Analog Projection Clock So Simple You Should Have Thought Of It

The image you see above is the result of a simple analog projection clock. It shows the time on the ceiling. We have one in our bedroom but it’s a red digital display which we don’t think is nearly as fun as this clever hack. Grab a cheap analog clock, a mirror, and a white LED and you can build your own.

The mirror is going to reflect light from the LED onto a ceiling or other surface. It acts as the clock face. The tick marks for each hour were made by scratching the reflective material (often called the silvering) from the back of the mirror. A hole is drilled at the center of the class and the analog clock is mounted with its hands on the business side. The one problem with this setup is that since the light is being reflected, the clock will appear to run backwards. Not a problem, if you just reverse the polarity of the coil which moves the clockwork the projection will move in the expected clockwise direction.

[via Make]

29 thoughts on “Analog Projection Clock So Simple You Should Have Thought Of It

  1. I like it, this could be adapter to all sorts of projection clocks, I’ed like to see what you could do with this technique and a search light! It’ BATTIME!

  2. I had one of these that was made as a promo for Budweiser or some such company. It had their logo at the bottom of the mirror, and the top half was an analog clock. When the sun would hit it in the afternoon, it would move a working clock projection across the floor. The backward part of the effect wasn’t that noticeable when we only glanced at it once every few hours.

    So while I didn’t think of it first, someone clearly did.

  3. what if you used the same method but cut card stock for the numbers and hand 2 wheels one stationary one mobile that would line up to the correct time as it rotated then projecting digital time while still fully analog if you wanted to go digital do the same thing but bounce the light thru a nokia type lcd with the backlight taken off like the lumenlab projectors

  4. At first, I thought “What?! that’s going to be backwards” But then I read the part about “reversing the polarity of the coil”.

    I don’t know if that’s going to work. But maybe you could use 2 mirrors or even a lens to invert the image.

  5. Thats cool but the extralight from the led would make the room too bright. Maybe some type shroud around the unit that would keep the extra light from going any way but up. A box with black plexi sides and a clear top should work great.
    Great hack.

  6. better option – put a laser diode on each hand with a linear prism (idk the term… the thing that makes a laser level line…) to create each hand of the clock. then simply add 4 lasers for the time markers at 3, 6, 9, and 12.

    no crazy amount of light bleed in the room, no huge white square on the ceiling, and even the reversing issue can be fixed by simply flipping the clock over and mounting the lasers to the underside of the hands.

    mount it all to a piece of plexy and done. no focusing required, and you could shoot it at the side of a building in full daylight.

    1. Er, Steve this was about a simple clock.
      So in your making it “better” we now need to consider how to get power to the lasers. Probably by a slip ring which adds resistance to the hand movement. Also your lasers add weight to the hands so on the “down” side the clock could run fast and on the “up” side run slow. Even if you keep it flat all the extra load of lasers and slip rings mean you might burn out the coil or at least need to recalibrate the whole thing. That may be a problem if it’s upright as well.

      Not really so simple now is it.

  7. I will admit my solution is not simple… but I can solve the problem of the huge white square. instead of mirrors for the face, mirror just the hands and the numbers.

    fastest way is chrome spray paint. if you have everything else black, you will considerably reduce ambient light output.

    another way to reduce ambient light – and probably the best solution overall while remaining simple, mounting a mechanism inside a telescope style setup with the LED behind it would give this same effect but would allow the LED to be concealed.

  8. @SteveO

    I’m not sure that chrome spray paint would be reflective enough to work effectively.

    If you want to invert the display (dark background, light hands), the best method would be to cut new hands from a thin mirror and mount these on the existing assembly.

    Or you could simply mount small circles of mirror on the ends of the existing hands, to keep the amount of light to a minimum.

  9. @SteveO & holly_smoke

    Is not as easy as it seems. You would need a very good alignment of all the little mirrors, specially the hands. Not to mention that these coils were designed to drag a very light piece of plastic, not a mirror.

    It’s a very good hack because of the simplicity.

  10. ok let me try again cut out the black bits like this example for the hours

    and this example for minutes
    would probably have to be laser cut (mirror image?)

    then use them as the hands on the clock .
    offset the center of the face so the cut out parts match a shroud at the same time as the back-light

    light shines thru cutout of current time making a projection on the ceiling without a mirror or fiddling with reversing the clockworks

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