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My little kid likes to press buttons too much, so I'd like to protect a shelf with my HiFi equipment with a door from acrylic glass (PMMA). My only concern is: Would I be able to practically use IR remote when the sensors are behind acrylic glass?

I've found this information on Wikipedia:

PMMA passes infrared light of up to 2,800 nm and blocks IR of longer wavelengths up to 25,000 nm. Colored PMMA varieties allow specific IR wavelengths to pass while blocking visible light (for remote control or heat sensor applications, for example).

Does it mean that plain transparent PMMA will pass beam from IR remote or I need some special coloured variation? I don't know what is the typical wavelength or IR remotes and I don't have any spare acrylic glass pane to just try it.

  • 2
    Worst case, IR extenders are pretty cheap and generally work pretty well. I've been using one (not the one I linked to, I just got a cheap generic one off ebay) for a couple years to operate a cable receiver in a wooden cabinet. – Johnny Jun 10 '16 at 21:52
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Here's a search result from ePlastics, a reliable plastics manufacturer (companies I have worked for have bought from them repeatedly).

Infrared transmitting (IRT) sheet was specifically formulated for projects requiring ultraviolet (UV) and visible light blockage while allowing infrared (IR) transmission starting about 750nm. The physical properties of this product are the same as standard extruded sheet and thus the same fabrication techniques apply. What makes this product special is its ability to transmit light in the IR region. We stock this in 0.060" and 0.118".

Note: All plexiglass sheet is infrared transmitting. This grade is opaque to visible light and allows infrared light through. Unlike glass, you can put all grades of plexiglass in front of DVR's, cable boxes, DVD players, etc. and your remote control, wireless router, etc. will still work. This particular acrylic material is black and only transmits infrared, which makes it ideal for hiding a CCD video camera.

While it's probably not safe to say that all acrylics transmit all frequencies of IR light, based on this I would say it's safe to say that most acrylics (and Plexiglas brand specifically) would allow transmission of remote control signals.

The particular result above is for a plastic that is opaque to visible light, but if you're looking for clear, you could probably call them and verify that the clear versions transmit IR light, even if you're not going to buy from them.

  • The thickness and any tint may degrade the signal but with fresh batteries and a direct line of site from the remote to the receiver I have had no complaints with 1/4" clear , the brown /gray tinted did have a large loss on a nice system and we changed to clear and the customer was happy with the cabinet but did like the tinted look better. Make sure your bits are sharp of cutting custom shapes and go slow spraying with water to prevent cracking and chipping. oil may dull the finish so I have learned to use water in a squirt bottle to help clear the chips. – Ed Beal Jun 10 '16 at 22:53
  • Remote controls etc use near-IR very close to visible red (some people can see some remote-control IR, albeit very dimly!), that will commonly but not always go through anything that is transparent to visible light. Far-IR (heat radiation) actually won't even go through real glass, but it is not used for IR communication. – rackandboneman Jan 20 '18 at 9:59
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A simple way to find out...

(1) Use your smartphone camera to view the remote: the camera is sensitive it the IR and will show up when you press a button on the remote.

(2) Now view the remote through a sample of the acrylic glass.

This is also a handy way of testing the remote e.g. for flat batteries.

HuwjOnes

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