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Thread: BWB-10-OEM 473nm laser module info thread

  1. #11

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    Quote Originally Posted by flecom View Post
    could you turn it back down somewhere? I am sure there is a bit of loss from the pickoff that really isnt nessicary for our purposes anyway?

    also I am guessing these things have no kind of modulation inputs right?
    Yep, without going so far as to connect the diode in series with a multimeter, I've nearly confirmed that the pot I labeled 3 on mophead's photo of the driver board controls the diode current, at least on the version 4.0 boards that have three pots total. If I remember correctly, turning pot 3 counterclockwise will decrease the diode current.

    If you do this, be sure to mark the original position of the pot if you want to return the laser to its original output later. Also turn the pot in small increments to be sure that I'm correct on the direction of rotation.

    EDIT: I believe these lasers accept TTL modulation via the thin black and white wires coming from the power supply. The seller twisted them together so that the laser would fire immediately after the 5 second emission delay. I'm not sure what the maximum modulation frequency is, however.
    Last edited by Kyle; 05-18-2010 at 20:42.

  2. #12
    Join Date
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    I will have to try that out... figure could probably run the diode at the same current and get a little extra power, or turn it down to even less current to maintain the current output minus losses...

    dont suppose anyone has an idea for decreasing divergence?

  3. #13

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    While I don't have a wide selection of lenses to choose from a simple double convex lens from a magnifying glass worked somewhat well, IIRC it decreased the divergence from something like 8mRad to under 2mRad, so it's not too great but is still a definite improvement.

    If you have a variety of lenses to chose from I'd try out different focal lengths, etc. to see what best collimates the beam. I'm thinking you won't need a complete beam telescope because single lenses seem to work fine as is and beam telescopes would increase the beam diameter about eight times to achieve ~1mRad divergence.

    You may get lucky and find a satisfactory lens with a short enough focal length to be mounted inside the laser head, as there is a bit of room available after the crystal set assembly. I'm not an expert on which epoxy or glue to use but you'll need something that doesn't outgas and has a low degree of shrinkage/expansion.

    - Kyle

  4. #14
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    Emmaus, PA
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    Looks to me like the output beam is straight from the crystals. I made a very nice beam with my units by making a simple beam expander from a short focal length lens and a longer focal length lens - you'll probably need to experiment with the focal lengths as these are just lenses I had laying around.

    I was lucky to get three of these units from the seller before they were all gone. With the pickup assembly they do about 10mW, on the one I removed it runs about 30mW. All have nice round spots although some have some spatter (I was told that this may just be from a dirty IR filter on the front of the unit but I have not tried to clean it yet)

  5. #15
    Join Date
    Oct 2006
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    Quote Originally Posted by MarioMaster View Post
    Looks to me like the output beam is straight from the crystals. I made a very nice beam with my units by making a simple beam expander from a short focal length lens and a longer focal length lens - you'll probably need to experiment with the focal lengths as these are just lenses I had laying around.

    I was lucky to get three of these units from the seller before they were all gone. With the pickup assembly they do about 10mW, on the one I removed it runs about 30mW. All have nice round spots although some have some spatter (I was told that this may just be from a dirty IR filter on the front of the unit but I have not tried to clean it yet)
    Moar pics...

  6. #16
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    May 2007
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    Minnesota
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    'I was told that this may just be from a dirty IR filter on the front of the unit but I have not tried to clean it yet'

    I've noticed that too on some of the units I have. On these, the cavity window/IR filter is scratched. I almost wonder if this was done on purpose, prior to them being sold to the surplus reseller...

  7. #17

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    Quote Originally Posted by MarioMaster View Post
    Looks to me like the output beam is straight from the crystals. I made a very nice beam with my units by making a simple beam expander from a short focal length lens and a longer focal length lens - you'll probably need to experiment with the focal lengths as these are just lenses I had laying around.

    I was lucky to get three of these units from the seller before they were all gone. With the pickup assembly they do about 10mW, on the one I removed it runs about 30mW. All have nice round spots although some have some spatter (I was told that this may just be from a dirty IR filter on the front of the unit but I have not tried to clean it yet)
    Yes, the output beam is coming straight from the crystals, as these lasers were designed to go straight to a fiber coupler a collimation assembly wasn't needed. I think I measured my unit to have about 8mRad raw divergence and was worried that I couldn't get the first lens of a beam expander close enough to the crystal to get a small one or two millimeter initial diameter out of the expander. I'll have to see if I can find some lenses with the right focal lengths so that I could place the first lens within the laser head itself and have the second lens on the outside.

