Subject:
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Re: Using the Motor as a Tachometer
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Newsgroups:
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lugnet.robotics
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Date:
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Mon, 9 Aug 1999 21:49:53 GMT
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Viewed:
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892 times
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In lugnet.robotics, "Ralph Hempel" <rhempel@bmts.com> writes:
> > Turning the motor increases the electrical potential (voltage) between its
> > two contacts. If the motor isn't connected to anything, then its easy to
> > turn - relatively little energy is required to make one of the motor
> > contacts sit at a higher potential than the other. If you short the motor
> > contacts together, however, then you have a different situation. In order
> > to maintain a difference in potential, you need a sizeable current moving
> > through the wires. This requires a lot of work, thus its hard to turn the
> > motor. Thus how "hard" it is to turn the first motor has to due with how
> > much current needs to be moved in order to maintain a certain voltage.
>
> In fact, this is how the RCX motor controller internally sets the motor up
> for "brake" instead of "off"...
No way! Really? Too cool! Does it do this with some kind of switching
relay or is it purely electronic?
--Todd
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Message has 2 Replies:
 | | RE: Using the Motor as a Tachometer
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| Any rotating motor becomes an instant generator too...I use motors to power the fiber optic kit instead of using a port on the RCX or a seperate battery pack. An example is at: (URL) Thompson richone@midsouth.rr.com (URL) Message----- From: (...) (25 years ago, 9-Aug-99, to lugnet.robotics)
| | | RE: Using the Motor as a Tachometer
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| (...) Totally electronic...but we used to do it with switching relays...use a non-proportional font for the following... /+---...--- V+ from power supply +--/ | +---+ +------+---+ | <- This is really a low value resistor --|MOTOR | | not connected (...) (25 years ago, 9-Aug-99, to lugnet.robotics)
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Message is in Reply To:
| | RE: Using the Motor as a Tachometer
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| (...) In fact, this is how the RCX motor controller internally sets the motor up for "brake" instead of "off"... Cheers, Ralph Hempel - P.Eng ---...--- Outside of a dog, a book is a man's best friend. Indside of a dog, it's too dark to read... (...) (25 years ago, 9-Aug-99, to lugnet.robotics)
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