PIR motion sensor - HC SR501 --> need low output on detection

Other Hardware General Electronics
1

Hi there!
I am working on an alarm clock. I'd like to make the screen light up when motion is detected and let the backlight go out again after a while.
This was no problem. But I'd also like to put my Arduino to sleep while I'm not using it using the powerDown sleepmode.

My problem is that I read it can only react to LOW level interrupts, while my PIR sensor outputs HIGH when motion is detected.

Is there a workaround for this?

Thanks!
Bram

2

Put a transistor between the output of your sensor and the Arduino input, this inverts the signal.
Are you sure you need this work around?

3

Grumpy_Mike:
Put a transistor between the output of your sensor and the Arduino input, this inverts the signal.
Are you sure you need this work around?

OK, that looks interesting. I'll have to look whether I won't have more leaking amps over there than just keeping the Arduino active.
Well, I think so....

Other than in active mode the external interrupt pins can only detect a LOW level

(ATmega328P wakeup from sleep via interrupt - heliosoph)