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Thread: DPSS Module may not touch grounded housing?

  1. #1
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    Default DPSS Module may not touch grounded housing?

    Hi guys!

    I'm new to Photonlexicon, so I hope I'm posting on the right forum. I've tried the search-feature but didn't find an answer to my question.

    I heard several people damaged their DPSS laser unit (China, 100mw 532nm) because they just mounted it on an aluminium baseplate or direct to a metal housing of a laser projector, that was grounded.

    Is this something I have to be careful with? Are there more things I have to watch out for ( - about electronics, not about safety for eyes etc.) when working with DPSS-modules, scanners and things?

    Thanks in advance,

    Jeroen

    (Pardon my French, I'm Dutch)

  2. #2
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    Hi and welcome here Jeroen!

    And yes I thing it's the right place to post that

    About grounding a DPSS laser, I always grounded mine and had no problem...
    Two reasons for that : to have a same ground potential on all the hardware (it's better, if possible), and to properly heat sink the laser, if mounted on a thick aluminium plate.

    But now the RED lasers case (with direct diode) often has to be insulated from the common ground, because they have the positive side at the case.

  3. #3
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    Quote Originally Posted by sbk View Post
    Hi and welcome here Jeroen!

    And yes I thing it's the right place to post that

    About grounding a DPSS laser, I always grounded mine and had no problem...
    Two reasons for that : to have a same ground potential on all the hardware (it's better, if possible), and to properly heat sink the laser, if mounted on a thick aluminium plate.

    But now the RED lasers case (with direct diode) often has to be insulated from the common ground, because they have the positive side at the case.
    Thank you for the quick reply.

    With the RED lasers case, I think you mean the diode-part inside the lasermodule? So if I just don't open the module, there's nothing to worry?

    Indeed, I was kinda confused because I was adviced to mount the module on a thick aluminium plate for cooling.

    I'm currently combining all the information I can find, I'm trying to order a FB-3 evaluation kit of Pangolin as a DAC (use with LivePro or the LA Freak-software) and I'm about to order Terascan 45 from Medialas (or other comparable scanners). The lasermodule is a 100mw 532nm DPSS with only TTL for testing, and if I'm confident with the projector it will be replaced by a 1000mw 532nm DPSS module.

    These are my first steps in the magic "laser-world".
    Last edited by JeroenVDV; 08-14-2007 at 01:43.

  4. #4
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    To find out if a laser can have case contact to ground, first put the laser on an insulated surface and power it. Even if it needs a heatsink this is ok if you do it for a very short time, a second at most, which is all you need to test with.

    Before powering, connect a voltmeter to the negative supply wire (usually black), and to the case. WHen you power up, watch the voltmeter to see if it reads anything other than zero. Note the reading if it's non-zero and steady, just in case you need to know later. Remove the power the moment you have seen the reading stable, or after 1 second if it does not stabilise.

    If the reading was zero, and ONLY if it was zero, try a second test with a continuity tester between the two points you just tested. If they read zero ohms, you can connect the case to ground with no trouble, so long as your power supplies are also negative ground.

    That series of tests is slightly overdone, but it's safe, and if you have unusual conditions, you'll get your first clues about what they are from that first test.

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    Quote Originally Posted by The_Doctor View Post
    That series of tests is slightly overdone, but it's safe, and if you have unusual conditions, you'll get your first clues about what they are from that first test.
    Thank you very much for the great reply. I'll do these (quite simple) tests for sure.

    I like the available knowledge and kind people on this forum, I'll keep you updated when I start building!

    Just another quick question to be sure I've got it right; When I want to test a DPSS laser with only 230v-input and TTL modulation input (red and black wire), I can safely connect a 5v DC supply to the red and black wire to test the laser? (black -, red +) --- (And, only power up the 5v supply when the laser has the 230v mains supplied and is powered up)

  6. #6
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    You got it. Some lasers shortcut the protections a bit, so as you say, make sure the laser is powered before risking anything on the modulation input.

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    Well, I think I've got a laser with strange behaviour. It's a China (module of a BigDipper K1000+) 100mw 532nm DPSS lasermodule with powersupply. 230v input and TTL-connection (red and black wire). I've connected the mains and the PSU powers up (fans blowing, everything seems allright.) When I connect the TTL red wire to +5 and the TTL black wire to 0. I tried this with a simple PSU I have (5V) and with 2 batteries (3V) but nothing happens.

    When I put a voltage-meter on the TTL-input of the lasermodule, I find 5v DC?!?!?!?!

    How can a TTL input have 5V power on it? Do I have a strange laser? How can I get it to work again?

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    "How can a TTL input have 5V power on it? Do I have a strange laser? How can I get it to work again?"

    You can have 5 volt on the input if the laser is holding that line high with a resistor from it's own 5v. Chances are that you have a laser that wants a 0 volt to turn on. IN other words if you short the two wires from the mod input it will pull that 5 volt low and turn the laser out put on.

    Active low

    Chad


    When the going gets weird, the weird turn pro.


  9. #9
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    Quote Originally Posted by chad View Post
    You can have 5 volt on the input if the laser is holding that line high with a resistor from it's own 5v. Chances are that you have a laser that wants a 0 volt to turn on. IN other words if you short the two wires from the mod input it will pull that 5 volt low and turn the laser out put on.
    Hi Chad,

    Thank you for your reply. However, shorting the two wires of the TTL input doesn't light up the laserunit.

    Just fyi:
    On the PSU are 2 LED's, one RED one and one GREEN one. The RED one lights up when I connect the mains. When I disconnect the mains the GREEN immediately lights up, the RED one turns off immediately and the GREEN fades out.

    I took 2 pictures:
    Overview: http://laser.smash-productions.nl/pl/overview.jpg
    PSU Zoom: http://laser.smash-productions.nl/pl/psu.jpg

    Top left is the TTL input, bottom left is the FAN output. On the right is the mains (230v) input.

  10. #10
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    That is a bummer. Do you know for a fact that this laser works?

    I am sorry I can't be of much more help I am not familiar with that laser. I am sure someone else here will be able to help.

    Good Luck

    Chad


    When the going gets weird, the weird turn pro.


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