360° Servo Conversions
-Method 5-

Method 6 Dumb Servo This method was first described by Simon Harbord and his description of the modification can be found on the "Build a Basic Rig" pages of his web site. The Dumb Servo Modification The principle of the Dumb Servo is to bypass the electronics in the servo case and power the servo motor with a 1.5 volt battery (Figure 1). A micro-switch is used to turn the motor off and on. The closed switch provides 1.5 volts directly to the servo motor, bypassing all the control circuitry of the normal Servo. The servo will turn as long as the switch is closed. The switch is closed by operating the Shutter Servo. The Shutter Servo in most cases only uses half of its operating range so this allows us to use the other half to close the micro-switch that activates the Dumb Servo. 1.The stops that prevent the gears from turning 360° must be removed (Figure 2). 2.Next remove the servo motor from the circuit board by desoldering the terminals from the circuit board (Figure 3). (Save the board with the wires and connectors for use as a switch as described in Method 5.) With the S3003 you can leave the pot attached to the circuit board, if you have a servo that needs the pot in place to support the final gear then just cut the leads going to the pot so you can remove the circuit board. If you leave the pot in the servo you will need to open the bottom of the pot and remove the internal stops in the pot to allow it to rotate 360°. If you have trouble desoldering the servo motor terminals then you can do as Simon Harbord did and use a pair of pliers and break off the circuit board up close to the motor. You should be able to solder over the existing solder. Simon mentions in his article that the capacitors on the circuit board should be left, if at all possible, to prevent possible interference with the receiver. With the S3003 it appears that there is a capacitor as shown in Figure 3. If you choose to desolder the motor from the board, a capacitor soldered from one motor terminal to the other should take care of any interference with the receiver. 3.The gears in Futaba S3003 can operate with the pot removed from the servo, if however, you are attempting to convert a servo that needs the pot output shaft to support the final output gear then you will have to remove the insides of the pot because it has stops in the case. You can open most pots from the bottom by bending the 3 or 4 tabs out of the way and removing the bottom. Then scrap, pry, or drill out the guts of the pot. 4.After the servo motor has been isolated, solder two lengths of wire to the motor terminals. These wires will run out of the case and connect to a seperate 1.5 volt battery and the mirco-switch (Figure 1). The micro-switch must be positioned so the Shutter Servo can actuate it when the transmitter stick is moved one direction and the shutter when the stick is moved in the other direction. 5.The Servo can now be reassembled. It should look no different, except now only two wires come from inside the case. The direction of rotation can be changed by reversing the battery. If you desire to have the servo operate in both directions you would have to add a second switch which would cause the polarity to the servo motor to reverse. The first micro-switch would operate when the transmitter stick was partially moved and the second micro-switch would operate when the stick was fully moved.

Figure 1                                        Figure 2                                                     Figure 3 Advantages- Eliminates the need for one channel. Two axis movement and shutter can be accomplished using a 2 channel R/C system, and 2 channel transmitters and receivers are cheaper. The rig can be hung directly from the servo output. External gears are not required. With no external gears the panning action will be at the servo's normal operating speed. Disadvantages- Servo must be open and modified. A seperate power source of 1.5 volts must be provided A micro-switch must be mounted to interact with the shutter servo. If you confuse Shutter operation with Pan operation you will be taking pictures when you meant to rotate the rig.