Infinite Rotation

So I don’t need to use this for anything, but I was curious: Is it possible to have an infinitely rotational system in Vex, where there are wires/sensors on the other end? Like having the top half of a robot mounted on a turntable, motors on the top and bottom with the microcontroller on one half, and able to spin the top/turret of the robot constantly in one direction for over 2 minutes/indefinitely. Any ideas?

Why would you do this?
Why not just turn the whole robot? Like we have wheels for a reason

Do you mean a never-ending rotation kind of thing?

To make this legally in VEX would be impossible at least in HS. College might be doable but you need to take into consideration lots of safety precautions, because you will have exposed wire leads. Basically the device you want to make is called a slip ring. They have lots of different kinds of them from liquid, air and even to electrical slip rings. They allow a single input of current or pressure in one spot to rotate freely infinitely around a point and have it come out the other side with no tangling or snagging of wires. Quite useful IMO but a heck of a lot of work to make a custom one for Competition Robotics Purposes. That being said it has been done in the realm of FRC by two teams I know of. Team 190 and team PWNAGE (forget new number sorry Nick).

To build one in VEX the device itself would be very inefficient I think. Considering you would rely on the current you can get through Aluminum or Steel which are not nearly as conductive as Copper as we all know. Perhaps Nick could expound upon his Slip Ring design that he did over the summer.

  • Andrew

the tank robot we have can move the turret infinitely but the turret portion has a second microcontroller on it so that would not be competition legal.

If there are only motors on one half, you could easily build a few drums of standoffs that transfer the power mechanically across the joint.

Let’s say, for example, you want to have two parts to your robot: the top manipulator and the bottom drive base. You would put the microcontroller on the top with all the motors and sensors.
For the drive base motors, simply have a left and a right side shaft running through the center of rotation of the robot, and mount your encoders for the drive base on the shafts on the upper portion of the robot. Put an encoder on your big turntable thing, and do some programming magic (subtraction) to find the actual rotations of your drive base wheels.

That’s the only way I would know how to do it in VEX. Slip rings would be all kinds of bad and cause all kinds of more bad in VEX.

If it does not have to be competition-legal, you could use two controllers.

You would be able to run them independently, but controllers wouldn’t be able to transmit information, unless you had some sort of wireless communication device between the halves, and then got it to work with the microcontroller (which is probably doable, but I wouldn’t know).

Slip rings would work for motors, although I think I heard from someone in electrical engineering that it probably has too much noise for sensors (sensitive ones, I presume).

pre-vexnet era
ratio receivers with the same crystal channel
Gladstone 721 TBA did this once as a side project thing

I know ROBOTC had a couple of robots using the XBee on display at Worlds last year. Info on XBee:

Wouldn’t drilling a hole in the vex turntable bearings work because all you need is the wires to follow the joint perfectly and you can then spin infinitely.
Edit (I just looked at the turntables and realized the larger size has a big hole in the middle. Wouldn’t this suffice?)

Couldn’t you also have a bunch of wire extensions wrapped around the winch and pulley piece with some sort of elastic powering so that it only had as much cable as you needed.

But you can only twist the wires so much before they break…

just mount the top half on top of a turn table and gear down the motors for more torque

slip rings would be the only way to do an Infinite Rotation machine as you describe

Now there is a New Vex Part Idea, a Turntable Bearing Kit with Built-In Slip-Rings…

If you could connect the wires via the axis of rotation you could use a jack plug and socket…although I only think they go up to 4 pole…

That would work for the Short Term, but would wear out after prolonged usage…

Right, you really want a slip-ring for this type of application.

The AdaFruit site has a few that are well-sized for use with Vex. (6-wire) (12-wire)


  • Dean