PIR sensor problem (wireless alarm)

[Albertxuxu]

Hi. Recently I was working on a small project which involves a PIR sensor and a walkie talkie (two way radio). Basically what the circuit is supposed to do when the PIR senses a motion, it triggers a relay which closes the contacts of the "call " button of the walkie talkie, thus sending a call to another radio. It is a simple wireless alarm.

With the radio swithed off, the PIR triggers the relay successfully. However when the radio is on and the PIR detects motion, the relay is activated as usual and sends a call BUT it keeps triggering on and of repeatedly.

This cycle won't stop until I turn off the radio or the PIR sensor.

What can I do in order to send only one call when motion is detected please ?

 

[FvM]

Either the battery voltage drop during call or picked-up RF is retriggering the circuit. Two options:

- Redesign the circuit that it's less sensitive to RF and supply voltage variations
- Add two monoflops to generate a call pulse of defined duration and blocks the trigger afterwards for some time.