1
\$\begingroup\$

I've just moved to a student accommodation,and they are using sensors to keep the lights in the room on(I'm almost sure that they are PIR). The problem is that they turn off way too quickly and it's really annoying to move around just to keep the lights on.

Can I use IR LEDs and send a pulse every couple of minutes to trigger the sensor? If the answer is yes,should I use a 555 timer in astable mode to pulse an array of LEDs or is there a simpler way of doing this? (I also don't know how many IR LEDs should be used or what area they should cover to trigger the sensor if this method works)

\$\endgroup\$
  • 1
    \$\begingroup\$ is there an adjustment on the switch/sensor, behind the faceplate? usually they are adjustable... If you can't control it, get a real lamp and put tape over the sensor. \$\endgroup\$ – dandavis Nov 3 '17 at 22:10
3
\$\begingroup\$

A PIR has a pyro-electric sensor, filter, and Fresnel lens that is designed to detect the IR from a human body, which has a wavelength of 5um to 10um. A IR LED usually emits in the region of 800nm to 900nm. So, a PIR will usually not detect the IR from a IR LED. You can easily prove this by aiming your TV remote at the PIR - it should not trigger it.

\$\endgroup\$
  • \$\begingroup\$ Can I use two filament lamps with a 9V battery to emit that type of wavelength? \$\endgroup\$ – OM222O Nov 3 '17 at 17:43

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.