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Continous servo in 3-5 minutes

The GWS servos are extremely easy to modify to continous rotation, here is how :)

Thanks to  for this: http://letsmakerobots.com/node/4873

and to for this:http://letsmakerobots.com/node/259

- Now I had some GWS-servos that I needed to modify for continous rotation, and I thought I was in for a lot of work.. Almost ordered some pre-made, but then I opened one, and found that they are extremely easy to modify!

The last one I modified took only 3 minutes!

First some theory, that I'd like somebody had told me:

Why modify a servo for continious rotation?

Because you get a small geared motor, that you can control by just one output, or a servo-controller. You can set it to "any" speed, and both directions, by just writing a single line, to a single output port.

What's the basic principle?

A servo is a geared motor with a potentiometer attached (see here) How to make your own servo

The servo is turning to what you tell it to by the pulse you send to it, and the potentiometer tells the servo when it is where it should be.

Now, if you hook off the potentiometer, where it is at center position, then:

Tell the servo to be at center position, and nothing happens = motor stop.

Tell the servo to turn a little to one side from center, and the motor turns slowly in that direction, the rest should give itself :)


How to modify the GWS:

Take off any "disc" on top of the servo.


Hook the servo up to your controller, and make it turn to the center.

Unplug the servo, and gently unscrew the 4 top screws.


Gently lift up the middle cogwheel. Gently, because we do not want to turn anything, we know it is placed in center. (If you mess up, no worries, see later)



Gently take off the large cogwheel, and see that it has a brass-like ring inside it (or it falls out :)

This wheel is the one turning the potmeter, and it is this function that we want to bypass.



Take out the ring, and inside it (which is the cool thing!) you'll find a little thingey that is supposed to lock on to the potmeter. Take it out & throw it away.


On the other side of that cogwheel you will find a little stop-thingey. 

Cut that off!


Insert the brass-like ring again.



Inside the top that you took off you'll find 2 small stop-thingeys - cut them off as well. It is quite easy once you have made a couple, I found that cutting down from top, along the side, and then making little cuts along "the roof" made it clean enough, in no time :)

The deal is of course just that the stopper on the wheel and these are cut enough off to enable the wheel to turn freely.


Put back togeter again, and you are done!

Make sure not to turn the potmeter when assambling :)

If you mess up (if you find that at "center" it does not stop completely or makes a slight humming sound), this is how to fix it:

Take it apart again, hook it up to your controller, and let it go to center. While still hooked up, turn the potmeter to the sides, till the motor stops. Put back together, and this time be more careful :P


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Oh! I missed the picture when it is shown how to remove the "little thingey that is supposed to lock on to the potmeter" and thought that it may be still connected to the gears :))

Thanks for the answers!

By mechanically disconnecting the pot, you are basically converting it into two fixed resistors. I have used fixed resistors in mine because I needed more accuracy than I was getting my mechanically centering the pot. Wether you use the potentiometer or build your own fixed potential divider (yes, that's what it's called) makes no difference usually.

New picture, jip?? You're much more pale than I thought....!

Actually it's my original picture from this site (at least I think so... my memory never really serves me very well).