Subject:
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RE: Help with connecting pyroelectric sensor
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Newsgroups:
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lugnet.robotics.rcx
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Date:
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Wed, 8 Sep 1999 02:12:39 GMT
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Viewed:
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3470 times
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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 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.
I read the sheet as saying the MINIMUM load is 125K, and the
block diagram indicates a buffered output. It would be a good
idea to buffer the output, but may not be strictly necessary.
The bit about the reference being 20uA capable is correct, and
it is really only there for an A/D converter or for differential
to single ended conversion. The output is, according to the sheet
offset to 2.5V, and I hope the 2.5V reference is relative to ground...
Cheers,
Ralph Hempel - P.Eng
--------------------------------------------------------
Check out pbFORTH for LEGO Mindstorms at:
<http://www.hempeldesigngroup.com/lego/pbFORTH>
--------------------------------------------------------
Reply to: rhempel at bmts dot com
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