These are two simple methods to turn your 9g servo into a continuous rotation servo. They will work for all servos but the 9g servos are constructed differently than say a 55g servo because of their size. Since Flitetest is so fond of the 9g servos I figured I would do a build log for the 9g rather than a bigger servo. These servos once hacked are great for fpv, small robots and much more. WARNING- this voids all warenties and it is possible to break the servo doing this. However it is really easy and the servos are dirt cheap. The two methods are either glueing the potentiometer(the variable resistor that senses servo movement and stops it after a certain degree of movement) or replacing the potentiometer with a voltage divider using 2.2k-ohm resistors. The voltage divider tricks the servo into thinking the potentiometer is constantly centered allowing the motor to constantly spin. This method is very reliable and works better, but it requires some soldering. Glueing the potentiometer only requires some good'ol hot glue. On the turnigy/flysky 9x I had trouble doing mixes using two of these hacked servos because it just spun without input. Also it worked on every channel except channel two. If you are just using it for a fpv pan not a robot it is perfect then! I tried my tactic and it worked flawlessly with mixes and it worked on channel two. It may have just been my turnigy transmitter though. If you have a turnigy 9x comment if mixing and channel two work for you i'm curious to know. If you are just using the servo for fpv pan or along those lines it works with any transmitter perfectly.
Remove the four screws from the servo. Make sure to keep track of these. They are really small and easy to lose. Trust me!
Next remove the outer casings of the servo exposing the gears and the electronics.
Remove the gears and place them aside. I put them in two colums which correspond to the shaft they were mounted on. I also staggered them so I remember the order to stack them in. Try to remember how they go or take a picture because if you mix them up or forget how they go it makes the whole process much slower.
Now is when you choose if you want to glue the potentiometer or solder in a voltage divider.
Method 1- If you choose the easiest but less reliable glue method plug the servo into your reciever and power it. Move the shaft of the potentiometer around until the servos motor stops spinning, if it was. Then move the stick on your tranmiter back and forth to check if you have control over both motor directions. If you do keep the potemtiometer in place and glue it well with hot glue so it can not move. Leave the servo powered so if the potentiometer gets moved you will see the motor move and you can adjust it.
This is what the potentiometer looks like. You move the center shaft back and forth to get the motor to stop. Then fill its basin with glue and pack it in using scrap foam or something like that.
Method 2- The voltage divider method is much more reliable but a little more indepth. You cut the potentiometer out of the servo(as shown two pictures above) and replace it with two resistors that mimic a potentiometer in its center position. For almost all servos except 5g you will use two 2.2k-ohm resistors. I used 1/4 watt for the 9g servos since they are not passing much current.
Pull the wires out of the servo and cut them at the potentiometers prongs. You still need to glue the potentiometer to the servo but only because the gears mount to it.
Cut at these prongs
Pull the wires apart and tin them. You need to solder a resistor between the black and white and the white and red.
It should look like this when your done. Resistors pass current multidrectionally so it does not matter which way they face.
Once you finish your chosen method cram the electronics in the servo and hold the bottom plate on. For the voltage divider I cut slots in the bottom plate to allow the wires out because the resistors did not fit in the servo case. If you find a way to get the resistors in the case please comment how!
Put the gears back on in the correct order. Drill the hole on the gears on the potentiomer a bit larger so they are not too tight which will cause the potentiometer to move. If the potentiometer moves it can screw up the glue method very badly! This step is imperative for the glue method. Place the top case on then screw it together. Your done!
These servos can be used for small robots or fpv pan systems and more! They are alot of fun and they come in handy!