For putting 8 PIR Sensors to one Arduino Mega, I would like to ask if it would be better to let all of them recieve Power (each needs 5V) from the Arduino or to attach them to an external Power Supply and the Arduino to another?
I would like to basicly daisy chain them to recieve power.
Also, does it cause problems when the signal output of the sensor goes through a 4 meter cable until it gets to the Arduino?
The PIR sensors don't draw much current(<100uA). You can drive 8 of them fine from the arduino. You can run the same lead to each of them in turn (daisy chain). I don't think that you'd even need to worry about decoupling it.
Because the PIR is fairly slow and is on-off I don't think the 4 metre cable would be an issue either.
I have to say that the PIR is easy to use but is not at all precise - what are you going to do with 8 of them?
Thanks, I am planning to do an installation which activates lights when people pass by. Do you maybe have a better solution then PIR?
That's Sounds like a great application for the PIR.