PRO
afcorson
Australia
Asked
What happens if you mix HDD servos with HD servos in your robot? Will only the HD servos jump around or will others move inadvertently too? Thanks.
Related Hardware EZ-B v4
HD is anologe and HDD is digital.
servo info
Left side: 2 x EZ-Robot HDD Servos (Digital)
Right side: 1 x EZ-Robot HD servo (Analogue)
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.
So the problems at startup are likely caused by power on and control floating for a few seconds, the analogue servo will interpret the voltage floating as impulses and will try to match with the feedback from the potentiometer, so you ll see the servos moving without "control".
With digital servos, they don't move until the controller sends pulses.
It's possible to mitigate the problem (Analog servos) using a different power source (not from EZB vin), controlled by relay (a good one with enough Amps to support the servo inrush) and using the relay Normally Open position, so when you power the Robot, the servos will not get the power, then you have plenty time to EZB to boot, Windows, ARC, initialization script to initialize all servos to the initial position.
When you are ready, you enable the relay, so the servos will get power and logic control at the same time.
Hitec servs, for example, are simply analog or digital, non such acronyms.
you gave a good example:
If you look well the Hitec's model HS-322HD uses the same terminology.
The devil is in the detail
btw: the Hitec descriptions are misleading. Has 2 Karbonite and 2 nylon gears and in light use they both break easily. It's not a heavy duty servo by any means. EZ-ROBOT should change to SHD Super Heavy Duty :), off course not all HITEC servos are equal.
ez-robot :HD =heavy duty , HDD=heavy duty digital
Hitec : HD =it should be heavy duty but itsn't necessarily