    Mine has some spatter around the raw beam and upon closer inspection it appears that the beam from the crystal is hitting the side of the crystal enclosure ever so slightly, causing a line to appear next to the main ovular beam.

  8. #18

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    aI am sorry I haven't been able to add much to this thread due to general lack of time, but I have got the serial ports working, it has 2 serial ports, which I am going to call 1 and 2. They are available from J10, and are RS232 compliant (can safely be connected directly to a computer). I haven't been able to figure a whole lot out, but it appears that one of them is associated with the automatic temperature tuning, and the other one lets you 'talk' to the laser.

    Port 1: (general laser control)
    9600 baud, 8 data bits, no parity, 1 stop bit
    TX - pin 7/8 (connect to pin 2 on a normal db9 serial port)
    RX - pin 9/10 (connect to pin 3 on a normal DB9 serial port)
    Gnd - pin 5/6 (connect to pin 5 of a normal DB9)

    Commands (all commands are followed with a new line, all appear to be case sensitive)
    b - ??? - mine just echoes back a B, occasionally sending back a BX
    e - setpoint? - mine responds E00829 - which matches with the setpoint read out from serial port 2, and does not change when the photodiode is blocked
    s - status? mine responds S00000 with the pd in place, or S00003 with it removed or before the laser has powered up
    v - version? - mine responds V45040
    w - warming up? - mine responds with W00001 after I first plug it in, and W000000 after a few minutes


    Port 2 - doubler temperature tune output
    115200 baud, 8 data bits, no parity, 1 stop bit
    TX - pin 3/4 (connect to pin 2 of a normal DB9)
    RX - pin 1/2 (connect to pin 3 of a normal DB9)
    gnd - pin 4/5 (connect to pin 5 of a normal DB9)

    When I first power it up I get:
    Code:
    Save[5]=1525 Save[6]=1 Tcon_ld=1526
    
    1895 0 1490 65503 1525 1
    KTP temperature has been tuned 0 times!
    
    Beginning temperature point tuning!
    From 1892 to 1898, step 3. 
    
    Tcon=1859
    And after a minute or so it will start scanning the doubler (it calls it KTP, I assume that is left over from driving a 532nm laser), giving a few thousand lines of:
    Code:
    Save[5]=1525 Save[6]=1 Tcon_ld=1526
    
    1895 0 1490 65503 1525 1
    KTP temperature has been tuned 0 times!
    
    Beginning temperature point tuning!
    From 1892 to 1898, step 3. 
    
    Tcon=1859
    k=1 m=0 Tcon=1859 Trt=1886
     k=2 m=0 Tcon=1865 Trt=1887
     k=3 m=0 Tcon=1865 Trt=1887
     k=4 m=0 Tcon=1865 Trt=1886
     k=5 m=0 Tcon=1865 Trt=1887
     k=6 m=0 Tcon=1865 Trt=1887
     k=7 m=0 Tcon=1865 Trt=1887
    [few hundred lines]
     k=999 m=1 Tcon=1864 Trt=1893
     k=1000 m=1 Tcon=1864 Trt=1893
     k=1001 m=1 Tcon=1864 Trt=1893
     k=1002 m=1 Tcon=1864 Trt=1893
    k=1003 m=1 Tcon=1864 Trt=1893
    got it!
    k=1004 m=2 Tcon=1864 Trt=1893
    got it!
    k=1005 m=3 Tcon=1864 Trt=1893
    got it!
    k=1006 m=4 Tcon=1864 Trt=1892
    got it!
    k=1007 m=5 Tcon=1864 Trt=1893
    got it!
    k=1008 m=6 Tcon=1864 Trt=1892
    got it!
    [few hundred lines]
    k=1499 m=497 Tcon=1864 Trt=1893
    got it!
    k=1500 m=498 Tcon=1864 Trt=1892
    got it!
    k=1501 m=499 Tcon=1864 Trt=1893
    got it!
    
    Pd=830
    
    Pd is higher than 800!
    
    Id=217
    
    Id is below 330!
    
    Id is below 300!
    
    judge2=0  down2=1  all_down2=1
    
    judge1=0  down1=1  all_down1=1
    
    judge=0  down=1  all_down=1
    
    [then it starts to repeat itself]
    
    Tcon=1866
    k=1 m=0 Tcon=1866 Trt=1895
    got it!
    k=2 m=1 Tcon=1866 Trt=1895
    ....

