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advice on PIR motion sensors

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samseif6

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Am working on a ready made PIR motion sensor which i innovate by wiring to a mobile phone, which when triggered, calls me on my cell phone. the sensor works properly except that the sensor's circuitry has a self triggering effect after every 2 hours, so as much as it notifies me on real alarm situations, it also calls me after every two hours.
Please advice on how to stop the self trigger, and only trigger when motion is sensed ie how to loop the circuitry and by pass the self trigger timer on its circuit board.
thanxxx.
 

You need to give more details. I don't know of PIR sensors which alarm every 2 hours for no reason. A more likely reason is something near the PIR is triggering it - some sort of electromagnetic interference maybe.

Keith
 

You gave no data for the motion sensor, so it’s really difficult to estimate what to do in order to change something. Better try to change the sensor…
 

A more likely reason is something near the PIR is triggering it - some sort of electromagnetic interference maybe.
E.g. the mobile phone's housekeeping communication with the base station.
 

P1080834.JPGP1080835.JPGdig problem1.JPGP1080833.JPGPIR Motion Sensor project.

The PIR Sensor used in this project was designed for another wireless Alarm system. I had to use this part of the system because, PIR sensor/circuits are not easily available at my area.
The problem is, how can i evade the timer which triggers a logic high output that is timed and goes high after every 2 hours.
I have short wired the high output and ground to a cell phone dial button, which subsiquently dials a pre-set number on a high signal.
All is well, when the sensor senses sudden heat motion, it triggers the circuit, i get a call. But it also gives me a call after every 2 hours, on accurate intervals.
It would really help if i could know which component compels the 2 hour timer, and how i could evade it, so that the security sytem would only give me a call on actual motion triggers.
Above are diagrams on the circuit. Your advice will be appreciated. Thanks.
 

E.g. the mobile phone's housekeeping communication with the base station.

View attachment 58828View attachment 58829View attachment 58830View attachment 58831PIR Motion Sensor project.

The PIR Sensor used in this project was designed for another wireless Alarm system. I had to use this part of the system because, PIR sensor/circuits are not easily available at my area.
The problem is, how can i evade the timer which triggers a logic high output that is timed and goes high after every 2 hours.
I have short wired the high output and ground to a cell phone dial button, which subsiquently dials a pre-set number on a high signal.
All is well, when the sensor senses sudden heat motion, it triggers the circuit, i get a call. But it also gives me a call after every 2 hours, on accurate intervals.
It would really help if i could know which component compels the 2 hour timer, and how i could evade it, so that the security sytem would only give me a call on actual motion triggers.
Above are diagrams on the circuit. Your advice will be appreciated. Thanks.
 

I think you didn’t choose the right output connection in the circuit.
 

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  • Phone connection.JPG
    Phone connection.JPG
    58.5 KB · Views: 182
Please advice on the right output connection.
 

Hi,
BISS0001 is an Micro Power PIR Motion Detector IC, with the builtin option of retriggerable & non-retriggerable mode. Pin 1 controls the function. Re-triggerable mode is enabled, when pin 1 has logic high. I think in this design, Re- triggerable mode has been enabled. Grounding the pin1 could solve the problem.
Kindly refer the attached datasheet.
 

Attachments

  • BISS0001.pdf
    273.5 KB · Views: 114
BISS0001
Pin 1 = Retriggerable & non-retriggerable mode select

You can set a Tx =The time duration during which the output pin (Vo) remains high after triggering and and a Ti = During this time period, triggering is inhibited. => In retriggerable mode select, pin1 set to Vcc,each additional pulse add extra time to the Tx, so maintain the status for Vo (detector output pin) level high.

So, no relation here between the pin 1 connection to Vcc/GND and the actual problem.
 
Thanx people, i solved the problem by placing a diode between the two points, logic hi and ground.
I realized the circuit had a continuous "closed circuit effect" on the phone dial switch, which only opens when the sensor switches, then closes again.
so the phone switches/resets after the two hours of a short circuit on the keypads, thus making the phone call since the dial switch returns to a "closed circuit" situation.
 

Thanxx mister_rf, that's exactly what i needed. Peace.
 

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