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Thread: DAC output voltages

  1. #1
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    Default DAC output voltages

    I measured my DAC output voltages for laser modulation and found something interesting:

    Moncha: USB Powered, Max output 4.4v
    Riya: USB Powered, Max output 4.4v: External P/S powered: didn't test.
    Easylase: External P/S, 4.8v.

    So, it appears that USB powered DACs might not be giving full output for laser modulation. At 4.4V, that is only 88% of the full 5v that is required for full power. So, 12% of laser power is lost right there! Depending on your laser module, you might be able to boost the laser driver output to compensate for the lower than ideal voltage. I can do that on my die4drive drivers. I can probably do the same on my Lasever but I am not going to touch it until I get it repaired or the warranty expires.

    I normally don't use my EasyLase DAC because it requires an external power supply but there is definitely a reason for an external p/s as you can see. But even still, the EasyLase is only at 4.8v which is only 96% of ideal.

  2. #2
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    Default

    I measured 4.85V on my Easylase. So yes, if your laser driver gives only its max output at 5V (or worse, maybe higher than 5V!), it's sort of dumb loss. But most of my tested lasers gives full output at 4-4.5V (exepted my Laserwave).

    Can't we do a simple electronic circuit (op amp based I think) which extend (linearly) the output voltage of the DAC to reach 5V? This would mean of course the use of a 12V power supply to power up the op amp...

  3. #3
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    Default

    hmm interesting!! good find!
    -Josh

  4. #4
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    Default

    What are you measuring and what are you measuring it with?
    Measurments will only be valid if you have no blanking and use a voltmeter or have blanking on and use a scope.
    Measuring with blanking on using a multimeter will give you a false reading as your common or garden DVM is designed to measure a static or slowly changing DC level. What you have on the output of the DAC will be a waveform that you cannot measure with a meter. Once you look at the waveform on a scope you will see and understand why - the 5V level will have little chops in it that go to zero which is the blank between frames.
    Rob
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  5. #5
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    Default

    gary,

    Did you use a scope ?

  6. #6
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    damnnn !! stanwax was faster!!!! wuahaha

  7. #7
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    Default

    For me, I measured the voltage on my Easylase with a voltmeter, without blanking (Mamba software allow no-blanking output). I think Carmangary did the same as he has the same result.

    Tomorrow I'll take an oscilloscope at my work to measure the output voltage on my FB3, since there's no way to output without blanking (and that's a shame ).

  8. #8
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    Default

    I used a multimeter but was sending a constant high signal from the DAC. I was using my own software so I know there was no blanking. I have a scope and I might verify it later but I am pretty sure of my findings.

  9. #9
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    Ukraine
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    Default

    Gary,
    I am not sure that you do measurings right : 4,4 Volt for X&Y output - it is not correct situation for our controller!

    Make please testing for RIYA controller from TestRIYA utilite: then you will see correct result.

    If you use other programs - you must be sure that your frame does not contain "black" points.

    Of course, will be better to meter voltage with oscilloscope!

    So, make testing again and write result please!

    Ihor

  10. #10
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    4.4V was color output, not X & Y. I will check with my scope the next time I am messing around with the stuff. I figured the 4.4v was due to a limitation of the USB stuff because I got the exact same measurement using the USB powered Moncha DAC.

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