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Thread: projector building: setting max driver current question

  1. #11
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    Quote Originally Posted by Finale View Post
    That DZ color board thing sounds like it does exactly what increasing the current would do, sounds like it just increases the modulation voltage to peak at 5 instead of 4.something.
    Yes, but it has its downside to in that it can slow down your diode response times. I consider it an invaluable tool for builds with dpss greens in them, but I don't use them for all-diode builds.

    I'm not really pushing my diodes to their curve peak where more current actually causes drop in power, but I want to push them closer to the peak where my housings can't keep them at a stable low temp anymore. That's a bit different.
    Agreed, but I would still expect that you would want to leave some headroom for unforeseen conditions such as running the projector in an ambient temperature higher than your testing environment. Its your projector, though, so do whatever you want!

    Quote Originally Posted by JohnYayas View Post
    I can't speak for other software, but with Spaghetti you can achieve max output by simply turning the minimum value of all lasers to max. This forces them to run at full power even when blanked.
    I stand corrected!

    -David
    "Help, help, I'm being repressed!"

  2. #12

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    Quote Originally Posted by dkumpula View Post
    Agreed, but I would still expect that you would want to leave some headroom for unforeseen conditions such as running the projector in an ambient temperature higher than your testing environment.
    You actually brought up another step I had forgotten to do, which is set the temperature in my test environment (room) to the max ambient temp I'm expecting to ever run this in.
    My guess is 95F and 5 hour run of a looping show is reasonable, right? Or is that a bit too hot for practice?

  3. #13
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    FULL STOP!

    How are you measuring voltage to your diode? If you aren't using an oscilloscope, you are not getting an accurate reading.

    You can't use a standard volt meter to measure modulation voltage - even if you are just displaying a static beam. Nearly all controllers will blank the laser periodically, and this will show up as a reduced voltage reading on a standard multimeter. That is why you must use an oscilloscope.

    Now, with that being said, it is true that many controllers don't output exactly 5.0 volts on the color modulation lines. But 4.8 V or so is close enough. You can tweak the driver if need be to get that last little bit of performance. (Truthfully though this is a minor factor in the overall brightness of the beam.)

    You need to realize that there are other factors at play that will make your laser look brighter when you have a constant 5V source on the modulation line verses running it off a controller trying to display a static beam. Chief among these is the fact that the controller is almost certainly blanking the beam at regular intervals while it refreshes the frame buffer. This means the laser will be off for a brief period of time (too short for your eyes to see it blink off and on), and this reduces the AVERAGE power over time, making the dot appear dimmer. Then there is the normal ramp-response of the diode itself, which means there is a delay from the time the modulation is back on until the diode gets back to full power. This also reduces average power over time.

    Note that none of this is the fault of the controller. They are designed this way, and they ALL do it. Yes, it is bothersome when you see your lasers running with a battery hooked to the modulation leads and they appear brighter, but take solace in the fact that any other projector using any other controller would behave the same way.

    If you want to double-check everything, connect an oscilloscope across the modulation leads on the output of your controller and look at the waveform. If the peak is anything over 4.8 volts, the controller is working correctly. But also take note of the off-periods where the modulation level drops to zero...

    Adam

  4. #14

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    Thanks Adam, but I'm measuring the current and with an LPM, no voltage. Simpledrives have pins which allow to measure the current with a voltmeter. With lower power simpledrives it's 100mV = 1A and with the 5A version it's 50mV = 1A.
    I don't know if the modulation would affect this reading. It probably would affect the LPM reading but 30% difference might be a bit too much. Or not?

  5. #15
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    Quote Originally Posted by Finale View Post
    Thanks Adam, but I'm measuring the current and with an LPM, no voltage. Simpledrives have pins which allow to measure the current with a voltmeter. With lower power simpledrives it's 100mV = 1A and with the 5A version it's 50mV = 1A.
    I don't know if the modulation would affect this reading. It probably would affect the LPM reading but 30% difference might be a bit too much. Or not?
    yes.. modulation will absolutely affect the current and lpm reading. modulation and blanking happens faster than meters can track.
    Last edited by swamidog; 06-27-2017 at 07:47.
    suppose you're thinkin' about a plate o' shrimp. Suddenly someone'll say, like, plate, or shrimp, or plate o' shrimp out of the blue, no explanation. No point in lookin' for one, either. It's all part of a cosmic unconciousness.

  6. #16
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    Quote Originally Posted by swamidog View Post
    modulation and blanking happens faster than maters can track.
    I like a lil salt, vinegar, and pepper on my maters. I eat 'em fresh from the garden that way.

  7. #17
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    Quote Originally Posted by JohnYayas View Post
    I like a lil salt, vinegar, and pepper on my maters. I eat 'em fresh from the garden that way.
    suppose you're thinkin' about a plate o' shrimp. Suddenly someone'll say, like, plate, or shrimp, or plate o' shrimp out of the blue, no explanation. No point in lookin' for one, either. It's all part of a cosmic unconciousness.

  8. #18
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    What you seems to want is great in audio called compression but. in laser. You will lose the subtle details by mashing the modulation. I set my drivers by using 5vdc. Then I live with the result. You want brighter get higher power projector. At a certain point low in power your eyes saturate. All get after that is a lose of background contrast as the reflected light lights up the room. I e en tried projecting on black cardboard to fight this. Dimmer image but better contrast. Don't push the diodes. They tried that in Egypt and ended up with plagues. Love they worker.

  9. #19
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    Quote Originally Posted by kecked View Post
    I even tried projecting on black cardboard to fight this. Dimmer image but better contrast.
    I use black or med grey felt as projection surfaces. (Based on Swamidog's advice, if memory serves.) Felt works great, but like cardboard, the stuff could go up in flames when using higher powers. A fire retardant treatment might be advised in such circumstances. Although I've never had so much as a mark on a wall or a hole in a couch to date, I keep a large fire extinguisher in the disco as well as an emergency escape ladder that has never been tested . . and hopefully never will. (It is a long ways down to a stone patio that could really ruin your day.)

    -David
    "Help, help, I'm being repressed!"

  10. #20
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    yes.. i tend to project on black felt for filming.

    i'm not too worried about fire as my little programming projector pumps out only about .5W at full white.

    Quote Originally Posted by dkumpula View Post
    I use black or med grey felt as projection surfaces. (Based on Swamidog's advice, if memory serves.) Felt works great, but like cardboard, the stuff could go up in flames when using higher powers. A fire retardant treatment might be advised in such circumstances. Although I've never had so much as a mark on a wall or a hole in a couch to date, I keep a large fire extinguisher in the disco as well as an emergency escape ladder that has never been tested . . and hopefully never will. (It is a long ways down to a stone patio that could really ruin your day.)

    -David
    suppose you're thinkin' about a plate o' shrimp. Suddenly someone'll say, like, plate, or shrimp, or plate o' shrimp out of the blue, no explanation. No point in lookin' for one, either. It's all part of a cosmic unconciousness.

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