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Encoders' measure 
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Joined: Wed May 28, 2008 12:47 pm
Posts: 2
Post Encoders' measure

I'm making a program with RobotC which has to read the rotation position of a NXT motor. I use nMotorEncoder(motor) but this function gives me absolute position of the encoder. If I move the motor backward, my measure turns to 360 and goes down, and I want it as -1ª, -2ª... It's a problem for me too that my measure passes from 360º increasing to 1º, and not to 361º
Is there a simple solution to this?


PD: I promise you to upload my program when I finish, a self-balancing robot with a Gyroscope.

Wed May 28, 2008 12:54 pm
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Joined: Wed Jan 31, 2007 3:39 am
Posts: 299
Location: San Diego, California. USA
Hi Albert

You can reset the encoder to whatever value you want anytime, here is the command to do this.

nMotorEncoder[motorA] = 0; // reset encoder to 0

Did this answer your question?

Good luck with your project B-)

Mmmm Legos B-)

My Robot Projects:

Thu May 29, 2008 12:26 am
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Joined: Fri Nov 09, 2007 4:51 am
Posts: 121
Location: Hungary, Europe
Post Re: Encoders' measure
Hi Albert,

You will need a new variable or a conditional statement to reach the behavior you need.

Fri May 30, 2008 5:15 am
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Joined: Wed Mar 05, 2008 8:14 am
Posts: 3589
Location: Rotterdam, The Netherlands
Out of curiousity, does resetting the encoders affect the motors' PID control at all?


Fri May 30, 2008 5:57 am
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Joined: Wed May 28, 2008 12:47 pm
Posts: 2
mightor, this is the question i'm trying to solve, because if I design a control it will run properly only between 0 and 360 degrees, not mor than this or with negative rotation.

What I want to use is the rotation position without encoder reset to obtain, for example, 450º or -80º,-500º. I don't understand why there isn't a function to read rotation in this way, because in the window "NXT Device Control Display", in all "Tacho" columns this kind of result is given.

EDIT: I solved this problem. The problem is that when you put the function degreesToRadians it returns you a value between 0 and 2*PI radians. To solve this, I used a definition #define DEG_RAD 0.01745 and I multiply this with the encoder value.


Sun Jun 01, 2008 12:22 pm
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