Subject:
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Re: NQC contolling motors
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Newsgroups:
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lugnet.robotics.rcx.nqc
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Date:
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Sun, 7 Nov 2004 21:09:15 GMT
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Viewed:
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5153 times
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In lugnet.robotics.rcx.nqc, Yavor Georgiev wrote:
> In NQC I see that I can set the speed of the motors
> at 8 different stages.
Not exactly. What NQC allows you to do is set one of 8 patterns of pulse
width modulation (PWM) for an output. So for instance the highest power level is
"always on" (9V for 100% of a cycle), while a lower power setting is a mixture
of "on" & "float" states (9V for 3/8ths of a cycle, output floated for the rest
of the cycle allowing the motor rotor to freely rotate).
> I can not find though how the stages which are set
> using SetPower function are related to the RPM.
The problem is they're not... well, not much. At 50% power and no load you
still get very close to the full rotational speed on an *unloaded* motor. If
there is a load on the motor, lower power results in lower speed (although
usually not in a simple way, and it depends on the load). But with an unloaded
motor especially, the power levels all result in something close to full
rotation speed.
Why do you need this sort of control?
> The other question is if anyone can give me a hint
> about online documenation or tutorial on calculating
> linear speed when knowing the rotation speed and the
> gears used for translating to linear motion.
Again, Perhaps the best way is to build it and time it. If what you want to
know is *distance*, rather than speed, it's a little easier. One rotation of the
wheel will move a distance of 2*pi*R, where R is the radius of the tire. One
rotation of the motor shaft will result in some number of roations of the tire,
depending on how you have the system geared. If an 8t gear on the motor drives a
40t gear on an output axle, each complete turn of the motor will result in 1/5th
of a turn of the 40t gear (or 8/40ths of a turn). An input axle with a 16t gear
driving an output axle with an 8t gear results in an increase by a factor of two
in output speed (each one turn of the 16t gear will induce two turns of the 8t
gear). Does that help? With a little effort, you can put this into math by
yourself.
--
Brian Davis
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Message is in Reply To:
 | | NQC contolling motors
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| Hi all, I have some questions about controling RCX motors using NQC. I am using Lego 43362 motors. As I understand it has maximum RPM 219 at 9V In NQC I see that I can st the speed of the motors at 8 different stages. I can not find though how the (...) (20 years ago, 7-Nov-04, to lugnet.robotics.rcx.nqc)
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