Does infrared bounce off a mirror? I know it’s a longer wavelength than visible light, but not much. I was thinking that perhaps I could hang a little bike mirror from the ceiling and control the stereo in the next room more cheaply than I could get the proper electronics at good ol’ Radio Shack.
How many laws of physics am I trying to break? Is Newton rolling in his grave?
–Alan Q
IR bounces nicely off mirrors and sometimes even your hand. Remember the good old inverse square law though. When you make the total path twice as long the signal strength is 1/4 as powerful at the reciever. IIRC Steve Wozniak of Apple II fame marketed a device that amplified the signal from the remote so it would bounce around walls without even being aimed and activate the desird device.
Yes it does reflect, thats how i control my stereo. The mirror that i use is very big, i don’t know if you could work it with a small bike mirror.
It bounces not only off mirrors, but other flat objects like walls, etc.
Yes, the IR signal will reflect off a mirror. You’ll need to orient the mirror so you can see the front of the TV in it from where you will be will be sitting. If you can’t see the TV, then the TV can’t “see” the IR signal from the remote. Also distance is a factor, since the signal strength drops off with increasing distance. How far away you can go with it depends on the output strength of the IR LED, the beamspread and the sensitivity of the receiving components. Also the mirror will probably not capture the entire cross section of the IR beam, so there’s further losses there. A larger mirror will work better. A mirror that has a convex curvature will cause greater beamspread than one with a planar or concave surface, but unfortunately, many side rearview mirrors are of the former type. None are convex. So, ideally, you want concave parabolic mirror with a large surface, and an appropriate curvature to focus as much of the IR as possible onto the receiver aperture. Good luck.
Of course I meant “None are concave”.
You don’t necessarily have to angle the mirror so the beam hits the device being controlled. Sometimes it works well enough to hit the opposite wall (i.e. the wall facing the device in question). In many cases the device’s sensor will “see” the spot of IR on the wall and respond to it just fine. These IR receivers are very sensitive and the IR LED’s in a remote control are usually very bright and a small mirror, while not ideal, might work just fine. Experiment! It’s fun, at least if you’re a hopeless geek like I am.
Padeye,
That sounds very similar to the stuff RS has for sale–and as more than one ex-girlfriend has told me, I’m very retro–hence the curiosity about mirrors. Yor comment about the “good old inverse square law” gives me a context for Q.E.D.'s comments–
Q.E.D.-- Convex mirrors makes me think of anti-shoplifting wide angle mirrors in stores, and I like the idea, but I suppose, as you said, effectivness would depend on the power of the transmitter, the light would scatter badly.
Long live the SDMB! (and Newton may not be rolling in his grave, but he’s probably chuckling to think most of his precepts still work!)
–Alan Q
SDStaff Karen has a report about this subject here: Why does the remote work if I point it at the TV’s reflection in a mirror? Plus: Why are there no clear metals?.
There are threads about this report in the “Comments on Staff Reports” section here and here.