    And with the photo diode removed off the front, I get:
    Code:
    Tcon=1859
    k=1 m=0 Tcon=1859 Trt=1885
     k=2 m=0 Tcon=1866 Trt=1885
     k=3 m=0 Tcon=1866 Trt=1885
     k=4 m=0 Tcon=1866 Trt=1885
     k=5 m=0 Tcon=1866 Trt=1884
     k=6 m=0 Tcon=1866 Trt=1885
     k=7 m=0 Tcon=1866 Trt=1885
     k=8 m=0 Tcon=1866 Trt=1885
     k=9 m=0 Tcon=1866 Trt=1885
     k=10 m=0 Tcon=1866 Trt=1885
     k=11 m=0 Tcon=1866 Trt=1884
     k=12 m=0 Tcon=1866 Trt=1885
     k=13 m=0 Tcon=1866 Trt=1885
     k=14 m=0 Tcon=1866 Trt=1885
     k=15 m=0 Tcon=1866 Trt=1885
     k=16 m=0 Tcon=1866 Trt=1885
     k=17 m=0 Tcon=1866 Trt=1885
     k=18 m=0 Tcon=1866 Trt=1884
     k=19 m=0 Tcon=1866 Trt=1885
     k=501 m=0 Tcon=1866 Trt=1893
    [few hundred lines]
    k=502 m=0 Tcon=1866 Trt=1893
    got it!
    k=503 m=1 Tcon=1866 Trt=1893
    got it!
    k=504 m=2 Tcon=1866 Trt=1892
    got it!
    k=505 m=3 Tcon=1866 Trt=1893
    got it!
    k=506 m=4 Tcon=1866 Trt=1893
    got it!
    k=507 m=5 Tcon=1866 Trt=1893
    got it!
    [few hundred lines]
    k=1000 m=498 Tcon=1866 Trt=1893
    got it!
    k=1001 m=499 Tcon=1866 Trt=1892
    got it!
    
    Pd=37
    No Pd detected! Pd=37
    
    Id=329
    
    Power's too low!
    
    judge2=0  down2=1  all_down2=1
    
    judge1=1  down1=0  all_down1=0
    
    judge=1  down=0  all_down=0
    
    Tcon=1869
    I am not sure what the numbers at the beginning mean, but Pd=xxx appears to be what the photodiode is reading, and Id appears to be the diode current. Its possible that Id reads in 10ma increments (ie Id=217 = 2.17A), but I have not been able to comfirm


    One last comment to anyone looking to build a nicer box for the laser, the supply needs to be heatsunk with a fairly decent heatsink, and it does not appear to have any form of overheat protection integrated into it. The laser head seems to be fine without any additional heatsink, but the power supply definitely will overheat without some help.
    Last edited by krazer; 05-22-2010 at 14:54. Reason: added info

  9. #19

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    Thanks for the pinouts and info, krazer! Really good work. I take it that you haven't been able to override the automatic temperature tuning and manually tune the temperature of the crystal set for higher output, no?

    And you're saying that the included heatsink is not sufficient? I've ran my unit for several hours at a time and the heatsink has never gotten extremely hot. I'll look around for a beefier heatsink to attack the driver to.

    - Kyle

  10. #20

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    The piece of metal it is mounted on seems to work fine, but in testing with that plate removed the supply quickly warmed up to dangerous levels.

    I haven't managed to get the laser to respond to anything on serial port 2, randomly mashing the keyboard seemed to have no response.

    A few comments I forgot to add in the previous post-
    1. serial port 1 - 9600 baud 8 bits no parity 1 stop bit
    2. serial port 2 - 115200 baud 8 bits no parity 1 stop bit
    3. the laser definitely has a light control loop, interrupting the beam before the photo diode sensor causes the current to very quickly ramp up to a maximum level. I lent my scope out so I can't see how quickly, but there might be hope to modulate this thing at a reasonable rate. You can see how much the current increases by looking at the printout in my previous post, with the pickoff in place it was running at 217 arbitrary units (I am guessing that means 2.17A?) and with it removed the current jumped up to 329 units (3.29A?). Has anyone been able to read the resistance of R53 (mounted on the heatsink between Q4 and Q6)? I am assuming it is the current sense for the diode, I measured 1.24v for 217 units of diode current as read out by the doubler tuning algorithm.
    4. The warranty sticker on the back doesn't actually do anything, by removing the 6 screws on the bottom you can lift the whole inside of the laser out (although you can't do a whole lot due to the short length of the wires). I just thought I should mention it, just because the sticker is still there the head could be completely stripped for all you know.
    5. Looking at the board, it appears that pots 5 and 4 appear to have been disabled (note how r54 and r55 labeled 0ohms have been removed), so I am assuming at least the settings those pots originally set are being set by the daughterboard on top.

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