. Then you will need to run wires from those test points to the appropriate Servo Output pins. As you mentioned, if you use a 3-pin servo connector (you can cut one off of a scrap ESC or servo), then you will be able to just plug this into one of the servo channel connectors. Use the camera port (D11) if you don’t want to write any new software, or you can use one of the spare ports (D9 or D10) if you want to write you own or use Dominik’s plugin.

Hope this helps.

-W


#6

I would like to thank everyone for their help and tips. I still don’t have the second servo plugin to play with but I did set it up in such a way that I was able to disconnect the camera servo and connect the grabber. I haven’t played around with where I am going to mount the grabber yet but was able to test and everything seems to be working great so far. Video of the test is available at: https://www.youtube.com/watch?v=OmFDCih7qCA&

Thanks again


#7

UPDATE-Got the grabber mounted via some go pro mounts a broken piece of fishing pole and some other odds and ends. Tested in salt water and turns out the servo is either not actually very waterproof or more likely the servo is not waterproof at depth as the servo stopped working completely, back to the drawing board for the grabber.


#8

Chan, at least you got out there and experimented. The OpenROV team has been working on a more robust waterproof servo that should be in the store soon.