Ask MAKE: Hidden LCD screen?

Ask MAKE is a weekly column where we answer reader questions, like yours. Write them in to mattm@makezine.comor drop us a line on Twitter. We can’t wait to tackle your conundrums!

Liz writes:

I’d like to install an outdoor wired (or wireless) low light stationary camera outside my residence – I’d like it to annunciate to a mirror sort of similar to the rear view mirror camera that only activates once the vehicle is in reverse. Is there a way to develop a mirror capable of switching to the camera on cue by using a light switch or something along those lines? The “mirror” would be located adjacent to my front door and framed aesthetically as it’s primary role would essentially be a mirror until you needed to access the camera. Thank you in advance for giving us a heads up!

Oh, that sounds like a fun project! You can’t really buy a mirror that can be turned on or off (at least to my knowledge). Instead, what you want is a ‘one-way’ or half-silvered mirror. These are the kind of mirror that you might see featured in a movie about an interrogation room, where observers can hide in an an adjacent room and look through.

The mirror doesn’t really only allow light to pass in one direction, though. Instead, it has a fine metal coating on it that reflects one half of the light that goes through it, and lets the other half pass through as if it were a regular pane of glass. The trick is that the secret observation room is kept much darker than the investigation room, so that any light that does make it the wrong way through the mirror is overpowered by the reflection from the main room. If the observers mistakenly turned on their lights (or lit a cigarette), the people in the investigation room would be able to see them!

If you build a little cabinet to hide the display for your camera, and put a piece of one-way mirror glass over the front, then I think you will get the effect that you want. To be able to see the feed from the camera, just turn on the display, and it will instantly visible. Look for TV mirror glass- it’s a product designed to do exactly what you are looking for. I was able to find a few manufacturers that are selling small sample sizes for ~$20, which should be more than adequate for a small camera monitor. Good luck with your project!