help picking a servo (existing project, quadra-ped)

[linux-works]

I'm thinking of building this:

http://www.thingiverse.com/thing:2204279

seen here:

https://hackaday.com/2017/04/22/hari-prints-an-awesome-spider-robot/

I'm not an expert with servos and need help understanding the diffs.

I can find the SG90 (plastic gear, lighter duty, right?) easily and cheap.  I can find mg90S (the S at the end) and it should have metal gears.  but what about mg90 without the 'S'?  is that important?  they are all pwm-based servos, right?  some vendors mark one as 'digital' and the other as 'analog' but I'm not sure if they are at all different.  or, is this the internal circuitry?  from the outside, its still simple pwm to control them, right?

finally, since there are SO MANY fakes out there; who is a good seller to buy from?  which brands (tower pro?) should I buy?  I see so many reports of junk being sold, I'd rather not waste time on junk.

[FreddyVictor]

The Analog/Digital servo thing is to do with the rate the PWM signals can be sent to the servo

Originally, the standard rate for RC was 50Hz, however since the advent of transistors (!) more modern electronics can accept much higher rates and these are so-called 'Digital' ones
With the higher rate, the servo will react slightly quicker - good for drones (Tri-copters)

As for the 'S' suffix, can't say

HobbyKing is the obvious place to buy from but alot of choice
There's also US based Servo City
Most cheap servos use brushed motors, but the better ones can use brushless motors which will wear less

I have had TowerPro servos myself but couldn't really say if they're any better than other brands TBH !

HTH

[rrinker]

 MG90 and MG90S differ mostly by speed. Supposedly slightly different types of bearings - even the RC sites are rather vague because the Tower data sheets also are. I wouldn't mix them, but either should be fine for this use. Much better than the plastic geared SG90. You can USUALLY tell the fakes as they won't say Tower Pro on the label.