I have an issue in my kitchen where the PIR, although optimally placed, is still too far to detect the small movements we make when we eat at the table.
I wanted to add another PIR close to the table, but I didn’t want to use another GPIO port on the Raspberry Pi when all I needed was another sensor for the same overall status: movement in the kitchen or not, (regardless of which sensor picks it up).
So what I’m after is a logical OR gate: if PIR1 OR PIR2 is on, then the status is on, otherwise it’s off.
The answer is actually quite simple and only requires 3 components: 2 diodes and a resistor:
- Connect  to the output of PIR1
- Connect  to the output of PIR2
- Connect  to the GPIO port on the Raspberry Pi
Et voila! 2 PIRs for improved motion coverage, but only 1 GPIO port used 😎