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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, sh*t, I forgot to have LMR-logo / URL on the pictures, argh! Sorry guys, I only remember it on the videos, damn, will do it next time!
If you file a slot into the pot shaft end, you can re-adjust the pot center by inserting a precision screwdriver down where the servo horn screw goes, without disassembling the servo.

Now that would be very hard :) Since the thing will be turning around the screwdriver, and you want to make very small ajustments :) But sure, it could be done.

I just made 5 servos, and only one I had to disasamble, and re-ajust, 4 screws off / on, no problem, I think it was a lot easier than filing slots in the all the potmeters, and trying to fit down a screwdriver etc.

But thanks for the input!

Actually, if you really wanted to insert the screwdriver into the hole, I think you would not need to file a slot first, as the potmeter gose so easy, just pressing and turning would do..

I still prefer just taking it apart and tuning it :)

Another mod I'd seen, was to drill a hole in the side servo, and point the pot shaft out through it for adjustment if needed.

F, I can't see node 1524.

PS - Get some friggin' sleep, dude. There's a whole lot more posts to read in the morning.

Feel free to delete this msg.

Thanks frits, I bought a gws mini servo a little while ago and this helps heaps. A big thankyou.

I just modified a towerpro sg-5010 in 5 minutes... many thanks! :D


[Edit] and i just did another one ^^

Sorry for stupid question...

But isn't it necessary to replace potentiometer with constant resistors?

You don't need to do that if you just make sure the potmeter is at its center position and take out the things that make it turn.