Subject:
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Re: Help with connecting pyroelectric sensor
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Newsgroups:
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lugnet.robotics
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Date:
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Wed, 8 Sep 1999 13:02:41 GMT
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Viewed:
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705 times
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Tripp,Edwin <lego-robotics@crynwr.com> wrote in message
news:72B89459DD2BD211B5CD0000F840094E01081E62@oa3-server.dev.oclc.org...
> Gentlemen
>
> The spec sheet for the part indicates that the 2.5 volt
> reference is an *output* for reference purposes only.
> The maximum load is 20 microamps. In other words, that
> pin should only be tied to a high impedance input on a
> voltage comparator or op amp used to detect the state
> of the main output on pin 2. Also, the allowed load
> on the output can be no lower than 125 Kohm. In other
> words, an op amp is a necessity for MindStorms use.
Looks like it pays to read the instructions and not just look at the
pictures. My guess is that the output sits at about 2.5v and moves up and
down with changes in IR. The sensor signal output spec actually says
125Kohm min. The RCX load is 10Kohm, but you might as well put an opamp in
there just in case. You may not need further gain, so the opamp circuit
would be more like my differential light circuit
http://www.plazaearth.com/usr/gasperi/dlite.htm . Hook the output of the
sensor to the + input of the opamp and provide a 125Kohm load to ground.
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Message is in Reply To:
 | | RE: Help with connecting pyroelectric sensor
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| Gentlemen The spec sheet for the part indicates that the 2.5 volt reference is an *output* for reference purposes only. The maximum load is 20 microamps. In other words, that pin should only be tied to a high impedance input on a voltage comparator (...) (25 years ago, 7-Sep-99, to lugnet.robotics)
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