Subject:
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Re: 9v Gear Motors
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Newsgroups:
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lugnet.robotics
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Date:
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Thu, 8 Jun 2000 22:19:54 GMT
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Viewed:
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688 times
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There's nothing specially clever about the 9v geared motors.
There are in fact only 2 terminals. The 4 connectors you see are just LEGO's
clever way of supplying power to the motor regardless of the orientation of
the power connector wire.
So forward is one polarity, reverse is the opposite, off is short-circuit and
float is open circuit.
I presume that the different power levels that the RCX can set are simply
different supply voltages (but this is just a guess). However, the actual
speed depends on the load, so the power levels are not really a very good way
of driving the motors at varying speeds.
That is why the power pulsing method is used. Driving the motor at full power,
but in short on/off bursts gives you much better speed control regardless of
the motor load.
Hope this helps.
Conrad.
In lugnet.robotics, Jerry Kalpin writes:
> I have been searching lugnet for more info on the standard Lego 9v
> gearmotors. I know there are 4 terminals. I know there is forward, reverse,
> off (with braking) and float (without).
>
> Mark Overmar's NQC tutorial which is included with Dave Baum's book/CD has a
> scheme to vary the speed by turning it off and on many times a second. I
> absolutely do not understand the code, but it works anyway! He says: "It
> constantly checks the variable speed to see what the current speed is." But
> is there speed monitoring, or current monitoring, or even something that would
> tell the RCX motor direction?
>
> If anyone knows how the motor works, or has any good links, let me know.
>
> Thanks, Jerry
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Message has 1 Reply:
 | | Re: 9v Gear Motors
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| Just went back and re-read the book, and in fact the RCX does do pulse width modulation and not voltage amplitude to set different power levels. In which case I'm not sure why effectively doing the same thing in NQC code works any better, but it (...) (24 years ago, 8-Jun-00, to lugnet.robotics)
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Message is in Reply To:
| | 9v Gear Motors
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| I have been searching lugnet for more info on the standard Lego 9v gearmotors. I know there are 4 terminals. I know there is forward, reverse, off (with braking) and float (without). Mark Overmar's NQC tutorial which is included with Dave Baum's (...) (24 years ago, 8-Jun-00, to lugnet.robotics)
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