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tesla80
Joined: 23 May 2007
Posts: 81
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| interfacing PIR sensor directly with PIC |
 Posted: Tue Jan 12, 2010 7:42 pm |
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Hi All,
How does it works?
Some people use big schemes with opamps to detect movement with PIR sensors, but here there is no any opamp..
Can we do this with PIC? |
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mcdnkfc
Joined: 08 Sep 2009
Posts: 4
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| Posted: Tue Jan 12, 2010 10:45 pm |
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I never use PIR sensor before.
But from the schematic, the C4 (1UF) can be use to block dc voltage, and the pin P07 of CY8C27 is an analog pin.
So, I guess this PIR sensor is giving you the analog signal depends on the movement it senses. |
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FvM
Joined: 27 Aug 2008
Posts: 2337
Location: Germany
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| Posted: Wed Jan 13, 2010 1:00 am |
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| Quote: | | Some people use big schemes with opamps to detect movement with PIR sensors, but here there is no any opamp.. |
Apparently you're not motivated to check the features of the involved PSoC respectively processor chips
yourself? It's always instructive, I think. Actually both have considerable internal signal gain. When your PIC
doesn't provide it, you better use external amplifiers. |
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tesla80
Joined: 23 May 2007
Posts: 81
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| Posted: Wed Jan 13, 2010 5:50 am |
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| FvM wrote: | Apparently you're not motivated to check the features of the involved PSoC respectively processor chips
yourself? It's always instructive, I think. Actually both have considerable internal signal gain. When your PIC
doesn't provide it, you better use external amplifiers. |
Yes you are right. MSP430 uses 4x internal gain.
But the opamp circuits for PIR don't contain only amplifier... Differentiator->amplifier->window comparator...
There is no PIC with internal gain, right? |
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FvM
Joined: 27 Aug 2008
Posts: 2337
Location: Germany
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| Posted: Wed Jan 13, 2010 6:56 am |
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The said MSP has a differential 32 mV full range 16-bit ADC, if I understand right. That means, the
detection sensitivity can be up to several 1000 times higher than with a PIC and 10 bit ADC. The circuit
is also involving a highpass, more processing can be done by software.
I think, there's no PIC with internal gain. General, you have to determine the required analog resolution for
your application. I've used PIR sensors for measurement applications, but not designed motion detectors,
so I can't suggest a value, but I assume sub mV. Thus an amplifier would be needed. |
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