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Thread: Building your own DAC controller

  1. #1
    Join Date
    Aug 2007
    Location
    Indianapolis, IN
    Posts
    196

    Default Building your own DAC controller

    OK, despite my best efforts to avoid it, it looks like I'm going to have to stand up and catch this bullet.

    For my laser harp project (read: obsession) I'm going to have build my own controller. Basically a PIC connected to a DAC. I have a programmer at home and a tub o' PICs but very little experience in programming them (However I have been a C/++/# programmer for a very *very* long time).

    So I need a PIC, and a host board (some kind of power conditioning, or can I just plug in a wall wart at 5V?)

    I do have a MIDIBOX (www.midibox.org) host board and PIC, which I guess I could subvert...

    MixedGas suggested that I connect a TLV5618A serial DAC to the chip. So I guess I would need a PIC that could send serial data, then every clock cycle just update the DAC with a new number, and set the blanking on another pin? This makes sense, but it's when people start adding resistors and capacitors that I get confused....

    One guy kept talking about hysterisis damping, so I looked at him like this

    So I could have a simple lookup table x for y cycles, x1 for y cycles, x2 for y cycles etc... for both the blanking and the D->A. Oh yes and some kind of on/off pin polling...

    How does that sound?

    Steve

    P.S. How do I calculate the analog frequencies required to render a certain frame at a certain PPS? What would be a typical safe frequency for a galvo full cycle?
    Last edited by shobley; 09-12-2007 at 05:32.

  2. #2
    Join Date
    Jan 2007
    Location
    Florida
    Posts
    4,382

    Default

    Wall warts are unregulated. If they say "5 Volts" they'll be putting out around 8-9V no load condition (depending on current rating) but that'll definitely blow stuff up that's rated for 5 V input.

  3. #3
    Join Date
    Jul 2007
    Location
    Brooklyn NYC
    Posts
    784

    Default voltage regulator

    you can use a 7805 voltage regulator for +5v and a 7905 voltage regulator for -5v
    basically the prefix 78xx is for positive voltage and the prefix 79xx is for negative voltage (IE a 7915 would be a -15v regulator)

    John
    VJ AIWAZ

  4. #4
    Join Date
    Nov 2005
    Location
    Melbourne, Australia
    Posts
    3,677

    Default

    If you have a understanding of micros, and also are experienced in C programing, have a look at the atmel AVR and the codevisionAVR compiler.

    AVR's run rings around the pic.

    Instead of a dac, you could even use a simple analogue multiplexer, that just picks off various set voltages on each input. Something like a 4067?



    Quote Originally Posted by shobley View Post
    OK, despite my best efforts to avoid it, it looks like I'm going to have to stand up and catch this bullet.

    For my laser harp project (read: obsession) I'm going to have build my own controller. Basically a PIC connected to a DAC. I have a programmer at home and a tub o' PICs but very little experience in programming them (However I have been a C/++/# programmer for a very *very* long time).

    So I need a PIC, and a host board (some kind of power conditioning, or can I just plug in a wall wart at 5V?)

    I do have a MIDIBOX (www.midibox.org) host board and PIC, which I guess I could subvert...

    MixedGas suggested that I connect a TLV5618A serial DAC to the chip. So I guess I would need a PIC that could send serial data, then every clock cycle just update the DAC with a new number, and set the blanking on another pin? This makes sense, but it's when people start adding resistors and capacitors that I get confused....

    One guy kept talking about hysterisis damping, so I looked at him like this

    So I could have a simple lookup table x for y cycles, x1 for y cycles, x2 for y cycles etc... for both the blanking and the D->A. Oh yes and some kind of on/off pin polling...

    How does that sound?

    Steve

    P.S. How do I calculate the analog frequencies required to render a certain frame at a certain PPS? What would be a typical safe frequency for a galvo full cycle?
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