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Problem with motion detector (PIR) Circuit

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Saeedk9574

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Hi everyone, I have a problem in circuitry of PIR. I am using the model D203B of PIR and I used a schematic (first picture) based on its datasheet. I do not no why it does not work. The connected LED to the output of IC (op-amp lm324) is always on. I have checked the health of lm324 and all the connection.
Here is the my schematic and PCB (2nd and 3rd pic)

Screenshot (191).png
Screenshot (192).png


Screenshot 2024-05-26 221517.png
 
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Your circuit misses AC coupling (C5 in original schematic) between sensor and first amplifier stage which is essential.
--- Updated ---

Sorry, I confused first with second stage. Schematic is basically correct.
--- Updated ---

I'd add a feature to adjust gain.

For debug check node voltages with multimeter, disable amplifier stages for test, disconnect 10k between first and second stage, reduce first stage gain to 1 by disconnecting 47k R10(R4), to find out where's the problem.
 
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Hi,

Consider to use a proper GND plane on your next design.
It gives a lot of improvements. In this case regarding noise and clean swtiching, but also better EMC immunity.
The circuit isn´t that complex and a GND plane should be doable without much effort.

Klaus
 
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FvM said:
Your circuit misses AC coupling (C5 in original schematic) between sensor and first amplifier stage which is essential.
--- Updated ---

Sorry, I confused first with second stage. Schematic is basically correct.
--- Updated ---

I'd add a feature to adjust gain.

For debug check node voltages with multimeter, disable amplifier stages for test, disconnect 10k between first and second stage, reduce first stage gain to 1 by disconnecting 47k R10(R4), to find out where's the problem.
Click to expand...
Before applying the changes that you suggested, I should say there is a problem in the first V ref (pin2) I have no stable signal so first v out (pin 1) is zero.
By the way, Output of (pin S) sensor on pin 3 is around 0.8 which I think is normal.
 
Last edited:
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I had made a mistake in soldering and c9 had not connected to the track of pin 2 so there was not v ref now it is solved.

Now how can I make the time and also sensivity of output adjustable ?
 
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