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Thread: laser diode driver circuit with 8bit digital control

  1. #11
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    Quote Originally Posted by -bart- View Post
    I think all our suggestions are prety worthles without you sharing some more details about your "very basic micro controller driven RGV projector".
    I don't really have any details, i'm going to let the project take shape as i go. More fun that way.

    Quote Originally Posted by -bart- View Post
    What graphics are you going to produce ?
    Again, not sure, i may not even be able to find any galvos or motors that are small enough to work. (I want to make the unit pocket sized.) If later on i can't get any gavos/motors to work i'll just have it for beams and use the atmega for creating a color changing staic beam or something etc..

    Quote Originally Posted by -bart- View Post
    Have you figured out how to drive your xy signals ?
    If i get that far i'll probably add a mcu with a built in FPGA so its fast enough to do the x/y scanning.

    Quote Originally Posted by -bart- View Post
    What atmel mega are you planning to use ?
    Probably start with one i already have, will be either ATmega8515 or ATmega640

    Quote Originally Posted by -bart- View Post
    What language will you be using ?
    will be using C (avrgcc) might write few bits in ASM if i absolutely have to.

    Quote Originally Posted by -bart- View Post
    Do you have experience with similar projects ?
    I have lots of electronics and microcontroller experience but only a little optical experience. I've got the KEX-400A sled apart and confirmed the two PBS cubes do combine light the way i expected (from rog8811's spiro project)

    Quote Originally Posted by -bart- View Post
    Personally I surely would build some kind of proof of concept first.
    Something with some 0832 dacs or similar with ttl blanking.
    Then enhance it with funky buffering and 24 bit color.
    Yeah, this version will probably be the proof of concept, except ill put it in a nice case and to make it useful. Any good ideas i have after doing it i may use to make a better one later on.

    Quote Originally Posted by -bart- View Post
    Before reinventing the wheel I surely think that this architecture can simply be modified for your purposes.
    aww, reinventing the wheel is fun, ya learn a lot from it
    but thanks for the circuit.

  2. #12
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    I also have some MOT2 lying around. I think anything smaller than a MOT2 is impossible.

    http://www.youtube.com/watch?v=zAYvsl7TuA4

  3. #13
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    Junktronix has the scanners that are small enough to work on a pocket projector, . Cambridges, 62XX series. At the price he's selling them its a once in a lifetime shot, too.

    Getting rid of the amplifier heat in a pocket may be interesting, though. How about trying for a 4" cube? Lithium ion cells are your friends for this one.

    If i get that far i'll probably add a mcu with a built in FPGA so its fast enough to do the x/y scanning.

    AVR MEGA is fast enough, see the link I sent you.


    I have lots of electronics and microcontroller experience but only a little optical experience. I've got the KEX-400A sled apart and confirmed the two PBS cubes do combine light the way i expected (from rog8811's spiro project)

    Not a problem.

    We can help :-)


    Steve
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  4. #14
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    Quote Originally Posted by mixedgas View Post
    Junktronix has the scanners that are small enough to work on a pocket projector, . Cambridges, 62XX series. At the price he's selling them its a once in a lifetime shot, too.

    Steve
    Can't see them, maybe he sold them?

  5. #15
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    Quote Originally Posted by Psi View Post
    Can't see them, maybe he sold them?
    I got the feeling when I bought my pair that they were not doing hot on ebay.

    yellow/ Red/Ir mirrors for one thing, but easily replaced with factory mirrors. When your doing a red diode to begin with.... :-)

    Still unless you got really lucky digging in a scrap equipment pile, you'd never find a pair of cambs for what he's asking. I bought a pair.

    Steve
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  6. #16
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    I have been using the Microchip MCP4921 DACs for my laser projects. They are 12-bit, with a /LDAC pin that you can common together. This gets around the fact that you can't load all the DACs with values at the same time, because they do not reflect the value in their register on the output until the /LDAC pin is asserted (pulled low). Therefore you can load X, Y, R, G and B up one at a time and then pull /LDAC and all the outputs change at the same instant.

  7. #17
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    Quote Originally Posted by mixedgas View Post
    And how is he gonna double buffer it so it looks good?
    Shift register with latch, latch output goes to the R2R input. Job done, and saves a crapload of I/O in the process.

  8. #18
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    Quote Originally Posted by Stoney3K View Post
    Shift register with latch, latch output goes to the R2R input. Job done, and saves a crapload of I/O in the process.

    Perhaps you want to rethink that?
    I can see the difference in graphics linarity using 1% metal film and 5% carbon, so he needs roughly 30 1% resistors for the R2R, plus a trim pot for offset, at that cost plus a jellybean opamp plus a shift register with or without a latch, he can afford the 12 bit serial dac from microchip.

    steve
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  9. #19
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    Quote Originally Posted by mixedgas View Post
    Perhaps you want to rethink that?
    I can see the difference in graphics linarity using 1% metal film and 5% carbon, so he needs roughly 30 1% resistors for the R2R, plus a trim pot for offset, at that cost plus a jellybean opamp plus a shift register with or without a latch, he can afford the 12 bit serial dac from microchip.

    steve
    Well, if the DAC comes in a through-hole package (DIP), it's worth considering. Soldering SMD components is kind of a pain.

  10. #20
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    Quote Originally Posted by Stoney3K View Post
    Well, if the DAC comes in a through-hole package (DIP), it's worth considering. Soldering SMD components is kind of a pain.
    MCP4921 is an 8 pin DIP. Nice: you can add more later if you want another colour...

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