What is Dead bandwidth?

This is largely discussed for its advantages and disadvantages. Dead bandwidth is a way to say how accurate the servo holds its position. Suppose a servo has a dead bandwidth of 5us (microsecond) and a command is sent to center a servo (which is 1.5ms). Now what happens if the pulse changes from 1.5ms to 1.5ms + 3us? Since the dead bandwidth of a servo is 5us, nothing happens until the pulse is greater than 1.5ms + 5us.

This is a technique used by servo manufacturers to avoid servo dancing at its center position by telling it to stay in position until the difference between new command and old command is greater than dead bandwidth.

What are Analog and Digital Servos?

Servos are either analog or digital. Difference is how the motor is controlled by the controller circuit. Motor in an analog servo receives a signal from the amplifier 30 to 50 times a second (30Hz-50Hz) known as position refresh speed of servo, allows amplifier to update motor position. In a digital servo, the amplifier sends signals more often at a rate of 300-400 times per second.
There are many advantages of a digital servo.

  1. Faster response: Digital Servo uses a faster microcontroller which is almost 10 times faster than the one in Analog servos

  2. Greater torque: Delivers full torque from start of movement with increased holding power

  3. Programmability: Although most digital servos are preprogrammed, user gets an option to program the servo for center and end points, direction of rotation, speed, dead bandwidth adjustment etc.

Digital servos are slightly on the expensive side compared to analog servos and also power hungry as they have to send more pulses, run a much faster processor along with few additional components.

Technically analog servos are very different than digital servos. From the user’s perspective, the functionality remains the same. Digital servos are controlled in the same way just like any other analog servos. The hard work is all done by the circuitry. If you are concerned about accuracy and control, go for digital servos. If you are concerned about cost and battery power, choose analog servos.


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