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1.7A Microboost Mod
Ok so some of you may have seen I had a build with a damaged microboost that was giving 1.8A seen here.
http://laserpointerforums.com/f52/2...1-8a-microboost-driver-72441.html#post1043039
With a little expermintation and some advice for a new resistor from drlava I have a good working mod. With this mod you can pretty consistently build a 2W+ laser with a M140 diode.
These are the resistors that he suggested I use so I ordered some up and some more Microboosts.
Digi-Key - RHM.13SCT-ND (Manufacturer - MCR25JZHFLR130)
Got them today and gave it a try.
Here is the resistor that I removed replacing with the one from Digikey.
Here is the unit as it is stock.
Here is one after I switched out the resistor. Note I just bridged the point for the larger resistor. You don't need to do anything with the smaller set of resistors as bridging them just gives too high a range and the nice part is if you accidentally desolder one of those small ones it can be a real pain in the ass to get it back in place. So this mod has an added bonus that you don't have to mess with them.
Once it was replaced I took some quick readings.
The driver with just the resistor replaced gave me a range from 1360mA-1720mA.
Here it is giving over 1.6A.
So I set the driver to 1.7A. I do currently suggest 1.5A/1.6A for best stability but this was my first build and still turned out great.
Now that the driver's current is set I need to heatsink it. The chip on this driver that needs to be heatsinked is in a somewhat tough spot but referring to Morgans skyray build where he showed a good way to do it.
He cut a small square piece of aluminum to mount on the chip that will give it the height for the rest of the driver to be sinked flat on a heatsink. The chip with the square of aluminum in this picture is the one we are after.
So for my first build will be in an Ehgemus host with his driver pocket. So I did like in the picture above then after the aluminum spacer was attached with thermal adhesive I made another piece of aluminum that will mount to the side of the driver pocket in the Ehgeums host.
I always like to recheck the drivers after being heatsinked.
So I adhered the heatsink in the driver pocket of my host with some thermal adheasive.
Wired the positive battery contact point.
Attached the diode and put the host together.
Now I did a four minute run with the unit. It held pretty stable about 100mW drop a minute. Also after the run I let it cool down for 5-10 second and started it up real quick and it was almost back to full strength so after a few minutes a 20-30 second cool down should be sufficient.
Ok so this seems to be a pretty sweet mod. I am going to do another tomorrow night and I will turn it down about 50mA and try to heatsink it better. I hope that will make it even more stable without sacrificing much in the way of output.
So that is where I am now. This looks very promising but keep in mind attempt this mod at your own risk.:beer:
EDIT BUILD #2
Alright put another together last night. This time I did sink the driver better. I used a copper mount on a gold dollar(copper) in the aluminum driver pocket of a 26650 Ehgemus host that I have been waiting to build.
I tested it and is seemed much more stable. Notice I purposely set it so the current draw was just under 3A @ 4.2V this way if the voltage spikes over 4.2V the output current will stay constant.
Next I finished building the host and tested it. I got really lucky with this diode. It was a random grab no cherry pick. @ 1.7A I am getting a peak of 2550mW.:eg:
So I proceeded to do a 7 minute run. I would have gone longer but I forgot my camera stops for some reason after 7 minutes.
EDIT BUILD #3
Ok so here a Saik build.
After switching out the resistor and bridging all the resistors shown above I cut a piece of copper out of some scrap I had. Then I attached it to my driver with some thermal adhesive.
After it dried about 15 minutes later I attached it to the back of the heatsink the same way.
Now I set the driver to about 1675mA and did a test. Looked pretty good. It has about 20 mA drop in the beginning and then held pretty steady.
Next I added a diode.
Gave it a quick test on the bench supply to see that the current draw was still the same with the diode. Right under 3A.
Next I proceeded to attach the contact points I set up on the pill.
On this host you first want to screw the pill into the body.
They you actually want to take the heatsink out of the head so it does not twist up the wires when you screw the head in to the host body. If you see I have exposed the metal in the head as this heatsink was really tight in there but it still fits in very snug with good thermal contact.
Then I secured the heatsink wiht the retaining ring, put in a lens and battery then did test run for 10 minutes. These host are damn tanks. I put my finger on the heatsink at the end and it was only mildly warm.:eg:
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