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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Thu, 7 Feb 2002 12:50:08 GMT
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Viewed:
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535 times
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Hi Peter,
lego-robotics@crynwr.com (PeterBalch) writes:
>
> > If you look at the schematics (say at
> http://philohome.free.fr/sensors/legorot.htm)
>
> busted link!
it works for me.
http://www.plazaearth.com/usr/gasperi/rotate.htm shows another
schematics that doesn't show the real rotation sensor circuit,
but has the same interface to the RCX.
> I was under the impression that some of the sensors had contained active
> components that amplified or buffered the signal.
Yes, that's the case.
> In which case which way=
> round the sensor is can give rise to problems unless the the designers ar=
> e quite clever.
That's what the rectifier bridges are for.
> But the light sensor can't be the equivalent of a resistor across the
> terminals. =
With the rectifier bridges it's diode-resistor-transistor-diode
(rotation sensor),
where there are several transistor to select the right resistor.
> But secondly, someone mentioned that there is an Op-Amp in
> the sensor. The signal from the photodiode is
> buffered. Which brings us back to my original point that
> it's hard to make a circuit that's connected to just two
> wires and doesn't care which way round those wires are
> connected.
Once you've seen it it's not that hard.
I think there is even a better way to do it that is
described in the Extreme Mindstorms book, which reduces the
nonlinearities due to the diodes.
Jürgen
--
Jürgen Stuber <stuber@loria.fr>
http://www.loria.fr/~stuber/
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Message has 1 Reply:
 | | Re: Question?
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| I've put a simple sensor interface design on Brickshelf which shows the key elements of providing a linear bi-polar connection to the RCX sensor input. (The two wire RCX connections are represented by the large circles to the right of the (...) (23 years ago, 7-Feb-02, to lugnet.robotics)
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Message is in Reply To:
| | Re: Question?
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| (...) I meant that the sensor can be connected either way round. (...) (URL) link! I've yet to find a working link to _any_ schematic of the light or rotation sensor (...) current, and "light" is full current, regardless of polarity. Maybe that is (...) (23 years ago, 7-Feb-02, to lugnet.robotics)
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