# Can your turret always rotate in one diretion?

Our team is using a turret. And l wonder whether a turret can rotate in one direction all the time. In this way, l just don’e need to limit the angle range available. Our team doesn’t have any experience of turret. Any answer is appreciated!

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Yes but no. There are wires that must power it that, unless cleverly designed, will eventually tangle and tear/break. Hence a bunch of turrets will have hardstops that will physically prevent rotation of more than a certain amount of degrees (less than 360 deg).

I also don’t see a reason for this, though…

I’d look at 254’s turret for more info and a better dive into turrets.

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While a turret without a limited angle is ideal, it is difficult to make work. The big limiting factor is cable length. Any cables going to motors or sensors on the turret need to be either really long or non existent because wires can’t just wrap around the turret indefinitely as you turn it in the same direction for the entire match. On my team’s 2020/2021 robot we could only turn out turret ~90 degrees to either side because of the cable length. Most elite teams with fancy mechanical systems to deal with this problem usually have a hard time getting more than one full rotation.

This year team 1690 managed to get about 400 degrees of rotation out of their turret.

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I got about 540 degrees of rotation out of our turret, but that involved long wires and a lot of hitting my head against the wall. It still isnt great though, but it sorta works.

Thanks, what is your basic method to write a turret program?

I have not written the code for it (i just designed it – large team) but I do know the sensors on it:

We have a NEO 550 and hence a motor encoder. We have a limit switch to center the rotation so we know it starts at 0* and not 1* or something off.

We used to just have mechanical hardstops (ie it would turn until it hit something and then the motor would just fight that – i’d assume you could detect that with your encoder and tell it to stop) but now we’re also adding magnetic limit switches but idk if they’re necessary. They tell us right before we hit the metal hardstops.

So I assume a lot of it has to do with the encoder itself. However, be wary of where your encoder is. Ours is on the motor, not the actual rotating disk. We’re using gears, so there is slop involved and I believe that is made worse by gear reductions (or is it the other way around, or for both?).

My recommendation would be to look around for a github for a team that has released their code from a year prior to understand their basic logic.

We do happen to have our code public: here. (I just realized.) However, I’m not sure if the code is completed. I have seen it run successfully but I’m not on the software side so, yeah.

It is possible, or used to be. In high school my team used a slip ring to give full rotation.

Turret Rotation Video from 2012.

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Note that, even if you do implement slip rings or some mechanical solution (e.g. like a swerve drive with a shooter wheel instead of a drive wheel), only being able to rotate one direction will significantly impact your ability to target the goal.

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Have you ever used AFX cars? Similar mechanisms are used in industry (eg transmitting electricity to a spinning propeller head) where a circle of contacts and brushes transmit power to a rotating system.
Using this sort of mechanism, it is theoretically possible to get infinite degrees of rotation. But in practice, it is far too complex to be worthwhile.

l do use a swerve drive but how can l do this? l think should open a new topic about the logic of writing a turret program.

I haven’t seen anyone do this, just raising it as a possibility. I doubt that a COTS swerve drive could be adapted to this, especially as most turrets are designed for the launched object to pass through the main bearing, and swerve drive modules are smaller than this year’s game piece. I was just referring to a system where the motor which powers the wheel is on the fixed side of the rotating turret. In this case, the wheel torque would likely be delivered via a ring gear rather than along the swerve/turret’s axis of rotation.

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