Society of Robots - Robot Forum

Electronics => Electronics => Topic started by: airman00 on November 11, 2007, 12:59:40 PM

Title: Pulse
Post by: airman00 on November 11, 2007, 12:59:40 PM

Lets say I have two servos - one needs 169 and another needs 175 to go forward at the same speed.


Those servos are using 5V. If i were to give them 6V instead of the 5V, would the PW numbers change? If so would the amount of change be equal for each servo?

Title: Re: Pulse
Post by: Half Shell on November 11, 2007, 01:28:40 PM

I believe it would change - motors operate on curves depending on the torque and current and voltage they are given.

I suggest optical encoders so you don't need to guess and check all the time.

Title: Re: Pulse
Post by: Steve Joblin on November 11, 2007, 01:38:12 PM

said another way... Let's say you have a robot that uses two servo motors and is all set up and works "perfectly" using 5v.  Now you add an extra battery changing the voltage to 6 volts.  The robot will behave just as it did before, but it will move faster.

Title: Re: Pulse
Post by: Rebelgium on November 11, 2007, 05:17:06 PM

Quote

said another way...

steve, you are contradicting the previous post, that's not "said another way"  ;)

I agree with Half Shell

Title: Re: Pulse
Post by: airman00 on November 11, 2007, 05:32:24 PM

Quote from: airman00 on November 11, 2007, 12:59:40 PM

If so would the amount of change be equal for each servo?

What about that question?

Title: Re: Pulse
Post by: paulstreats on November 11, 2007, 05:46:44 PM

in short no.

it is likely due to be a curvature type change as far as the motors are concerned and not a linear change, theoretically a servo should operate linearly but remember that they still operate with motors ie. coils of wire.

because its such a small change in voltage, you may get away with it not causing too much drift to one side, its likely you may have had a slight drift to start with that you didnt notice. its the type of thing where a greater change will produce an even greater effect, the only way to really know if it will work for you is to test it yourself.

Title: Re: Pulse
Post by: Admin on November 11, 2007, 07:27:09 PM

If you look at the spec sheet it says that servo speed increases with voltage, which makes sense . . . but the direction won't change.

For a robot operating in a very uncontrolled environment, that increase in speed won't affect your robot's ability to work so I wouldn't sweat it. For example with my Stampy sumo bot, I just guessed at speed values and said 'thats good enough, its rotating in the right direction . . .'