Converting servos 360 degree continuous rotation

[SmallHaul]

Not sure if this the right place to post this. It would be cool if we had a general "Tips, Trix & FaQ's" section.

Some people have asked me about converting servos to 360 degree continuous rotation so, I thought I would give explaining it a shot.

Think of a servo as a 200:1 gearbox that has a potentiometer (pot) that turns with the final output shaft and the shaft has a physical "stop" on it so that it can only rotate 180 degrees or so and there is an electronic speed control that is regulated by the position of the pot.

Now to convert the servo so that it runs continuously to be a winch or to drive a wheel You need to do 3 things.

1) Remove the physical stop that prevents the servo from rotating continuously. On metal gear servos there is usually a metal pin stuck in the output gear that needs to be pulled out or cut off. Most servos with plastic gears just have a little plastic nub that needs to be cut off.

2) Eliminate the physical connection between the pot and the output gear. Some servos are easy to do this because they have a little clip inside the output gear that the pot shaft sits in that moves it. On a servo with a clip you just push the clip out through the bottom and that step is done. Some mini & micro servos are more difficult though because the pot shaft is what the main output gear actually rides on. So, in this case the end of the pot shaft will be keyed. You just need to cut the keyed end off but, MAKE SURE you don't let the shaft get hot enough to melt or damage the pot or its mount! Make sure the servos runs smoothly before final assembly to make sure you didn't cause the gears to bind at all when you cut the pot shaft.

3) Lock the pot into one position. power the servo up and set your trim on your radio to neutral then rotate the pot until the servo motor stops turning. Then glue the pot shaft so that it won't move.

Here is a link to pictures that might explain it better:

http://www.societyofrobots.com/actua...ifyservo.shtml

If you have any old or week servos laying around take them apart and convert them for practice.

Good luck!

[doodlebug]

Hey small haul, the link get's me to the site, and an error 404 message popped up. So I just clicked "accuator's on the left side of the page, and it came up that way. Had the same problem with radio shack tonight. Thank's for the info! Later, Neil#2 aka doodlebug.

[SmallHaul]

Thanks Neil, I fixed the link.

[doodlebug]

Yer welcome!

[D8R]

Thanks for description,
Dan

[9W Monighan]

I think if you eliminate the pot and solder two 5K resisters in the place of the pot. This would keep it centered.
I used 3 hacked servos to control my 90V motor drives on the dragline but removed the motors soldered leads then manually centered the pots. This gave me a cheap ESC. This worked fine until somebody would tamper with their setting as we found out last year at Cabin Fever.