That's correct, only the HD servos will move on initial power up the HDD servos will not move (they have a completely different internal electronic design).

Deleted. Look away.

What are  the  HD and HDD servos ? I only know usual servos .

leonardo46

HD is anologe and HDD is digital.

HD and HDD  don't help understanding . Both seem digital ("D" and "DD"). I never saw those  acronyms for servos.

HDD comes from heavy duty digital servo.

servo info

Quote:

I never saw those acronyms for servos.

Left side: 2 x EZ-Robot HDD Servos (Digital) Right side: 1 x EZ-Robot HD servo (Analogue)

Analogue x Digital servos:

There is no physical or main component difference between a digital servo or analog servo. The servo case, motor, gears, potentiometer all have the same purpose in both types., the exception is the PCB i.e. board.

The difference between the two is in how the signal from the receiver is processed and how this information is used to send power to the servo motor.

Analog: An analog servo controls the speed of the motor by alternating on and off voltage signals or pulses to the motor.

Digital: A small microprocessor int the servo PCB analyzes the receiver signals and processes these into very high frequency voltage pulses to the servo motor. Instead of 50 pulses per second, the motor will receive upwards of 300 pulses per second. The pulses will be shorter in length, but with so many voltage pulses occurring, the motor will speed up much quicker and provide constant torque.