Earthing and case positive devices.

Discussion in 'General Electronics Chat' started by Diachi1, May 27, 2009.

  1. Diachi1

    Thread Starter New Member

    May 27, 2009
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    Hello,

    Quick Introduction before I ask my question !

    My name is Adam Gordon, I am from the UK. I am a Laser Hobbiest and I have built many lasers. I have a keen interest in electronics and Gerneral physics, and I am currently studying Higher level physics and chemistry.

    Today I recieved my new green laser which is to be installed in my laser projector build. However this laser is case positive and the housing for the projector is earthed, will it be safe to install this laser in this case without having insulation between the case and the laser module ? I really don't want to cause a short and blow up £50 worth of laser !


    Any help is much appreciated ! :D

    Regards,

    Adam
     
  2. Wendy

    Moderator

    Mar 24, 2008
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    Talk about the power supplies. Many of them aren't grounded nowdays, are both of these?

    Welcome aboard. I used to have to mess with lasers, for soldering and adjusting resistors.

    The green xenon's were pretty fun, we used them to cut gold traces.
     
  3. Diachi1

    Thread Starter New Member

    May 27, 2009
    3
    0
    Both power supplies are mains powered, one is earthed the other is not. the one that is earthed is bolted onto the case, which is all metal, this power supply provides power to all the Galvo amps and DMX board. The laser power supply will be mounted above the metal case, so thats not a problem. it's the laser head that is case positive. :) I wanted to bolt the head straight onto the case, but I'm unsure if this would cause problems or not. I've not done too much with mains power, it's mainly voltage/current regulated drivers I've built , but they were powered by regulated voltage or batteries.

    Lasers are great ! The green xenons you are talking about, I think your talking about xenon flashlamp pumped green lasers ? A few guys I know use them for laser shows. :cool:
     
  4. Wendy

    Moderator

    Mar 24, 2008
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    Far as I know (and it's been way too long) the xenon was the gas being excited, and green was one of the resonant colors. Much like a HeNe laser, complete with mirrors. If the power supply that isn't earthed is isolated you shouldn't have a problem, but you're going to have to be careful here.

    As to the laser head being grounded to the positive side of the PS, that shouldn't be a huge deal, just something to be aware of.

    Can you measure any voltage, AC or DC, between the power supply chassis?
     
  5. Diachi1

    Thread Starter New Member

    May 27, 2009
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    I don't really get the question. Do you mean measure a voltage between the output of the PSU and the case of the PSU ?

    Not seen many xenon lasers before, if any ! Sounds neat ! :D
     
  6. Wendy

    Moderator

    Mar 24, 2008
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    Take a multimeter, DVM or other, and measure voltage on bare metal of the case, AC or DC. Is there any? If not, then measure resistance.

    I suspect Xenon are being replaced by solid state equivalents, but I could be wrong. I notice HeNe is still doing OK. We used them for targeting the infrared CO2 laser that melted the solder (10W variable).
     
  7. radiohead

    Active Member

    May 28, 2009
    474
    31
    I've had a little experience with case-positive electronics. I would advise you to insulate the case-positive device from the grounded case. Make sure you use appropriate warning labels so nobody gets shocked.
     
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