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[Rich griff]

It's probably been covered before but I cannot find a thread about the subject.


What is the difference between digital and analogue servos please ?


I know that various servos have different operating voltages, minimum and maximum, but will an oldish 27meg and 35meg radio set, tx and Rx, operating oldish analogue servos, also operate modern digital servos, particularly the smaller very light servos please ?


Thanks

[Circlip]

Asked the same question years ago and didn't get an answer then.


  Regards   Ian.

[JimG]

In simple terms:-An analogue servo varies the voltage to the motor depending on how far it has to move. Full voltage for large movments to give max speed but as it reaches the endpoint the voltage reduces slowing it down until it stops. If it is pushes off of the endpoint by the force of the controlled surface it only uses low power to recenter so the centering force is low.Digital servos always use full voltage but pulse it to vary the speed, always on for max speed and movement then reducing the on pulses to slow it down towards the end point until it stops. If it is deflected from the endpoint by control forces it will give full voltage to reset it so greater force holding it in place. Many digital servos if held off center will make a whining noise, this is the motor pulsing with the power input.Digital servos hold their position much better than analogue ones, this shows up at the extreme positions where digital servos often need less movement of the control as analogue servos can blow back and give less than the expected movement. A friend who changed from analogue to digital servos on an aerobatic plane reconned that he only needed half the movement of the control surfaces for the same control.As for can older radio gear use digital servos the basic answer is in most cases yes. Often used digital servos on 35MHz though never felt the need for them in boats. However care must be take with some of the more modern ones which are designed for receivers which use a faster data rate. The servo is then getting less data than expected from older receivers so will work slower. Similarly older digital (and analogue ) have problems with newer (mostly 2.4GHz) receivers working at higher data rates where they are receiving the signal faster than they can cope and may try to move too fast causing overheating. So for older sets check the digital is not a high speed one and you will be OK.
Jim

[Rich griff]

Thanks Jim, info I didn't know, thanks.


Will check with supplier about fast and slower servos, 4 gram type dimensions and volts supply dependant.


Thanks.