I've completed my Arduino alphanumeric laser projector project and I am excited to share details about it here. My projector works based on the properties of persistence of vision. A laser pointer is aimed into a spinning array of six mirrors. Each mirror is at a slightly different angle to the laser and is responsible for scanning the beam across a different height line. With the laser switched on and the mirrors spinning, six horizontal lines are drawn. By pulsing the laser at carefully timed intervals, I can draw only the desired segments of each line. In effect, it creates a virtual display that is 6 pixels tall by about 112 pixels wide.
I built it on and inside of a gutted out DVD player case. The DVD player's power supply and front buttons and LEDs were used in the project, but the rest of the DVD player's internals were removed. The laser, mirrors, motor, and an optical rotary encoder are mounted on top. The spinning mirror platform is hot glued to a brushless fan motor taken from an old computer power supply. An aluminum flap protrudes from the spinning platform and triggers the encoder once per rotation. Inside is a very cheaply made circuit board for holding in place the connections to a couple of transistors and four resistors. Up near the front is an Arduino with its USB port accessible through what was the disc tray slot.
The projector is capable of displaying 14 characters of text at a time. It can also scroll text that is longer. When operating, it cycles through a few different display modes. First it displays some statistics, then the time, the date, and finally it scrolls one of currently about 30 pre-programmed strings.
I've posted a couple of videos on YouTube demonstrating the projector.
I posted here in the hopes that others will find my work interesting and that I may give them ideas for their own projects. I look forward to getting feedback from others and I'll be happy to elaborate more if there are any questions.
Sweet... I'll check vid at home. I did a spirograph harvested the diode from a blue Ray, pressed into an axiz module with a tool I got from a guy over at laserpointerforums.com another fella here has better code than mine but I like how mine is for me ;).
Must have been a b*tch setting up the mirrors at the right angles!
Your not kidding. First time was a b*tch because I didn't know what I was doing. Second time I developed a few techniques along the way that made it much easier. If I had to make a third mirror array, I bet I could do it with little fuss. It all has to do with how you go about it. I have been meaning to write up a long explanation that explains all the tips and tricks I learned while building mine. Perhaps if a few more people express interest in building their own I will write up a tutorial of sorts.
Awesome work! I bet you can put your stuff inside of a glass dome or something!
Oh, one quick question: what is the transparent glue stuff you used on your wires to keep them down on the inside of the dvd box? I want some for my project.
I think if I were doing this, I would go about setting up the mirror wheel in a much more complex manner:
Use acrylic mirror strips around 1/4 inch wide.
Drill a hole at each end of the strip.
Use a lathe or find some kind of round stock, about 3 inches in diameter or so (whatever the diameter needs to be for the 1/4 inch separations to work out to a whole number for the circumference).
In a short segment of this stock, drill holes for the mirror strips the same distance as the holes in the mirrors, but slightly smaller.
Use screws to mount the mirrors to the round piece; screw thru the mirror, and a spring behind the mirror over the screw.
This way, you could have many, many more segments (more scanned lines), and each mirror could be adjustable by turning the screws appropriate amounts. Start the first mirror "flat" with the both screws at mid-point level. Then adjust each mirror around the circular base piece.
If you increased the diameter of the base piece, you could gain even more scanned lines; you do run into issues of potentially mirror flying off at higher speeds - most of these issues were encountered though by designers of early mechanical scanning television. So, if you were serious about improving this design, looking there for ideas would be the first place to start.
I always like to see these scanned systems though, whatever the source and implementation; this one was particularly cool - great job!
Oh, one quick question: what is the transparent glue stuff you used on your wires to keep them down on the inside of the dvd box? I want some for my project.
I haven't looked at what you are referring to but I presume it is just hot melt glue...
Thank you mowcius. I'll get myself one of those applicators!
cr0sh, how did you all about those old things? Just curious. Yes, some old-fashion large screen TVs were having rotating parts (a prism) but people back then had no micro controllers! Poor 20th century people. I remember my professor talked about making a big projection TV as a project given from the very top of the food chain, so every small village, regardless of how remote they are, could watch Chairman Mao every day. They didn't get it to work as a commerical product but neighbors all gathered around every night to watch that TV. Occasionally one laser was down and the color would be off. Other times they wanted to do some testing/troubleshooting that would temporally lose the image and the audience would yell stop, stop. They couldn't get it perfect because people wanted to watch it all the time, even if it was fuzzy. ;D
I'm on a research trip right now and our dorm building has a large TV having color issues. Made me remember all those old stuff. But still people from all over the world would occasionally sit in front of it and watch the storm-garbled satellite TV program, the power of TV! Sorry fellas.
cr0sh, how did you all about those old things? Just curious.
There's a word missing in that sentence, so if what I write below makes no sense, then please supply the missing word...?
Basically, I know about all of this because I read - I read way too much, way too often, about way too many things. Early television is one of the subjects which I have studied; you can't understand the history of computers (another love of mine) without running across it.
I have personal library at home covering a range of subjects, both fiction and non-fiction, over 1000 volumes. That doesn't count the amount of stuff I have read online (some of which I have saved on my home file server), nor that which I have read from books checked out from the library, nor all the magazines I have read and own.
I'm an information junkie, a bibliophile, a voracious reader. Used book sales are like crack to me. My wife is no different, though she has different interests than I do. We're contemplating turning a room in our house into a small library and reading room; one wall in my office (12' x 8') is a large bookshelf made from steel shelving - we have another full wall-sized (12' x 8') bookshelf in our family room. Other books are hidden in various other nooks and crannies throughout the house.
The sad thing is (well, to me) - I'm not a fast reader; I wish I read faster (my greatest problem is sub-vocalization).
"know" sorry, memory hole. I'm not a fast reader either. I ctrl+f on web pages to help me "read". I don't know if that is same as reading. I'm starting a CPU collection and hope to turn it into a museum in 30 years.
Just be on the careful side of the street, some lasers are not meant to be taken out of their enclosures without harming people's eye sigts (you can't see their infrared emissions, which could be strong). I suggest a laser pointer for starters, safer.
