In this instructable I well show you how to modify a Futaba S3001 dual ball bearing servo for continuous rotation. Why you might ask, you can get already modified servos from Parralax? Two reasons, one I like to tinker with things and two my local hobby shop had a box of these for $15 each so I probably saved a couple of dollars by not having to pay for shipping.
Step 1: Materials and Tools
1 - Futaba S3001 servo
- #1 Phillips screwdriver
- Dremal with a cutoff wheel
- Needle nose pliers
Step 2: Disassemble
Lets begin by disassembling the servo:
1) Use the screwdriver to remove the four screws holding the servo casing together.
2) Gently separate the two halves of the case being careful not to lose any of the pieces.
Step 3: Modify the Servo(disengaging the Potentiometer)
To get a servo to rotate continuously you have to do two thing, disengage the potentiometer that tells the servo the position of the control arm and remove the mechanical stop that keeps the servo from rotating too far and damaging the pot. To disengage the pot begin by looking at the inside of the top of the case where you well see three gears, two small and one larger gear with a metal ring in the center. If you notice, under that ring is a bit with a flattened out hole in it, this is what engages the pot to tell the servo the position of the arm. To remove it you simply have to pop the metal ring out and pop the bit inside with the flattened hole in it out. Once the drive bit is out replace the metal ring in the gear, this engaged the bearing.
Step 4: Modify the Servo(removing the Mechanical Stop)
Now that the servos electronics well allow it to continuously rotate we have to make it so that it well continuously rotate mechanically. All servos have a mechanism to keep it from rotating to far and damaging the pot, no longer a problem in our case.
- To begin, remove the screw holding the control horn on and pull the control horn off the out put shaft.
- Now that the control horn is removed, slide the output gear out of the top of the case by pushing on the shaft until it pops out.
- On the shaft you well notice there is a bit that protrudes from the shaft, if you look on the inside of the case where the gear and shaft were there are two bits that stick out and catch the bit that is protruding from the shaft, this is the mechanical stop.
- Take the Dremal with the cutoff wheel and carefully cut the bit that is protruding from the shaft away, being careful not to damage the gear itself.
- Put the gear back into the top of the case and check that it rotates all the way around without binding.
- If it doesn't bind carefully reassemble the servo, taking care to get the gears and shafts lined up properly and your done. If it does bind up still, you well need to remove more of the protruding bit and try again.