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Thread: S-KY 200mW 532nm handheld PG-200 Review

  1. #1
    Join Date
    Oct 2006
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    Cleveland, Ohio
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    2,333

    Default S-KY 200mW 532nm handheld PG-200 Review

    With so many portable lasers available now, and many sporting >100mW ratings, it can be difficult to find a true value performer in the hype. Which lasers have IR filters? Which lasers actually put out their rated power? Which lasers are overdriven knockoffs that will die in a few weeks? This reivew sets out to determine whether the PG-200 from S-KY (formerly laserbtb) is a true value, an island of refuge in the sea of laser choices.

    First, S-KY as a company seems to be very eager to break into this market, and their communication is very good for a company so far away. They even have MSN chat communications if you happen to be up late and have a question. The laser in question is covered by a 6 month warranty.

    The packing: Packing for this laser was good, it came in its own storage box with foam cutouts for the keys, interlock, charger, and laser. On the sides were marked '532' and '200mW'.

    Large Version

    The laser itself was wrapped in antistatic shielding material:


    Large Version

    The charger is an automatic Li-Ion 18650 smart battery charger, it has an LED that is red during charging and turns green when charging has completed. I personally like the 18650 battery choice as they have a high energy density and are commonly used in laptop battery packs, so replacements are readily available from many sources.

    The laser has a very good feel in the hand. It is constructed out of aluminum, I estimate the battery wall thickness to be about 3mm, with a plastic tube insert around the battery as insulation. The battery goes in with the positive end towards the tailcap/interlock. The outer shell is coated in a hard black textured finish that provides a decent grip and will help keep the laser looking good after it's been around the block.


    Large Version

    Safety mechanisms include a tailcap interlock, key switch, bright blue 'lasing' indicator light, and shutter. There was no perceptible emission delay. Fortunately the key switch is not captive while on, which means you can turn the keyswitch on and remove the key. The red operation button is a toggle switch, so it will lock in the on position for extended and hands-free operation. I had no trouble depressing the switch halfway for a momentary operation mode. The tailcap interlock is a standard 3.5mm headphone jack style, and if you find it unsightly, a plug could be fashioned that would serve to engage the interlock while not protruding from the tail.

    Dimensions: 38mm dia by 195mm length:

    Large Version

    For the emission tests, I ran the laser for 3 minutes continuously and recorded the results on a Scientech 365 thermopile bench laser meter. I ran 3 tests using a fully charged battery, and one test with a regulated supply set to 4.1V. Although the head never got too warm to the touch, in between tests the laser was allowed to return to room temperature (21.5 C) for 10-15 minutes.



    As you can see, this beast starts off at an incredible 310-340mW and stays above 200mW for over a minute and a half. As the crystals continue to heat, efficiency then drops and levels out around 150-160mW at 3 minutes. Many laser manufacturers choose only to show laser power for the first 10-30 seconds or so, and after that you never know what you'll get. This laser maintains its rated power for much longer, and when it does drop off, it does so smoothly, without changing modes. At no point in the tests did the laser drop into multimode or split beam operation. Output stayed gaussian the entire test. This is one of the benefits of using higher quality crystals over the common MCA (microchip assembly) design in smaller lasers. When this laser is used in momentary mode (a few seconds on and off continuously), its output remains above 200mW. If this were a lab laser with cooling, it would probably be rated for 250-270mW and could do 320mW out of the box. Very nice.
    I'm thinking of building a TEC mount adapter for just this purpose.

    There was no significant IR output measured, so IR is less than (<)5% in the beam.


    The beam output diameter was about 1.5mm at the aperture, and focused to a burning spot of about 0.7mm 3 feet in front of the laser. From there, the divergence was measured to be 1.2mrad. I beleive the spec of <1 mrad could be acheived with tweaking of the focus, and eliminating the 3 foot focal point. As it stands, though, the divergence is good enough and it provides a very nice focused spot for burning, if that's your bag baby.

    With a constant current draw of 1450mA, a 2200mAh battery will be consumed in a total of 1.5 hours of operation. After that the output will begin to drop off. Fortunately, the Li-Ion batteries have no memory effect so it is easy to pop it in the smart charger at any time.

    Every portable laser company has a different method of rating their lasers. While lasershow lasers are rated to put out at least the rated power over their lifetime, portable lasers with a limited cooling (no TEC) and power source are usually different, so the value of the laser is considered the true output over time, not necissarily the rated output. Comparing this laser at close to an aries-150 at $689, but getting the power output of a $1000 hercules for the first 30 seconds is a great feat for this $355 (Group Buy) laser! Well done, S-KY! You exceeded my expectations, as this is a very good laser for the money.


    Here is one more beam picture taken with incense burning in the room to really solidify the beam:

    Large Version

    Have a look and post in the group buy thread if you are interested!
    http://www.photonlexicon.com/forums/...ead.php?t=3496

  2. #2
    Join Date
    Oct 2006
    Location
    Cleveland, Ohio
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    Default

    Part 2: Internals.


    While the PG-200 performed well for the price, no review of a new product would be complete without at least a partial teardown and look at the insides. It was aparent that this unit came apart at the junction between the finned head and the battery/driver casing, but it was glued together. After some work the two halves came apart and revealed a spring contact connecting the cathode of the laser diode to the driver board.



    Once the positive wire was disconnected from the set ring in the battery tube, the ring unscrewed and allowed access for disassembly of the keyswitch and removal of the control board.





    The circuit design is a standard op-amp-transistor current regulator with a 0.26 ohm shunt for sampling. The only oddity was that the gnd of the op amp was connected to the pot wiper instead of the gnd of the circuit. Despite this, the circuit seemed to operate fine, regulating at 1.45A. Note in the schematic the capacitors that have 0 value.. there are spots for them on the board but they were empty.

    The laser module unscrews from the finned heatsink bore. Because of the glue residue on the bore threads still, it was very difficult to get off and in this struggle I learned that the heatsink is made from a rather hard and high quality aluminum alloy. After much struggling and some cutting I prevailed. On the laser module's end is a copper contact to which the cathode of the laser diode is screwed. The the copper contact was removed and the cathode wire screwed down to the module, protecting the laser diode during disassembly.



    The final lens is mounted in an endcap at the top of the module, and inside that the beam expander is visible:



    In this shot you can see that the rest of the laser module is heavily glued together with some kind of hard dental or bone cement that did not soften with solvent. From the way this module is put together, it is likely (and S-KY confirms) that a c-mount laser is used, screwed on the block of aluminum.

    GREEN lasing threshold was at 450mA, and Vd reached 2.2V at 1400mA.

    These are the parameters of the common c-block laser diodes available:
    1W: Threshold: <300mA Max operating current: 1400mA at 2.2V max. 100um stripe
    2W: Threshold: <700mA Max operating current: 2800mA at 2.2V max. 200um stripe

    In conclusion, the laser is sturdily assembled, although it may be difficult to replace the pump diode due to all the glue. The regulator board is adjustable and has plenty of current headroom to install a 2W diode.. if you can get the module open. The diode that is installed could be a 1W c-mount laser, which would fit (with rather good crystal matching) with the 150mW settled output. S-KY has stated that this unit has a 2W pump diode, however the threshold and operating current make me question that.

    Perhaps one more faimiliar in the field of pump diodes can add their opinion to this question?

  3. #3
    Join Date
    Dec 2007
    Location
    Texas
    Posts
    98

    Default

    I ordered one yesterday and am looking forward to it. The adjustable focus and 2W diode make it a very good buy. I just hope I can find a way to cool it better so it can run more than 10 mins continuous.

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