DIY Laser projector

So yes! Hello!!! This time I built a laser projector, it was built using a toy laser pointer, a pillbox, a cooler fan and an arduino microcontroller.



Check out this video if you want to see it in motion (note that its a bit dark, but towards the end I turn on the lights)

Here is how it works!

In the picture below you can see the whole setup, the heptagon is a pillbox, its sitting on top of a cooling fan so it spins very quickly. Each side of the pillbox has a mirror that reflects the laser beam onto the screen.



Because the mirrors are moving the reflected laser dot sweeps the screen from left to right, because it does it very quickly your eyes actually see an horizontal solid line, in this case you see 7 lines one on top of the other because the each mirror is at an angle.

So I would get something like this:

-------------------------------------------------
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if I turn off the laser at the right time, I could get to display something like this

--    -- -------- --      --         -----     --
--    -- --       --      --        --    --   --
--    -- --       --      --        --    --   --
-------- -------- --      --        --    --   --
--    -- --       --      --        --    --   --
--    -- --       --      --        --    --
--    -- -------- ------- --------   -----     --

Then with a little bit of software magic you can get the text to scroll, wave, and so on.

We are not there yet!

The spinning speed of the fan is very critical, any slowdown will cause the image to wobble, that is why I put this fins on the pillbox, when they spin they pass thought an optical sensor (pretty much like the one elevators have to keep its doors open when people leave or enter the elevator) A micro controller can use this data to compute the fan speed and adjust the laser blinking to the image looks correct.

Tricky part! (warning quite geeky stuff coming up!)

So how does the micro controller know when is the first mirror coming? The fins, because I glued them myself by hand, are not really equally spaced, some are closer that the others, the micro controller notices this and uses this info to tell which one is the first mirror... for example the two fins before the first mirror are a bit closer than the others.

That's all, I hope you enjoyed!


Other Laser projectors:

http://heim.ifi.uio.no/haakoh/avr/