I recently discovered the existence of VEX Servo Motors. I know from past knowledge that servos are really good for keeping control of systems that don’t need to go more than a set degree (for vex, the set angle limit is 120 degrees). I thought about using these for a mogo lift because mogo lifts don’t need to go past 120 degrees of rotational motion. I read more about the servos and apparently, they continuously draw power to keep its position. Yikes. I know power is very important because other systems like lifts need it. Also, if I want to have a 1:5 torque ratio for my mogo lift, I would need a servo that can go past 120 degrees because one revolution in the 12 tooth gear is only going to make the 60 tooth gear turn one-fifth of a revolution. If I want my mogo lift to turn 120 degrees max, I would need a servo that can turn 600 degrees. I’m I looking at this the wrong way? Or do I have some sense in my points? Are VEX Servo Motors even viable?
Not for a mogo lift IMO. Maybe for a small chainbar
I originally had a servo motor for my robot’s claw because I thought that the auto-stabilization that it had to keep its position was very useful, but upon using it I realized two things:
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It’s auto-stabilization was not as accurate as I thought it was, and even with it drawing power to keep its position, it still had around 30* of give, which was more than enough to drop a cone.
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It would be much more efficient to just use a regular motor with a potentiometer, as you can use the potentiometer to effectively accomplish the same thing with the auto-stabilization, but with 0 give instead of 30*.
I highly recommend always using regular motors with potentiometers/encoders if possible.
I’ve used a servo for my claw with success, I would recommend it for that type of use, and if not a servo, the 3 wire motors for the weight savings (that is if you’re only using it for an intake or another light duty application).
Servo motors are fantastic for what they’re designed for. They don’t provide a lot of torque. That 30 degrees of give stated above is when using them improperly. They lock in an angle far, far better than that. Plus, by using them you use a single motor port instead of a motor port plus an analog port. But if you are trying to use them to provide a lot of torque, then you’re not using them properly and you won’t get what you want out of them. Use them in ways such as what @BottomNotch said. If the rotation axis is parallel to the direction force needs to be applied, then nearly no torque is needed at all and servo motors are the way to go (assuming you only want limited rotation).
So while I would highly recommend using a regular motor for the use you state as it may well require significant torque, I strongly disagree with @Mystellianne 's advice to always use regular motors and potentiometers/encoders.