In the beginning just like many electronic devices, servos used to come only in analogue form, and now with progress like everything else, they come in a digital form too. Before we determine which type of RC servo is better, let us have a look at the functionalities of both these types. The components, circuit, mechanism, everything remains same. The whole difference is in the way the PWM signal is processed. The digital servos have digitally controlled pulses which are far faster than the analogue servos.
Digital servos though have the same parts as analogue including the wire plug, the difference is the way PWM is processed, as discussed earlier. The digital servo has a small microprocessor that receives the signals and process them into a high power pulses to servo motor. This is being minimised now a days with the manufacturers bringing out higher powered batteries, but power consumption is definitely on the higher side with digital servos. So to summarise, digital servos are always better than analogue ones when come to performance and speed.
These are the standard 3 pole electric DC motor which has 3 conductor commutator with 2 brushes feeding positive and negative current.
There is then another variant in the brushed motor with 5 poles instead of 3. As a result, this gives more torque and acceleration. RC powered vehicles need more torque for desired functionality.
While a 5 pole motor works faster than a 3 pole one the same is true for both analogue and digital. However, this motor uses a steel core with wires wound around it, and on the end is a commutator. The drawback of this motor is all the weight due to steel and magnets and it takes time for the motor to start and speed up. Coreless servo motors eliminate this disadvantage of slow starts by removing the steel core from the motor. Many RTR vehicles will include this type of servo to operate its controls.
For better or increased performance it is possible to upgrade the servo. This will ensure full control over the vehicle in terms of direction. On a plane it is important to have enough torque on the elevator channel. At higher speeds the load of a control surface is much higher. A stalled servo is a scenario where the servo does not have enough torque to overcome a load. A stalled elevator servo ultimately may result in a crash of your plane, boat, or car.
Be certain your RC has the proper torque requirements for a servo. Each servo is best suited to smaller applications where size or weight would be an issue.
It may be beneficial to save weight or size if torque requirements are met utilizing this class of servo. High speed servos vary in torque depending on which one is selected. They usually are in the 65in oz range but can vary over a large range.
These servos have a much quicker response time. They will rotate the servo arm at a quicker speed then a servo of a different class. This results in quicker snappier controls. The usual frequency of these PWM signals is 50 Hz, which is every 20 milliseconds. In simple terms, the servo is updated every 20 milliseconds. RC servos have a rotating shaft and a potentiometer that detects it position.
When there is a pulse from the control signal, sent by the driver from the transmitter, it applies current to the motor that makes the shaft move until the potentiometer indicates that the position is in line with the width of the pulse. That movement is what the driver has asked for to control the model around the twists and turns of an RC car track.
In the beginning servos used to come only in analogue form. Now they come in a digital form which is the common standard for all servos in the s. Before we determine which type of RC servo is better, let us have a look at the functionalities of both these types.
The components, circuit, mechanism, everything remains same. The whole difference is in the way the PWM signal is processed. Analogue systems used 50 pulses per second. Digital systems receive over pulses per second! This not only improves the accuracy of the servo, it also improves the speed of the movement. The digital servos have many more advantages over analogue servos. They are fast, have quick response, higher resolution and more power.
More power means more power consumption from the onboard battery. However, the increase in power needed is so small compared to the capacity of the battery used, this is a minor drawback.
Indeed, if you want an analogue servo you have to ask for one!
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