Low Cost Hobby Servo XY Table

Step 6 Modify the Servos for Continuous Rotation and Remove the Potentiometer

We won't go into too much detail on hacking a servo for continuous rotation - there are plenty of sites on the web, and Instructables too. Some servos are easier, and if it looks tricky, ServoCity sells modified servos with the potentiometer outside already. For the HS-6965HBs, we pulled the gears, then popped the motor down by wedging a tiny screwdriver between the motor gear and the housing to force it down. We then removed the pot and pulled the wires out through a small hole we drilled in the case. We have no idea if this is the proper way to do it. The HS-425BBs we originally used were even easier since the circuit board comes right out.

In both cases, we also cut off the limiting tab on the main gear. We used a Dremel tool for this - but we had to clean it well after that.

(June 2009) Note that for the Y axis (the one on top), the servo motor is working fine, but for the X axis, we have had some issues. So the current system is using a
Pololu 3A Motor Controller with Feedback and a 12VDC 250RPM DC Gearhead Motor. The board from Pololu works just like a servo control board, and we already have the external potentiometer. The motor is much more robust, and has been working well. One minor issue is that the PID algorithm sometimes overshoots a bit, but it's not too much, and the board allows you to set the PID constants - just need time for fiddling. :-) You can also use a servo board and adapt it for the same use - we'll look into that sometime too.