hi all
What is the difference between digital and analog servo?
I want a servo to change the position very smoothly for example i want to control the position with accuracy of 1 degree . which kind of servo must i choose to reach at this target?
tanks in advance
Digital servos have more resolution than analog. Digital servos are stronger and will reject any out of range pulses sent to it, so you can’t instruct a digital servo to move a full 180deg unless a programmer is used to change the internal controller.
There is more in these forums, just got to search a bit.
pretty much what SN96 said…
digital servos have a small microcontroller built in which gives them the ability to run a higher resolution and typically higher power control over the servo motor. some digital servos also have the ability to be programmed externally to adjust limits of travel for a given input signal range.
the response of an analog servo is limited by the 50hz r/c signal coming from a receiver or controller. while cheaper to manufacture than digital servo control boards (internal to the servo) the trade off is they generally are not as accurate and given the same gear train they effectively have less torque available. probably a good example for comparison (if you wanted to test) would be the Hitec HS-645MG vs HS-5645MG which appear to have the same motor+gears but different control boards.
I am not sure that hobby grade r/c servos are going to repeatedly be able to hold +/- 1 degree over the life of the servo. even the potentionmeters used internal to the servos are not, um, especially high quality. I think in practice though most people tend to wear out other aspects of a servo before the potentiometer… stripped gears, burned control board, shorted motor, etc. 
Anyway this topic has been re-hashed more than a few times on this forum alone, frequently started either by some grad student trying to low ball the costs of doing some research project, or some idealist person who discovers a $50 servo doesn’t hold +/- 0.1 degree over it’s full torque range and can’t seem to fathom why there are DC servo systems costing hundreds even thousands of dollars to do just that. 
´hi all
thanks for your information.
Has anybody actually done an objective observable test to verify the higher digital servo resolution claim? It might just be another misrepresentation of the similar .09 deg. resolution claim of an analog servo.
I don’t remember Hitec claiming anything as far as resolution goes. We have listed the 0.09° thing as what the SSC-32 is capable of generating.
2500uS- 500uS = 2000uS
180° / 2000uS = 0.09°
The current analog servos respond to this 2000uS range. Standard digital servos only respond to 1100uS to 1900uS.
1900uS - 1100uS = 800uS
140° / 800uS = 0.18°
The HMI robot digital servos respond to 600uS to 2400uS.
2400uS - 600uS - 1800uS
180° / 1800uS = 0.10°
Then of course there is the deadband issue to deal with. It’s probably 6uS to 10uS at best with analog servos. The digital servos state deadbands as low as 1uS. So the clear winner is the HSR-5980 or 5990 digital servos. A real life test would be interesting.
and old thread but i didn’t want to start another one.
im looking to replace some of my HS-*645MG *for HS-5645MG, but not all of them.
Will adding HS-5645MG along side HS-*645MG *be ok as far as analogue and digital mixed. Can i just plug them into my regular pins, in place of the HS-645MG
obviously without programming them i wont get the same res, but this isn’t an issue at the moment.
thanks in return.
What is your reason for changing servos? I’d suggest buying one of the HS-5645MG servos and do a performance and ease of use comparison between the two.
Need power dude,
645’s= 133 oz/in.
5645= 168 oz/in.
unless you know of any alternatives around the same price range?
i have one on order anyway so i will test it and see what happends.
cheers
