# Arduino Forum

## Using Arduino => Motors, Mechanics, and Power => Topic started by: Peps on Jun 13, 2018, 05:18 am

Title: Calibrate rotation speed 2 SM-S4303R
Post by: Peps on Jun 13, 2018, 05:18 am
Hi guys

I'm currently stuck in a college project: a floating turtle that swims powered by 2 SM-S4303R continuous rotation servos and a simple row mechanism. Thing is, we can't calibrate both to rotate at the same speed, as you can see in the video below:

video (https://youtu.be/lRNM10Nbbys)

Any ideas on how to calibrate them? We've tried some delays values or different rpm but we can't manage to do it properly. Also consider that 1 servo is rotating backwards.

Title: Re: Calibrate rotation speed 2 SM-S4303R
Post by: Johan_Ha on Jun 13, 2018, 07:27 am
Either you connect them mechanically or you add encoder plates to control their speed.
Title: Re: Calibrate rotation speed 2 SM-S4303R
Post by: Peps on Jun 13, 2018, 07:04 pm
Either you connect them mechanically or you add encoder plates to control their speed.
how can you conect them mechanically if they rotate in opposite directions?
The encoder plates is a great idea, I'll give it a shot. Thank you!
Title: Re: Calibrate rotation speed 2 SM-S4303R
Post by: Johan_Ha on Jun 13, 2018, 09:14 pm
Looking at the video, it almost seems as the rotating plates were cog wheels rotating against each other. If that were the case, your problem would be solved.

Although the encoder plates would be the geek way to do it. Just mechanically connecting them would lead to two motors doing the same job. One would force the other if you don't know exactly how much power you need to put to each of them. With the encoder plates you could have them in perfect sync. But you could also have them run in different speed, making the turtle turn.
Title: Re: Calibrate rotation speed 2 SM-S4303R
Post by: jremington on Jun 14, 2018, 03:31 am
Servo pulse width controls speed and direction.
Have you tried adjusting the pulse width to one of the servos such that the two speeds match?