PIR Sensor's output go high when GSM Module transmits or receives signal

Discussion in 'The Projects Forum' started by softlab, Dec 9, 2014.

  1. softlab

    Thread Starter New Member

    Jun 12, 2011
    3
    0
    Dear Friends,

    I have connected GSM Module (SIM900B) , PIR Sensor and PIC MCU parallel from single LI_ION Battery (3.7v, 1450mAh).

    Batt -> GSM Module -> PIR Sensor
    Batt -> Diode -> PIC MCU

    Both GSM Module and PIC MCU placed on same PCB and works fine. But 300mV Voltage Drop out occurs when transmit burst* happens at GSM Module, as said in SIM900B datasheet. PIC did not reset and works as usual. I have bought PIR sensor from ebay and added to the existing PCB and connect its output pin to PIC MCU. Power supplied from batt directly (through wires, 6 CM length approx), i.e. parallel to GSM Module. I have connected 1000uF/25v elect capacitor at VDD pin of PIR Sensor to avoid resetting PIR when 300mV drop out occurred.

    1. When I run the circuit, manytimes, PIR sensor output go high whenever GSM Module transmits or receives. Only sometimes working as expected. What could be the problem?

    2. HT7133, 30mA LDO used on PIR Sensor Modue. I have removed that LDO and caps (22uf and 10uf) and power given directly to the output pin of LDO from PIC MCU pin (around 3.27V). But PIR Sensor module output always fluctuates between On and Off every seconds.

    The working voltage of BIS0001 IC is 3 to 5V
    The working voltage of PIR Sesnor is also 3 to 5V (But Vref mentioned as 3.6v in datasheet).

    3. If LDO removed and power from Battery through diode also won't work. the same problem occurs as I powered from PIC PIN.

    4. If no GSM Module powered, PIR Sensor modules works well with PIC MCU (but powered from battery directly NOT from PIC PIN power supply).

    PIC MCU: PIC16LF1938
    PIR SENSOR: RE200B
    PIR SENSOR IC: BIS0001

    datasheets attached

    PIR Sensor Product details can be found at : http://www.ebay.in/itm/like/171539352406

    Any help would be highly appreciated.

    thanks
    pmk
     
  2. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    5,791
    1,103
    Try this (no guarantee :)) :-
    Diode-isolated-supplies.gif
     
  3. softlab

    Thread Starter New Member

    Jun 12, 2011
    3
    0
    PIR Sensor Module already has protection diode on the board. I tested that also. But only works sometimes as I already said. PIR Sensor module uses HT7133, 30mA LDO and it supplies 3.3v to the Module. It works sometime. I also supply the 3.27V from PIC Pin but never works. Why? The entire module only consumes max current 50uA only at conversion. But in idle only 6uA current consumed by LDO. What could be the problem in the supply from PIC Pin. It can source up to 20mA.

    thanks
    pmk
     
  4. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    5,791
    1,103
    Well, if what you've now got doesn't work it's time to try something else :). One diode in the PIR may not be effective. Have you tried my suggested arrangement (3 diodes, no LDO)?
     
  5. alfacliff

    Well-Known Member

    Dec 13, 2013
    2,449
    428
    the gsm module puts out rf, something on the pir board is detecting (rectifying) the rf and turning on the output. shield the pir board from if.
     
    softlab likes this.
  6. softlab

    Thread Starter New Member

    Jun 12, 2011
    3
    0
    Hello alfacliff,

    First I thought your answer is completely irrelevant to my issue that I posted here. After some in-depth study after your reply, I came to know that you are fully right. I have checked some mobile phones PCB and I saw that all ICs on the PCB are enclosed with the RFI/EMI Shield. Also, same issue that has been experienced by another user and got the solution by increasing the distance by 1 to 2 CM from RF component. Now, I have shielded the PIR Module (ICs side) using tin paper and doing the testing. Will wait until tomorrow to check whether this method works. If not, I can move the PIR Module apart from GSM Module (Antenna) and see the result. Once if I get the solution I will update.

    url: https://forums.electricimp.com/discussion/1898/pir-motion-sensor-get-rf-interference/p1

    thanks a lot alfacliff.

    pmk
     
  7. alfacliff

    Well-Known Member

    Dec 13, 2013
    2,449
    428
    we have had a lot of rf issues around here, even a multi channel chart reecorder jumping 10 degrees when a forklift driver transmitted on his two way radio nearby. good luck.,
     
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