Subject:
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Re: To all sensor developers, why use voltage drive ?
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Newsgroups:
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lugnet.robotics.rcx
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Date:
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Sat, 3 Mar 2001 13:35:14 GMT
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Viewed:
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1738 times
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Stef Mientki <s.mientki@ids.kun.nl> wrote in message
news:3AA0BF7B.46088EFE@ids.kun.nl...
> So here I disagree with you , you are correct if you'r saying the inside
AD-converter is measuring voltage, but we're not dealing with the
AD-converter alone, but with a combination of the AD-converter, the pull up
resistor, the diodes and may be more, in short the outside RCX terminals.
The RCX reads the input in powered mode just like it reads the input in
passive mode. The voltage on the terminals. It happens there is a 10K
pull up to make using simple sensors easier. The reason for the 1K resistor
on the opamp is to keep the opamp from getting in the way of the power part
of the powered mode. The results you get with the current interfaces are
better I admit. Look at the real LEGO light sensor circuit
http://www.plazaearth.com/usr/gasperi/light.htm . It has a transistor on
the output like yours too. They get away with what amounts to 1n4148 diodes
for power and ground. I like the opamp they use, but Radio Shack retail
doesn't sell them.
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