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|05-29-2015, 03:43 AM||#17|
Class 3B Laser
Join Date: Jan 2014
Posts: 4,304Rep Power: 2141
Re: T67 Grande 850nm IR Illuminator Torch
Took me awhile and some experimentation, but I made an adjustable focus laser flashlight which can be focused from smaller than the size of a dime to huge spot as well as infinity between the two extremes. My primary interest in doing this mod was to create a low divergence laser beam which can put a spot on some very high clouds, its use as a variable spot beam flashlight is of little interest to me, but some might want to build their own for that purpose, I see laser flashlights on ebay being sold for that use.
I replaced the LED with the copper end of a DTR module hack sawed off so my 50mw rated single mode 520nm diodes head is flush with what remains of the copper, put a 11mm copper crush washer on the side the module housing screws on to and mounted in the original flashlight pill (had to drill a hole for the wires to go through the it). Had to also replace the original crappy (for laser) lens which came with it with a couple of +10 67mm macro PCX lenses which are cheap on ebay (one lens on top of the other) but the final product works, you get one hell of a lot of beam expansion and ultra low divergence
The black ring threads back into the pill and compresses the copper diode holder tightly down on to the aluminum which serves as a heat sink. The hole I drilled through it for the wires should be much smaller, it ended up that large when I tried to drill a hole through it to tap for 11mm (that tap isn't easy to find, but I found one) so I could screw the copper part of the DTR module into it, but I accidentally drilled it off center and then switched to this method. The first method I wanted to try might be the better way to do this, but the threaded copper end of the module the G2 etc. lens normally screws into might clip the output of the laser diode some of it isn't removed. Although the method I ended up using would save you from having to buy a 11mm tap, you then need to buy a 11mm copper crush washer, also available on ebay. I soldered the crush washer to the copper to allow better heat transfer, I hope.
The Osram 50mw 520nm laser diode works great without a driver if using two 4.20VDC Li-Ion batteries in series (late edit: As long as they are not charged beyond 4.1 VDC each, the diode doesn't run well and non-destructively dims with two 4.2 VDC batteries at a total of 8.4 VDC, let the batteries drain down to 4.1 VDC each and no problem). I know, the diode is supposed to overheat and die without a constant current regulator, but I've abused this diode letting it pull too much current many times and all it will do is dim down until the current is reduced. Don't try this with any other diode, this is the only one I know of which behaves this way.
Unless you want to clean off the parts from the original PCB driver and use that you will need to replace it with a 17mm diameter battery PCB to solder the lead wires from the diode onto, also available on ebay (see link below). In the second and third photo's (above) you can see the back side of the pill where the 17mm PCB with a battery pad spring inserts into it for soldering the ground or negative side of the PCB to the brass ring on the back side.
Copper Crush Washer Washers ID M11 11mm 6 Pack | eBay
Free Shipping 17mm Flashlight Switch PCB Board Type B1 | eBay
11mm x 5 Metric HSS Right Hand Tap M11 x 0 5mm Pitch | eBay
Two each with a threaded spacer between them: 67mm Macro Close Up 10 Lens Filter 67mm Close Up No 10 | eBay
Edit: One each +20 macro lens: I believe this will be a much better lens than using two of the +10's on the above link, I have not received mine yet to test but it should be much better: http://www.ebay.com/itm/281610703207
Although simple, researching this to find the right pieces and lenses took a lot of time! If I could find a 67mm +20 macro lens this would be even easier, the 67mm macro lens does not thread into the flashlight hood, but fits nicely and can be held in place with a strip of black electrical tape. To be able to thread the two 67mm +10 lenses together, I had to use the holder from a +1 macro lens, lens removed, in between the two lenses and use half of the threads from each +10mm lens, they bulge out too much to screw all the way down but there are enough threads and it holds well, the lenses actually touch together when tightened down.
At first, I tried to use this macro lens set Zeikos 67mm Closeup Macro 1 2 4 10 Filter Kit | eBay but found they weren't enough, so ordered another +10 macro lens and put the two +10's together to allow the unit to focus to infinity. Maybe I can find a better lens holder and spacer for the two lenses which screw on to the threads of the flashlight, that would be awesome, even better a single +20 macro lens but I can't find one at a good price.
