Last month, i bought HITEC HS-5645MG servo for upgrading torque of my robot arm. it said digital servo. i was wondering "what is different of analog servo and digital servo?". Physically, There aren't different. They are basically same. The different between them isn't the physical or component aspect of the servos. The only different is the signal and how it is processed from reciever to the servo.
As analog or standart servos go, the signal which is used is Pulse Width Modulation (PWM). When the signal is high. it called "on-time".When it's low. it called "off-time". To describe the amount of "on-time", we called it as Duty Cycle. So, the percentage duty cycle describes the percentage of time a digital signal within interval or period of time. The interval or period of time is able to be gotten by inverse of frequency of the waveform. So, The larger movement, the longer "on-time" pulse will be in order to move the servo quickly to desired position and produce more torque.
Digital servos has as same as signal the analog servos, but, unlike analog servos frequency, digital servos has small microprocessor inside in order to analyzes the reciever signal and process them into very high frequency pulses to the servo. So, the pulses will be shorter in length. With so many voltage pulses occurring, the motor will speed up much quicker and provide constant torque. For example, if the analog servos need 50 pulses per second to move to 30 degree, The digital servos will take 300 pulses per second to move to. So, the digital servos has ability to send pulses 300 pulses per second. That's why digital servo is more expensive than analog servo. For more information about digital servos.
I have tested them by plugging in a digital servo and an analog servo to my receiver. The result is a digital servo that has a faster response, quicker and smoother acceleration. But, some people say digital servos are power hungry. i'm not sure it's true or not. Maybe, it may come out from all those hundreds of power pulses per second.
Choose wisely, don't be sucker who spends money for no reason!
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