Circuitry Problem with PIR

Thread Starter

Saeedk9574

Joined Jan 1, 2024
19
I am using D203B model of PIR and I used the circuit that was suggested on its datasheet (first pic). I do not know what the problem is, as the output (pin the 8 and 14) of op-amp (LM324)is always on (which is connected to the transistor and LED). In fact, It does not react based on PIR output as I disconnected the PIR from op-amp and the output of op-amp was still on. By the way, I have checked LM324 and it was healthy so problem is in my circuit. Here are my circuit schematic and PCB (2nd and 3rd pics). I appreciate you, if you realize the problem.
 

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Thread Starter

Saeedk9574

Joined Jan 1, 2024
19
Hi,
With the PIR sensor disconnected, take the signal (S) to the +12v via a 1k0 or similar, see if the output goes low.
Good luck...........
S pin of sensor is around 0.8 which I think it is normal. Next, I should say there is a problem in the first V ref (pin2) as I have no stable signal on it so first v out (pin 1) is zero.
 

MisterBill2

Joined Jan 23, 2018
19,466
First, if both of the opamp outputs, pins #8 and #14arehigh, then either the input is oscillating or both sections have their inputs exchanged. The voltage at pin7 should be between the voltages between the three resistor divider.midpoints.Or possibly the ends of that divider string are reversed.
In addition, I see way too much gain in the DC amplifier section driving the two opamps used as comparators. Running a low-precision opamp as a high gain DC amplifier is begging for problems.
 

Thread Starter

Saeedk9574

Joined Jan 1, 2024
19
hi S,
What time range and sensitivity?
E
What I mean is that the time of being on of the output. With this circuit output is on as long as it sense a motion, I want it be on for a few seconds after detecting motion. In addition, I want to be able to adjust its sensitivity to the motions.
 

Thread Starter

Saeedk9574

Joined Jan 1, 2024
19
First, if both of the opamp outputs, pins #8 and #14arehigh, then either the input is oscillating or both sections have their inputs exchanged. The voltage at pin7 should be between the voltages between the three resistor divider.midpoints.Or possibly the ends of that divider string are reversed.
In addition, I see way too much gain in the DC amplifier section driving the two opamps used as comparators. Running a low-precision opamp as a high gain DC amplifier is begging for problems.
I took this circuit from PIR schematic. If lm324 which is suggested is not precise, which op-amp is better to use with PIR.
 

ericgibbs

Joined Jan 29, 2010
19,121
hi Saeed,
Note the change to a simple MOSFET and a 1meg/1uF delay, you can extend the On time.
Increase value of C12 to increase On time
R17 represents the Relay coil
E
EG57_ 1781.png
 

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MisterBill2

Joined Jan 23, 2018
19,466
What I mean is that the time of being on of the output. With this circuit output is on as long as it sense a motion, I want it be on for a few seconds after detecting motion. In addition, I want to be able to adjust its sensitivity to the motions.
OK, adjusting the sensitivity will mean adjusting the gain of the amplifier stages. reducing the on time will require adjusting the RC time constant of the relay driver transistor base drive circuit. Changing the output to switch off after a short time will require the addition of a non-retriggerable timer into the switch transistor base circuit.
So now I wonder just what the application of this circuit is supposed to be.
 
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