Now that I see this can be made to work, next is a 700mw 520nm laser diode and a 17mm driver for it and this will be one hell of a flashlight but more work might need to be done to keep the diode cooler such as using Arctic Silver heat sink compound on the threads the pill screws into.
Late edit: With freshly charged Li-On batteries to 4.2VDC each I'm finding the laser dims almost immediately. At first I took the problem to be due to the copper slug the diode is mounted in needing better heat sinking, I then used some Arctic Silver thermal epoxy to glue the copper crush washer and DTR copper module down onto the aluminum pill and no difference. I then started pulsing the on-off switch and found that the laser would put out full power for a short period of time during each on-off cycle, but quickly dim. After much testing I've found the diode is pulling so much current it stops lasing, turning it off and on it will come back to life each time, but dim pretty quick. I kept doing this until the batteries drained down enough the laser was no longer pulling so much current it would shut down. Problem solved, two 4.2 VDC batteries in series is just too much voltage and thus current, when at a full charge. I will need to install a CC regulator to get the flashlight to operate properly. I used this same diode in other hosts without this problem, but they all had very thin wires which were fairly long, the flashlight uses thick wires and they are short, thus less voltage loss, just enough less that the diode isn't happy with the voltage at a total of 8.4 VDC but runs quite nicely without a constant current regulator at 8.2 VDC. This is one tuff little laser diode to be able to take so much abuse and keep on ticking.
Once I fix this issue I believe this will be a rock solid conversion into a laser flashlight, especially if I can find a 67mm diameter +20 macro lens. Edit: Found one http://www.ebay.com/itm/281610703207
Final edit: I received the +20 Fox Macro Lens and found the focal length was a couple of inches too long but I was able to use it anyway by placing the flashlights original end piece without the lens back on the unit and then put the macro lens on top of that, securing it with tape. This reduces the number of lenses I needed before from three to one, just the +20 macro lens.
As you can see in the bottom photograph, the output is generally rectangular for the most intense part of the spot, this is due to the physical structure or shape of the laser diode semiconductor chip, only beam shaping optics can make it more round, regardless the divergence is very low.
If you buy one of these flashlights to do this mod, the part of the pill the LED is mounted in unscrews the wrong direction! You have to turn it clockwise or to the right! Took me awhile to figure that out, I kept complaining to myself why in the world the manufacturer would spin the top down so hard I couldn't remove it while I was actually tightening it more going the wrong direction.
You can also buy a smaller version of this much cheaper here: http://www.ebay.com/itm/New-Night-Vi...-/391154741184 but this unit is 532nm, sensitive to cold and only 5-20mw depending upon temperature, mine is 75-100mw regardless of temp. with freshly charged batteries. Here's another one costing far more which I believe is 50mw, maybe less: http://www.ebay.com/itm/OEM-Hunting-...-/271717218544
Laser Safety: http://www.laserpointersafety.com/index.html
Angular Size Calculator; use with diode angle of radiation specification to calculate the needed lens diameter for a given FL:
Divergence to spot size calculator: http://tinyurl.com/spotsize - 1 mRad is about .057 degrees which from the earth would expand to be ~10% the diameters of the moon or sun at their distances.
Divergence Calculator: http://www.pseudonomen.com/lasers/ca...alculator.html - Measure your lasers beamwidth at 1 foot & then at a further distance to calculate the divergence.
Online calculator to determine spot intensity at different mRad's & powers @ distances: http://tinyurl.com/divergence-calculator
Laser Power Density Calculator: http://www.ophiropt.com/laser-measur...ity-calculator
How to build a laser beam expander to reduce divergence: http://tinyurl.com/BeamExpander
RHD's Relative Perceived Brightness Calculator. Compare brightness @nm: http://lsrtools.1apps.com/relativebrightness
YAG Power Calculator, i.e. convert ns @ mJ to peak power in watts http://tinyurl.com/YAG-Pulse
The forum costs more to run than donations received, if you wish to help click this link: http://laserpointerforums.com/donations.htm
Last edited by Alaskan; 06-12-2015 at 03:48 AM. Reason: Posted a bit prematurely, still had a bug to work out. Post edited.
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