Hello,
I have a passive infrared sensor (PIR), typically used in motion detectors, connected to an opamp. The PIR signal fluctuates about 0.7V. The opamp output, v1, is 0.7V + the derivative of the PIR's signal. When there's no motion in front of the PIR, v1 = 0.7V. When there's motion, v1 is greater or less than 0.7V. How do I amplify (v1 - 0.7V)? In other words, I want to amplify any difference from the base voltage of 0.7V when nothing is moving.
I've tried using another opamp with v1 in one terminal and something close to 0.7V that I generate with a voltage divider, but since I need to amplify the difference 100 fold, if the voltage divider is slightly off, the slight error gets magnified 100 times and the opamp hits a rail. I've also tried standard motion detector circuits that use two opamps, but the second opamp ends up producing the 2nd derivative of the PIR signal.
Thanks in advance for your help.
I have a passive infrared sensor (PIR), typically used in motion detectors, connected to an opamp. The PIR signal fluctuates about 0.7V. The opamp output, v1, is 0.7V + the derivative of the PIR's signal. When there's no motion in front of the PIR, v1 = 0.7V. When there's motion, v1 is greater or less than 0.7V. How do I amplify (v1 - 0.7V)? In other words, I want to amplify any difference from the base voltage of 0.7V when nothing is moving.
I've tried using another opamp with v1 in one terminal and something close to 0.7V that I generate with a voltage divider, but since I need to amplify the difference 100 fold, if the voltage divider is slightly off, the slight error gets magnified 100 times and the opamp hits a rail. I've also tried standard motion detector circuits that use two opamps, but the second opamp ends up producing the 2nd derivative of the PIR signal.
Thanks in advance for your help.
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