The 3212 is a standard servo that has been built by SpringRC specifically for continuous rotation (up to 60 RPM at 4.8 V), and it produces a lot of torque (12 kg-cm at 4.8 V). It features two ball bearings on the output shaft for reduced friction, and it offers easy access to the rest-point adjustment potentiometer. Essentially, it is a gear motor that can be controlled by an RC servo controller. It is not normally used as an actuator, as there is no way of commanding it to move to a particular position, as a standard RC servo does.
The 3212 continuous rotation servo converts RC servo position pulses into continuous rotation speed. The default rest point is 1.5 ms, but this can be adjusted by using a small slotted screwdriver to turn the middle-point positioner (see the Mechanical Drawing). Pulse widths above the rest point result in counterclockwise rotation, with speed increasing as the pulse width increases; pulse widths below the rest point result in clockwise rotation, with speed increasing as the pulse width decreases.
Normal servos can be adapted to continuous rotation use, but the problem is that the range of positions that result in the motor being stopped or operating at less than maximum speed is very narrow. Continuous rotation servos, depending on the position commanded, can go forward or reverse at different speeds. With an adapted continuous rotation servo, the position range for the different speeds is very narrow, making it difficult to produce a specific speed.
These dedicated continuous rotation servos are superior because they have a very wide “deadband” so you can be sure the motor is stopped when you command it, and the position range for forward or reverse motion is very wide, giving lots of speed resolution.
RC servos are hobbyist remote control servos typically used in radio-controlled models, where they provide actuation for various mechanical systems such as the steering of a car, the flaps on a plane, or the rudder of a boat. These servos are not industrial grade and are not recommended for continuous heavy use.
|Motor Type||Continuous Rotation Servo|
|Rated Torque||12.2 kg·cm|
|Maximum Speed at Rated Voltage||50 RPM|
|Gear Train Material||Metal|
|Bearing Type||Double Ball Bearing|
|Motor Length||39.5 mm|
|Motor Width||42 mm|
|Motor Depth||20.5 mm|
|Wire Length||280 mm|
|Rated Voltage||5 V DC|
|Rated Current (on 1061 controller)||155 mA|
|Rated Current (on 1066 controller)||165 mA|
|Stall Current (on 1061 controller)||1.8 A|
|Stall Current (on 1066 controller)||417 mA|
This servo motor needs to be connected to a servo controller board. If you're looking for higher torque, you should select a servo controller with an external power jack so it doesn't have to rely solely on USB power, which is limited. You can plug this servo directly to any of the boards in the list below by matching the color of the wire with the label on the board. Note that some servos have a white data wire and others have a yellow one- in both cases this wire corresponds to the "W" pin on the servo controllers.
|Image||Part Number||Price||Motor Type||Range of Rotation||Rated Torque||Maximum Speed at Rated Voltage|
|3000_1||$12.00||Limited Rotation Servo||180°||3 kg·cm||286°/s|
|3200_0||$52.00||Limited Rotation Servo||180°||19.8 kg·cm||125°/s|
|3201_0||$57.75||Limited Rotation Servo||Approx. 2700°||11 kg·cm||225°/s|
|3202_0||$18.75||Continuous Rotation Servo||—||2.8 kg·cm||44 RPM|
|3203_0||$19.00||Limited Rotation Servo||180°||4.8 kg·cm||272°/s|
|3204_0||$40.50||Limited Rotation Servo||180°||7.7 kg·cm||300°/s|
|3205_1||$11.00||Limited Rotation Servo||175°||2.2 kg·cm||545°/s|
|3207_0||$12.50||Limited Rotation Servo||180°||2.4 kg·cm||375°/s|
|3209_0||$10.00||Limited Rotation Servo||180°||3.5 kg·cm||400°/s|
|3212_0||$18.00||Continuous Rotation Servo||—||12.2 kg·cm||50 RPM|