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Thread: AC driver for laser pointer...

  1. #1
    Join Date
    Aug 2007
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    Indianapolis, IN
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    Default AC driver for laser pointer...

    Is there a reference for building an AC adapter circuit for a laser pointer?

    I have a project that requires about 20 laser pointers, and it would be much better to design something that can be run from AC power, than batteries.

    Steve

  2. #2
    Join Date
    Jan 2008
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    Stockholm, Sweden
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    You want to power laser pointers from wall outlets? That's easy because they already have the driver circuit built in. All you need to do is supply them with a neat 3VDC voltage (if you're replacing 2 alkaline batteries). This is easily done with a transformer, rectifier, voltage regulator and some capacitors to smooth out the voltage. It's even easier if you're starting from a DC source as all you need then is a voltage regulator.

    The easiest way though is just to buy an adapter that supplies 3VDC from the beginning. They should be readily available as battery eliminators. One battery eliminator can power several lasers in parallel as long as the current is sufficient.

  3. #3
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    Mar 2008
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    Canton, GA USA
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    Measure the current used by one pointer, multiply that times 20, add 15% or so to give yourself some margin, and go buy a wall-wart that has that current capability at 3V from American Science & Surplus, Jameco, Digikey, Mouser, etc. Cake & pie...

    Tim

  4. #4
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    Aug 2007
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    Indianapolis, IN
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    OK, is that really all there is to it?

    I thought you had to be very careful with the current/voltage as spikes can fry the laser pointers.

    Don't you need to match the voltage exactly to get the laser to do its LASING...

  5. #5
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    For laser diodes, yes. However, as laser pointers typically contain a current regulating circuit with some protection against bad inputs you don't need to be as careful. Laser pointers are built to work with different battery chemistry (=> voltages) and have to allow a certain degree of variation in input voltage.

  6. #6
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    Mar 2008
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    Canton, GA USA
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    That's what the laser pointer driver does. Check how many batteries your pointers use. They're usually 1.5V each. They might use 2 (3V) or they might use 3 (4.5V). Test it out on one pointer first. I don't think you'll have a problem.

    Tim

  7. #7
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    Jan 2006
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    Charleston, SC
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    2,147,489,119

    Smile

    You won't have a problem at all. I've managed to run a bunch of those cheap bullet-style pointers off a 5 volt computer power supply for hours without any problem. Yeah, that was .5 volts too much (they normally ran off 3 button batteries at 1.5 volts each), but the current regulation board inside each one was able to handle the extra voltage just fine.

    Adam

  8. #8
    Join Date
    Sep 2012
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    4

    Default

    Hello everyone. I know I dug this thread up out of the grave but I searched through the forums here for the last couple hours and couldn't find a newer thread that addresses this issue. I wish the answer was already here but my problem is slightly different.

    I am just getting into lasers and I have a couple questions regarding using an ac power supply that I hope you can answer. First, I am using an inexpensive 5mW 532nm green laser for a Halloween prop commonly referred to as a green laser vortex. It uses an angled mirror spinning on a computer fan or other motor to produce a cone from the laser. Then you pass fog through the cone and a cool effect is achieved.

    Batteries by themselves only last like 10 minutes so I need to power from standard USA AC outlet (110-120v). When I tried to hook it up to a 3.3v 500mA wall wart (ac/dc transformer) it produces a visible flickering or pulsing in the laser beam which detracts from the effect. You can see a video here:
    http://s232.photobucket.com/albums/e...ps8c18e633.mp4
    So you can see the flickering or pulsing... makes it look like a helicopter blade or the spoke on a bicycle.

    So I hooked up some rechargeable batteries in parallel with the wall wart and that seemed to solve the problem but it only lasts a few hours before it starts flickering again as the batteries drain. You can see the difference here:
    http://www.facebook.com/photo.php?v=...8875728&type=3
    The camera still displays a looping gap in the green cone but this is not really visible to the human eye. It looks pretty solid when powered with batteries or batteries and wall wart.

    I would like to know what I can do, without using batteries, to eliminate the pulsing effect I see. I also need to tie in a PWM control for the 12v computer fan to the same power supply as it is part of the prop. So if I use an IC it needs to supply 12v DC and then I will have to cut that down to 3v for the laser. Can anyone help with advice on a circuit for this prop or at least point me in the right direction? Any help you can offer would be very much appreciated.

    Thanks, Mike

  9. #9
    Join Date
    Apr 2012
    Location
    Beaverton, OR
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    262

    Default

    You need a filter capacitor. Electrolytic, probably 2000uf out to be enough.

    Or fins a better wall wart. The very light ones that are switching power supplies have virtually no ripple which is what you are seeing in the beam.

  10. #10
    Join Date
    Sep 2012
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    4

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    Thank you. What do I search for to find one of those 'very light switching power supplies' with virtually no ripple? Are all 'switching' power supplies ok? Is that the key word?

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