Motor ticks per revolution

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Title: NooBot
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The documentation says that the motor turns 1100 ticks per revolution but our experiments show it to be closer to 800. We were wondering if anybody has narrowed it down more specifically.

-Amy coach to Twister Robotics

ruler501's picture
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It depends very strongly on the motor you are using and your robot.
The mean is about 1100. 800 seems remarkably low to me so you might want to try a better testing system
Here is an example of how I'd do it. I'd get extremely accurate measurements of diameter(to within 1mm) and then have it run for ~5000 ticks and measure the distance it has traveled(has to be in the same units as the diameter)
ticks*rot/tick = distance/(pi*diameter)
tick = (pi*diameter*5000)/distance

Jeremy Rand
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Hi Amy,

If you're trying to figure out how far your robot has traveled, using motor revolutions really isn't a particularly reliable way to do it, because wheels slip. What I generally recommend is telling the robot to drive for a fairly long distance (say 20,000 ticks), measure how far it traveled with a tape measure, and compute the ratio of ticks/mm. Once you've done that, tell it to drive 1 meter using that ratio, and adjust the ratio until you're reliably traveling exactly 1 meter. You can now use the ratio you've found to travel arbitrary distances, and wheel slip is already factored in (assuming that the slip is constant... not exactly accurate, but better than assuming the slip is zero).

-Jeremy Rand
Senior Programmer, Team SNARC (2012-2013), Norman Advanced (2010-2011), Norman HS (2008-2009), Norman North (2005-2007), Whittier MS (2003-2004)
2012-2013 VP of Tech, 2011 President, Botball YAC (2009-2013)
Mentor, Alcott and Whittier MS

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The mean is about 1100. 800 seems remarkably low to me so you might want to try a better testing system

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The older motors scale tics to ~ 1100/rev; the newest (2016 - Botball lables) have only 800tics/rev. You can quickly validate which motor you have and calibrate it with the motor test screen. If you want your bots to go straight, please match the drive motors, and add a small trim if needed. [do not mix old and new motors.]

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