Question about Mini Digital Servo HD-1810MG

Power HD Mini Digital Servo HD-1810MG

I am total noob. I like this servo because it is small, strong, digital and within my price range.

But, can it continuously rotate in the same direction? My application needs servo that can go several full revolutions in one direction. Is that controlled from the controller or is there some kind of mechanical limiter that prevents servos going around and around and around.


In general, servos don’t turn more than about 160-180 degrees because the feedback system only supports that range. Some servos are modified for continuous rotation by disconnecting that feedback system, but you then give up any sort of position control. There are some specialty servos that can do multiple turns while maintaining position, but I haven’t seen them on the mini/micro scale.

- Jan

How is feedback system disconnected? Do I just do the disconnection from the servo controller software, via some instruction or do I need to physically cut the wire leading to the feedback controller?

Basically I want to rotate a knob, that is usually rotated by hand, only I want to rotate it with servo, but with quite few revolutions. The knob is about 20mm (4/5") in dia and it needs to be rotated in 6 deg increments.

If I disconnect servo’s feedback system, can I just stop servo very quickly by getting info externally, via sensor on the knob?

On a second thought, maybe I can accomplish that with gearmotor, like this one: 210:1 Micro Metal Gearmotor HP

The details will vary from servo to servo (some servos don’t even have full gears on the output stage, so those are really bad candidates for conversion to continuous rotation. You should search for something like “convert servo to continuous rotation” for more info on the conversion. Once you do that, you’re basically changing the servo to a motor with a gearbox and motor controller; if you close the loop externally, that should be fine.

- Jan

You said you wanted your knob to rotate in 6 degree increments. Maybe you could use a stepper motor and a stepper motor driver. -David

Thanks David,

that is a new angle. What kind of motor is compatible with these drivers? Can they start and stop on the dot?

We don’t have any stepper motors (yet), but they are available all over online and possibly in some old printers and other equipment you might have lying around. The limitation of our driver is that it is just a driver, so you would still have to generate the low-level pulses to tell the motor driver to move the motor over a step. If your load is predictable, you can get consistent starting and stopping points without any feedback, though you typically need some kind of initial registration when you turn on the system. If you already have external feedback from your knob, that would take care of your initial absolute position, and then the stepper should be a decent solution.

- Jan