need to protect PIR MODULE from resetting while voltage drop out due to GSM Module

Dear friends,

Circuit consists:

1. SIM900B GSM MODULE (3.2V to 4.8V)
2. PIC16F1938 (1.8V TO 5V)
3. PIR MODULE (available on all online store - 3.6 to 5v)

Power Supply: 3.7v, 1450mAh Li_Ion Battery.

Only single power supply used for the entire circuit. I have PCB that was already designed and connect the PIR Module (purchased separately) from PCB.

BATT -> GSM Module
BATT -> 270R resistor -> PIR Sensor
BATT -> Diode -> PIC MCU

PIR OUTPUT Pin connected to PIC MCU EXT INT Pin.

Problem: When GSM Module sends/receives SMS/Call the current consumption can raise up to 2A suddenly. Due to this peak current, voltage drop up to 300mV will occur. At this time, PIR Module also suffer and output pin of PIR Module go high and ext interrupt occurred falsely. I tried to use 1000uF elec cap at input of PIR MODULE. It works fine (no resetting problem and thus no false ext int occurred) sometimes and sometimes NOT. I have tried to use resistor (270 ohms) between batt and PIR Module (as mentioned above here). Sometime works fine and sometimes NOT. Even when not using 1000uF and Resistor, PIR Module works fine sometimes and sometimes NOT.

HT7133, 30mA, LDO used on PIR Module.

What could be the problem? Any idea pl?

thank you
pmk

any help?

pmk

I found that it is NOT a problem (PIR Output) due to voltage drop of 300mV. It is because of RF Interference. I got one recommendation from one of my friends to use RFI/EMI shield to protect PIR module from RFI/EMI interference. I have used tin foil as a shield and put backside (components) of PIR Module. As of now (6 hrs), no errors happened and it is still under testing. Will wait for 24 hrs to confirm that this is the actual issue. Once succeeded will update.

ref url; **broken link removed**

thanks
pmk

Even i am facing the same issue. now can you please help me to guide about the shield did it work or not?
what did you do to get this issue solved??