One could just move the clock radio really close, but why go for the simple solution when a complicated one will do? I wanted a clock like this for years.
To make one, you need the following main components:
When the image is projected through the lens it ends up reversed, so to flip it around again you need to reflect it in a mirror. A regular household mirror has the reflecting material on the back, so you get a ghost reflection from the front of the glass. For this project you need a front-silvered mirror. I got mine out of a broken 35mm SLR camera, but a more likely source is a broken laser printer, FAX machine or scanner.
The lens may be the hardest part to find. Mine is an 80mm f/3.5 viewing lens from a cheap old twin-lens reflex camera. It has a built-in focusing mechanism, and projects an image about 1m across onto the wall from the other side of the room. The next best thing would be a slide projector lens which would give you a brighter but smaller image (typically they are 100mm f/2.8.)
Construction is pretty simple, with bits of sheet metal and a lot of epoxy glue. You can either build it very accurately, or you can bend things around a lot until the projected image is level and has consistent focus from corner to corner. I used the latter approach as you can probably see from the picture of the guts.
The whole thing is powered by a wall wart. The two pushbuttons are connected to the clock setting contacts. The box is a generic metal project box, with the hole for the lens gouged out by a rasp bit on a dremel tool. The threaded ring that the lens screws into is glued onto the inside of the lid with epoxy.
The focusing range is the same as that of the camera was, about 1m to infinity. I have the clock on top of my bookshelf, aimed down at the white wall just over my bed. The resulting display is large enough to read easily without glasses on, and just bright enough. When it gets light enough outside to make it unreadable, I shouldn't be in bed anyway.
A perfect project for a junk and garage sale hound. I can't imagine where you'd go to buy the necessary components new.
I bought this clock for my parents for Christmas, and I like it. If it was available back in 1998 and if I had known about it, I probably wouldn't have bothered building mine. It projects a sharp red display. The projected display is only about a foot across when projected from 4 metres away, not huge like mine, but in return it is brighter. The clock makes an impression of good quality. There are only two things wrong with it: The "AM" or "PM" display above the projected time is huge, out of proportion with the numbers, and the green backlight for the nice LCD display on the clock itself cannot be set to stay on, even when the clock is plugged into the wall -- you have to press the snooze button to light it for 5 seconds or so.
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