Hey all, first I wasn’t sure what thread to post on.
What I’m looking to do is use a pixhawk to control my trolling motor. I’ve got down how to do forward and reverse. But I’m not sure how I should go about setting up a stepper motor for turning the trolling motor or some kind of linear actuator. Any suggestions would be greatly appreciated!
Use a RC servo motor, not a stepper.
Just go for a waterproof jumbo servo to which I would add a king of mechanical fail-safe on the servo/rudder axis.
Tested those one years ago : Turnigy TGY58166M more than enough for just rotating a trolling motor around its axis, you will certainly need some bearings and perfect axis alignment thought.
Agree with @space_sailor . Linear actuators have been used but performance is typically poor. In most cases they have been replaced with a large servo. A servo “motor” if used would require a position feedback sensor of some type.
mat, thanks so much for your advice and recommendations!
The servo I use I really want to be high quality, I’ve used so many cheap servos over the years in my rc gear but nothing really “solid”. With that in mind would you still recommend the Turnigy TGY58166M?
as for the “mechanism” to actually connect to the shaft of trolling motor how would you recommend going about that?
also you mentioned bearings and a perfect axis alignment, could you explain more?
Thank you SO MUCH for your time!
Dave thanks for your feedback,
looking at position feedback sensors online, would there be a combo of servo and position sensor you could point me in the direction of?
With a standard Servo you don’t need a position sensor. A Servo Motor, typically continuous rotation, you would need one.
So after looking endlessly I think I’m going to be using this Steering bracket for trolling motors to attach to a servo…or am what i needing is a servo motor? I’m sorry, I am confused.
The servos we are talking about are of this type. This one happens to be large and waterproof:
that looks beefy enough!
what kind of rod can i use to go from the servo horn (i think thats what its called) to the steering columm piece i linked?
I think some stainless clevis rod ends would work if the servo horn is on the same plane as the steering bracket. Or a ball joint link if it’s not. Threaded rod between them.
Depending on what horns are supplied with the servo perhaps you will have to fabricate an adapter on the servo as horns tend to have holes for M3 hardware.
Perfect, I can have them on the same plane I have to make a bracket anyways.
Any idea of how to step down the voltage from my 12v marine deep cycle battery to 4.8 ~ 8.4 (the voltage for the servo y’all recommended from data sheet)?
It does look like they’re holes for m3’s I’ll google about the horn.
For that servo I see a Stall current of 10A! Pololu has some 7.5V out high current buck regulators.
Like this one:
Dave, you’ve been invaluable in this process my brother. I googled and have no idea what a stall current is still. Does this essentially mean the servo draws 10A when it moves?
No, if it’s stalled or prevented from turning while driven. This is worst case which is what you plan for with electronics!
ohh ok so if hypothetically the servo is trying to turn the trolling motor but the motor is stuck against an object and it cant move at that point. Then the servo will draw a max of 10A?
I suspect i should use a fuse, after the dc stepdown? or is that not needed in these servos?
You could use a fuse. It’s difficult to say how much current it will draw under max steering load which I suppose would be at max accleration/speed. You’ll just have to try it out!
hey guys sorry got busy and I see that Dave helped a lot !
A mechanical fuse might be the best to protect the electronics of the servo as well as the gears etc in case of something geting stuck or a shock that will certainly happen at some point anyway.
The mechanical fuse is configured to break upon exertion of a predetermined force, was used on small propellers and avoided exploding the propellers in case of an underwater shock.
A torque limiter shall do the job as well with the advantage of not breaking any parts (fuse) How do ball detent torque limiters work and when are they used?
This is excellent advice. I have such a device on my Rover. The plastic spur gear fails quickly when the vehicle is stalled under load and they are cheap to replace! It’s driven by a brass pinion which strips it.
I have build motor mount for my inflatable canoe. Trolling motor is old MinnKota and it is steered by cheap giant RC servo. MinnKota is set to FWD speed 5 and connected to Traxxas Brushed ESC. Both are connected to Matek F405-WING running Ardurover.
Biggest challenge was to fix servo on trolling motor and keep tilting mechanism working and keep oportunity to quickly pull motor out of water in case of emergency. What I have build is not pretty and look kind of convoluted but it works.
Unfortunately default PIDs are not working for this setup so I have not yet made an autonomous journey.
When I get home I will post more images and information.