Can I use a digital servo in the same way as the analogue ones? I ask because looking at the Hobbyking site, the cheapest servos (almost) seem to be digital. I always thought that digital servos were high end types with lots of torque or high speed and expense to match.
Barrie
Yes, with the caveat that their power supply needs to be stable enough for the job.
"Digital" is a heavily misused expression used to imply wondrous properties for whatever is being sold, without ever saying just how the wonders are performed, and there is a wide range of digitalness.
In an analogue servo, the signal from the RX is observed, and the pulse length measured by charging a capacitor up to whatever voltage it can - this is then compared to the voltage on the wiper of the position sensing pot. If there is a difference, the motor is instructed to drive the pot to a position where it does agree. As a by-product, the output arm, being attached to the pot spindle, also moves to the new position.
A fully digital servo would register the pulse length by counting while the pulse was "on" and using the result of that count as a numerical value. It must then compare the numerical value of the position sensing device with that and drive the motor until agreement is reached. In a fully digital one, a stepper motor would do the driving, precise, but thirsty. In reality, I suspect that the input end is done like that, but the position is still sensed by a pot feeding a voltage to an ADC element in the controlling chip, and as such, would still be liable to jitter derived from marginal voltage supply variations. Quite probably, the motor is a regular brushed can type.
While most digital servos will have some technical changes that might justify buying at the higher price, I suspect it will be some time before there is a fully digital servo at the same price as the established analogue type.
