Has anybody tried this with a servo?

[alpacaman]

A servo has an internal pot which turns as the motor turn and senses the motors position. The mechanical stop protects the pot from being turned beyond it's limits.
Has anyone removed the mechanical stops and the pot. Then wire the pot back into the servo with extended wires?
Seems to me that if you then send the servo a servo command of say 150 the motor would turn until you physically turn the pot to it's middle (150) position. You can make the motor turn in either direction, for as many turns as you want, by simply turning the pot in either directions from middle. The motor would stop where ever you want it to. All with a single command from the picaxe.

 

[BeanieBots]

This is an age-old hack done by many roboteers.
Look it up on Goggle, "servo hack".
It can be used to give proportional forward/reverse drive using the servo command.

I once replaced the pot (internally) with a ten turn version.
It worked but there was very little torque and considerable hysterisis close to the 'demand' position. Other than that, a very simple and cheap alternative to a 'winch' servo.

 

[Wrenow]

Actually, what you are talking about is done here:http://www.servocity.com/html/spg425a_standard_rotation.html
They have many models available, including a multiple turn version like BB mentioned http://www.servocity.com/html/spg400a-bm-mr_multi-rotation.html (though it is more expensive than the Hitec sail-winch servo, which I have found on sale for less than the current USD$39.95 http://www.servocity.com/html/hs-785hb_3_5_rotations.html at times.

Cheers,

Wreno

 

[Andrew Cowan]

I have also done the pot mod - relacing the standard pot with a 20 turn version.

As long as you can live with a very vague centrepoint, it is great.

A