Hello, i am making a project with GSM module and some sensors.Hall sensor,PIR,ultrasonic.
Everything is working fine but something when i make call to GSM seems the PIR sensor 'see' a high signal and gives false alarm.
The Tx/Rx wires and PIR wires and very very close, almost toucthing each other.Is possibly the UART signals or GSM recieve signal confuses the sensor?
Move them apart, use different pins, and see what happens. Put grounded shied between them if still a problem.
Weedpharma
Most likley RF interferance from the GSM shield. GSM uses TDMA which causes RF pulses to be transmitted from the GSM shield when a call is in progress. Move the PIR sensor away from the GSM shield, and see if the problem dissapears.