Subject:
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Re: Question?
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Newsgroups:
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lugnet.robotics
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Date:
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Mon, 4 Feb 2002 10:51:53 GMT
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Viewed:
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694 times
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lego-robotics@crynwr.com (T. Alexander Popiel) writes:
>
> In message: <200202031206_MC3-F079-6BD5@compuserve.com>
> PeterBalch <PeterBalch@compuserve.com> writes:
> > > When set to use "active" sensors, the
> > > inputs actually output power most of the time, switching briefly to
> > > input mode (no power output) to take a reading.
> >
> > What I don't understand is how this works if the sensor is connected
> > backwards.
> >
> > Sure, a bridge rectifier will get the power sorted out but how does the
> > sensor send back a voltage in the right range? If say "light" is 8V and
> > "dark" is 0V then when the sensor is connected backwards, "light" will
> > be 0V and "dark" will be 8V.
>
> My guess (having never looked at the schematics, or taken one apart)
> is that when connected backwards, "dark" would be 0V and "light" would
> be -8V. Again, a simple bridge rectifier (this time in the RCX) would
> get it sorted out.
No, there's no bridge in the RCX, just a pull-up to 5V (10kOhm IIRC).
If you look at the schematics
(say at http://philohome.free.fr/sensors/legorot.htm)
you see that there is another bridge rectifier in the sensor
between ground and the raw sensor output.
The ground half of the bridge is shared with the power supply bridge.
Jürgen
--
Jürgen Stuber <stuber@loria.fr>
http://www.loria.fr/~stuber/
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Message is in Reply To:
 | | Re: Question?
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| (...) My guess (having never looked at the schematics, or taken one apart) is that when connected backwards, "dark" would be 0V and "light" would be -8V. Again, a simple bridge rectifier (this time in the RCX) would get it sorted out. It might be (...) (23 years ago, 4-Feb-02, to lugnet.robotics)
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